/* libmspack -- a library for working with Microsoft compression formats.

  * (C) 2003-2019 Stuart Caie <kyzer@cabextract.org.uk>

  *
  * libmspack is free software; you can redistribute it and/or modify it under
  * the terms of the GNU Lesser General Public License (LGPL) version 2.1
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
 /** \mainpage
  *
  * \section intro Introduction
  *
  * libmspack is a library which provides compressors and decompressors,
  * archivers and dearchivers for Microsoft compression formats.
  *
  * \section formats Formats supported
  *
  * The following file formats are supported:
  * - SZDD files, which use LZSS compression
  * - KWAJ files, which use LZSS, LZSS+Huffman or deflate compression
  * - .HLP (MS Help) files, which use LZSS compression
  * - .CAB (MS Cabinet) files, which use deflate, LZX or Quantum compression
  * - .CHM (HTML Help) files, which use LZX compression
  * - .LIT (MS EBook) files, which use LZX compression and DES encryption
  * - .LZX (Exchange Offline Addressbook) files, which use LZX compression
  *
  * To determine the capabilities of the library, and the binary
  * compatibility version of any particular compressor or decompressor, use
  * the mspack_version() function. The UNIX library interface version is
  * defined as the highest-versioned library component.
  *
  * \section starting Getting started
  *
  * The macro MSPACK_SYS_SELFTEST() should be used to ensure the library can
  * be used. In particular, it checks if the caller is using 32-bit file I/O
  * when the library is compiled for 64-bit file I/O and vice versa.
  *
  * If compiled normally, the library includes basic file I/O and memory
  * management functionality using the standard C library. This can be
  * customised and replaced entirely by creating a mspack_system structure.
  *
  * A compressor or decompressor for the required format must be
  * instantiated before it can be used. Each construction function takes
  * one parameter, which is either a pointer to a custom mspack_system
  * structure, or NULL to use the default. The instantiation returned, if
  * not NULL, contains function pointers (methods) to work with the given
  * file format.
  * 
  * For compression:
  * - mspack_create_cab_compressor() creates a mscab_compressor
  * - mspack_create_chm_compressor() creates a mschm_compressor
  * - mspack_create_lit_compressor() creates a mslit_compressor
  * - mspack_create_hlp_compressor() creates a mshlp_compressor
  * - mspack_create_szdd_compressor() creates a msszdd_compressor
  * - mspack_create_kwaj_compressor() creates a mskwaj_compressor
  * - mspack_create_oab_compressor() creates a msoab_compressor
  *
  * For decompression:
  * - mspack_create_cab_decompressor() creates a mscab_decompressor
  * - mspack_create_chm_decompressor() creates a mschm_decompressor
  * - mspack_create_lit_decompressor() creates a mslit_decompressor
  * - mspack_create_hlp_decompressor() creates a mshlp_decompressor
  * - mspack_create_szdd_decompressor() creates a msszdd_decompressor
  * - mspack_create_kwaj_decompressor() creates a mskwaj_decompressor
  * - mspack_create_oab_decompressor() creates a msoab_decompressor
  *
  * Once finished working with a format, each kind of
  * compressor/decompressor has its own specific destructor:
  * - mspack_destroy_cab_compressor()
  * - mspack_destroy_cab_decompressor()
  * - mspack_destroy_chm_compressor()
  * - mspack_destroy_chm_decompressor()
  * - mspack_destroy_lit_compressor()
  * - mspack_destroy_lit_decompressor()
  * - mspack_destroy_hlp_compressor()
  * - mspack_destroy_hlp_decompressor()
  * - mspack_destroy_szdd_compressor()
  * - mspack_destroy_szdd_decompressor()
  * - mspack_destroy_kwaj_compressor()
  * - mspack_destroy_kwaj_decompressor()
  * - mspack_destroy_oab_compressor()
  * - mspack_destroy_oab_decompressor()
  *
  * Destroying a compressor or decompressor does not destroy any objects,
  * structures or handles that have been created using that compressor or
  * decompressor. Ensure that everything created or opened is destroyed or
  * closed before compressor/decompressor is itself destroyed.
  *
  * \section errors Error codes
  *
  * All compressors and decompressors use the same set of error codes. Most
  * methods return an error code directly. For methods which do not
  * return error codes directly, the error code can be obtained with the
  * last_error() method.
  *
  * - #MSPACK_ERR_OK is used to indicate success. This error code is defined
  *   as zero, all other code are non-zero.
  * - #MSPACK_ERR_ARGS indicates that a method was called with inappropriate
  *   arguments.
  * - #MSPACK_ERR_OPEN indicates that mspack_system::open() failed.
  * - #MSPACK_ERR_READ indicates that mspack_system::read() failed.
  * - #MSPACK_ERR_WRITE indicates that mspack_system::write() failed.
  * - #MSPACK_ERR_SEEK indicates that mspack_system::seek() failed.
  * - #MSPACK_ERR_NOMEMORY indicates that mspack_system::alloc() failed.
  * - #MSPACK_ERR_SIGNATURE indicates that the file being read does not
  *   have the correct "signature". It is probably not a valid file for
  *   whatever format is being read.
  * - #MSPACK_ERR_DATAFORMAT indicates that the file being used or read
  *   is corrupt.
  * - #MSPACK_ERR_CHECKSUM indicates that a data checksum has failed.
  * - #MSPACK_ERR_CRUNCH indicates an error occured during compression.
  * - #MSPACK_ERR_DECRUNCH indicates an error occured during decompression.
  *
  * \section threading Multi-threading
  *
  * libmspack methods are reentrant and multithreading-safe when each
  * thread has its own compressor or decompressor.
 
  * You should not call multiple methods simultaneously on a single
  * compressor or decompressor instance.
  *
  * If this may happen, you can either use one compressor or
  * decompressor per thread, or you can use your preferred lock,
  * semaphore or mutex library to ensure no more than one method on a
  * compressor/decompressor is called simultaneously. libmspack will
  * not do this locking for you.
  *
  * Example of incorrect behaviour:
  * - thread 1 calls mspack_create_cab_decompressor()
  * - thread 1 calls open()
  * - thread 1 calls extract() for one file
  * - thread 2 simultaneously calls extract() for another file
  *
  * Correct behaviour:
  * - thread 1 calls mspack_create_cab_decompressor()
  * - thread 2 calls mspack_create_cab_decompressor()
  * - thread 1 calls its own open() / extract()
  * - thread 2 simultaneously calls its own open() / extract()
  *
  * Also correct behaviour:
  * - thread 1 calls mspack_create_cab_decompressor()
  * - thread 1 locks a mutex for with the decompressor before
  *   calling any methods on it, and unlocks the mutex after each
  *   method returns.
  * - thread 1 can share the results of open() with thread 2, and both
  *   can call extract(), provided they both guard against simultaneous
  *   use of extract(), and any other methods, with the mutex
  */
 
 #ifndef LIB_MSPACK_H
 #define LIB_MSPACK_H 1
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 #include <sys/types.h>
 #include <stdlib.h>
 
 /**
  * System self-test function, to ensure both library and calling program
  * can use one another.
  *
  * A result of MSPACK_ERR_OK means the library and caller are
  * compatible. Any other result indicates that the library and caller are
  * not compatible and should not be used. In particular, a value of
  * MSPACK_ERR_SEEK means the library and caller use different off_t
  * datatypes.
  *
  * It should be used like so:
  *
  * @code
  * int selftest_result;
  * MSPACK_SYS_SELFTEST(selftest_result);
  * if (selftest_result != MSPACK_ERR_OK) {
  *   fprintf(stderr, "incompatible with this build of libmspack\n");
  *   exit(0);
  * }
  * @endcode
  *
  * @param  result   an int variable to store the result of the self-test
  */
 #define MSPACK_SYS_SELFTEST(result)  do { \
   (result) = mspack_sys_selftest_internal(sizeof(off_t)); \
 } while (0)
 
 /** Part of the MSPACK_SYS_SELFTEST() macro, must not be used directly. */
 extern int mspack_sys_selftest_internal(int);
 
 /**
  * Enquire about the binary compatibility version of a specific interface in
  * the library. Currently, the following interfaces are defined:
  *
  * - #MSPACK_VER_LIBRARY: the overall library
  * - #MSPACK_VER_SYSTEM: the mspack_system interface
  * - #MSPACK_VER_MSCABD: the mscab_decompressor interface
  * - #MSPACK_VER_MSCABC: the mscab_compressor interface
  * - #MSPACK_VER_MSCHMD: the mschm_decompressor interface
  * - #MSPACK_VER_MSCHMC: the mschm_compressor interface
  * - #MSPACK_VER_MSLITD: the mslit_decompressor interface
  * - #MSPACK_VER_MSLITC: the mslit_compressor interface
  * - #MSPACK_VER_MSHLPD: the mshlp_decompressor interface
  * - #MSPACK_VER_MSHLPC: the mshlp_compressor interface
  * - #MSPACK_VER_MSSZDDD: the msszdd_decompressor interface
  * - #MSPACK_VER_MSSZDDC: the msszdd_compressor interface
  * - #MSPACK_VER_MSKWAJD: the mskwaj_decompressor interface
  * - #MSPACK_VER_MSKWAJC: the mskwaj_compressor interface
  * - #MSPACK_VER_MSOABD: the msoab_decompressor interface
  * - #MSPACK_VER_MSOABC: the msoab_compressor interface
  *
  * The result of the function should be interpreted as follows:
  * - -1: this interface is completely unknown to the library
  * - 0: this interface is known, but non-functioning
  * - 1: this interface has all basic functionality
  * - 2, 3, ...: this interface has additional functionality, clearly marked
  *   in the documentation as "version 2", "version 3" and so on.
  *
  * @param entity the interface to request current version of
  * @return the version of the requested interface
  */
 extern int mspack_version(int entity);
 
 /** Pass to mspack_version() to get the overall library version */
 #define MSPACK_VER_LIBRARY   (0)
 /** Pass to mspack_version() to get the mspack_system version */
 #define MSPACK_VER_SYSTEM    (1)
 /** Pass to mspack_version() to get the mscab_decompressor version */
 #define MSPACK_VER_MSCABD    (2)
 /** Pass to mspack_version() to get the mscab_compressor version */
 #define MSPACK_VER_MSCABC    (3)
 /** Pass to mspack_version() to get the mschm_decompressor version */
 #define MSPACK_VER_MSCHMD    (4)
 /** Pass to mspack_version() to get the mschm_compressor version */
 #define MSPACK_VER_MSCHMC    (5)
 /** Pass to mspack_version() to get the mslit_decompressor version */
 #define MSPACK_VER_MSLITD    (6)
 /** Pass to mspack_version() to get the mslit_compressor version */
 #define MSPACK_VER_MSLITC    (7)
 /** Pass to mspack_version() to get the mshlp_decompressor version */
 #define MSPACK_VER_MSHLPD    (8)
 /** Pass to mspack_version() to get the mshlp_compressor version */
 #define MSPACK_VER_MSHLPC    (9)
 /** Pass to mspack_version() to get the msszdd_decompressor version */
 #define MSPACK_VER_MSSZDDD   (10)
 /** Pass to mspack_version() to get the msszdd_compressor version */
 #define MSPACK_VER_MSSZDDC   (11)
 /** Pass to mspack_version() to get the mskwaj_decompressor version */
 #define MSPACK_VER_MSKWAJD   (12)
 /** Pass to mspack_version() to get the mskwaj_compressor version */
 #define MSPACK_VER_MSKWAJC   (13)
 /** Pass to mspack_version() to get the msoab_decompressor version */
 #define MSPACK_VER_MSOABD    (14)
 /** Pass to mspack_version() to get the msoab_compressor version */
 #define MSPACK_VER_MSOABC    (15)
 
