使用zlib压缩解压缩文件的详细过程

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);

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);