重复文件句柄以避免共享违例错误消息

Question

我试图在一个增量备份系统上工作，当我运行我的脚本时，我总是得到"由于共享冲突而无法打开文件"，因为我试图打开进行增量备份的文件已经被另一个进程使用。我知道我可以终止这个进程，释放文件并进行增量备份，但这是我必须避免的事情。我读到，在Win32 API中，我可以复制文件处理程序，那么我该怎么做呢?

下面是我的一段代码:

FILE *GetFileHandle(WIN32_FIND_DATA *pWfdStruct, BOOL bWrite){
FILE *fFile;
DWORD nGLE;
fFile = fopen(pWfdStruct->cFileName, "rb");
if (!fFile)
{
    nGLE = GetLastError();
    if (nGLE == ERROR_SHARING_VIOLATION)    // 32
    {
        char szCurDir[8192];
        GetCurrentDirectory(8192, szCurDir);
        ODS("WARN: cannot open %s file due to sharing violation [fRenameFile: %s\%s]n",
            bWrite ? "dst" : "src", szCurDir, pWfdStruct->cFileName);
        return 0;
    }
    if (nGLE == ERROR_ACCESS_DENIED)        // 5
    {
        char szCurDir[8192];
        GetCurrentDirectory(8192, szCurDir);
        ODS("WARN: cannot open %s file, access denied [fRenameFile: %s\%s]n",
            bWrite ? "dst" : "src", szCurDir, pWfdStruct->cFileName);
        return 0;
    }
    if (nGLE == ERROR_FILE_NOT_FOUND)       // 2
    {
        char szCurDir[8192];
        GetCurrentDirectory(8192, szCurDir);
        ODS("WARN: cannot open %s file, file not present [fRenameFile: %s\%s]n",
            bWrite ? "dst" : "src", szCurDir, pWfdStruct->cFileName);
        return 0;
    }
    char szCurDir[8192];
    GetCurrentDirectory(8192, szCurDir);
    if (bWrite)
    {
        ODS("WARN: cannot open dst file [fRenameFile: %s\%s] [GLE: %d]n",
            szCurDir, pWfdStruct->cFileName, nGLE);
        return 0;
    }
    ODS("WARN: cannot open src file [fRenameFile: %s\%s] [GLE: %d] trying alt name [%s]n",
        szCurDir, pWfdStruct->cFileName, nGLE, pWfdStruct->cAlternateFileName);
    ReportSystemError("GetFileHandle", nGLE);
    __try
    {
        if (pWfdStruct->cAlternateFileName[0])
        {
            fFile = fopen(pWfdStruct->cAlternateFileName, "rb");
        }
    }
    __except(EXCEPTION_EXECUTE_HANDLER)
    {
        ODS("Exception caughtn");  // give up
    }
    if (!fFile)
    {
        nGLE = GetLastError();
        ReportSystemError("GetFileHandle 2nd try", nGLE);
        FATALODS("FATAL error, cannot open src file [%s] [GLE: %d]", pWfdStruct->cFileName, nGLE);
    }
    else
    {
        ODS("File: %s open successn", pWfdStruct->cAlternateFileName);
    }
}
return fFile;} // GetFileHandle

你能帮帮我吗?

Answer 1

如果文件被其他进程锁定，则无法打开。时期。

Windows有专门用于构建备份客户端的卷影复制服务(VSS)。它提供了复制锁定文件、确保一致性快照等功能。这个API有点复杂，但如果你想要一个健壮的备份解决方案，没有其他办法。

你可以看看一个开源的HoboCopy备份工具，作为一个使用VSS的例子。

EDIT:经过一些谷歌搜索，我找到了两个例子，做你想要的。我不能保证这些方法有效，但至少它们看起来是可行的。

第一个示例，清晰且注释良好(该语言是Basic的某种方言，但非常可读):

$include "windowssdk.inc"
$include "ntddk.inc"
$include "undocumented.inc"
$include "stdio.inc"
$use "_crtdll.lib"

