/*
  * LZW encoder
  * Copyright (c) 2007 Bartlomiej Wolowiec
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg 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 FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 /**

  * @file

  * LZW encoder

  * @author Bartlomiej Wolowiec
  */
 
 #include "avcodec.h"

 #include "put_bits.h"

 #include "lzw.h"
 
 #define LZW_MAXBITS 12
 #define LZW_SIZTABLE (1<<LZW_MAXBITS)
 #define LZW_HASH_SIZE 16411
 #define LZW_HASH_SHIFT 6
 
 #define LZW_PREFIX_EMPTY -1
 #define LZW_PREFIX_FREE -2
 
 /** One code in hash table */
 typedef struct Code{
     /// Hash code of prefix, LZW_PREFIX_EMPTY if empty prefix, or LZW_PREFIX_FREE if no code
     int hash_prefix;
     int code;               ///< LZW code
     uint8_t suffix;         ///< Last character in code block
 }Code;
 
 /** LZW encode state */
 typedef struct LZWEncodeState {
     int clear_code;          ///< Value of clear code
     int end_code;            ///< Value of end code
     Code tab[LZW_HASH_SIZE]; ///< Hash table
     int tabsize;             ///< Number of values in hash table
     int bits;                ///< Actual bits code
     int bufsize;             ///< Size of output buffer
     PutBitContext pb;        ///< Put bit context for output
     int maxbits;             ///< Max bits code
     int maxcode;             ///< Max value of code
     int output_bytes;        ///< Number of written bytes
     int last_code;           ///< Value of last output code or LZW_PREFIX_EMPTY

     enum FF_LZW_MODES mode;  ///< TIFF or GIF
     void (*put_bits)(PutBitContext *, int, unsigned); ///< GIF is LE while TIFF is BE

 }LZWEncodeState;
 
 
 const int ff_lzw_encode_state_size = sizeof(LZWEncodeState);
 
 /**
  * Hash function adding character
  * @param head LZW code for prefix
  * @param add Character to add
  * @return New hash value
  */
 static inline int hash(int head, const int add)
 {
     head ^= (add << LZW_HASH_SHIFT);
     if (head >= LZW_HASH_SIZE)
         head -= LZW_HASH_SIZE;

     av_assert2(head >= 0 && head < LZW_HASH_SIZE);

     return head;
 }
 
 /**
  * Hash function calculates next hash value
  * @param head Actual hash code
  * @param offset Offset calculated by hashOffset
  * @return New hash value
  */
 static inline int hashNext(int head, const int offset)
 {
     head -= offset;
     if(head < 0)
         head += LZW_HASH_SIZE;
     return head;
 }
 
 /**
  * Hash function calculates hash offset
  * @param head Actual hash code
  * @return Hash offset
  */
 static inline int hashOffset(const int head)
 {
     return head ? LZW_HASH_SIZE - head : 1;
 }
 
 /**
  * Write one code to stream
  * @param s LZW state
  * @param c code to write
  */
 static inline void writeCode(LZWEncodeState * s, int c)
 {

     av_assert2(0 <= c && c < 1 << s->bits);

     s->put_bits(&s->pb, s->bits, c);

 }
 
 
 /**
  * Find LZW code for block
  * @param s LZW state
  * @param c Last character in block
  * @param hash_prefix LZW code for prefix
  * @return LZW code for block or -1 if not found in table
  */
 static inline int findCode(LZWEncodeState * s, uint8_t c, int hash_prefix)
 {
     int h = hash(FFMAX(hash_prefix, 0), c);
     int hash_offset = hashOffset(h);
 
     while (s->tab[h].hash_prefix != LZW_PREFIX_FREE) {
         if ((s->tab[h].suffix == c)
             && (s->tab[h].hash_prefix == hash_prefix))
             return h;
         h = hashNext(h, hash_offset);
     }
 
