/* This file is part of libmspack.
* (C) 2003-2010 Stuart Caie.
*
* SZDD is a format used in the MS-DOS commands COMPRESS.EXE and
* EXPAND.EXE. The compression method is attributed to Steven Zeck,
* however it's pretty much identical to LZSS.
*
* 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
*
* For further details, see the file COPYING.LIB distributed with libmspack
*/
/* SZDD decompression implementation */
#include <system.h>
#include <szdd.h>
/* prototypes */
static struct msszddd_header *szddd_open(
struct msszdd_decompressor *base, const char *filename);
static void szddd_close(
struct msszdd_decompressor *base, struct msszddd_header *hdr);
static int szddd_read_headers(
struct mspack_system *sys, struct mspack_file *fh,
struct msszddd_header *hdr);
static int szddd_extract(
struct msszdd_decompressor *base, struct msszddd_header *hdr,
const char *filename);
static int szddd_decompress(
struct msszdd_decompressor *base, const char *input, const char *output);
static int szddd_error(
struct msszdd_decompressor *base);
/***************************************
* MSPACK_CREATE_SZDD_DECOMPRESSOR
***************************************
* constructor
*/
struct msszdd_decompressor *
mspack_create_szdd_decompressor(struct mspack_system *sys)
{
struct msszdd_decompressor_p *self = NULL;
if (!sys) sys = mspack_default_system;
if (!mspack_valid_system(sys)) return NULL;
if ((self = (struct msszdd_decompressor_p *) sys->alloc(sys, sizeof(struct msszdd_decompressor_p)))) {
self->base.open = &szddd_open;
self->base.close = &szddd_close;
self->base.extract = &szddd_extract;
self->base.decompress = &szddd_decompress;
self->base.last_error = &szddd_error;
self->system = sys;
self->error = MSPACK_ERR_OK;
}
return (struct msszdd_decompressor *) self;
}
/***************************************
* MSPACK_DESTROY_SZDD_DECOMPRESSOR
***************************************
* destructor
*/
void mspack_destroy_szdd_decompressor(struct msszdd_decompressor *base)
{
struct msszdd_decompressor_p *self = (struct msszdd_decompressor_p *) base;
if (self) {
struct mspack_system *sys = self->system;
sys->free(self);
}
}
/***************************************
* SZDDD_OPEN
***************************************
* opens an SZDD file without decompressing, reads header
*/
static struct msszddd_header *szddd_open(struct msszdd_decompressor *base,
const char *filename)
{
struct msszdd_decompressor_p *self = (struct msszdd_decompressor_p *) base;
struct msszddd_header *hdr;
struct mspack_system *sys;
struct mspack_file *fh;
if (!self) return NULL;
sys = self->system;
fh = sys->open(sys, filename, MSPACK_SYS_OPEN_READ);
hdr = (struct msszddd_header *) sys->alloc(sys, sizeof(struct msszddd_header_p));
if (fh && hdr) {
((struct msszddd_header_p *) hdr)->fh = fh;
self->error = szddd_read_headers(sys, fh, hdr);
}
else {
if (!fh) self->error = MSPACK_ERR_OPEN;
if (!hdr) self->error = MSPACK_ERR_NOMEMORY;
}
if (self->error) {
if (fh) sys->close(fh);
sys->free(hdr);
hdr = NULL;
}
return hdr;
}
/***************************************
* SZDDD_CLOSE
***************************************
* closes an SZDD file
*/
static void szddd_close(struct msszdd_decompressor *base,
struct msszddd_header *hdr)
{
struct msszdd_decompressor_p *self = (struct msszdd_decompressor_p *) base;
struct msszddd_header_p *hdr_p = (struct msszddd_header_p *) hdr;