 /* --- file I/O abstraction ------------------------------------------------ */
 
 /**
  * A structure which abstracts file I/O and memory management.
  *
  * The library always uses the mspack_system structure for interaction
  * with the file system and to allocate, free and copy all memory. It also
  * uses it to send literal messages to the library user.
  *
  * When the library is compiled normally, passing NULL to a compressor or
  * decompressor constructor will result in a default mspack_system being
  * used, where all methods are implemented with the standard C library.
  * However, all constructors support being given a custom created
  * mspack_system structure, with the library user's own methods. This
  * allows for more abstract interaction, such as reading and writing files
  * directly to memory, or from a network socket or pipe.
  *
  * Implementors of an mspack_system structure should read all
  * documentation entries for every structure member, and write methods
  * which conform to those standards.
  */
 struct mspack_system {
   /**
    * Opens a file for reading, writing, appending or updating.
    *
    * @param self     a self-referential pointer to the mspack_system
    *                 structure whose open() method is being called. If
    *                 this pointer is required by close(), read(), write(),
    *                 seek() or tell(), it should be stored in the result
    *                 structure at this time.
    * @param filename the file to be opened. It is passed directly from the
    *                 library caller without being modified, so it is up to
    *                 the caller what this parameter actually represents.
    * @param mode     one of #MSPACK_SYS_OPEN_READ (open an existing file
    *                 for reading), #MSPACK_SYS_OPEN_WRITE (open a new file
    *                 for writing), #MSPACK_SYS_OPEN_UPDATE (open an existing
    *                 file for reading/writing from the start of the file) or
    *                 #MSPACK_SYS_OPEN_APPEND (open an existing file for
    *                 reading/writing from the end of the file)
    * @return a pointer to a mspack_file structure. This structure officially
    *         contains no members, its true contents are up to the
    *         mspack_system implementor. It should contain whatever is needed
    *         for other mspack_system methods to operate. Returning the NULL
    *         pointer indicates an error condition.
    * @see close(), read(), write(), seek(), tell(), message()
    */
   struct mspack_file * (*open)(struct mspack_system *self,

                                const char *filename,
                                int mode);

 
   /**
    * Closes a previously opened file. If any memory was allocated for this
    * particular file handle, it should be freed at this time.
    * 
    * @param file the file to close
    * @see open()
    */
   void (*close)(struct mspack_file *file);
 
   /**
    * Reads a given number of bytes from an open file.
    *
    * @param file    the file to read from
    * @param buffer  the location where the read bytes should be stored
    * @param bytes   the number of bytes to read from the file.
    * @return the number of bytes successfully read (this can be less than
    *         the number requested), zero to mark the end of file, or less

    *         than zero to indicate an error. The library does not "retry"
    *         reads and assumes short reads are due to EOF, so you should
    *         avoid returning short reads because of transient errors.

    * @see open(), write()
    */
   int (*read)(struct mspack_file *file,

               void *buffer,
               int bytes);

 
   /**
    * Writes a given number of bytes to an open file.
    *
    * @param file    the file to write to
    * @param buffer  the location where the written bytes should be read from
    * @param bytes   the number of bytes to write to the file.
    * @return the number of bytes successfully written, this can be less
    *         than the number requested. Zero or less can indicate an error
    *         where no bytes at all could be written. All cases where less
    *         bytes were written than requested are considered by the library
    *         to be an error.
    * @see open(), read()
    */
   int (*write)(struct mspack_file *file,

                void *buffer,
                int bytes);

 
   /**
    * Seeks to a specific file offset within an open file.
    *
    * Sometimes the library needs to know the length of a file. It does
    * this by seeking to the end of the file with seek(file, 0,
    * MSPACK_SYS_SEEK_END), then calling tell(). Implementations may want
    * to make a special case for this.
    *
    * Due to the potentially varying 32/64 bit datatype off_t on some
    * architectures, the #MSPACK_SYS_SELFTEST macro MUST be used before
    * using the library. If not, the error caused by the library passing an
    * inappropriate stackframe to seek() is subtle and hard to trace.
    *
    * @param file   the file to be seeked
    * @param offset an offset to seek, measured in bytes
    * @param mode   one of #MSPACK_SYS_SEEK_START (the offset should be
    *               measured from the start of the file), #MSPACK_SYS_SEEK_CUR
    *               (the offset should be measured from the current file offset)
    *               or #MSPACK_SYS_SEEK_END (the offset should be measured from
    *               the end of the file)
    * @return zero for success, non-zero for an error
    * @see open(), tell()
    */
   int (*seek)(struct mspack_file *file,

               off_t offset,
               int mode);

 
   /**
    * Returns the current file position (in bytes) of the given file.
    *
    * @param file the file whose file position is wanted
    * @return the current file position of the file
    * @see open(), seek()
    */
   off_t (*tell)(struct mspack_file *file);
   
   /**
    * Used to send messages from the library to the user.
    *
    * Occasionally, the library generates warnings or other messages in
    * plain english to inform the human user. These are informational only
    * and can be ignored if not wanted.
    *
    * @param file   may be a file handle returned from open() if this message
    *               pertains to a specific open file, or NULL if not related to
    *               a specific file.
    * @param format a printf() style format string. It does NOT include a
    *               trailing newline.
    * @see open()
    */
   void (*message)(struct mspack_file *file,

                   const char *format,
                   ...);

 
   /**
    * Allocates memory.
    *
    * @param self     a self-referential pointer to the mspack_system
    *                 structure whose alloc() method is being called.
    * @param bytes    the number of bytes to allocate
    * @result a pointer to the requested number of bytes, or NULL if
    *         not enough memory is available
    * @see free()
    */
   void * (*alloc)(struct mspack_system *self,

                   size_t bytes);

   
   /**
    * Frees memory.
    * 

    * @param ptr the memory to be freed. NULL is accepted and ignored.

    * @see alloc()
    */
   void (*free)(void *ptr);
 
   /**
    * Copies from one region of memory to another.
    * 
    * The regions of memory are guaranteed not to overlap, are usually less
    * than 256 bytes, and may not be aligned. Please note that the source
    * parameter comes before the destination parameter, unlike the standard
    * C function memcpy().
    *
    * @param src   the region of memory to copy from
    * @param dest  the region of memory to copy to
    * @param bytes the size of the memory region, in bytes
    */
   void (*copy)(void *src,

                void *dest,
                size_t bytes);

 
   /**
    * A null pointer to mark the end of mspack_system. It must equal NULL.
    *
    * Should the mspack_system structure extend in the future, this NULL
    * will be seen, rather than have an invalid method pointer called.
    */
   void *null_ptr;
 };
 
 /** mspack_system::open() mode: open existing file for reading. */
 #define MSPACK_SYS_OPEN_READ   (0)
 /** mspack_system::open() mode: open new file for writing */
 #define MSPACK_SYS_OPEN_WRITE  (1)
 /** mspack_system::open() mode: open existing file for writing */
 #define MSPACK_SYS_OPEN_UPDATE (2)
 /** mspack_system::open() mode: open existing file for writing */
 #define MSPACK_SYS_OPEN_APPEND (3)
 
 /** mspack_system::seek() mode: seek relative to start of file */
 #define MSPACK_SYS_SEEK_START  (0)
 /** mspack_system::seek() mode: seek relative to current offset */
 #define MSPACK_SYS_SEEK_CUR    (1)
 /** mspack_system::seek() mode: seek relative to end of file */
 #define MSPACK_SYS_SEEK_END    (2)
 
 /** 
  * A structure which represents an open file handle. The contents of this
  * structure are determined by the implementation of the
  * mspack_system::open() method.
  */
 struct mspack_file {
   int dummy;
 };
 
 /* --- error codes --------------------------------------------------------- */
 
 /** Error code: no error */
 #define MSPACK_ERR_OK          (0)
 /** Error code: bad arguments to method */
 #define MSPACK_ERR_ARGS        (1)
 /** Error code: error opening file */
 #define MSPACK_ERR_OPEN        (2)
 /** Error code: error reading file */
 #define MSPACK_ERR_READ        (3)
 /** Error code: error writing file */
 #define MSPACK_ERR_WRITE       (4)
 /** Error code: seek error */
 #define MSPACK_ERR_SEEK        (5)
 /** Error code: out of memory */
 #define MSPACK_ERR_NOMEMORY    (6)
 /** Error code: bad "magic id" in file */
 #define MSPACK_ERR_SIGNATURE   (7)
 /** Error code: bad or corrupt file format */
 #define MSPACK_ERR_DATAFORMAT  (8)
 /** Error code: bad checksum or CRC */
 #define MSPACK_ERR_CHECKSUM    (9)
 /** Error code: error during compression */
 #define MSPACK_ERR_CRUNCH      (10)
 /** Error code: error during decompression */
 #define MSPACK_ERR_DECRUNCH    (11)
 
 /* --- functions available in library -------------------------------------- */
 
 /** Creates a new CAB compressor.
  * @param sys a custom mspack_system structure, or NULL to use the default
  * @return a #mscab_compressor or NULL
  */
 extern struct mscab_compressor *
   mspack_create_cab_compressor(struct mspack_system *sys);
 
 /** Creates a new CAB decompressor.
  * @param sys a custom mspack_system structure, or NULL to use the default
  * @return a #mscab_decompressor or NULL
  */
 extern struct mscab_decompressor *
   mspack_create_cab_decompressor(struct mspack_system *sys);
 
 /** Destroys an existing CAB compressor.
  * @param self the #mscab_compressor to destroy
  */
 extern void mspack_destroy_cab_compressor(struct mscab_compressor *self);
 
 /** Destroys an existing CAB decompressor.
  * @param self the #mscab_decompressor to destroy
  */
 extern void mspack_destroy_cab_decompressor(struct mscab_decompressor *self);
 
 
 /** Creates a new CHM compressor.
  * @param sys a custom mspack_system structure, or NULL to use the default
  * @return a #mschm_compressor or NULL
  */
 extern struct mschm_compressor *
   mspack_create_chm_compressor(struct mspack_system *sys);
 