     return h;
 }
 
 /**
  * Add block to LZW code table
  * @param s LZW state
  * @param c Last character in block
  * @param hash_prefix LZW code for prefix
  * @param hash_code LZW code for bytes block
  */
 static inline void addCode(LZWEncodeState * s, uint8_t c, int hash_prefix, int hash_code)
 {
     s->tab[hash_code].code = s->tabsize;
     s->tab[hash_code].suffix = c;
     s->tab[hash_code].hash_prefix = hash_prefix;
 
     s->tabsize++;
 

     if (s->tabsize >= (1 << s->bits) + (s->mode == FF_LZW_GIF))

         s->bits++;
 }
 
 /**
  * Clear LZW code table
  * @param s LZW state
  */
 static void clearTable(LZWEncodeState * s)
 {
     int i, h;
 
     writeCode(s, s->clear_code);
     s->bits = 9;
     for (i = 0; i < LZW_HASH_SIZE; i++) {
         s->tab[i].hash_prefix = LZW_PREFIX_FREE;
     }
     for (i = 0; i < 256; i++) {
         h = hash(0, i);
         s->tab[h].code = i;
         s->tab[h].suffix = i;
         s->tab[h].hash_prefix = LZW_PREFIX_EMPTY;
     }
     s->tabsize = 258;
 }
 
 /**
  * Calculate number of bytes written
  * @param s LZW encode state
  * @return Number of bytes written
  */
 static int writtenBytes(LZWEncodeState *s){

     int ret = put_bits_count(&s->pb) >> 3;

     ret -= s->output_bytes;
     s->output_bytes += ret;
     return ret;
 }
 
 /**
  * Initialize LZW encoder. Please set s->clear_code, s->end_code and s->maxbits before run.
  * @param s LZW state
  * @param outbuf Output buffer
  * @param outsize Size of output buffer
  * @param maxbits Maximum length of code
  */

 void ff_lzw_encode_init(LZWEncodeState *s, uint8_t *outbuf, int outsize,
                         int maxbits, enum FF_LZW_MODES mode,
                         void (*lzw_put_bits)(PutBitContext *, int, unsigned))

 {
     s->clear_code = 256;
     s->end_code = 257;
     s->maxbits = maxbits;
     init_put_bits(&s->pb, outbuf, outsize);
     s->bufsize = outsize;

     av_assert0(s->maxbits >= 9 && s->maxbits <= LZW_MAXBITS);

     s->maxcode = 1 << s->maxbits;
     s->output_bytes = 0;
     s->last_code = LZW_PREFIX_EMPTY;
     s->bits = 9;

     s->mode = mode;
     s->put_bits = lzw_put_bits;

 }
 
 /**
  * LZW main compress function
  * @param s LZW state
  * @param inbuf Input buffer
  * @param insize Size of input buffer
  * @return Number of bytes written or -1 on error
  */
 int ff_lzw_encode(LZWEncodeState * s, const uint8_t * inbuf, int insize)
 {
     int i;
 
     if(insize * 3 > (s->bufsize - s->output_bytes) * 2){
         return -1;
     }
 

     if (s->last_code == LZW_PREFIX_EMPTY)

         clearTable(s);
 
     for (i = 0; i < insize; i++) {
         uint8_t c = *inbuf++;

         int code = findCode(s, c, s->last_code);

         if (s->tab[code].hash_prefix == LZW_PREFIX_FREE) {

             writeCode(s, s->last_code);
             addCode(s, c, s->last_code, code);

             code= hash(0, c);

         }

         s->last_code = s->tab[code].code;

         if (s->tabsize >= s->maxcode - 1) {
             clearTable(s);
         }
     }
 
     return writtenBytes(s);
 }
 
 /**
  * Write end code and flush bitstream
  * @param s LZW state
  * @return Number of bytes written or -1 on error
  */

 int ff_lzw_encode_flush(LZWEncodeState *s,
                         void (*lzw_flush_put_bits)(PutBitContext *))

 {
     if (s->last_code != -1)
         writeCode(s, s->last_code);
     writeCode(s, s->end_code);

     if (s->mode == FF_LZW_GIF)
         s->put_bits(&s->pb, 1, 0);
 

     lzw_flush_put_bits(&s->pb);

     s->last_code = -1;
 
     return writtenBytes(s);
 }