skype怎么接电话:lzw压缩算法的c语言实现 - soubam software workshop

1 程序由五个模块组成。

(1)  lzw.h      定义了一些基本的数据结构，常量，还有变量的初始化等。

#ifndef __LZW_H__
#define __LZW_H__
//------------------------------------------------------------------------------
#include
#include
#include
#include
//------------------------------------------------------------------------------
#define LZW_BASE    0x102//  The code base
#define CODE_LEN       12   //  Max code length
#define TABLE_LEN      4099 // It must be prime number and bigger than 2^CODE_LEN=4096.
       // Such as 5051 is also ok.
#define BUFFERSIZE     1024
//------------------------------------------------------------------------------
typedef struct
{
    HANDLE      h_sour;  // Source file handle.
    HANDLE      h_dest;  // Destination file handle.
   
    HANDLE      h_suffix; // Suffix table handle.
    HANDLE      h_prefix; // Prefix table handle.
    HANDLE      h_code;  // Code table handle.
   
    LPWORD      lp_prefix; // Prefix table head pointer.
    LPBYTE      lp_suffix; // Suffix table head pointer.
    LPWORD      lp_code; // Code table head pointer.

    WORD        code;
    WORD        prefix;
    BYTE        suffix;

    BYTE        cur_code_len; // Current code length.[ used in Dynamic-Code-Length mode ]

}LZW_DATA,*PLZW_DATA;

typedef struct
{
    WORD        top;
    WORD        index;

    LPBYTE      lp_buffer;
    HANDLE      h_buffer;
   
    BYTE        by_left;
    DWORD       dw_buffer;

    BOOL        end_flag;

}BUFFER_DATA,*PBUFFER_DATA;

typedef struct                  //Stack used in decode
{
 WORD        index;
 HANDLE      h_stack;
 LPBYTE      lp_stack;

}STACK_DATA,*PSTACK_DATA;
//------------------------------------------------------------------------------
VOID stack_create( PSTACK_DATA stack )
{
 stack->h_stack  = GlobalAlloc( GHND , TABLE_LEN*sizeof(BYTE) );
 stack->lp_stack = GlobalLock( stack->h_stack );
 stack->index = 0;
}
//------------------------------------------------------------------------------
VOID stack_destory( PSTACK_DATA stack )
{
 GlobalUnlock( stack->h_stack );
    GlobalFree  ( stack->h_stack );
}
//------------------------------------------------------------------------------
VOID buffer_create( PBUFFER_DATA    buffer )
{
    buffer->h_buffer   = GlobalAlloc(  GHND,  BUFFERSIZE*sizeof(BYTE)  );
    buffer->lp_buffer  = GlobalLock( buffer->h_buffer );
    buffer->top        = 0;
    buffer->index      = 0;
    buffer->by_left    = 0;
    buffer->dw_buffer  = 0;
    buffer->end_flag   = FALSE;
}
//------------------------------------------------------------------------------
VOID buffer_destory( PBUFFER_DATA   buffer )
{
    GlobalUnlock( buffer->h_buffer );
    GlobalFree  ( buffer->h_buffer );
}
//------------------------------------------------------------------------------
VOID re_init_lzw( PLZW_DATA lzw )    //When code table reached its top it should
{                                    //be reinitialized.     
    memset( lzw->lp_code, 0xFFFF, TABLE_LEN*sizeof(WORD) );
    lzw->code          = LZW_BASE;
    lzw->cur_code_len  = 9;
}
//------------------------------------------------------------------------------
VOID lzw_create(PLZW_DATA    lzw,    HANDLE h_sour,    HANDLE h_dest)
{
 WORD i;
    lzw->h_code        = GlobalAlloc( GHND, TABLE_LEN*sizeof(WORD) );
    lzw->h_prefix      = GlobalAlloc( GHND, TABLE_LEN*sizeof(WORD) );
    lzw->h_suffix      = GlobalAlloc( GHND, TABLE_LEN*sizeof(BYTE) );
    lzw->lp_code       = GlobalLock( lzw->h_code   );
    lzw->lp_prefix     = GlobalLock( lzw->h_prefix );
    lzw->lp_suffix     = GlobalLock( lzw->h_suffix );
    lzw->code          = LZW_BASE;
    lzw->cur_code_len  = 9;
    lzw->h_sour        = h_sour;
    lzw->h_dest        = h_dest;
    memset( lzw->lp_code, 0xFFFF, TABLE_LEN*sizeof(WORD) );

}
//------------------------------------------------------------------------------
VOID lzw_destory(PLZW_DATA    lzw)
{ 
    GlobalUnlock( lzw->h_code   );
    GlobalUnlock( lzw->h_prefix );
    GlobalUnlock( lzw->h_suffix );
 
 GlobalFree( lzw->h_code  );
    GlobalFree( lzw->h_prefix );
    GlobalFree( lzw->h_suffix );   
}
//------------------------------------------------------------------------------
#endif