 /** Creates a new CHM decompressor.
  * @param sys a custom mspack_system structure, or NULL to use the default
  * @return a #mschm_decompressor or NULL
  */
 extern struct mschm_decompressor *
   mspack_create_chm_decompressor(struct mspack_system *sys);
 
 /** Destroys an existing CHM compressor.
  * @param self the #mschm_compressor to destroy
  */
 extern void mspack_destroy_chm_compressor(struct mschm_compressor *self);
 
 /** Destroys an existing CHM decompressor.
  * @param self the #mschm_decompressor to destroy
  */
 extern void mspack_destroy_chm_decompressor(struct mschm_decompressor *self);
 
 
 /** Creates a new LIT compressor.
  * @param sys a custom mspack_system structure, or NULL to use the default
  * @return a #mslit_compressor or NULL
  */
 extern struct mslit_compressor *
   mspack_create_lit_compressor(struct mspack_system *sys);
 
 /** Creates a new LIT decompressor.
  * @param sys a custom mspack_system structure, or NULL to use the default
  * @return a #mslit_decompressor or NULL
  */
 extern struct mslit_decompressor *
   mspack_create_lit_decompressor(struct mspack_system *sys);
 
 /** Destroys an existing LIT compressor.
  * @param self the #mslit_compressor to destroy
  */
 extern void mspack_destroy_lit_compressor(struct mslit_compressor *self);
 
 /** Destroys an existing LIT decompressor.
  * @param self the #mslit_decompressor to destroy
  */
 extern void mspack_destroy_lit_decompressor(struct mslit_decompressor *self);
 
 
 /** Creates a new HLP compressor.
  * @param sys a custom mspack_system structure, or NULL to use the default
  * @return a #mshlp_compressor or NULL
  */
 extern struct mshlp_compressor *
   mspack_create_hlp_compressor(struct mspack_system *sys);
 
 /** Creates a new HLP decompressor.
  * @param sys a custom mspack_system structure, or NULL to use the default
  * @return a #mshlp_decompressor or NULL
  */
 extern struct mshlp_decompressor *
   mspack_create_hlp_decompressor(struct mspack_system *sys);
 
 /** Destroys an existing hlp compressor.
  * @param self the #mshlp_compressor to destroy
  */
 extern void mspack_destroy_hlp_compressor(struct mshlp_compressor *self);
 
 /** Destroys an existing hlp decompressor.
  * @param self the #mshlp_decompressor to destroy
  */
 extern void mspack_destroy_hlp_decompressor(struct mshlp_decompressor *self);
 
 
 /** Creates a new SZDD compressor.
  * @param sys a custom mspack_system structure, or NULL to use the default
  * @return a #msszdd_compressor or NULL
  */
 extern struct msszdd_compressor *
   mspack_create_szdd_compressor(struct mspack_system *sys);
 
 /** Creates a new SZDD decompressor.
  * @param sys a custom mspack_system structure, or NULL to use the default
  * @return a #msszdd_decompressor or NULL
  */
 extern struct msszdd_decompressor *
   mspack_create_szdd_decompressor(struct mspack_system *sys);
 
 /** Destroys an existing SZDD compressor.
  * @param self the #msszdd_compressor to destroy
  */
 extern void mspack_destroy_szdd_compressor(struct msszdd_compressor *self);
 
 /** Destroys an existing SZDD decompressor.
  * @param self the #msszdd_decompressor to destroy
  */
 extern void mspack_destroy_szdd_decompressor(struct msszdd_decompressor *self);
 
 
 /** Creates a new KWAJ compressor.
  * @param sys a custom mspack_system structure, or NULL to use the default
  * @return a #mskwaj_compressor or NULL
  */
 extern struct mskwaj_compressor *
   mspack_create_kwaj_compressor(struct mspack_system *sys);
 
 /** Creates a new KWAJ decompressor.
  * @param sys a custom mspack_system structure, or NULL to use the default
  * @return a #mskwaj_decompressor or NULL
  */
 extern struct mskwaj_decompressor *
   mspack_create_kwaj_decompressor(struct mspack_system *sys);
 
 /** Destroys an existing KWAJ compressor.
  * @param self the #mskwaj_compressor to destroy
  */
 extern void mspack_destroy_kwaj_compressor(struct mskwaj_compressor *self);
 
 /** Destroys an existing KWAJ decompressor.
  * @param self the #mskwaj_decompressor to destroy
  */
 extern void mspack_destroy_kwaj_decompressor(struct mskwaj_decompressor *self);
 
 
 /** Creates a new OAB compressor.
  * @param sys a custom mspack_system structure, or NULL to use the default
  * @return a #msoab_compressor or NULL
  */
 extern struct msoab_compressor *
   mspack_create_oab_compressor(struct mspack_system *sys);
 
 /** Creates a new OAB decompressor.
  * @param sys a custom mspack_system structure, or NULL to use the default
  * @return a #msoab_decompressor or NULL
  */
 extern struct msoab_decompressor *
   mspack_create_oab_decompressor(struct mspack_system *sys);
 
 /** Destroys an existing OAB compressor.
  * @param self the #msoab_compressor to destroy
  */
 extern void mspack_destroy_oab_compressor(struct msoab_compressor *self);
 
 /** Destroys an existing OAB decompressor.
  * @param self the #msoab_decompressor to destroy
  */
 extern void mspack_destroy_oab_decompressor(struct msoab_decompressor *self);
 
 
 /* --- support for .CAB (MS Cabinet) file format --------------------------- */
 
 /**
  * A structure which represents a single cabinet file.
  *
  * All fields are READ ONLY.
  *
  * If this cabinet is part of a merged cabinet set, the #files and #folders
  * fields are common to all cabinets in the set, and will be identical.
  *
  * @see mscab_decompressor::open(), mscab_decompressor::close(),
  *      mscab_decompressor::search()
  */
 struct mscabd_cabinet {
   /**
    * The next cabinet in a chained list, if this cabinet was opened with
    * mscab_decompressor::search(). May be NULL to mark the end of the
    * list.
    */
   struct mscabd_cabinet *next;
 
   /**
    * The filename of the cabinet. More correctly, the filename of the
    * physical file that the cabinet resides in. This is given by the
    * library user and may be in any format.
    */
   const char *filename;
   
   /** The file offset of cabinet within the physical file it resides in. */
   off_t base_offset;
 
   /** The length of the cabinet file in bytes. */
   unsigned int length;
 
   /** The previous cabinet in a cabinet set, or NULL. */
   struct mscabd_cabinet *prevcab;
 
   /** The next cabinet in a cabinet set, or NULL. */
   struct mscabd_cabinet *nextcab;
 
   /** The filename of the previous cabinet in a cabinet set, or NULL. */
   char *prevname;
 
   /** The filename of the next cabinet in a cabinet set, or NULL. */
   char *nextname;
 
   /** The name of the disk containing the previous cabinet in a cabinet
    * set, or NULL.
    */
   char *previnfo;
 
   /** The name of the disk containing the next cabinet in a cabinet set,
    * or NULL.
    */
   char *nextinfo;
 
   /** A list of all files in the cabinet or cabinet set. */
   struct mscabd_file *files;
 
   /** A list of all folders in the cabinet or cabinet set. */
   struct mscabd_folder *folders;
 
   /** 
    * The set ID of the cabinet. All cabinets in the same set should have
    * the same set ID.
    */
   unsigned short set_id;
 
   /**
    * The index number of the cabinet within the set. Numbering should
    * start from 0 for the first cabinet in the set, and increment by 1 for
    * each following cabinet.
    */
   unsigned short set_index;
 
   /**
    * The number of bytes reserved in the header area of the cabinet.
    *
    * If this is non-zero and flags has MSCAB_HDR_RESV set, this data can
    * be read by the calling application. It is of the given length,
    * located at offset (base_offset + MSCAB_HDR_RESV_OFFSET) in the
    * cabinet file.
    *
    * @see flags
    */
   unsigned short header_resv;
 
   /**
    * Header flags.
    *
    * - MSCAB_HDR_PREVCAB indicates the cabinet is part of a cabinet set, and
    *                     has a predecessor cabinet.
    * - MSCAB_HDR_NEXTCAB indicates the cabinet is part of a cabinet set, and
    *                     has a successor cabinet.
    * - MSCAB_HDR_RESV indicates the cabinet has reserved header space.
    *
    * @see prevname, previnfo, nextname, nextinfo, header_resv
    */
   int flags;
 };
 
 /** Offset from start of cabinet to the reserved header data (if present). */
 #define MSCAB_HDR_RESV_OFFSET (0x28)
 
 /** Cabinet header flag: cabinet has a predecessor */
 #define MSCAB_HDR_PREVCAB (0x01)
 /** Cabinet header flag: cabinet has a successor */
 #define MSCAB_HDR_NEXTCAB (0x02)
 /** Cabinet header flag: cabinet has reserved header space */
 #define MSCAB_HDR_RESV    (0x04)
 
 /**
  * A structure which represents a single folder in a cabinet or cabinet set.
  *
  * All fields are READ ONLY.
  *
  * A folder is a single compressed stream of data. When uncompressed, it
  * holds the data of one or more files. A folder may be split across more
  * than one cabinet.
  */
 struct mscabd_folder {
   /**
    * A pointer to the next folder in this cabinet or cabinet set, or NULL
    * if this is the final folder.
    */
   struct mscabd_folder *next;
 
   /** 
    * The compression format used by this folder.
    *
    * The macro MSCABD_COMP_METHOD() should be used on this field to get
    * the algorithm used. The macro MSCABD_COMP_LEVEL() should be used to get
    * the "compression level".
    *
    * @see MSCABD_COMP_METHOD(), MSCABD_COMP_LEVEL()
    */
   int comp_type;
 
   /**
    * The total number of data blocks used by this folder. This includes
    * data blocks present in other files, if this folder spans more than
    * one cabinet.
    */
   unsigned int num_blocks;
 };
 
 /**
  * Returns the compression method used by a folder.
  *
  * @param comp_type a mscabd_folder::comp_type value
  * @return one of #MSCAB_COMP_NONE, #MSCAB_COMP_MSZIP, #MSCAB_COMP_QUANTUM
  *         or #MSCAB_COMP_LZX
  */
 #define MSCABD_COMP_METHOD(comp_type) ((comp_type) & 0x0F)
 /**
  * Returns the compression level used by a folder.
  *
  * @param comp_type a mscabd_folder::comp_type value
  * @return the compression level. This is only defined by LZX and Quantum
  *         compression
  */
 #define MSCABD_COMP_LEVEL(comp_type) (((comp_type) >> 8) & 0x1F)
 
 /** Compression mode: no compression. */
 #define MSCAB_COMP_NONE       (0)
 /** Compression mode: MSZIP (deflate) compression. */
 #define MSCAB_COMP_MSZIP      (1)
 /** Compression mode: Quantum compression */
 #define MSCAB_COMP_QUANTUM    (2)
 /** Compression mode: LZX compression */
 #define MSCAB_COMP_LZX        (3)
 
