lzw压缩算法的c语言完成

= (DWORD)next << (24-buffer->by_left);
  buffer->by_left   += 8;
}
code = buffer->dw_buffer >> ( 32 - lzw->cur_code_len );
buffer->dw_buffer <<= lzw->cur_code_len;
buffer->by_left    -= lzw->cur_code_len;

return code;
}
//------------------------------------------------------------------------------
VOID do_decode( PBUFFER_DATA in, PBUFFER_DATA out, PLZW_DATA lzw, PSTACK_DATA stack)
{
WORD code;
WORD tmp;
while( in->index != in->top  )
{
  code = get_next_code( in ,lzw );

  if( code < 0x100 )
  {
   // code already in table
   // then simply output the code
   lzw->suffix = (BYTE)code;
  }
  else
  {
   if( code < lzw->code  )
   {
    // code also in table
    // then output code chain
    
    tmp = lzw->lp_prefix[ code ];
    while( tmp > 0x100 )
    {
     tmp = lzw->lp_prefix[ tmp ];
    }
    lzw->suffix = (BYTE)tmp;
   }
   else
   {
    // code == lzw->code
    // code not in table
    // add code into table
    // and out put code
    tmp = lzw->prefix;
    while( tmp > 0x100 )
    {
     tmp = lzw->lp_prefix[ tmp ];
    }
    lzw->suffix = (BYTE)tmp;
   }
  }
  insert_2_table( lzw );
  out_code(code,out,lzw,stack);

  lzw->prefix = code;

}

}
//------------------------------------------------------------------------------
VOID decode( HANDLE h_sour, HANDLE h_dest )
{
    LZW_DATA        lzw;
    BUFFER_DATA     in ;
    BUFFER_DATA     out;
STACK_DATA      stack;
BOOL   first_run;

first_run = TRUE;


    lzw_create( &lzw ,h_sour,h_dest );
    buffer_create( &in );
    buffer_create( &out );
stack_create(&stack );

    while( load_buffer( h_sour, &in ) )
    {
  if( first_run )
  {
   lzw.prefix = get_next_code( &in, &lzw );
   lzw.suffix = lzw.prefix;
   out_code(lzw.prefix, &out, &lzw , &stack);
   first_run = FALSE;
  }
        do_decode(&in , &out, &lzw, &stack);
    }

    empty_buffer( &lzw,&out);

    lzw_destory( &lzw );
    buffer_destory( &in );
    buffer_destory( &out );
stack_destory( &stack);
}

#endif

2  下面给出一个应用上面模块的简单例子

#include <stdio.h>
#include <stdlib.h>
//------------------------------------------------------------------------------

#include "lzw.h"
#include "hash.h"
#include "fileio.h"
#include "encode.h"
#include "decode.h"

//------------------------------------------------------------------------------
HANDLE h_file_sour;  
HANDLE h_file_dest;
HANDLE h_file;
CHAR*  file_name_in = "d:\\code.c";
CHAR*  file_name_out= "d:\\encode.e";
CHAR*  file_name    = "d:\\decode.d";


//------------------------------------------------------------------------------
int main(int argc, char *argv[])
{
    h_file_sour = file_handle(file_name_in);
    h_file_dest = file_handle(file_name_out);
    h_file     = file_handle(file_name);


  encode(h_file_sour, h_file_dest);  
// decode(h_file_dest,h_file);


    CloseHandle(h_file_sour);
    CloseHandle(h_file_dest);  
    CloseHandle(h_file);

  return 0;      
}    

3  后语

  之前研究gif文件格式时偶然接触了lzw压缩算法，于是就想自己动手实现。从一开始看人家的原码，然后跟着模仿，到现在用自己的语言表达出来，从理解原理到代码的实现花费了不少时间与精力，但是真正的快乐也就在这里，现在把她拿出来跟大家分享也就是分享快乐。

关键词：lzw压缩算法的c语言完成