if (!self || !self->system) return;
/* close the file handle associated */
self->system->close(hdr_p->fh);
/* free the memory associated */
self->system->free(hdr);
self->error = MSPACK_ERR_OK;
}
/***************************************
* SZDDD_READ_HEADERS
***************************************
* reads the headers of an SZDD format file
*/
static unsigned char szdd_signature_expand[8] = {
0x53, 0x5A, 0x44, 0x44, 0x88, 0xF0, 0x27, 0x33
};
static unsigned char szdd_signature_qbasic[8] = {
0x53, 0x5A, 0x20, 0x88, 0xF0, 0x27, 0x33, 0xD1
};
static int szddd_read_headers(struct mspack_system *sys,
struct mspack_file *fh,
struct msszddd_header *hdr)
{
unsigned char buf[8];
/* read and check signature */
if (sys->read(fh, buf, 8) != 8) return MSPACK_ERR_READ;
if ((memcmp(buf, szdd_signature_expand, 8) == 0)) {
/* common SZDD */
hdr->format = MSSZDD_FMT_NORMAL;
/* read the rest of the header */
if (sys->read(fh, buf, 6) != 6) return MSPACK_ERR_READ;
if (buf[0] != 0x41) return MSPACK_ERR_DATAFORMAT;
hdr->missing_char = buf[1];
hdr->length = EndGetI32(&buf[2]);
}
else if ((memcmp(buf, szdd_signature_qbasic, 8) == 0)) {
/* special QBasic SZDD */
hdr->format = MSSZDD_FMT_QBASIC;
if (sys->read(fh, buf, 4) != 4) return MSPACK_ERR_READ;
hdr->missing_char = '\0';
hdr->length = EndGetI32(buf);
}
else {
return MSPACK_ERR_SIGNATURE;
}
return MSPACK_ERR_OK;
}
/***************************************
* SZDDD_EXTRACT
***************************************
* decompresses an SZDD file
*/
static int szddd_extract(struct msszdd_decompressor *base,
struct msszddd_header *hdr, const char *filename)
{
struct msszdd_decompressor_p *self = (struct msszdd_decompressor_p *) base;
struct mspack_file *fh, *outfh;
struct mspack_system *sys;
off_t data_offset;
if (!self) return MSPACK_ERR_ARGS;
if (!hdr) return self->error = MSPACK_ERR_ARGS;
sys = self->system;
fh = ((struct msszddd_header_p *) hdr)->fh;
/* seek to the compressed data */
data_offset = (hdr->format == MSSZDD_FMT_NORMAL) ? 14 : 12;
if (sys->seek(fh, data_offset, MSPACK_SYS_SEEK_START)) {
return self->error = MSPACK_ERR_SEEK;
}
/* open file for output */
if (!(outfh = sys->open(sys, filename, MSPACK_SYS_OPEN_WRITE))) {
return self->error = MSPACK_ERR_OPEN;
}
/* decompress the data */
self->error = lzss_decompress(sys, fh, outfh, SZDD_INPUT_SIZE,
hdr->format == MSSZDD_FMT_NORMAL
? LZSS_MODE_EXPAND
: LZSS_MODE_QBASIC);
/* close output file */
sys->close(outfh);
return self->error;
}
/***************************************
* SZDDD_DECOMPRESS
***************************************
* unpacks directly from input to output
*/
static int szddd_decompress(struct msszdd_decompressor *base,
const char *input, const char *output)
{
struct msszdd_decompressor_p *self = (struct msszdd_decompressor_p *) base;
struct msszddd_header *hdr;
int error;
if (!self) return MSPACK_ERR_ARGS;
if (!(hdr = szddd_open(base, input))) return self->error;
error = szddd_extract(base, hdr, output);
szddd_close(base, hdr);
return self->error = error;
}
/***************************************
* SZDDD_ERROR
***************************************
* returns the last error that occurred
*/
static int szddd_error(struct msszdd_decompressor *base)
{
struct msszdd_decompressor_p *self = (struct msszdd_decompressor_p *) base;
return (self) ? self->error : MSPACK_ERR_ARGS;
}