'-------------------------- example
$include "shlwapi.inc"
$define REPLACE_ALWAYS
' open youtube in internet explorer, watch any video (should be downloaded in 100%)
' then run this program to copy the locked fla***.tmp file from your TEMP directory
istring tmppath[MAX_PATH]
' 1. enumerate fla*.tmp files in TEMP directory
ExpandEnvironmentStrings("%TEMP%\", tmppath, MAX_PATH)
int pathlen = len(tmppath)
strcpy(&tmppath[pathlen], "fla*.tmp")
UINT hFind = findopen(tmppath)
int nFilesFound = 0
int nFilesCopied = 0
if (hFind)
    istring name[256] = findnext(hFind)
    while (name[0] <> 0)
        strncpy(&tmppath[pathlen], name, MAX_PATH-pathlen)
        ' tmppath = local path to flash video
        ' 2. copy the file with renamed extension (supported by media player classic)
        istring newpath[MAX_PATH]
        newpath = tmppath
        PathRenameExtension(newpath, ".flv")
        ' check if we can open the file directly
        HANDLE hFile = CreateFile(tmppath, GENERIC_READ, FILE_SHARE_READ _
            | FILE_SHARE_WRITE | FILE_SHARE_DELETE, 0, OPEN_EXISTING, 0, 0)
        if (hFile <> INVALID_HANDLE_VALUE)
            ' file opened, so you can copy it with your favorite file manager
            CloseHandle(hFile)
        else
            nFilesFound++
            ' the file is opened with exclusive access, call the subroutine below to open it
            HANDLE hProcess
            hFile = OpenFileEx(tmppath, &hProcess)
            if (hFile = INVALID_HANDLE_VALUE)
                ' failed
                MessageBox 0, "failed to open " + tmppath, ""
            else
                ' copy it now ...
$ifdef REPLACE_ALWAYS
                HANDLE hOutFile = CreateFile(newpath, GENERIC_WRITE, 0, 0, CREATE_ALWAYS, 0, 0)
$else
                HANDLE hOutFile = CreateFile(newpath, GENERIC_WRITE, 0, 0, CREATE_NEW, 0, 0)
$endif
                if (hOutFile = INVALID_HANDLE_VALUE)
                    ' failed ?
                    MessageBox 0, "failed to create " + newpath, ""
                else
                    ' ... but first suspend the owner process (because the handle is duplicated, and
                    ' if the owner process changes file pointer, it will be reflected also in this process)
                    declare import, NtSuspendProcess(HANDLE hProcess), NTSTATUS
                    declare import, NtResumeProcess(HANDLE hProcess), NTSTATUS
                    NtSuspendProcess(hProcess)
                    ' save original file pointer in originalFilePos variable
                    LARGE_INTEGER originalFilePos
                    LARGE_INTEGER nullFilePos
                    nullFilePos.QuadPart = 0q
                    SetFilePointerEx(hFile, nullFilePos, &originalFilePos, FILE_CURRENT)
                    ' seek to beginning
                    SetFilePointerEx(hFile, nullFilePos, NULL, FILE_BEGIN)
                    '  copy, using string name as the buffer
                    DWORD BytesRead, BytesWriten
                    while (ReadFile(hFile, &name, 256, &BytesRead, 0) and BytesRead)
                        WriteFile(hOutFile, name, BytesRead, &BytesWriten, 0)
                    endwhile
                    '
                    nFilesCopied++
                    ' restore file pointer
                    SetFilePointerEx(hFile, originalFilePos, NULL, FILE_BEGIN)
                    ' cleanup
                    CloseHandle(hOutFile)
                    ' resume the process
                    NtResumeProcess(hProcess)
                endif
                CloseHandle(hFile)
            endif
        endif
        name = findnext(hFind)
    endwhile
    findclose(hFind)
endif
if (MessageBox(0, using("Copied # from # locked .FLV files. Open Directory ?", nFilesCopied, nFilesFound), "", MB_YESNO) = IDYES)
    tmppath[pathlen-1] = 0
    system tmppath
endif
'-------------------------- code
type SYSTEM_HANDLE_ENTRY
    ULONG OwnerPid
    BYTE ObjectType
    BYTE HandleFlags
    USHORT HandleValue
    PVOID ObjectPointer
    ACCESS_MASK GrantedAccess
endtype
type SYSTEM_HANDLE_INFORMATION
    ULONG HandleCount
    SYSTEM_HANDLE_ENTRY Handles[1]
endtype
type MY_OBJECT_TYPE_INFORMATION
    OBJECT_TYPE_INFORMATION t
    iwstring buffer[64]
endtype
type MY_OBJECT_NAME_INFORMATION
    OBJECT_NAME_INFORMATION t
    iwstring buffer[280]
endtype
declare import, NtQuerySystemInformation(_
    int SystemInformationClass,_
    PVOID SystemInformation,_
    ULONG SystemInformationLength,_
    pointer ReturnLength),NTSTATUS
const SystemHandleInformation = 16


