LPSTREAM 将整个 Stream 内容读入 unsigned char* 数组

Question

我在复合存储中有一个流。我想将它的数据读入一个字节数组。我对我需要在 lpSrc->Read() 的第二个参数中放入什么感到困惑。我想将整个文件读入我的 unsigned char* (byte*) 数组：

        unsigned char* rawData;
        LPSTREAM lpSrc = NULL;
        HRESULT hrRet = STG_E_INVALIDPARAMETER;

        TRY
        { 
            USES_CONVERSION;
            HRESULT hrSrc = pStg->GetStg()->OpenStream(CT2COLE(szStream),
            NULL,
            STGM_READ | STGM_SHARE_EXCLUSIVE,
            0,
            &lpSrc);

            if (hrSrc != NOERROR)
            {
                hrRet = hrSrc;
            }
            else
            {               
                ULONG ul;
                hrRet = lpSrc->Read(rawData, /*???*/, &ul);             
            }

        }
        CATCH_ALL(e)
        {
            hrRet = STG_E_UNKNOWN;
        }
        END_CATCH_ALL

我已经尝试过很多读取流的变体，所以我不完全确定这是我首先应该做的方式。我该如何解决这个问题？

Answer 1

I'm confused about what I need to put in the second parameter of lpSrc->Read().

答案在文档中：

ISequentialStream::Read method

pv [out]

A pointer to the buffer which the stream data is read into.

cb [in]

The number of bytes of data to read from the stream object.

pcbRead [out]

A pointer to a ULONG variable that receives the actual number of bytes read from the stream object.

您必须指定要从流中读取到缓冲区中的字节数。

I want to read the ENTIRE file into my unsigned char* (byte*) array:

这意味着您必须首先知道流中有多少字节可用。你可以从 IStream::Stat() 方法中得到它。然后，您必须先将 rawData 缓冲区分配到该大小，然后才能将数据读入缓冲区。

尝试这样的事情：

#ifndef SIZE_MAX
#define SIZE_MAX ((size_t)(-1))
#endif

unsigned char* rawData;
LPSTREAM lpSrc = NULL;
HRESULT hrRet = STG_E_INVALIDPARAMETER;

TRY
{ 
    USES_CONVERSION;
    hrRet = pStg->GetStg()->OpenStream(
        CT2COLE(szStream),
        NULL,
        STGM_READ | STGM_SHARE_EXCLUSIVE,
        0,
        &lpSrc);

    if (hrRet == S_OK)
    {
        STATSTG stat;
        hrRet = lpSrc->Stat(&stat, STATFLAG_NONAME);
        if (hrRet == S_OK)
        {
            if (stat.cbSize.QuadPart > SIZE_MAX)
            {
                hrRet = HRESULT_FROM_WIN32(ERROR_FILE_TOO_LARGE);
            }
            else
            {
                size_t size = (size_t) stat.cbSize.QuadPart;

                rawData = malloc(size);
                if (!rawData)
                {
                    hrRet = E_OUTOFMEMORY;
                }
                else
                {
                    unsigned char *ptr = rawData;
                    size_t sizeLeft = size;

                    while (sizeLeft != 0)
                    {
                        ULONG ul;
                        hrRet = lpSrc->Read(ptr, (sizeLeft >= MAXDWORD) ? MAXDWORD : (DWORD) sizeLeft, &ul);             
                        if (FAILED(hrRet) || (ul == 0)) break;
                        ptr += ul;
                        sizeLeft -= ul;
                    }

                    if (SUCCEEDED(hrRet))
                    {
                        if (sizeLeft != 0) size -= sizeLeft;
                        // use rawData up to size number of bytes as needed...
                    }

                    free(rawData);
                }
            }
        }

        lpSrc->Release();
    }
}
CATCH_ALL(e)
{
    hrRet = E_UNEXPECTED;
}
END_CATCH_ALL

LPSTREAM 将整个 Stream 内容读入 unsigned char* 数组

LPSTREAM Read entire Stream contents into unsigned char* array

c

winapi

ole

file

stream