使用zlib压缩解压缩文件的详细过程
转自：http://www.cppblog.com/woaidongmao/archive/2009/01/01/70923.aspx
zlib是一套公开源代码的压缩，解压缩的函数库，提供了很多文件操作的方法，但是他不是一套类库，所以有兴趣的人都可以把他进行封装，实现自己的类库，和更高层的接口。
具体的介绍可以参考http://www.gzip.org/zlib/主页，这里有详细介绍。
这里简单实现了zlib的最简单的用法，压缩一个文件，通过使用文件映射来实现的。
包含头文件 zlib.h 和 zconf.h 和 zlib.lib
在stdafx.h 中加入：
#ifdef _DEBUG
#pragma comment(lib,"zlibd.lib")
#else
#pragma comment(lib,"zlib.lib")
#endif
#include "zlib.h"
#include "zconf.h"
压缩代码：
HANDLE hFile, hFileToWrite;
CString strFilePath;
m_ctrEdit.GetWindowText(strFilePath);
//打开要进行压缩的文件
hFile = CreateFile(strFilePath, // file name
GENERIC_READ, // open for reading
FILE_SHARE_READ, // share for reading
NULL, // no security
OPEN_EXISTING, // existing file only
FILE_ATTRIBUTE_NORMAL, // normal file
NULL); // no attr. template
if (hFile == INVALID_HANDLE_VALUE)
{
AfxMessageBox("Could not open file to read"); // process error
return;
}
HANDLE hMapFile, hMapFileToWrite;
//创建一个文件映射
hMapFile = CreateFileMapping(hFile, // Current file handle.
NULL, // Default security.
PAGE_READONLY, // Read/write permission.
0, // Max. object size.
0, // Size of hFile.
"ZipTestMappingObjectForRead"); // Name of mapping object.
if (hMapFile == NULL)
{
AfxMessageBox("Could not create file mapping object");
return;
}
LPVOID lpMapAddress, lpMapAddressToWrite;
//创建一个文件映射的视图用来作为source
lpMapAddress = MapViewOfFile(hMapFile, // Handle to mapping object.
FILE_MAP_READ, // Read/write permission
0, // Max. object size.
0, // Size of hFile.
0); // Map entire file.
if (lpMapAddress == NULL)
{
AfxMessageBox("Could not map view of file");
return;
}
//////////////////////////////////////////////////////////////////////////////////
DWORD dwFileLength,dwFileLengthToWrite;
dwFileLength = GetFileSize(hFile, NULL);
m_dwSourceFileLength = dwFileLength;
//因为压缩函数的输出缓冲必须比输入大0.1% + 12 然后一个DWORD用来保存压缩前的大小，
// 解压缩的时候用，当然还可以保存更多的信息，这里用不到
dwFileLengthToWrite = (double)dwFileLength*1.001 + 12 + sizeof(DWORD);
//以下是创建一个文件，用来保存压缩后的文件
hFileToWrite = CreateFile("demoFile.rar", // demoFile.rar
GENERIC_WRITE|GENERIC_READ, // open for writing
0, // do not share
NULL, // no security
CREATE_ALWAYS, // overwrite existing
FILE_ATTRIBUTE_NORMAL , // normal file
NULL); // no attr. template
if (hFileToWrite == INVALID_HANDLE_VALUE)
{
AfxMessageBox("Could not open file to write"); // process error
return;
}
hMapFileToWrite = CreateFileMapping(hFileToWrite, // Current file handle.
NULL, // Default security.
PAGE_READWRITE, // Read/write permission.
0, // Max. object size.
dwFileLengthToWrite, // Size of hFile.
"ZipTestMappingObjectForWrite"); // Name of mapping object.
if (hMapFileToWrite == NULL)
{
AfxMessageBox("Could not create file mapping object for write");
return;
}
lpMapAddressToWrite = MapViewOfFile(hMapFileToWrite, // Handle to mapping object.
FILE_MAP_WRITE, // Read/write permission
0, // Max. object size.
0, // Size of hFile.
0); // Map entire file.