(2) fileio.h   定义了一些文件操作

#ifndef __FILEIO_H__
#define __FILEIO_H__
//------------------------------------------------------------------------------
#include
#include
#include
//------------------------------------------------------------------------------
HANDLE  file_handle(CHAR* file_name)
{
    HANDLE h_file;
    h_file = CreateFile(file_name,
                       GENERIC_READ|GENERIC_WRITE,
                       FILE_SHARE_READ|FILE_SHARE_WRITE,
                       NULL,
                       OPEN_ALWAYS,
                       0,
                       NULL
                       );
    return h_file;
}
//------------------------------------------------------------------------------
WORD load_buffer(HANDLE h_sour, PBUFFER_DATA buffer)  // Load file to buffer
{
    DWORD ret;
    ReadFile(h_sour,buffer->lp_buffer,BUFFERSIZE,&ret,NULL);
    buffer->index = 0;
    buffer->top = (WORD)ret;
    return (WORD)ret;
}
//------------------------------------------------------------------------------
WORD empty_buffer( PLZW_DATA lzw, PBUFFER_DATA buffer)// Output buffer to file
{
  
    DWORD ret;
    if(buffer->end_flag) // The flag mark the end of decode
 {
  if( buffer->by_left )
  {
   buffer->lp_buffer[ buffer->index++ ] = (BYTE)( buffer->dw_buffer >> 32-buffer->by_left )<<(8-buffer->by_left);
  }
 }
 WriteFile(lzw->h_dest, buffer->lp_buffer,buffer->index,&ret,NULL);
    buffer->index = 0;
    buffer->top = ret;
    return (WORD)ret;
}
//------------------------------------------------------------------------------
#endif

(3) hash.h  定义了压缩时所用的码表操作函数，为了快速查找使用了hash算法，还有处理hash冲突的函数

#ifndef __HASH_H__
#define __HASH_H__
//------------------------------------------------------------------------------
#include
#include
#include
//------------------------------------------------------------------------------
#define   DIV       TABLE_LEN
#define   HASHSTEP  13         // It should bigger than 0.
//------------------------------------------------------------------------------
WORD get_hash_index( PLZW_DATA lzw )
{
    DWORD tmp;
    WORD result;
    DWORD prefix;
    DWORD suffix;
    prefix = lzw->prefix;
    suffix = lzw->suffix;
    tmp = prefix<<8 | suffix;
    result = tmp % DIV;
    return result;
}
//------------------------------------------------------------------------------
WORD re_hash_index( WORD hash ) // If hash conflict occured we must recalculate
{                               // hash index .
    WORD result;
    result = hash + HASHSTEP;
    result = result % DIV;
    return result;
}
//------------------------------------------------------------------------------
BOOL in_table( PLZW_DATA lzw ) // To find whether current code is already in table.
{
    BOOL result;
    WORD hash;

    hash = get_hash_index( lzw );
    if( lzw->lp_code[ hash ] == 0xFFFF )
    {
        result = FALSE;   
    }
    else
    {
        if( lzw->lp_prefix[ hash ] == lzw->prefix &&
            lzw->lp_suffix[ hash ] == lzw->suffix )
        {
            result = TRUE;
        }
        else
        {
            result = FALSE;
            while( lzw->lp_code[ hash ] != 0xFFFF )
            {
                if( lzw->lp_prefix[ hash ] == lzw->prefix &&
                    lzw->lp_suffix[ hash ] == lzw->suffix )
                {
                        result = TRUE;
                        break;   
                }
                hash = re_hash_index( hash );
            }
        }
    }
    return result;
}
//------------------------------------------------------------------------------
WORD get_code( PLZW_DATA lzw )
{
    WORD hash;
    WORD code;
    hash = get_hash_index( lzw );
    if( lzw->lp_prefix[ hash ] == lzw->prefix &&
        lzw->lp_suffix[ hash ] == lzw->suffix )
    {
        code = lzw->lp_code[ hash ];
    }
    else
    {
        while( lzw->lp_prefix[ hash ] != lzw->prefix ||
               lzw->lp_suffix[ hash ] != lzw->suffix )
        {
                hash = re_hash_index( hash );   
        }
        code = lzw->lp_code[ hash ];
    }
    return code;
}
//------------------------------------------------------------------------------
VOID insert_table( PLZW_DATA lzw )
{
 
    WORD hash;
    hash = get_hash_index( lzw );
    if( lzw->lp_code[ hash ] == 0xFFFF )
    {
        lzw->lp_prefix[ hash ] = lzw->prefix;
        lzw->lp_suffix[ hash ] = lzw->suffix;
        lzw->lp_code[ hash ]   = lzw->code;
    }
    else
    {
        while( lzw->lp_code[ hash ] != 0xFFFF )
        {
                hash = re_hash_index( hash );   
        }
        lzw->lp_prefix[ hash ] = lzw->prefix;
        lzw->lp_suffix[ hash ] = lzw->suffix;
        lzw->lp_code[ hash ]   = lzw->code;
    }

}
//------------------------------------------------------------------------------