在 Windows 上以编程方式对文件进行碎片整理

Question

我正在尝试学习本教程：Defragmenting Files。

我在C: 卷的句柄上使用FSCTL_GET_VOLUME_BITMAP 调用DeviceIoControl()，我得到了正确的响应。

然后我成功打开另一个文件的句柄（我尝试了从 10KB 到几 MB 的文件），然后我用 FSCTL_GET_RETRIEVAL_POINTERS 调用 DeviceIoControl()，它成功了，没有最后一个错误或失败结果，但是 @987654327 @ 未填写。

我也尝试在C: 卷句柄上调用它，但即使尝试将OVERLAPPED 偏移量设置为0，并将带有SetFilePointer() 的文件指针设置为相对于文件的开头。

BOOL dic(HANDLE dev, DWORD code, LPVOID in, DWORD ins, LPVOID out, LPDWORD outs)
{
    HANDLE h = GetProcessHeap();
    DWORD s = 1000;
    DWORD r = 0;
    out = HeapAlloc(h,HEAP_ZERO_MEMORY,s);
    while (!DeviceIoControl(dev, code, in, ins, out, s, &r, 0))
    {
        if (ERROR_INSUFFICIENT_BUFFER == GetLastError() || ERROR_MORE_DATA == GetLastError())
        {
            s *= 10;
            LPVOID t = HeapReAlloc(h, HEAP_ZERO_MEMORY, out, s);
            if(!t){
                HeapFree(h, 0, out);
                return 0;
            }
            out = t;
        }
        else
        {
            HeapFree(h, 0, out);
            printf("dic unk: %d\n", GetLastError());
            return 0;
        }
    }
    *outs = s;
    return 1;
}

BOOL getvolptr(HANDLE volh, PRETRIEVAL_POINTERS_BUFFER rpb, LPDWORD rpbs)
{
    STARTING_VCN_INPUT_BUFFER vcn = { 0 };
    return dic(volh, FSCTL_GET_RETRIEVAL_POINTERS, &vcn, sizeof(vcn), rpb, rpbs);
}

    RETRIEVAL_POINTERS_BUFFER rpb = { 0 };
    DWORD rpbs = 0;
    ULONGLONG cluster_cnt=0;
    HANDLE fi = openfile("C:\\Windows\\System32\\Kernel32.dll");
    if (INVALID_HANDLE_VALUE == fi)
    {
        printf("failed to open file! (%d)\n", GetLastError());
        getchar();
    }
    r = getvolptr(fi, &rpb, &rpbs);
    if (!r)
    {
        printf("failed to get vol ptrs! (%d)\n", GetLastError());
        getchar();
    }
    for (int i = 0; i < rpb.ExtentCount; ++i)
    {
        cluster_cnt = (ULONGLONG)(rpb.Extents[i].NextVcn.QuadPart) - (ULONGLONG)(rpb.StartingVcn.QuadPart);
        printf("%d) size: %llu clusters (0x%016X)\n", i, cluster_cnt, rpb.Extents[i].Lcn.QuadPart);
    }

Answer 1

您没有检查第一个 HeapAlloc() 是否失败。并且HeapFree() 可以在打印之前擦除DeviceIoControl() 中的最后一个错误代码。

但更重要的是，您没有将out 数据正确地传回给调用者，因此您正在泄漏分配的内存，而调用者最终会得到垃圾输出。

由于调用者是传入自己的RETRIEVAL_POINTERS_BUFFER 来接收数据，所以需要将分配内存的内容复制到该缓冲区中，例如：

BOOL dic(HANDLE dev, DWORD code, LPVOID in, DWORD ins, LPVOID out, LPDWORD outs)
{
    if (!in || !out || !outs)
    {
        SetLastError(ERROR_INVALID_PARAMETER);
        return FALSE;
    }

    *outs = 0;

    HANDLE h = GetProcessHeap();
    DWORD s = 1000;

    LPVOID buf = HeapAlloc(h, HEAP_ZERO_MEMORY, s);
    if (!buf)
        return FALSE;

    DWORD r = 0;
    while (!DeviceIoControl(dev, code, in, ins, buf, s, &r, 0))
    {
        if (ERROR_INSUFFICIENT_BUFFER == GetLastError() || ERROR_MORE_DATA == GetLastError())
        {
            s *= 10;
            LPVOID t = HeapReAlloc(h, HEAP_ZERO_MEMORY, buf, s);
            if (!t)
            {
                HeapFree(h, 0, buf);
                return FALSE;
            }
            buf = t;
        }
        else
        {
            printf("dic unk: %u\n", GetLastError());
            HeapFree(h, 0, buf);
            return FALSE;
        }
    }

    if (s > *outs)
    {
        HeapFree(h, 0, buf);
        SetLastError(ERROR_INSUFFICIENT_BUFFER);
        return FALSE; 
    }