 /**
  * A structure which represents a single file in a cabinet or cabinet set.
  *
  * All fields are READ ONLY.
  */
 struct mscabd_file {
   /**
    * The next file in the cabinet or cabinet set, or NULL if this is the
    * final file.
    */
   struct mscabd_file *next;
 
   /**
    * The filename of the file.
    *
    * A null terminated string of up to 255 bytes in length, it may be in
    * either ISO-8859-1 or UTF8 format, depending on the file attributes.
    *
    * @see attribs
    */
   char *filename;
 
   /** The uncompressed length of the file, in bytes. */
   unsigned int length;
 
   /**
    * File attributes.
    *
    * The following attributes are defined:
    * - #MSCAB_ATTRIB_RDONLY indicates the file is write protected.
    * - #MSCAB_ATTRIB_HIDDEN indicates the file is hidden.
    * - #MSCAB_ATTRIB_SYSTEM indicates the file is a operating system file.
    * - #MSCAB_ATTRIB_ARCH indicates the file is "archived".
    * - #MSCAB_ATTRIB_EXEC indicates the file is an executable program.
    * - #MSCAB_ATTRIB_UTF_NAME indicates the filename is in UTF8 format rather
    *   than ISO-8859-1.
    */
   int attribs;
 
   /** File's last modified time, hour field. */
   char time_h;
   /** File's last modified time, minute field. */
   char time_m;
   /** File's last modified time, second field. */
   char time_s;
 
   /** File's last modified date, day field. */
   char date_d;
   /** File's last modified date, month field. */
   char date_m;
   /** File's last modified date, year field. */
   int date_y;
 
   /** A pointer to the folder that contains this file. */
   struct mscabd_folder *folder;
 
   /** The uncompressed offset of this file in its folder. */
   unsigned int offset;
 };
 
 /** mscabd_file::attribs attribute: file is read-only. */
 #define MSCAB_ATTRIB_RDONLY   (0x01)
 /** mscabd_file::attribs attribute: file is hidden. */
 #define MSCAB_ATTRIB_HIDDEN   (0x02)
 /** mscabd_file::attribs attribute: file is an operating system file. */
 #define MSCAB_ATTRIB_SYSTEM   (0x04)
 /** mscabd_file::attribs attribute: file is "archived". */
 #define MSCAB_ATTRIB_ARCH     (0x20)
 /** mscabd_file::attribs attribute: file is an executable program. */
 #define MSCAB_ATTRIB_EXEC     (0x40)
 /** mscabd_file::attribs attribute: filename is UTF8, not ISO-8859-1. */
 #define MSCAB_ATTRIB_UTF_NAME (0x80)
 
 /** mscab_decompressor::set_param() parameter: search buffer size. */
 #define MSCABD_PARAM_SEARCHBUF (0)
 /** mscab_decompressor::set_param() parameter: repair MS-ZIP streams? */
 #define MSCABD_PARAM_FIXMSZIP  (1)
 /** mscab_decompressor::set_param() parameter: size of decompression buffer */
 #define MSCABD_PARAM_DECOMPBUF (2)

 /** mscab_decompressor::set_param() parameter: salvage data from bad cabinets?
  * If enabled, open() will skip file with bad folder indices or filenames
  * rather than reject the whole cabinet, and extract() will limit rather than
  * reject files with invalid offsets and lengths, and bad data block checksums
  * will be ignored. Available only in CAB decoder version 2 and above.
  */
 #define MSCABD_PARAM_SALVAGE   (3)

 
 /** TODO */
 struct mscab_compressor {
   int dummy; 
 };
 
 /**
  * A decompressor for .CAB (Microsoft Cabinet) files
  *
  * All fields are READ ONLY.
  *
  * @see mspack_create_cab_decompressor(), mspack_destroy_cab_decompressor()
  */
 struct mscab_decompressor {
   /**
    * Opens a cabinet file and reads its contents.
    *
    * If the file opened is a valid cabinet file, all headers will be read
    * and a mscabd_cabinet structure will be returned, with a full list of
    * folders and files.
    *
    * In the case of an error occuring, NULL is returned and the error code
    * is available from last_error().
    *
    * The filename pointer should be considered "in use" until close() is
    * called on the cabinet.
    *
    * @param  self     a self-referential pointer to the mscab_decompressor
    *                  instance being called
    * @param  filename the filename of the cabinet file. This is passed
    *                  directly to mspack_system::open().
    * @return a pointer to a mscabd_cabinet structure, or NULL on failure
    * @see close(), search(), last_error()
    */
   struct mscabd_cabinet * (*open) (struct mscab_decompressor *self,

                                    const char *filename);

 
   /**
    * Closes a previously opened cabinet or cabinet set.
    *
    * This closes a cabinet, all cabinets associated with it via the
    * mscabd_cabinet::next, mscabd_cabinet::prevcab and
    * mscabd_cabinet::nextcab pointers, and all folders and files. All
    * memory used by these entities is freed.
    *
    * The cabinet pointer is now invalid and cannot be used again. All
    * mscabd_folder and mscabd_file pointers from that cabinet or cabinet
    * set are also now invalid, and cannot be used again.
    *
    * If the cabinet pointer given was created using search(), it MUST be
    * the cabinet pointer returned by search() and not one of the later
    * cabinet pointers further along the mscabd_cabinet::next chain.
 
    * If extra cabinets have been added using append() or prepend(), these
    * will all be freed, even if the cabinet pointer given is not the first
    * cabinet in the set. Do NOT close() more than one cabinet in the set.
    *
    * The mscabd_cabinet::filename is not freed by the library, as it is
    * not allocated by the library. The caller should free this itself if
    * necessary, before it is lost forever.
    *
    * @param  self     a self-referential pointer to the mscab_decompressor
    *                  instance being called
    * @param  cab      the cabinet to close
    * @see open(), search(), append(), prepend()
    */
   void (*close)(struct mscab_decompressor *self,

                 struct mscabd_cabinet *cab);

 
   /**
    * Searches a regular file for embedded cabinets.
    *
    * This opens a normal file with the given filename and will search the
    * entire file for embedded cabinet files
    *
    * If any cabinets are found, the equivalent of open() is called on each
    * potential cabinet file at the offset it was found. All successfully
    * open()ed cabinets are kept in a list.
    *
    * The first cabinet found will be returned directly as the result of
    * this method. Any further cabinets found will be chained in a list
    * using the mscabd_cabinet::next field.
    *
    * In the case of an error occuring anywhere other than the simulated
    * open(), NULL is returned and the error code is available from
    * last_error().
    *
    * If no error occurs, but no cabinets can be found in the file, NULL is
    * returned and last_error() returns MSPACK_ERR_OK.
    *
    * The filename pointer should be considered in use until close() is
    * called on the cabinet.
    *
    * close() should only be called on the result of search(), not on any
    * subsequent cabinets in the mscabd_cabinet::next chain.
    *
    * @param  self     a self-referential pointer to the mscab_decompressor
    *                  instance being called
    * @param  filename the filename of the file to search for cabinets. This
    *                  is passed directly to mspack_system::open().
    * @return a pointer to a mscabd_cabinet structure, or NULL
    * @see close(), open(), last_error()
    */
   struct mscabd_cabinet * (*search) (struct mscab_decompressor *self,

                                      const char *filename);

 
   /**
    * Appends one mscabd_cabinet to another, forming or extending a cabinet
    * set.
    *
    * This will attempt to append one cabinet to another such that
    * <tt>(cab->nextcab == nextcab) && (nextcab->prevcab == cab)</tt> and
    * any folders split between the two cabinets are merged.
    *
    * The cabinets MUST be part of a cabinet set -- a cabinet set is a
    * cabinet that spans more than one physical cabinet file on disk -- and
    * must be appropriately matched.
    *
    * It can be determined if a cabinet has further parts to load by
    * examining the mscabd_cabinet::flags field:
    *
    * - if <tt>(flags & MSCAB_HDR_PREVCAB)</tt> is non-zero, there is a
    *   predecessor cabinet to open() and prepend(). Its MS-DOS
    *   case-insensitive filename is mscabd_cabinet::prevname
    * - if <tt>(flags & MSCAB_HDR_NEXTCAB)</tt> is non-zero, there is a
    *   successor cabinet to open() and append(). Its MS-DOS case-insensitive
    *   filename is mscabd_cabinet::nextname
    *
    * If the cabinets do not match, an error code will be returned. Neither
    * cabinet has been altered, and both should be closed seperately.
    *
    * Files and folders in a cabinet set are a single entity. All cabinets
    * in a set use the same file list, which is updated as cabinets in the
    * set are added. All pointers to mscabd_folder and mscabd_file
    * structures in either cabinet must be discarded and re-obtained after
    * merging.
    *
    * @param  self     a self-referential pointer to the mscab_decompressor
    *                  instance being called
    * @param  cab      the cabinet which will be appended to,
    *                  predecessor of nextcab
    * @param  nextcab  the cabinet which will be appended,
    *                  successor of cab
    * @return an error code, or MSPACK_ERR_OK if successful
    * @see prepend(), open(), close()
    */
   int (*append) (struct mscab_decompressor *self,

                  struct mscabd_cabinet *cab,
                  struct mscabd_cabinet *nextcab);

 
   /**
    * Prepends one mscabd_cabinet to another, forming or extending a
    * cabinet set.
    *
    * This will attempt to prepend one cabinet to another, such that
    * <tt>(cab->prevcab == prevcab) && (prevcab->nextcab == cab)</tt>. In
    * all other respects, it is identical to append(). See append() for the
    * full documentation.
    *
    * @param  self     a self-referential pointer to the mscab_decompressor
    *                  instance being called
    * @param  cab      the cabinet which will be prepended to,
    *                  successor of prevcab
    * @param  prevcab  the cabinet which will be prepended,
    *                  predecessor of cab
    * @return an error code, or MSPACK_ERR_OK if successful
    * @see append(), open(), close()
    */
   int (*prepend) (struct mscab_decompressor *self,

                   struct mscabd_cabinet *cab,
                   struct mscabd_cabinet *prevcab);

 
   /**
    * Extracts a file from a cabinet or cabinet set.
    *
    * This extracts a compressed file in a cabinet and writes it to the given
    * filename.
    *
    * The MS-DOS filename of the file, mscabd_file::filename, is NOT USED
    * by extract(). The caller must examine this MS-DOS filename, copy and
    * change it as necessary, create directories as necessary, and provide
    * the correct filename as a parameter, which will be passed unchanged
    * to the decompressor's mspack_system::open()
    *
    * If the file belongs to a split folder in a multi-part cabinet set,
    * and not enough parts of the cabinet set have been loaded and appended
    * or prepended, an error will be returned immediately.
    *
    * @param  self     a self-referential pointer to the mscab_decompressor
    *                  instance being called
    * @param  file     the file to be decompressed
    * @param  filename the filename of the file being written to
    * @return an error code, or MSPACK_ERR_OK if successful
    */
   int (*extract)(struct mscab_decompressor *self,

                  struct mscabd_file *file,
                  const char *filename);

