zutils.cpp

概述：数据的纵向收集

/*
 * Copyright (C) 2001-2005 Jacek Sieka, arnetheduck on gmail point com
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */
#include "StdAfx.h"
#include "ZUtils.h"

const double ZFilter::MIN_COMPRESSION_LEVEL = 0.9;

ZFilter::ZFilter() : totalIn(0), totalOut(0), compressing(true) 
{
	memset(&zs, 0, sizeof(zs));

	if(deflateInit(&zs, 3) != Z_OK) {
	}
}

ZFilter::~ZFilter() {
	deflateEnd(&zs);
}

bool ZFilter::operator()(const void* in, size_t& insize, void* out, size_t& outsize) {
	if(outsize == 0)
		return false;

	zs.next_in = (Bytef*)in;
	zs.next_out = (Bytef*)out;

	// Check if there's any use compressing; if not, save some cpu...
	if(compressing && insize > 0 && outsize > 16 && (totalIn > (64*1024)) && ((static_cast<double>(totalOut) / totalIn) > 0.95)) {
		zs.avail_in = 0;
		zs.avail_out = outsize;
		if(deflateParams(&zs, 0, Z_DEFAULT_STRATEGY) != Z_OK) {
		}
		zs.avail_in = insize;
		compressing = false;

		// Check if we ate all space already...
		if(zs.avail_out == 0) {
			outsize = outsize - zs.avail_out;
			insize = insize - zs.avail_in;
			totalOut += outsize;
			totalIn += insize;
			return true;
		}
	} else {
		zs.avail_in = insize;
		zs.avail_out = outsize;
	}

	if(insize == 0) {
		int err = ::deflate(&zs, Z_FINISH);
		if(err != Z_OK && err != Z_STREAM_END)
		{
			return 0;
		}

		outsize = outsize - zs.avail_out;
		insize = insize - zs.avail_in;
		totalOut += outsize;
		totalIn += insize;
		return err == Z_OK;
	} else {
		int err = ::deflate(&zs, Z_NO_FLUSH);
		if(err != Z_OK)
		{
			return 0;
		}

		outsize = outsize - zs.avail_out;
		insize = insize - zs.avail_in;
		totalOut += outsize;
		totalIn += insize;
		return true;
	}
}

UnZFilter::UnZFilter() {
	memset(&zs, 0, sizeof(zs));

	//2007.3.2,sunwang
	/*
		windowBits can also be greater than 15 for optional gzip encoding. Add
		16 to windowBits to write a simple gzip header and trailer around the
		compressed data instead of a zlib wrapper. The gzip header will have no
		file name, no extra data, no comment, no modification time (set to zero),
		no header crc, and the operating system will be set to 255 (unknown).  If a
		gzip stream is being written, strm->adler is a crc32 instead of an adler32.
	*/
	if(inflateInit2(&zs,MAX_WBITS+16) != Z_OK)
	{
		;
	}
}

UnZFilter::~UnZFilter() {
	inflateEnd(&zs);
}

bool UnZFilter::operator()(const void* in, size_t& insize, void* out, size_t& outsize) {
	if(outsize == 0)
		return 0;

	zs.avail_in = insize;
	zs.next_in = (Bytef*)in;
	zs.avail_out = outsize;
	zs.next_out = (Bytef*)out;

	int err = ::inflate(&zs, Z_NO_FLUSH);

	// see zlib/contrib/minizip/unzip.c, Z_BUF_ERROR means we should have padded
	// with a dummy byte if at end of stream - since we don't do this it's not a real
	// error
	if(!(err == Z_OK || err == Z_STREAM_END || (err == Z_BUF_ERROR && in == NULL)))
	{
		return 0;
	}
	outsize = outsize - zs.avail_out;
	insize = insize - zs.avail_in;
	//return err == Z_OK;
	return (err >= Z_OK);
}

/**
 * @file
 * $Id: ZUtils.cpp,v 1.10 2006/01/29 18:48:25 arnetheduck Exp $
 */