GetFileSizeEx 文件映射失败

发布于 2024-12-07 10:22:46 字数 974 浏览 0 评论 0原文

我在创建命名共享内存并检查其大小时遇到问题。当我在这样的函数中调用 GetFileSizeEx 函数时，它会失败。关于如何调试这个有什么想法吗？

void test_getsize(const char* lpName, int size){

    HANDLE handle = CreateFileMapping(
                     INVALID_HANDLE_VALUE,    // use paging file
                     NULL,                    // default security
                     PAGE_READWRITE,          // read/write access
                     0,                       // maximum object size (high-order DWORD)
                     size,                // maximum object size (low-order DWORD)
                     lpName);                 // name of mapping object

    if (handle== NULL || handle== INVALID_HANDLE_VALUE){
        last_error = get_error_from_errorno();
        *error_return =1;
    }


    LARGE_INTEGER new_size;

    err = GetFileSizeEx(handle, &new_size);

    if (err==0){ printf("err ");} else {printf("pass ");}
    printf("size=%lu\n", (unsigned long)new_size.QuadPart);
}

原文

Im having trouble creating a named shared memory and inspecting its size. The function GetFileSizeEx fails when I call it in a function like this. Any ideas on how to debug this?

void test_getsize(const char* lpName, int size){

    HANDLE handle = CreateFileMapping(
                     INVALID_HANDLE_VALUE,    // use paging file
                     NULL,                    // default security
                     PAGE_READWRITE,          // read/write access
                     0,                       // maximum object size (high-order DWORD)
                     size,                // maximum object size (low-order DWORD)
                     lpName);                 // name of mapping object

    if (handle== NULL || handle== INVALID_HANDLE_VALUE){
        last_error = get_error_from_errorno();
        *error_return =1;
    }


    LARGE_INTEGER new_size;

    err = GetFileSizeEx(handle, &new_size);

    if (err==0){ printf("err ");} else {printf("pass ");}
    printf("size=%lu\n", (unsigned long)new_size.QuadPart);
}

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回忆追雨的时光 2024-12-14 10:22:46

您传递给 GetFileSizeEx 的句柄必须是文件的句柄。您将一个文件句柄传递给它映射，这是完全不同的事情，所以它不起作用。

由于显然您需要文件映射的大小（称为节对象），并且我认为 Win32 API 不提供此功能，因此您需要使用名为 NtQuerySection。这是它如何工作的一个想法（我还没有尝试过）：

typedef enum _SECTION_INFORMATION_CLASS
{
    SectionBasicInformation,
    SectionImageInformation
} SECTION_INFORMATION_CLASS;

typedef struct _SECTION_BASIC_INFORMATION {
  PVOID         Base;
  ULONG         Attributes;
  LARGE_INTEGER Size;
} SECTION_BASIC_INFORMATION;

typedef DWORD (WINAPI* NTQUERYSECTION)
    (HANDLE, SECTION_INFORMATION_CLASS, PVOID, ULONG, PULONG);
NTQUERYSECTION NtQuerySection =
    (NTQUERYSECTION)GetProcAddress(LoadLibrary("ntdll.dll"), "NtQuerySection");

SECTION_BASIC_INFORMATION SectionInfo = { 0 };
NTSTATUS = NtQuerySection(handle, SectionBasicInformation, &SectionInfo,
    sizeof(SectionInfo), 0);

The handle you pass to GetFileSizeEx must be a handle to a file. You are passing it a handle to a file mapping, which is a completely different thing, so it won't work.

Since apparently you want the size of the file mapping (called a section object), and I don't think the Win32 API provides this feature, you would need to use the native Windows API called NtQuerySection. Here's an idea of how it might work (I haven't tried it):

typedef enum _SECTION_INFORMATION_CLASS
{
    SectionBasicInformation,
    SectionImageInformation
} SECTION_INFORMATION_CLASS;

typedef struct _SECTION_BASIC_INFORMATION {
  PVOID         Base;
  ULONG         Attributes;
  LARGE_INTEGER Size;
} SECTION_BASIC_INFORMATION;

typedef DWORD (WINAPI* NTQUERYSECTION)
    (HANDLE, SECTION_INFORMATION_CLASS, PVOID, ULONG, PULONG);
NTQUERYSECTION NtQuerySection =
    (NTQUERYSECTION)GetProcAddress(LoadLibrary("ntdll.dll"), "NtQuerySection");

SECTION_BASIC_INFORMATION SectionInfo = { 0 };
NTSTATUS = NtQuerySection(handle, SectionBasicInformation, &SectionInfo,
    sizeof(SectionInfo), 0);

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