 
   /**
    * Sets a CAB decompression engine parameter.
    *
    * The following parameters are defined:
    * - #MSCABD_PARAM_SEARCHBUF: How many bytes should be allocated as a
    *   buffer when using search()? The minimum value is 4.  The default
    *   value is 32768.
    * - #MSCABD_PARAM_FIXMSZIP: If non-zero, extract() will ignore bad
    *   checksums and recover from decompression errors in MS-ZIP
    *   compressed folders. The default value is 0 (don't recover).
    * - #MSCABD_PARAM_DECOMPBUF: How many bytes should be used as an input
    *   bit buffer by decompressors? The minimum value is 4. The default
    *   value is 4096.
    *
    * @param  self     a self-referential pointer to the mscab_decompressor
    *                  instance being called
    * @param  param    the parameter to set
    * @param  value    the value to set the parameter to
    * @return MSPACK_ERR_OK if all is OK, or MSPACK_ERR_ARGS if there
    *         is a problem with either parameter or value.
    * @see search(), extract()
    */
   int (*set_param)(struct mscab_decompressor *self,

                    int param,
                    int value);

 
   /**
    * Returns the error code set by the most recently called method.
    *
    * This is useful for open() and search(), which do not return an error
    * code directly.
    *
    * @param  self     a self-referential pointer to the mscab_decompressor
    *                  instance being called
    * @return the most recent error code
    * @see open(), search()
    */
   int (*last_error)(struct mscab_decompressor *self);
 };
 
 /* --- support for .CHM (HTMLHelp) file format ----------------------------- */
 
 /**
  * A structure which represents a file to be placed in a CHM helpfile.
  *
  * A contiguous array of these structures should be passed to
  * mschm_compressor::generate(). The array list is terminated with an
  * entry whose mschmc_file::section field is set to #MSCHMC_ENDLIST, the
  * other fields in this entry are ignored.
  */
 struct mschmc_file {
   /** One of #MSCHMC_ENDLIST, #MSCHMC_UNCOMP or #MSCHMC_MSCOMP. */
   int section;
 
   /** The filename of the source file that will be added to the CHM. This
    * is passed directly to mspack_system::open(). */
   const char *filename;
 
   /** The full path and filename of the file within the CHM helpfile, a
    * UTF-1 encoded null-terminated string. */
   char *chm_filename;
 
   /** The length of the file, in bytes. This will be adhered to strictly
    * and a read error will be issued if this many bytes cannot be read
    * from the real file at CHM generation time. */
   off_t length;
 };
 
 /**
  * A structure which represents a section of a CHM helpfile.
  *
  * All fields are READ ONLY.
  *
  * Not used directly, but used as a generic base type for
  * mschmd_sec_uncompressed and mschmd_sec_mscompressed.
  */
 struct mschmd_section {
   /** A pointer to the CHM helpfile that contains this section. */
   struct mschmd_header *chm;
 
   /**
    * The section ID. Either 0 for the uncompressed section
    * mschmd_sec_uncompressed, or 1 for the LZX compressed section
    * mschmd_sec_mscompressed. No other section IDs are known.
    */
   unsigned int id;
 };
 
 /**
  * A structure which represents the uncompressed section of a CHM helpfile.
  * 
  * All fields are READ ONLY.
  */
 struct mschmd_sec_uncompressed {
   /** Generic section data. */
   struct mschmd_section base;
 
   /** The file offset of where this section begins in the CHM helpfile. */
   off_t offset;
 };
 
 /**
  * A structure which represents the LZX compressed section of a CHM helpfile. 
  * 
  * All fields are READ ONLY.
  */
 struct mschmd_sec_mscompressed {
   /** Generic section data. */
   struct mschmd_section base;
 
   /** A pointer to the meta-file which represents all LZX compressed data. */
   struct mschmd_file *content;
 
   /** A pointer to the file which contains the LZX control data. */
   struct mschmd_file *control;
 
   /** A pointer to the file which contains the LZX reset table. */
   struct mschmd_file *rtable;
 
   /** A pointer to the file which contains the LZX span information.
    * Available only in CHM decoder version 2 and above.
    */
   struct mschmd_file *spaninfo;
 };
 
 /**
  * A structure which represents a CHM helpfile.
  * 
  * All fields are READ ONLY.
  */
 struct mschmd_header {
   /** The version of the CHM file format used in this file. */
   unsigned int version;
 
   /**
    * The "timestamp" of the CHM helpfile. 
    *
    * It is the lower 32 bits of a 64-bit value representing the number of
    * centiseconds since 1601-01-01 00:00:00 UTC, plus 42. It is not useful
    * as a timestamp, but it is useful as a semi-unique ID.
    */
   unsigned int timestamp;
       
   /**
    * The default Language and Country ID (LCID) of the user who ran the
    * HTMLHelp Compiler. This is not the language of the CHM file itself.
    */
   unsigned int language;
 
   /**
    * The filename of the CHM helpfile. This is given by the library user
    * and may be in any format.
    */
   const char *filename;
 
   /** The length of the CHM helpfile, in bytes. */
   off_t length;
 
   /** A list of all non-system files in the CHM helpfile. */
   struct mschmd_file *files;
 
   /**
    * A list of all system files in the CHM helpfile.
    *
    * System files are files which begin with "::". They are meta-files
    * generated by the CHM creation process.
    */
   struct mschmd_file *sysfiles;
 
   /** The section 0 (uncompressed) data in this CHM helpfile. */
   struct mschmd_sec_uncompressed sec0;
 
   /** The section 1 (MSCompressed) data in this CHM helpfile. */
   struct mschmd_sec_mscompressed sec1;
 
   /** The file offset of the first PMGL/PMGI directory chunk. */
   off_t dir_offset;
 
   /** The number of PMGL/PMGI directory chunks in this CHM helpfile. */
   unsigned int num_chunks;
 
   /** The size of each PMGL/PMGI chunk, in bytes. */
   unsigned int chunk_size;
 
   /** The "density" of the quick-reference section in PMGL/PMGI chunks. */
   unsigned int density;
 
   /** The depth of the index tree.
    *
    * - if 1, there are no PMGI chunks, only PMGL chunks.
    * - if 2, there is 1 PMGI chunk. All chunk indices point to PMGL chunks.
    * - if 3, the root PMGI chunk points to secondary PMGI chunks, which in
    *         turn point to PMGL chunks.
    * - and so on...
    */
   unsigned int depth;
 
   /**
    * The number of the root PMGI chunk.
    *
    * If there is no index in the CHM helpfile, this will be 0xFFFFFFFF.
    */
   unsigned int index_root;
 
   /**
    * The number of the first PMGL chunk. Usually zero.
    * Available only in CHM decoder version 2 and above.
    */
   unsigned int first_pmgl;
 
   /**
    * The number of the last PMGL chunk. Usually num_chunks-1.
    * Available only in CHM decoder version 2 and above.
    */
   unsigned int last_pmgl;
 
   /**
    * A cache of loaded chunks, filled in by mschm_decoder::fast_find().
    * Available only in CHM decoder version 2 and above.
    */
   unsigned char **chunk_cache;
 };
 
 /**
  * A structure which represents a file stored in a CHM helpfile.
  * 
  * All fields are READ ONLY.
  */
 struct mschmd_file {
   /**
    * A pointer to the next file in the list, or NULL if this is the final
    * file.
    */
   struct mschmd_file *next;
 
   /**
    * A pointer to the section that this file is located in. Indirectly,
    * it also points to the CHM helpfile the file is located in.
    */
   struct mschmd_section *section;
 
   /** The offset within the section data that this file is located at. */
   off_t offset;
 
   /** The length of this file, in bytes */
   off_t length;
 
   /** The filename of this file -- a null terminated string in UTF-8. */
   char *filename;
 };
 
 /** mschmc_file::section value: end of CHM file list */
 #define MSCHMC_ENDLIST   (0)
 /** mschmc_file::section value: this file is in the Uncompressed section */
 #define MSCHMC_UNCOMP    (1)
 /** mschmc_file::section value: this file is in the MSCompressed section */
 #define MSCHMC_MSCOMP    (2)
  
 /** mschm_compressor::set_param() parameter: "timestamp" header */
 #define MSCHMC_PARAM_TIMESTAMP  (0)
 /** mschm_compressor::set_param() parameter: "language" header */
 #define MSCHMC_PARAM_LANGUAGE   (1)
 /** mschm_compressor::set_param() parameter: LZX window size */
 #define MSCHMC_PARAM_LZXWINDOW  (2)
 /** mschm_compressor::set_param() parameter: intra-chunk quickref density */
 #define MSCHMC_PARAM_DENSITY    (3)
 /** mschm_compressor::set_param() parameter: whether to create indices */
 #define MSCHMC_PARAM_INDEX      (4)
 
 /**
  * A compressor for .CHM (Microsoft HTMLHelp) files.
  *
  * All fields are READ ONLY.
  *
  * @see mspack_create_chm_compressor(), mspack_destroy_chm_compressor()
  */
 struct mschm_compressor {
   /**
    * Generates a CHM help file.
    *
    * The help file will contain up to two sections, an Uncompressed
    * section and potentially an MSCompressed (LZX compressed)
    * section.
    *
    * While the contents listing of a CHM file is always in lexical order,
    * the file list passed in will be taken as the correct order for files
    * within the sections.  It is in your interest to place similar files
    * together for better compression.
    *
    * There are two modes of generation, to use a temporary file or not to
    * use one. See use_temporary_file() for the behaviour of generate() in
    * these two different modes.
    *
    * @param  self        a self-referential pointer to the mschm_compressor
    *                     instance being called
    * @param  file_list   an array of mschmc_file structures, terminated
    *                     with an entry whose mschmc_file::section field is
    *                     #MSCHMC_ENDLIST. The order of the list is
    *                     preserved within each section. The length of any
    *                     mschmc_file::chm_filename string cannot exceed
    *                     roughly 4096 bytes. Each source file must be able
    *                     to supply as many bytes as given in the
    *                     mschmc_file::length field.
    * @param  output_file the file to write the generated CHM helpfile to.
    *                     This is passed directly to mspack_system::open()
    * @return an error code, or MSPACK_ERR_OK if successful
    * @see use_temporary_file() set_param()
    */
   int (*generate)(struct mschm_compressor *self,

                   struct mschmc_file file_list[],
                   const char *output_file);

