decode.h

LZW 压缩与解压源码, 已经封装成动态链接库, 方便调用.

#ifndef __DECODE_H__
#define __DECODE_H__
//------------------------------------------------------------------------------
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
//------------------------------------------------------------------------------
VOID out_code( WORD code ,PBUFFER_DATA buffer,PLZW_DATA lzw,PSTACK_DATA stack)
{
	WORD tmp;
	if( code < 0x100 )
	{
		stack->lp_stack[ stack->index++ ] = (unsigned char)code;
	}
	else
	{
		stack->lp_stack[ stack->index++ ] = lzw->lp_suffix[ code ];
		tmp = lzw->lp_prefix[ code ];
		while( tmp > 0x100 )
		{
			stack->lp_stack[ stack->index++ ] = lzw->lp_suffix[ tmp ];
			tmp = lzw->lp_prefix[ tmp ];
		}
		stack->lp_stack[ stack->index++ ] = (BYTE)tmp;
		
	}
	
	
	while( stack->index )
	{
		if( buffer->index == BUFFERSIZE )
		{
			empty_buffer(lzw,buffer);
		}
		buffer->lp_buffer[ buffer->index++ ] = stack->lp_stack[ --stack->index ] ;
	}
}
//------------------------------------------------------------------------------
VOID insert_2_table(PLZW_DATA lzw )
{
	
	lzw->lp_code[ lzw->code ]   = lzw->code;
	lzw->lp_prefix[ lzw->code ] = lzw->prefix;
	lzw->lp_suffix[ lzw->code ] = lzw->suffix;
	lzw->code++;
	
	if( lzw->code == ((WORD)1<<lzw->cur_code_len)-1 )
	{
		lzw->cur_code_len++;
		if( lzw->cur_code_len == CODE_LEN+1 )
			lzw->cur_code_len = 9;
	}
	if(lzw->code >= 1<<CODE_LEN )
	{
		re_init_lzw(lzw);
	}
	
}
//------------------------------------------------------------------------------
WORD get_next_code( PBUFFER_DATA buffer , PLZW_DATA lzw )
{
	
	BYTE next;
	WORD code;
	while( buffer->by_left < lzw->cur_code_len )
	{
		if( buffer->index == BUFFERSIZE )
		{
			load_buffer( lzw->h_sour, buffer );
		}
		next = buffer->lp_buffer[ buffer->index++ ];
		buffer->dw_buffer |= (DWORD)next << (24-buffer->by_left);
		buffer->by_left   += 8;
	}
	code = (unsigned short)(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 = (unsigned char)(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