    CopyMemory(out, buf, s);
    *outs = s;

    HeapFree(h, 0, buf);
    return TRUE;
}

BOOL getvolptr(HANDLE volh, PRETRIEVAL_POINTERS_BUFFER rpb, LPDWORD rpbs)
{
    STARTING_VCN_INPUT_BUFFER vcn = { 0 };
    return dic(volh, FSCTL_GET_RETRIEVAL_POINTERS, &vcn, sizeof(vcn), rpb, rpbs);
}

HANDLE fi = openfile("C:\\Windows\\System32\\Kernel32.dll");
if (INVALID_HANDLE_VALUE == fi)
{
    printf("failed to open file! (%u)\n", GetLastError());
    getchar();
}
else
{
    RETRIEVAL_POINTERS_BUFFER rpb = { 0 };
    DWORD rpbs = sizeof(rpb);

    if (!getvolptr(fi, &rpb, &rpbs))
    {
        printf("failed to get vol ptrs! (%u)\n", GetLastError());
        getchar();
    }
    else
    {
        ULONGLONG cluster_cnt = 0;
        for (int i = 0; i < rpb.ExtentCount; ++i)
        {
            cluster_cnt = (ULONGLONG)(rpb.Extents[i].NextVcn.QuadPart) - (ULONGLONG)(rpb.StartingVcn.QuadPart);
            printf("%d) size: %llu clusters (0x%016X)\n", i, cluster_cnt, rpb.Extents[i].Lcn.QuadPart);
        }
    }

    closefile(fi);
}

或者，您可以将指向已分配内存的指针返回给调用者，调用者在使用完毕后必须释放内存，例如：

BOOL dic(HANDLE dev, DWORD code, LPVOID in, DWORD ins, LPVOID* out, LPDWORD outs)
{
    if (!in || !out || !outs)
    {
        SetLastError(ERROR_INVALID_PARAMETER);
        return FALSE;
    }

    *out = NULL;
    *outs = 0;

    HANDLE h = GetProcessHeap();
    DWORD s = 1000;

    LPVOID buf = HeapAlloc(h, HEAP_ZERO_MEMORY, s);
    if (!buf)
        return FALSE;

    DWORD r = 0;
    while (!DeviceIoControl(dev, code, in, ins, buf, s, &r, 0))
    {
        if (ERROR_INSUFFICIENT_BUFFER == GetLastError() || ERROR_MORE_DATA == GetLastError())
        {
            s *= 10;
            LPVOID t = HeapReAlloc(h, HEAP_ZERO_MEMORY, buf, s);
            if (!t)
            {
                HeapFree(h, 0, buf);
                return FALSE;
            }
            buf = t;
        }
        else
        {
            printf("dic unk: %u\n", GetLastError());
            HeapFree(h, 0, buf);
            return FALSE;
        }
    }

    *out = buf;
    *outs = s;

    return TRUE;
}

BOOL getvolptr(HANDLE volh, PRETRIEVAL_POINTERS_BUFFER* rpb, LPDWORD rpbs)
{
    STARTING_VCN_INPUT_BUFFER vcn = { 0 };
    return dic(volh, FSCTL_GET_RETRIEVAL_POINTERS, &vcn, sizeof(vcn), (void**)rpb, rpbs);
}

HANDLE fi = openfile("C:\\Windows\\System32\\Kernel32.dll");
if (INVALID_HANDLE_VALUE == fi)
{
    printf("failed to open file! (%u)\n", GetLastError());
    getchar();
}
else
{
    PRETRIEVAL_POINTERS_BUFFER rpb = NULL;
    DWORD rpbs = 0;

    if (!getvolptr(fi, &rpb, &rpbs))
    {
        printf("failed to get vol ptrs! (%u)\n", GetLastError());
        getchar();
    }
    else
    {
        ULONGLONG cluster_cnt = 0;
        for (int i = 0; i < rpb->ExtentCount; ++i)
        {
            cluster_cnt = (ULONGLONG)(rpb->Extents[i].NextVcn.QuadPart) - (ULONGLONG)(rpb->StartingVcn.QuadPart);
            printf("%d) size: %llu clusters (0x%016X)\n", i, cluster_cnt, rpb->Extents[i].Lcn.QuadPart);
        }

        HeapFree(GetProcessHeap(), 0, rpb);
    }

    closefile(fi);
}