 
   /**
    * Specifies whether a temporary file is used during CHM generation.
    *
    * The CHM file format includes data about the compressed section (such
    * as its overall size) that is stored in the output CHM file prior to
    * the compressed section itself. This unavoidably requires that the
    * compressed section has to be generated, before these details can be
    * set. There are several ways this can be handled. Firstly, the
    * compressed section could be generated entirely in memory before
    * writing any of the output CHM file. This approach is not used in
    * libmspack, as the compressed section can exceed the addressable
    * memory space on most architectures.
    *
    * libmspack has two options, either to write these unknowable sections
    * with blank data, generate the compressed section, then re-open the
    * output file for update once the compressed section has been
    * completed, or to write the compressed section to a temporary file,
    * then write the entire output file at once, performing a simple
    * file-to-file copy for the compressed section.
    *
    * The simple solution of buffering the entire compressed section in
    * memory can still be used, if desired. As the temporary file's
    * filename is passed directly to mspack_system::open(), it is possible
    * for a custom mspack_system implementation to hold this file in memory,
    * without writing to a disk.
    *
    * If a temporary file is set, generate() performs the following
    * sequence of events: the temporary file is opened for writing, the
    * compression algorithm writes to the temporary file, the temporary
    * file is closed.  Then the output file is opened for writing and the
    * temporary file is re-opened for reading. The output file is written
    * and the temporary file is read from. Both files are then closed. The
    * temporary file itself is not deleted. If that is desired, the
    * temporary file should be deleted after the completion of generate(),
    * if it exists.
    *
    * If a temporary file is set not to be used, generate() performs the
    * following sequence of events: the output file is opened for writing,
    * then it is written and closed. The output file is then re-opened for
    * update, the appropriate sections are seek()ed to and re-written, then
    * the output file is closed.
    *
    * @param  self          a self-referential pointer to the
    *                       mschm_compressor instance being called
    * @param  use_temp_file non-zero if the temporary file should be used,
    *                       zero if the temporary file should not be used.
    * @param  temp_file     a file to temporarily write compressed data to,
    *                       before opening it for reading and copying the
    *                       contents to the output file. This is passed
    *                       directly to mspack_system::open().
    * @return an error code, or MSPACK_ERR_OK if successful
    * @see generate()
    */
   int (*use_temporary_file)(struct mschm_compressor *self,

                             int use_temp_file,
                             const char *temp_file);

   /**
    * Sets a CHM compression engine parameter.
    *
    * The following parameters are defined:
 
    * - #MSCHMC_PARAM_TIMESTAMP: Sets the "timestamp" of the CHM file
    *   generated. This is not a timestamp, see mschmd_header::timestamp
    *   for a description. If this timestamp is 0, generate() will use its
    *   own algorithm for making a unique ID, based on the lengths and
    *   names of files in the CHM itself. Defaults to 0, any value between
    *   0 and (2^32)-1 is valid.
    * - #MSCHMC_PARAM_LANGUAGE: Sets the "language" of the CHM file
    *   generated.  This is not the language used in the CHM file, but the
    *   language setting of the user who ran the HTMLHelp compiler. It
    *   defaults to 0x0409. The valid range is between 0x0000 and 0x7F7F.
    * - #MSCHMC_PARAM_LZXWINDOW: Sets the size of the LZX history window,
    *   which is also the interval at which the compressed data stream can be
    *   randomly accessed. The value is not a size in bytes, but a power of
    *   two. The default value is 16 (which makes the window 2^16 bytes, or
    *   64 kilobytes), the valid range is from 15 (32 kilobytes) to 21 (2
    *   megabytes).
    * - #MSCHMC_PARAM_DENSITY: Sets the "density" of quick reference
    *   entries stored at the end of directory listing chunk. Each chunk is
    *   4096 bytes in size, and contains as many file entries as there is
    *   room for. At the other end of the chunk, a list of "quick reference"
    *   pointers is included. The offset of every 'N'th file entry is given a
    *   quick reference, where N = (2^density) + 1. The default density is
    *   2. The smallest density is 0 (N=2), the maximum is 10 (N=1025). As
    *   each file entry requires at least 5 bytes, the maximum number of
    *   entries in a single chunk is roughly 800, so the maximum value 10
    *   can be used to indicate there are no quickrefs at all.
    * - #MSCHMC_PARAM_INDEX: Sets whether or not to include quick lookup
    *   index chunk(s), in addition to normal directory listing chunks. A
    *   value of zero means no index chunks will be created, a non-zero value
    *   means index chunks will be created. The default is zero, "don't
    *   create an index".
    *
    * @param  self     a self-referential pointer to the mschm_compressor
    *                  instance being called
    * @param  param    the parameter to set
    * @param  value    the value to set the parameter to
    * @return MSPACK_ERR_OK if all is OK, or MSPACK_ERR_ARGS if there
    *         is a problem with either parameter or value.
    * @see generate()
    */
   int (*set_param)(struct mschm_compressor *self,

                    int param,
                    int value);

 
   /**
    * Returns the error code set by the most recently called method.
    *
    * @param  self     a self-referential pointer to the mschm_compressor
    *                  instance being called
    * @return the most recent error code
    * @see set_param(), generate()
    */
   int (*last_error)(struct mschm_compressor *self);
 };
 
 /**
  * A decompressor for .CHM (Microsoft HTMLHelp) files
  *
  * All fields are READ ONLY.
  *
  * @see mspack_create_chm_decompressor(), mspack_destroy_chm_decompressor()
  */
 struct mschm_decompressor {
   /**
    * Opens a CHM helpfile and reads its contents.
    *
    * If the file opened is a valid CHM helpfile, all headers will be read
    * and a mschmd_header structure will be returned, with a full list of
    * files.
    *
    * In the case of an error occuring, NULL is returned and the error code
    * is available from last_error().
    *
    * The filename pointer should be considered "in use" until close() is
    * called on the CHM helpfile.
    *
    * @param  self     a self-referential pointer to the mschm_decompressor
    *                  instance being called
    * @param  filename the filename of the CHM helpfile. This is passed
    *                  directly to mspack_system::open().
    * @return a pointer to a mschmd_header structure, or NULL on failure
    * @see close()
    */
   struct mschmd_header *(*open)(struct mschm_decompressor *self,

                                 const char *filename);

 
   /**
    * Closes a previously opened CHM helpfile.
    *
    * This closes a CHM helpfile, frees the mschmd_header and all
    * mschmd_file structures associated with it (if any). This works on
    * both helpfiles opened with open() and helpfiles opened with
    * fast_open().
    *
    * The CHM header pointer is now invalid and cannot be used again. All
    * mschmd_file pointers referencing that CHM are also now invalid, and
    * cannot be used again.
    *
    * @param  self     a self-referential pointer to the mschm_decompressor
    *                  instance being called
    * @param  chm      the CHM helpfile to close
    * @see open(), fast_open()
    */
   void (*close)(struct mschm_decompressor *self,

                 struct mschmd_header *chm);

 
   /**
    * Extracts a file from a CHM helpfile.
    *
    * This extracts a file from a CHM helpfile and writes it to the given
    * filename. The filename of the file, mscabd_file::filename, is not
    * used by extract(), but can be used by the caller as a guide for
    * constructing an appropriate filename.
    *
    * This method works both with files found in the mschmd_header::files
    * and mschmd_header::sysfiles list and mschmd_file structures generated
    * on the fly by fast_find().
    *
    * @param  self     a self-referential pointer to the mschm_decompressor
    *                  instance being called
    * @param  file     the file to be decompressed
    * @param  filename the filename of the file being written to
    * @return an error code, or MSPACK_ERR_OK if successful
    */
   int (*extract)(struct mschm_decompressor *self,

                  struct mschmd_file *file,
                  const char *filename);

 
   /**
    * Returns the error code set by the most recently called method.
    *
    * This is useful for open() and fast_open(), which do not return an
    * error code directly.
    *
    * @param  self     a self-referential pointer to the mschm_decompressor
    *                  instance being called
    * @return the most recent error code
    * @see open(), extract()
    */
   int (*last_error)(struct mschm_decompressor *self);
 
   /**
    * Opens a CHM helpfile quickly.
    *
    * If the file opened is a valid CHM helpfile, only essential headers
    * will be read. A mschmd_header structure will be still be returned, as
    * with open(), but the mschmd_header::files field will be NULL. No
    * files details will be automatically read.  The fast_find() method
    * must be used to obtain file details.
    *
    * In the case of an error occuring, NULL is returned and the error code
    * is available from last_error().
    *
    * The filename pointer should be considered "in use" until close() is
    * called on the CHM helpfile.
    *
    * @param  self     a self-referential pointer to the mschm_decompressor
    *                  instance being called
    * @param  filename the filename of the CHM helpfile. This is passed
    *                  directly to mspack_system::open().
    * @return a pointer to a mschmd_header structure, or NULL on failure
    * @see open(), close(), fast_find(), extract()
    */
   struct mschmd_header *(*fast_open)(struct mschm_decompressor *self,

                                      const char *filename);

 
   /**
    * Finds file details quickly.
    *
    * Instead of reading all CHM helpfile headers and building a list of
    * files, fast_open() and fast_find() are intended for finding file
    * details only when they are needed. The CHM file format includes an
    * on-disk file index to allow this.
    *
    * Given a case-sensitive filename, fast_find() will search the on-disk
    * index for that file.
    *
    * If the file was found, the caller-provided mschmd_file structure will
    * be filled out like so:
    * - section: the correct value for the found file
    * - offset: the correct value for the found file
    * - length: the correct value for the found file
    * - all other structure elements: NULL or 0
    *
    * If the file was not found, MSPACK_ERR_OK will still be returned as the
    * result, but the caller-provided structure will be filled out like so:
    * - section: NULL
    * - offset: 0
    * - length: 0
    * - all other structure elements: NULL or 0
    *
    * This method is intended to be used in conjunction with CHM helpfiles
    * opened with fast_open(), but it also works with helpfiles opened
    * using the regular open().
    *
    * @param  self     a self-referential pointer to the mschm_decompressor
    *                  instance being called
    * @param  chm      the CHM helpfile to search for the file
    * @param  filename the filename of the file to search for
    * @param  f_ptr    a pointer to a caller-provded mschmd_file structure
    * @param  f_size   <tt>sizeof(struct mschmd_file)</tt>
    * @return an error code, or MSPACK_ERR_OK if successful
    * @see open(), close(), fast_find(), extract()
    */
   int (*fast_find)(struct mschm_decompressor *self,

                    struct mschmd_header *chm,
                    const char *filename,
                    struct mschmd_file *f_ptr,
                    int f_size);

 };
 
 /* --- support for .LIT (EBook) file format -------------------------------- */
 
 /** TODO */
 struct mslit_compressor {
   int dummy; 
 };
 
 /** TODO */
 struct mslit_decompressor {
   int dummy; 
 };
 
 
 /* --- support for .HLP (MS Help) file format ------------------------------ */
 
 /** TODO */
 struct mshlp_compressor {
   int dummy; 
 };
 
 /** TODO */
 struct mshlp_decompressor {
   int dummy; 
 };
 
 
 /* --- support for SZDD file format ---------------------------------------- */
 
 /** msszdd_compressor::set_param() parameter: the missing character */
 #define MSSZDDC_PARAM_MISSINGCHAR (0)
 
