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利用内存映射拷贝大文件

yoours2011-03-03 16:15:08 阅读 1157

简介一边听听音乐，一边写写文章。

一、失败的解决办法（未测试）

//不是物理内存不足，而是连续的虚拟地址空间不足

//因为Map需要连续的虚拟地址空间，当进程中未使用的最大虚拟地址空间小于MapView的大小时就会失败

//获取当前进程中未使用的最大虚拟地址空间大小

DWORD GetMaxMemoryBlock()

{

DWORD maxBlock = 0;

PBYTE p = NULL;

while(true)

{

MEMORY_BASIC_INFORMATION mbi;

if (VirtualQuery(p, &mbi, sizeof(mbi)) == 0)

break;

p = (PBYTE)mbi.BaseAddress + mbi.RegionSize;

if (mbi.AllocationBase != NULL)

continue;

if (mbi.RegionSize > maxBlock)

maxBlock = (DWORD)mbi.RegionSize;

}

return maxBlock;

}

//释放当前进程内存

void FreeMem()

{

// 获得Debug权限

// 。。。。。。。

DWORD pid = ::GetCurrentProcessId();

HANDLE hProcess = OpenProcess(PROCESS_SET_QUOTA, FALSE, pid);

if (hProcess != NULL)

{

SetProcessWorkingSetSize(hProcess, (DWORD)-1, (DWORD)-1);

CloseHandle(hProcess);

}

二、大文件拷贝代码

int CMyMapFileDlg::MyCopyFileUseMapFile(char* SourceFile, char* DestFile)

{

// 读文件

HANDLE hFileIn = CreateFile(SourceFile, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_FLAG_SEQUENTIAL_SCAN/*告诉系统，我会顺序读取文件（系统会为我缓存文件）。系统会读取比我要求读取的字节数要多*/, NULL);

if(hFileIn == INVALID_HANDLE_VALUE)

{

return -1;

}

//写文件

HANDLE hFileOut = CreateFile(DestFile, GENERIC_WRITE | GENERIC_READ, FILE_SHARE_READ, NULL, /*OPEN_EXISTING*/CREATE_ALWAYS/*追加，还是覆盖*/, FILE_FLAG_SEQUENTIAL_SCAN, NULL);

if(hFileOut == INVALID_HANDLE_VALUE)

{

CloseHandle(hFileIn);

return -1;

}

// 获得输入文件的大小

LARGE_INTEGER val;

val.LowPart = GetFileSize(hFileIn, (DWORD*)&val.HighPart);

if(val.LowPart == 0xFFFFFFFF && GetLastError() != NO_ERROR)

{

CloseHandle(hFileIn);

CloseHandle(hFileOut);

return -2;

}

// 创建读文件映射内核对象，句柄保存于hFileInMapping

HANDLE hFileInMapping = CreateFileMapping(hFileIn, NULL, PAGE_READONLY, 0, 0, NULL);

if(hFileInMapping == INVALID_HANDLE_VALUE || hFileInMapping == NULL)

{

CloseHandle(hFileIn);

CloseHandle(hFileOut);

return -3;

}

// 释放输入文件内核对象

CloseHandle(hFileIn);

// 创建写文件映射内核对象，句柄保存于hFileOutMapping

HANDLE hFileOutMapping = CreateFileMapping(hFileOut, NULL, PAGE_READWRITE, val.HighPart, val.LowPart, NULL);

if(hFileOutMapping == INVALID_HANDLE_VALUE || hFileOutMapping == NULL)

{

CloseHandle(hFileInMapping);

CloseHandle(hFileOut);

return -3;

}

// 释放写文件内核对象

CloseHandle(hFileOut);

/* 文件大于4G的处理代码 */

__int64 qwFileSize = val.QuadPart;// 文件总大小

DWORD dwBytesInBlock = 0;//每次读取的大小

// 根据系统信息获得：系统分配粒度

SYSTEM_INFO sinf;

GetSystemInfo(&sinf);

__int64 qwFileOffset = 0;//读文件视图的偏移量

__int64 qwmyFileOffset = 0;//写文件视图的偏移量

while(qwFileSize > 0)

{

dwBytesInBlock = sinf.dwAllocationGranularity;//分配粒度。必须为粒度的整数倍

if(qwFileSize < sinf.dwAllocationGranularity)//文件小于系统分配粒度

dwBytesInBlock = (DWORD)qwFileSize;//偏移量为文件大小

// 将读文件数据映射到进程的地址空间映射空间大小指定一个粒度

BYTE* pbFileIn = (PBYTE)MapViewOfFile(hFileInMapping, FILE_MAP_READ, (DWORD)(qwFileOffset >> 32), (DWORD)(qwFileOffset & 0xFFFFFFFF), dwBytesInBlock);

if (pbFileIn == NULL)

{

CloseHandle(hFileInMapping);

CloseHandle(hFileOutMapping);

return -4;

}

// 将写文件数据映射到进程的地址空间

BYTE* pbFileOut = (PBYTE)MapViewOfFile(hFileOutMapping, FILE_MAP_WRITE, (DWORD)(qwmyFileOffset >> 32), (DWORD)(qwmyFileOffset & 0xFFFFFFFF), dwBytesInBlock);

if (pbFileOut == NULL)

{

UnmapViewOfFile(pbFileIn);

CloseHandle(hFileInMapping);

CloseHandle(hFileOutMapping);

return -4;

}

//拷贝文件数据

memcpy(pbFileOut, pbFileIn, dwBytesInBlock);

// 从进程的地址空间撤消文件数据映像

UnmapViewOfFile(pbFileIn);

UnmapViewOfFile(pbFileOut);