if (lpMapAddressToWrite == NULL)
{
AfxMessageBox("Could not map view of file");
return;
}
//这里是将压缩前的大小保存在文件的第一个DWORD里面
LPVOID pBuf = lpMapAddressToWrite;
(*(DWORD*)pBuf) = dwFileLength;
pBuf = (DWORD*)pBuf + 1;
//////////////////////////////////////////////////////////////////////
//这里就是最重要的，zlib里面提供的一个方法，将源缓存的数据压缩至目的缓存
//原形如下：
//int compress (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen);
//参数destLen返回实际压缩后的文件大小。
compress((Bytef*)pBuf,&dwFileLengthToWrite, (Bytef*)lpMapAddress, dwFileLength);
//////////////////////////////////////////////////////////////////////
UnmapViewOfFile(lpMapAddress);
CloseHandle(hMapFile);
CloseHandle(hFile);
UnmapViewOfFile(lpMapAddressToWrite);
CloseHandle(hMapFileToWrite);
//这里将文件大小重新设置一下
SetFilePointer(hFileToWrite,dwFileLengthToWrite + sizeof(DWORD) ,NULL,FILE_BEGIN);
SetEndOfFile(hFileToWrite);
CloseHandle(hFileToWrite);
解压缩的方法其他地方都一样，不同的就是使用方法是uncompress而不是compress
原形如下：
int uncompress (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen);
解压缩代码如下：
HANDLE hFile, hFileToWrite;
CString strFilePath;
m_ctrEdit.GetWindowText(strFilePath);
//打开要进行解压缩的文件
hFile = CreateFile(strFilePath, // file name
GENERIC_READ, // open for reading
FILE_SHARE_READ, // share for reading
NULL, // no security
OPEN_EXISTING, // existing file only
FILE_ATTRIBUTE_NORMAL, // normal file
NULL); // no attr. template
if (hFile == INVALID_HANDLE_VALUE)
{
AfxMessageBox("Could not open file to read"); // process error
return;
}
HANDLE hMapFile, hMapFileToWrite;
//创建一个文件映射
hMapFile = CreateFileMapping(hFile, // Current file handle.
NULL, // Default security.
PAGE_READONLY, // Read/write permission.
0, // Max. object size.
0, // Size of hFile.
"ZipTestMappingObjectForRead"); // Name of mapping object.
if (hMapFile == NULL)
{
AfxMessageBox("Could not create file mapping object");
return;
}
LPVOID lpMapAddress, lpMapAddressToWrite;
//创建一个文件映射的视图用来作为source
lpMapAddress = MapViewOfFile(hMapFile, // Handle to mapping object.
FILE_MAP_READ, // Read/write permission
0, // Max. object size.
0, // Size of hFile.
0); // Map entire file.
if (lpMapAddress == NULL)
{
AfxMessageBox("Could not map view of file");
return;
}
//////////////////////////////////////////////////////////////////////////////////
DWORD dwFileLength,dwFileLengthToWrite;
dwFileLength = GetFileSize(hFile, NULL) - sizeof(DWORD);
//因为压缩函数的输出缓冲必须比输入大0.1% + 12 然后一个DWORD用来保存压缩前的大小，
// 解压缩的时候用，当然还可以保存更多的信息，这里用不到
// dwFileLengthToWrite = (double)dwFileLength*1.001 + 12 + sizeof(DWORD);
dwFileLengthToWrite = (*(DWORD*)lpMapAddress);
LPVOID pSourceBuf = lpMapAddress;
pSourceBuf = (DWORD*)pSourceBuf + 1;
//以下是创建一个文件，用来保存压缩后的文件
hFileToWrite = CreateFile("demoFile.pdf", // create demo.gz
GENERIC_WRITE|GENERIC_READ, // open for writing
0, // do not share
NULL, // no security
CREATE_ALWAYS, // overwrite existing
FILE_ATTRIBUTE_NORMAL , // normal file
NULL); // no attr. template
if (hFileToWrite == INVALID_HANDLE_VALUE)
{
AfxMessageBox("Could not open file to write"); // process error
return;
}
hMapFileToWrite = CreateFileMapping(hFileToWrite, // Current file handle.
NULL, // Default security.
PAGE_READWRITE, // Read/write permission.
0, // Max. object size.
dwFileLengthToWrite, // Size of hFile.
"ZipTestMappingObjectForWrite"); // Name of mapping object.
if (hMapFileToWrite == NULL)
{
AfxMessageBox("Could not create file mapping object for write");
return;
}
lpMapAddressToWrite = MapViewOfFile(hMapFileToWrite, // Handle to mapping object.
FILE_MAP_WRITE, // Read/write permission
0, // Max. object size.
0, // Size of hFile.
0); // Map entire file.
if (lpMapAddressToWrite == NULL)
{
AfxMessageBox("Could not map view of file");
return;
}
//这里是将压缩前的大小保存在文件的第一个DWORD里面
LPVOID pBuf = lpMapAddressToWrite;
//////////////////////////////////////////////////////////////////////
//这里就是最重要的，zlib里面提供的一个方法，将源缓存的数据压缩至目的缓存
//原形如下：
//int compress (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen);
//参数destLen返回实际压缩后的文件大小。
uncompress((Bytef*)pBuf,&dwFileLengthToWrite, (Bytef*)pSourceBuf, dwFileLength);
//////////////////////////////////////////////////////////////////////
UnmapViewOfFile(lpMapAddress);
CloseHandle(hMapFile);
CloseHandle(hFile);
UnmapViewOfFile(lpMapAddressToWrite);
CloseHandle(hMapFileToWrite);
//这里将文件大小重新设置一下
SetFilePointer(hFileToWrite,dwFileLengthToWrite ,NULL,FILE_BEGIN);
SetEndOfFile(hFileToWrite);
CloseHandle(hFileToWrite);
以上代码通过测试，如果有疑问可以联系[email protected]