 /** msszddd_header::format value - a regular SZDD file */
 #define MSSZDD_FMT_NORMAL (0)
 
 /** msszddd_header::format value - a special QBasic SZDD file */
 #define MSSZDD_FMT_QBASIC (1)
 
 /**
  * A structure which represents an SZDD compressed file.
  *
  * All fields are READ ONLY.
  */
 struct msszddd_header {
   /** The file format; either #MSSZDD_FMT_NORMAL or #MSSZDD_FMT_QBASIC */
   int format;
 
   /** The amount of data in the SZDD file once uncompressed. */
   off_t length;
 
   /**
    * The last character in the filename, traditionally replaced with an
    * underscore to show the file is compressed. The null character is used
    * to show that this character has not been stored (e.g. because the
    * filename is not known). Generally, only characters that may appear in
    * an MS-DOS filename (except ".") are valid.
    */
   char missing_char;
 };
 
 /**
  * A compressor for the SZDD file format.
  *
  * All fields are READ ONLY.
  *
  * @see mspack_create_szdd_compressor(), mspack_destroy_szdd_compressor()
  */
 struct msszdd_compressor {
   /**
    * Reads an input file and creates a compressed output file in the
    * SZDD compressed file format. The SZDD compression format is quick
    * but gives poor compression. It is possible for the compressed output
    * file to be larger than the input file.
    *
    * Conventionally, SZDD compressed files have the final character in
    * their filename replaced with an underscore, to show they are
    * compressed.  The missing character is stored in the compressed file
    * itself. This is due to the restricted filename conventions of MS-DOS,
    * most operating systems, such as UNIX, simply append another file
    * extension to the existing filename. As mspack does not deal with
    * filenames, this is left up to you. If you wish to set the missing
    * character stored in the file header, use set_param() with the
    * #MSSZDDC_PARAM_MISSINGCHAR parameter.
    *
    * "Stream" compression (where the length of the input data is not
    * known) is not possible. The length of the input data is stored in the
    * header of the SZDD file and must therefore be known before any data
    * is compressed. Due to technical limitations of the file format, the
    * maximum size of uncompressed file that will be accepted is 2147483647
    * bytes.
    *
    * @param  self    a self-referential pointer to the msszdd_compressor
    *                 instance being called
    * @param  input   the name of the file to compressed. This is passed
    *                 passed directly to mspack_system::open()
    * @param  output  the name of the file to write compressed data to.
    *                 This is passed directly to mspack_system::open().
    * @param  length  the length of the uncompressed file, or -1 to indicate
    *                 that this should be determined automatically by using
    *                 mspack_system::seek() on the input file.
    * @return an error code, or MSPACK_ERR_OK if successful
    * @see set_param()
    */
   int (*compress)(struct msszdd_compressor *self,

                   const char *input,
                   const char *output,
                   off_t length);

 
   /**
    * Sets an SZDD compression engine parameter.
    *
    * The following parameters are defined:
 
    * - #MSSZDDC_PARAM_CHARACTER: the "missing character", the last character
    *   in the uncompressed file's filename, which is traditionally replaced
    *   with an underscore to show the file is compressed. Traditionally,
    *   this can only be a character that is a valid part of an MS-DOS,
    *   filename, but libmspack permits any character between 0x00 and 0xFF
    *   to be stored. 0x00 is the default, and it represents "no character
    *   stored".
    *
    * @param  self     a self-referential pointer to the msszdd_compressor
    *                  instance being called
    * @param  param    the parameter to set
    * @param  value    the value to set the parameter to
    * @return MSPACK_ERR_OK if all is OK, or MSPACK_ERR_ARGS if there
    *         is a problem with either parameter or value.
    * @see compress()
    */
   int (*set_param)(struct msszdd_compressor *self,

                    int param,
                    int value);

 
   /**
    * Returns the error code set by the most recently called method.
    *
    * @param  self     a self-referential pointer to the msszdd_compressor
    *                  instance being called
    * @return the most recent error code
    * @see compress()
    */
   int (*last_error)(struct mschm_decompressor *self);
 };
 
 /**
  * A decompressor for SZDD compressed files.
  *
  * All fields are READ ONLY.
  *
  * @see mspack_create_szdd_decompressor(), mspack_destroy_szdd_decompressor()
  */
 struct msszdd_decompressor {
   /**
    * Opens a SZDD file and reads the header.
    *
    * If the file opened is a valid SZDD file, all headers will be read and
    * a msszddd_header structure will be returned.
    *
    * In the case of an error occuring, NULL is returned and the error code
    * is available from last_error().
    *
    * The filename pointer should be considered "in use" until close() is
    * called on the SZDD file.
    *
    * @param  self     a self-referential pointer to the msszdd_decompressor
    *                  instance being called
    * @param  filename the filename of the SZDD compressed file. This is
    *                  passed directly to mspack_system::open().
    * @return a pointer to a msszddd_header structure, or NULL on failure
    * @see close()
    */
   struct msszddd_header *(*open)(struct msszdd_decompressor *self,

                                  const char *filename);

 
   /**
    * Closes a previously opened SZDD file.
    *
    * This closes a SZDD file and frees the msszddd_header associated with
    * it.
    *
    * The SZDD header pointer is now invalid and cannot be used again.
    *
    * @param  self     a self-referential pointer to the msszdd_decompressor
    *                  instance being called
    * @param  szdd     the SZDD file to close
    * @see open()
    */
   void (*close)(struct msszdd_decompressor *self,

                 struct msszddd_header *szdd);

 
   /**
    * Extracts the compressed data from a SZDD file.
    *
    * This decompresses the compressed SZDD data stream and writes it to
    * an output file.
    *
    * @param  self     a self-referential pointer to the msszdd_decompressor
    *                  instance being called
    * @param  szdd     the SZDD file to extract data from
    * @param  filename the filename to write the decompressed data to. This
    *                  is passed directly to mspack_system::open().
    * @return an error code, or MSPACK_ERR_OK if successful
    */
   int (*extract)(struct msszdd_decompressor *self,

                  struct msszddd_header *szdd,
                  const char *filename);

 
   /**
    * Decompresses an SZDD file to an output file in one step.
    *
    * This opens an SZDD file as input, reads the header, then decompresses
    * the compressed data immediately to an output file, finally closing
    * both the input and output file. It is more convenient to use than
    * open() then extract() then close(), if you do not need to know the
    * SZDD output size or missing character.
    *
    * @param  self     a self-referential pointer to the msszdd_decompressor
    *                  instance being called
    * @param  input    the filename of the input SZDD file. This is passed
    *                  directly to mspack_system::open().
    * @param  output   the filename to write the decompressed data to. This
    *                  is passed directly to mspack_system::open().
    * @return an error code, or MSPACK_ERR_OK if successful
    */
   int (*decompress)(struct msszdd_decompressor *self,

                     const char *input,
                     const char *output);

 
   /**
    * Returns the error code set by the most recently called method.
    *
    * This is useful for open() which does not return an
    * error code directly.
    *
    * @param  self     a self-referential pointer to the msszdd_decompressor
    *                  instance being called
    * @return the most recent error code
    * @see open(), extract(), decompress()
    */
   int (*last_error)(struct msszdd_decompressor *self);
 };
 
 /* --- support for KWAJ file format ---------------------------------------- */
 
 /** mskwaj_compressor::set_param() parameter: compression type */
 #define MSKWAJC_PARAM_COMP_TYPE  (0)
 
 /** mskwaj_compressor::set_param() parameter: include the length of the
  * uncompressed file in the header?
  */
 #define MSKWAJC_PARAM_INCLUDE_LENGTH (1)
 
 /** KWAJ compression type: no compression. */
 #define MSKWAJ_COMP_NONE (0)
 /** KWAJ compression type: no compression, 0xFF XOR "encryption". */
 #define MSKWAJ_COMP_XOR (1)
 /** KWAJ compression type: LZSS (same method as SZDD) */
 #define MSKWAJ_COMP_SZDD (2)
 /** KWAJ compression type: LZ+Huffman compression */
 #define MSKWAJ_COMP_LZH (3)
 /** KWAJ compression type: MSZIP */
 #define MSKWAJ_COMP_MSZIP (4)
 
 /** KWAJ optional header flag: decompressed file length is included */
 #define MSKWAJ_HDR_HASLENGTH (0x01)
 
 /** KWAJ optional header flag: unknown 2-byte structure is included */
 #define MSKWAJ_HDR_HASUNKNOWN1 (0x02)
 
 /** KWAJ optional header flag: unknown multi-sized structure is included */
 #define MSKWAJ_HDR_HASUNKNOWN2 (0x04)
 
 /** KWAJ optional header flag: file name (no extension) is included */
 #define MSKWAJ_HDR_HASFILENAME (0x08)
 
 /** KWAJ optional header flag: file extension is included */
 #define MSKWAJ_HDR_HASFILEEXT (0x10)
 
 /** KWAJ optional header flag: extra text is included */
 #define MSKWAJ_HDR_HASEXTRATEXT (0x20)
 
 /**
  * A structure which represents an KWAJ compressed file.
  *
  * All fields are READ ONLY.
  */
 struct mskwajd_header {
   /** The compression type; should be one of #MSKWAJ_COMP_NONE,
    * #MSKWAJ_COMP_XOR, #MSKWAJ_COMP_SZDD or #MSKWAJ_COMP_LZH
    */
   unsigned short comp_type;
 
   /** The offset in the file where the compressed data stream begins */
   off_t data_offset;
 
   /** Flags indicating which optional headers were included. */
   int headers;
 
   /** The amount of uncompressed data in the file, or 0 if not present. */
   off_t length;
 
   /** output filename, or NULL if not present */
   char *filename;
 
   /** extra uncompressed data (usually text) in the header.
    * This data can contain nulls so use extra_length to get the size.
    */
   char *extra;
 
   /** length of extra uncompressed data in the header */
   unsigned short extra_length;
 };
 
 /**
  * A compressor for the KWAJ file format.
  *
  * All fields are READ ONLY.
  *
  * @see mspack_create_kwaj_compressor(), mspack_destroy_kwaj_compressor()
  */
 struct mskwaj_compressor {
   /**
    * Reads an input file and creates a compressed output file in the
    * KWAJ compressed file format. The KWAJ compression format is quick
    * but gives poor compression. It is possible for the compressed output
    * file to be larger than the input file.
    *
    * @param  self    a self-referential pointer to the mskwaj_compressor
    *                 instance being called
    * @param  input   the name of the file to compressed. This is passed
    *                 passed directly to mspack_system::open()
    * @param  output  the name of the file to write compressed data to.
    *                 This is passed directly to mspack_system::open().
    * @param  length  the length of the uncompressed file, or -1 to indicate
    *                 that this should be determined automatically by using
    *                 mspack_system::seek() on the input file.
    * @return an error code, or MSPACK_ERR_OK if successful
    * @see set_param()
    */
   int (*compress)(struct mskwaj_compressor *self,

                   const char *input,
                   const char *output,
                   off_t length);

