如何通过 C# 将 IStream 存储到文件？

发布于 2024-08-07 19:21:57 字数 782 浏览 8 评论 0原文

我正在使用返回 IStream 对象 (System.Runtime.InteropServices.ComTypes.IStream) 的第 3 方组件。我需要获取该 IStream 中的数据并将其写入文件。我已经成功地完成了这一任务，但我对代码并不满意。

“strm”是我的 IStream，这是我的测试代码...

// access the structure containing statistical info about the stream
System.Runtime.InteropServices.ComTypes.STATSTG stat;
strm.Stat(out stat, 0);
System.IntPtr myPtr = (IntPtr)0;

// get the "cbSize" member from the stat structure
// this is the size (in bytes) of our stream.
int strmSize = (int)stat.cbSize; // *** DANGEROUS *** (long to int cast)
byte[] strmInfo = new byte[strmSize];
strm.Read(strmInfo, strmSize, myPtr);

string outFile = @"c:\test.db3";
File.WriteAllBytes(outFile, strmInfo);

至少，我不喜欢上面评论的 long 到 int 转换，但我想知道是否没有更好的方法来获取原始流长度以上？我对 C# 有点陌生，所以感谢您的指点。

原文

I'm working with a 3rd party component that returns an IStream object (System.Runtime.InteropServices.ComTypes.IStream). I need to take the data in that IStream and write it to a file. I've managed to get that done, but I'm not really happy with the code.

With "strm" being my IStream, here's my test code...

// access the structure containing statistical info about the stream
System.Runtime.InteropServices.ComTypes.STATSTG stat;
strm.Stat(out stat, 0);
System.IntPtr myPtr = (IntPtr)0;

// get the "cbSize" member from the stat structure
// this is the size (in bytes) of our stream.
int strmSize = (int)stat.cbSize; // *** DANGEROUS *** (long to int cast)
byte[] strmInfo = new byte[strmSize];
strm.Read(strmInfo, strmSize, myPtr);

string outFile = @"c:\test.db3";
File.WriteAllBytes(outFile, strmInfo);

At the very least, I don't like the long to int cast as commented above, but I wonder if there's not a better way to get the original stream length than the above? I'm somewhat new to C#, so thanks for any pointers.

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剩余の解释 2024-08-14 19:21:57

您不需要执行该转换，因为您可以从 IStream 源中分块读取数据。

// ...
System.IntPtr myPtr = (IntPtr)-1;
using (FileStream fs = new FileStream(@"c:\test.db3", FileMode.OpenOrCreate))
{
    byte[] buffer = new byte[8192];
    while (myPtr.ToInt32() > 0)
    {
        strm.Read(buffer, buffer.Length, myPtr);
        fs.Write(buffer, 0, myPtr.ToInt32());
    }
}

这种方式（如果有效）的内存效率更高，因为它只使用一个小内存块在流之间传输数据。

You don't need to do that cast, as you can read data from IStream source in chunks.

// ...
System.IntPtr myPtr = (IntPtr)-1;
using (FileStream fs = new FileStream(@"c:\test.db3", FileMode.OpenOrCreate))
{
    byte[] buffer = new byte[8192];
    while (myPtr.ToInt32() > 0)
    {
        strm.Read(buffer, buffer.Length, myPtr);
        fs.Write(buffer, 0, myPtr.ToInt32());
    }
}

This way (if works) is more memory efficient, as it just uses a small memory block to transfer data between that streams.

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