了解 VerQueryValue [英] Understanding VerQueryValue

问题描述

在 MSDN 上，我注意到 VerQueryValue 函数的以下内容:

On MSDN I noticed the following for the VerQueryValue function:

lplpBuffer [输出]
LPVOID
当此方法返回时，包含指向 pBlock 指向的缓冲区中所请求版本信息的指针的地址.lplpBuffer 指向的内存在相关 pBlock 内存被释放时被释放._

lplpBuffer [out]
LPVOID
When this method returns, contains the address of a pointer to the requested version information in the buffer pointed to by pBlock. The memory pointed to by lplpBuffer is freed when the associated pBlock memory is freed._

既然 pBlock 是由调用者分配的，系统如何知道 pBlock 何时被释放?

How does the system know when pBlock is freed since pBlock is allocated by the caller?

我正在使用以下代码:

UINT reqSize = ::GetSystemDirectoryW(nullptr, 1);

std::vector<wchar_t> winDirectory (reqSize, 0);

UINT retVal = ::GetSystemDirectoryW(&winDirectory[0], reqSize);

std::wstring filePath(winDirectory.begin(), winDirectory.end()-1);

filePath.append(L"\\kernel32.dll");

DWORD bufSize = ::GetFileVersionInfoSizeW(
    filePath.c_str(),
    nullptr);

std::vector<BYTE> fileInfo (bufSize, 0);

::GetFileVersionInfoW(
    filePath.c_str(),
    0,
    bufSize,
    &fileInfo[0]);

UINT size = 0;

VS_FIXEDFILEINFO * ptr = nullptr;

BOOL error = ::VerQueryValueW(
    &fileInfo[0],
    L"\\",
    reinterpret_cast<LPVOID*>(&ptr),
    &size);

推荐答案

VerQueryValue 返回一个指向您分配的初始内存块内某处的指针(GetFileVersionInfoSize 返回一个块的大小，该块的大小足以包含整个版本资源+ ansi 到 unicode 转换等所需的任何空间)

VerQueryValue returns a pointer to somewhere inside the initial block of memory that you allocate (GetFileVersionInfoSize returns the size of a block that is large enough to contain the whole version resource + any space required for ansi to unicode conversion etc)

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