sub OpenFileEx(string path, pointer pphProcess),HANDLE
    MY_OBJECT_TYPE_INFORMATION htype
    MY_OBJECT_NAME_INFORMATION name
    *<HANDLE>pphProcess = 0
    HANDLE h = INVALID_HANDLE_VALUE
    ' convert c: to DeviceHardDiskVolume...
    ' 1. extract partition letter
    iwstring root[4]
    root[0] = path[0], 58, 0
    ' 2. convert it to DeviceHardDiskVolumeX
    iwstring wszNTPath[280]
    int cch = QueryDosDeviceW(root, wszNTPath, 280)
    if (!cch) then return INVALID_HANDLE_VALUE
    ' 3. append remaining folders and file name from string path parameter
    ' so <path> "c:Program Files" gets converted to <wszNTPath> "DeviceHardDiskVolume1Program Files"
    cch = wcslen(wszNTPath)
    _snwprintf(&wszNTPath[cch], 280-cch, L"%S", &path[2])
    ' now get the list of all handles, and find the handle which name is equal to wszNTPath
    ULONG BytesNeeded, BufferSize = 4096
    pointer handles = new(char, BufferSize) ' SYSTEM_HANDLE_INFORMATION*
    while (handles)
        ' get the list of all user-mode handles
        NTSTATUS status = NtQuerySystemInformation(SystemHandleInformation, handles, BufferSize, &BytesNeeded)
        if (status = STATUS_INFO_LENGTH_MISMATCH)
            ' BytesNeeded is not adjusted, so we need to increase buffer size
            delete handles
            BufferSize += 32768
            handles = new(char, BufferSize)
        elseif (!status)
            settype handles, SYSTEM_HANDLE_INFORMATION
            ' sort handles by owning process id
            qsort(&*handles.Handles, *handles.HandleCount, len(SYSTEM_HANDLE_ENTRY), &SortHandlesCb)
            pointer node = *handles.Handles
            settype node, SYSTEM_HANDLE_ENTRY
            ULONG OwnerPid = 0
            HANDLE hProcess = 0
            HANDLE hThisProcess = GetCurrentProcess()
            BYTE ObjectTypeFile = 0
            while (*handles.HandleCount)
                *handles.HandleCount--
                if (*node.GrantedAccess & FILE_READ_DATA) ' 13019F
                    if (OwnerPid <> *node.OwnerPid)
                        OwnerPid = *node.OwnerPid
                        if (hProcess) then CloseHandle(hProcess)
                        hProcess = OpenProcess(PROCESS_DUP_HANDLE|PROCESS_SUSPEND_RESUME, FALSE, OwnerPid)
                    endif
                    if (hProcess)
                        HANDLE hObject
                        if (DuplicateHandle(hProcess, *node.HandleValue, hThisProcess, &hObject, 0, FALSE, DUPLICATE_SAME_ACCESS))
                            if (GetFileType(hObject) = FILE_TYPE_DISK)
                                if (!ObjectTypeFile) ' query object type name as "integer"
                                    if (!NtQueryObject(hObject, ObjectTypeInformation, &htype, len(htype), &BytesNeeded))
                                        if (!_wcsnicmp(htype.t.TypeName.Buffer, L"File", 4))
                                            ObjectTypeFile = *node.ObjectType
                                        endif
                                    endif
                                endif
                                ' do not query object name with granted access 0x0012019f (deadloock)
                                if (ObjectTypeFile and (ObjectTypeFile = *node.ObjectType) and (*node.GrantedAccess <> 0x0012019f))
                                    ' query file name
                                    if (!NtQueryObject(hObject, ObjectNameInformation, &name, len(name), &BytesNeeded))
                                        if (name.t.Name.Buffer and !wcsicmp(name.t.Name.Buffer, wszNTPath)) ' compare
                                            *<HANDLE>pphProcess = hProcess
                                            delete handles
                                            return hObject
                                        endif
                                    endif
                                endif
                            endif
                            CloseHandle(hObject)
                        endif
                    endif
                endif
                node = &*node[1]
            endwhile
            if (hProcess) then CloseHandle(hProcess)
            delete handles
        else
            ' NtQuerySystemInformation failed
            delete handles
        endif
    endwhile
    if (handles) then delete handles
    return h
endsub

declare cdecl SortHandlesCb(SYSTEM_HANDLE_ENTRY p1, SYSTEM_HANDLE_ENTRY p2),int
sub SortHandlesCb(SYSTEM_HANDLE_ENTRY p1, SYSTEM_HANDLE_ENTRY p2),int
    if (p1.OwnerPid = p2.OwnerPid) then return 0
    if (p1.OwnerPid > p2.OwnerPid) then return 1
    return -1
endsub

另一个杂乱的例子是http://forum.sysinternals.com/topic7974.html。

注意，这两个例子都使用了原生API函数和一些未记录的功能。

基本步骤如下:

1. 获取锁定进程所看到的文件句柄值。这是通过调用NtQuerySystemInformation来获取系统中所有句柄的列表，并调用NtQueryObject来查找具有匹配文件名的句柄来完成的。注意文件名必须转换为NT设备格式。
2. 打开拥有足够权限的句柄(OpenProcess)的进程(PROCESS_DUP_HANDLE和PROCESS_SUSPEND_RESUME)，并调用DuiplicateHandle(以该进程为源，以步骤1的句柄值为目标，以您的进程为目标)。
3. 使用NtSuspendProcess"暂停"进程，防止它修改文件指针和文件内容。
4. 使用重复句柄复制文件
5. 恢复文件指针，关闭句柄，调用NtResumeProcess取消进程

EDIT2:我个人使用另一种方式访问锁定的文件-使用手动NTFS解析的原始磁盘访问。例如，给定文件名，找到它的MFT条目，解码数据运行位置并从原始磁盘读取它们。原始磁盘访问总是可用的(前提是您拥有管理员权限)，因此任何文件都是可读的。缺点是零一致性保证，因此不适合用于备份目的。

p。如果我是你，我还是会选择官方支持的VSS。备份软件不应该依赖黑客。