zlib.cpp

概述：数据的纵向收集

// Copy in the contents of these files here before compiling
#include "StdAfx.h"
#include "ZLib.h"

BYTE* CZLib::Compress(LPCVOID pInput, DWORD nInput, DWORD* pnOutput, DWORD nSuggest)
{
	// If we were given nSuggest, use it as the output buffer size, otherwise call compressBound to set it
	*pnOutput = nSuggest ? nSuggest : compressBound( nInput ); // compressBound just uses math to guess, it doesn't look at the data

	// Allocate a new buffer of pnOutput bytes
	BYTE* pBuffer = new BYTE[ *pnOutput ];

	// Compress the data at pInput into pBuffer, putting how many bytes it wrote under pnOutput
	if ( compress(            // Compress data from one buffer to another, returns Z_OK 0 false if it works
		pBuffer,			  // The output buffer where ZLib can write compressed data
		pnOutput,             // Reads how much space it has there, writes how much space it used
		(const BYTE *)pInput, // The source buffer with data to compress
		nInput ) != Z_OK )    // The number of bytes there
	{
		// The compress function reported error
		delete[] pBuffer;
		return NULL;
	}

	return pBuffer;
}

//////////////////////////////////////////////////////////////////////
// CZLib decompression

// Takes a pointer to compressed input bytes, and how many are there
// Decompresses the memory into a new buffer this function allocates
// Returns a pointer to the new buffer, and writes its size under pnOutput
BYTE* CZLib::Decompress(LPCVOID pInput, DWORD nInput, DWORD* pnOutput, DWORD nSuggest)
{
	// Guess how big the data will be decompressed, use nSuggest, or just guess it will be 6 times as big
	*pnOutput = nSuggest ? nSuggest : nInput * 6;

	// Allocate a buffer that big
	BYTE* pBuffer = new BYTE[ *pnOutput ];

	// Uncompress the data from pInput into pBuffer, writing how big it is now in pnOutput
	if ( uncompress( // Uncompress data
		pBuffer,            // Destination buffer where uncompress can write uncompressed data
		pnOutput,                 // Reads how much space it has there, and writes how much space it used
		(const BYTE *)pInput,     // Source buffer of compressed data
		nInput ) != Z_OK )        // Number of bytes there
	{
		// The uncompress function returned an error, delete the buffer we allocated and return error
		delete[] pBuffer;
		return NULL;
	}

	return pBuffer;
}