//------------------------------------------------------------------------------
#endif
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;
}
}
//------------------------------------------------------------------------------
#endif
encode.h 压缩程序主函数
#ifndef __ENCODE_H__
#define __ENCODE_H__
//------------------------------------------------------------------------------
#include
#include
#include
//------------------------------------------------------------------------------
VOID output_code( DWORD code ,PBUFFER_DATA out, PLZW_DATA lzw)
{
out->dw_buffer |= code << ( 32 - out->by_left - lzw->cur_code_len );
out->by_left += lzw->cur_code_len;
while( out->by_left >= 8 )
{
if( out->index == BUFFERSIZE )
{
empty_buffer( lzw,out);
}
out->lp_buffer[ out->index++ ] = (BYTE)( out->dw_buffer >> 24 );
out->dw_buffer <<= 8;
out->by_left -= 8;
}
}
//------------------------------------------------------------------------------
VOID do_encode( PBUFFER_DATA in, PBUFFER_DATA out, PLZW_DATA lzw)
{
WORD prefix;
while( in->index != in->top )
{
if( !in_table(lzw) )
{
// current code not in code table
// then add it to table and output prefix
insert_table(lzw);
prefix = lzw->suffix;
output_code( lzw->prefix ,out ,lzw );
lzw->code++;
if( lzw->code == (WORD)1<< lzw->cur_code_len )
{
// code reached current code top(1< // then current code length add one
lzw->cur_code_len++;
if( lzw->cur_code_len == CODE_LEN + 1 )
{
re_init_lzw( lzw );
}
}
}
else
{
// current code already in code table
// then output nothing
prefix = get_code(lzw);
}
lzw->prefix = prefix;
lzw->suffix = in->lp_buffer[ in->index++ ];
}
}
//------------------------------------------------------------------------------
VOID encode(HANDLE h_sour,HANDLE h_dest)
{
LZW_DATA lzw;
BUFFER_DATA in ;
BUFFER_DATA out;
BOOL first_run = TRUE;
lzw_create( &lzw ,h_sour,h_dest );
buffer_create( &in );
buffer_create( &out );
while( load_buffer( h_sour, &in ) )
{
if( first_run )
{// File length should be considered but here we simply
// believe file length bigger than 2 bytes.
lzw.prefix = in.lp_buffer[ in.index++ ];
lzw.suffix = in.lp_buffer[ in.index++ ];
first_run = FALSE;
}
do_encode(&in , &out, &lzw);
}
output_code(lzw.prefix, &out , &lzw);
output_code(lzw.suffix, &out , &lzw);
out.end_flag = TRUE;
empty_buffer( &lzw,&out);
lzw_destory( &lzw );
buffer_destory( &in );
buffer_destory( &out );
}