encode.h

LZW 压缩与解压源码, 已经封装成动态链接库, 方便调用.

#ifndef __ENCODE_H__
#define __ENCODE_H__
//------------------------------------------------------------------------------
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>

//------------------------------------------------------------------------------
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<<cur_code_len)
				// 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 );
}

//------------------------------------------------------------------------------

#endif