 
   /**
    * Sets an KWAJ compression engine parameter.
    *
    * The following parameters are defined:
    *
    * - #MSKWAJC_PARAM_COMP_TYPE: the compression method to use. Must
    *   be one of #MSKWAJC_COMP_NONE, #MSKWAJC_COMP_XOR, #MSKWAJ_COMP_SZDD
    *   or #MSKWAJ_COMP_LZH. The default is #MSKWAJ_COMP_LZH.
    *
    * - #MSKWAJC_PARAM_INCLUDE_LENGTH: a boolean; should the compressed
    *   output file should include the uncompressed length of the input
    *   file in the header? This adds 4 bytes to the size of the output
    *   file. A value of zero says "no", non-zero says "yes". The default
    *   is "no".
    *
    * @param  self     a self-referential pointer to the mskwaj_compressor
    *                  instance being called
    * @param  param    the parameter to set
    * @param  value    the value to set the parameter to
    * @return MSPACK_ERR_OK if all is OK, or MSPACK_ERR_ARGS if there
    *         is a problem with either parameter or value.
    * @see generate()
    */
   int (*set_param)(struct mskwaj_compressor *self,

                    int param,
                    int value);

 
 
   /**
    * Sets the original filename of the file before compression,
    * which will be stored in the header of the output file.
    *
    * The filename should be a null-terminated string, it must be an
    * MS-DOS "8.3" type filename (up to 8 bytes for the filename, then
    * optionally a "." and up to 3 bytes for a filename extension).
    *
    * If NULL is passed as the filename, no filename is included in the
    * header. This is the default.
    *
    * @param  self     a self-referential pointer to the mskwaj_compressor
    *                  instance being called
    * @param  filename the original filename to use
    * @return MSPACK_ERR_OK if all is OK, or MSPACK_ERR_ARGS if the
    *         filename is too long
    */
   int (*set_filename)(struct mskwaj_compressor *self,

                       const char *filename);

 
   /**
    * Sets arbitrary data that will be stored in the header of the
    * output file, uncompressed. It can be up to roughly 64 kilobytes,
    * as the overall size of the header must not exceed 65535 bytes.
    * The data can contain null bytes if desired.
    *
    * If NULL is passed as the data pointer, or zero is passed as the
    * length, no extra data is included in the header. This is the
    * default.
    *
    * @param  self     a self-referential pointer to the mskwaj_compressor
    *                  instance being called
    * @param  data     a pointer to the data to be stored in the header
    * @param  bytes    the length of the data in bytes
    * @return MSPACK_ERR_OK if all is OK, or MSPACK_ERR_ARGS extra data
    *         is too long
    */
   int (*set_extra_data)(struct mskwaj_compressor *self,

                         void *data,
                         size_t bytes);

 
   /**
    * Returns the error code set by the most recently called method.
    *
    * @param  self     a self-referential pointer to the mskwaj_compressor
    *                  instance being called
    * @return the most recent error code
    * @see compress()
    */
   int (*last_error)(struct mschm_decompressor *self);
 };
 
 /**
  * A decompressor for KWAJ compressed files.
  *
  * All fields are READ ONLY.
  *
  * @see mspack_create_kwaj_decompressor(), mspack_destroy_kwaj_decompressor()
  */
 struct mskwaj_decompressor {
   /**
    * Opens a KWAJ file and reads the header.
    *
    * If the file opened is a valid KWAJ file, all headers will be read and
    * a mskwajd_header structure will be returned.
    *
    * In the case of an error occuring, NULL is returned and the error code
    * is available from last_error().
    *
    * The filename pointer should be considered "in use" until close() is
    * called on the KWAJ file.
    *
    * @param  self     a self-referential pointer to the mskwaj_decompressor
    *                  instance being called
    * @param  filename the filename of the KWAJ compressed file. This is
    *                  passed directly to mspack_system::open().
    * @return a pointer to a mskwajd_header structure, or NULL on failure
    * @see close()
    */
   struct mskwajd_header *(*open)(struct mskwaj_decompressor *self,

                                  const char *filename);

 
   /**
    * Closes a previously opened KWAJ file.
    *
    * This closes a KWAJ file and frees the mskwajd_header associated
    * with it. The KWAJ header pointer is now invalid and cannot be
    * used again.
    *
    * @param  self     a self-referential pointer to the mskwaj_decompressor
    *                  instance being called
    * @param  kwaj     the KWAJ file to close
    * @see open()
    */
   void (*close)(struct mskwaj_decompressor *self,

                 struct mskwajd_header *kwaj);

 
   /**
    * Extracts the compressed data from a KWAJ file.
    *
    * This decompresses the compressed KWAJ data stream and writes it to
    * an output file.
    *
    * @param  self     a self-referential pointer to the mskwaj_decompressor
    *                  instance being called
    * @param  kwaj     the KWAJ file to extract data from
    * @param  filename the filename to write the decompressed data to. This
    *                  is passed directly to mspack_system::open().
    * @return an error code, or MSPACK_ERR_OK if successful
    */
   int (*extract)(struct mskwaj_decompressor *self,

                  struct mskwajd_header *kwaj,
                  const char *filename);

 
   /**
    * Decompresses an KWAJ file to an output file in one step.
    *
    * This opens an KWAJ file as input, reads the header, then decompresses
    * the compressed data immediately to an output file, finally closing
    * both the input and output file. It is more convenient to use than
    * open() then extract() then close(), if you do not need to know the
    * KWAJ output size or output filename.
    *
    * @param  self     a self-referential pointer to the mskwaj_decompressor
    *                  instance being called
    * @param  input    the filename of the input KWAJ file. This is passed
    *                  directly to mspack_system::open().
    * @param  output   the filename to write the decompressed data to. This
    *                  is passed directly to mspack_system::open().
    * @return an error code, or MSPACK_ERR_OK if successful
    */
   int (*decompress)(struct mskwaj_decompressor *self,

                     const char *input,
                     const char *output);

 
   /**
    * Returns the error code set by the most recently called method.
    *
    * This is useful for open() which does not return an
    * error code directly.
    *
    * @param  self     a self-referential pointer to the mskwaj_decompressor
    *                  instance being called
    * @return the most recent error code
    * @see open(), search()
    */
   int (*last_error)(struct mskwaj_decompressor *self);
 };
 
 /* --- support for .LZX (Offline Address Book) file format ----------------- */
 
 /**
  * A compressor for the Offline Address Book (OAB) format.
  *
  * All fields are READ ONLY.
  *
  * @see mspack_create_oab_compressor(), mspack_destroy_oab_compressor()
  */
 struct msoab_compressor {
   /**
    * Compress a full OAB file.
    *
    * The input file will be read and the compressed contents written to the
    * output file.
    *
    * @param  self     a self-referential pointer to the msoab_decompressor
    *                  instance being called
    * @param  input    the filename of the input file. This is passed
    *                  directly to mspack_system::open().
    * @param  output   the filename of the output file. This is passed
    *                  directly to mspack_system::open().
    * @return an error code, or MSPACK_ERR_OK if successful
    */
   int (*compress) (struct msoab_compressor *self,

                    const char *input,
                    const char *output);

 
   /**
    * Generate a compressed incremental OAB patch file.
    *
    * The two uncompressed files "input" and "base" will be read, and an
    * incremental patch to generate "input" from "base" will be written to
    * the output file.
    *
    * @param  self     a self-referential pointer to the msoab_compressor
    *                  instance being called
    * @param  input    the filename of the input file containing the new
    *                  version of its contents. This is passed directly
    *                  to mspack_system::open().
    * @param  base     the filename of the original base file containing
    *                  the old version of its contents, against which the
    *                  incremental patch shall generated. This is passed
    *                  directly to mspack_system::open().
    * @param  output   the filename of the output file. This is passed
    *                  directly to mspack_system::open().
    * @return an error code, or MSPACK_ERR_OK if successful
    */
   int (*compress_incremental) (struct msoab_compressor *self,

                                const char *input,
                                const char *base,
                                const char *output);

 };
 
 /**
  * A decompressor for .LZX (Offline Address Book) files
  *
  * All fields are READ ONLY.
  *
  * @see mspack_create_oab_decompressor(), mspack_destroy_oab_decompressor()
  */
 struct msoab_decompressor {
   /**
    * Decompresses a full Offline Address Book file.
    *
    * If the input file is a valid compressed Offline Address Book file, 
    * it will be read and the decompressed contents will be written to
    * the output file.
    *
    * @param  self     a self-referential pointer to the msoab_decompressor
    *                  instance being called
    * @param  input    the filename of the input file. This is passed
    *                  directly to mspack_system::open().
    * @param  output   the filename of the output file. This is passed
    *                  directly to mspack_system::open().
    * @return an error code, or MSPACK_ERR_OK if successful
    */
   int (*decompress) (struct msoab_decompressor *self,

                      const char *input,
                      const char *output);

 
   /**
    * Decompresses an Offline Address Book with an incremental patch file.
    *
    * This requires both a full UNCOMPRESSED Offline Address Book file to
    * act as the "base", and a compressed incremental patch file as input.
    * If the input file is valid, it will be decompressed with reference to
    * the base file, and the decompressed contents will be written to the
    * output file.
    *
    * There is no way to tell what the right base file is for the given
    * incremental patch, but if you get it wrong, this will usually result
    * in incorrect data being decompressed, which will then fail a checksum
    * test.
    *
    * @param  self     a self-referential pointer to the msoab_decompressor
    *                  instance being called
    * @param  input    the filename of the input file. This is passed
    *                  directly to mspack_system::open().
    * @param  base     the filename of the base file to which the
    *                  incremental patch shall be applied. This is passed
    *                  directly to mspack_system::open().
    * @param  output   the filename of the output file. This is passed
    *                  directly to mspack_system::open().
    * @return an error code, or MSPACK_ERR_OK if successful
    */
   int (*decompress_incremental) (struct msoab_decompressor *self,

                                  const char *input,
                                  const char *base,
                                  const char *output);
 
   /**
    * Sets an OAB decompression engine parameter. Available only in OAB
    * decompressor version 2 and above.
    *
    * - #MSOABD_PARAM_DECOMPBUF: How many bytes should be used as an input
    *   buffer by decompressors? The minimum value is 16. The default value
    *   is 4096.
    *
    * @param  self     a self-referential pointer to the msoab_decompressor
    *                  instance being called
    * @param  param    the parameter to set
    * @param  value    the value to set the parameter to
    * @return MSPACK_ERR_OK if all is OK, or MSPACK_ERR_ARGS if there
    *         is a problem with either parameter or value.
    */
   int (*set_param)(struct msoab_decompressor *self,
                    int param,
                    int value);
 

 };
 

 /** msoab_decompressor::set_param() parameter: size of decompression buffer */
 #define MSOABD_PARAM_DECOMPBUF (0)
 

 #ifdef __cplusplus
 }
 #endif
 
 #endif