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MSDN C# DeflateStream 示例代码问题

发布于 2024-07-14 12:10:11 字数 281 浏览 7 评论 0原文

知道为什么在下面的示例中我们需要添加 100 (buffer.Length + 100) 吗？ buffer.Length 应与解压后的缓冲区长度相同，因此无需再添加 100。 :-)

http://msdn.microsoft.com/en-us/library /bc2dbwea.aspx

提前致谢，乔治

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够运 2024-07-21 12:10:11

我不知道他们为什么这样做，但这通常不是一个很好的例子 - 例如，他们在 Close 上使用显式调用（不在finally块中） >FileStream 而不是使用 using 语句，并且还假设对 Read 的单个调用将读取整个文件。哎呀，即使将整个文件读入缓冲区也是一个坏主意 - 最好一次直接将一个块复制到 DeflateStream 中。

这些事情向我表明，不值得担心该示例中这个特定的奇怪代码（额外的 100 字节）。当然不要将其视为“最佳实践”。

MSDN 的例子通常比这个更好——尽管还有很多其他奇怪的例子。

编辑：重新阅读代码和 CodeMelt 的答案后，它确实需要额外的 100 个字节 - 但这只是因为 ReadAllBytesFromStream 实现得如此糟糕。这是一个更好的实现，它总是要求流填充缓冲区的其余部分：（

public static int ReadAllBytesFromStream(Stream stream, byte[] buffer) 
{
    int offset = 0;
    int bytesRead;
    while ((bytesRead = stream.Read(buffer, offset, 
                                    buffer.Length-offset)) > 0) 
    {
        offset += bytesRead;
    }
    return offset;
}

请注意，不需要 offset 和 totalCount 因为它们始终具有相同的值价值。）

I don't know why they're doing that, but it's not a great example in general - for instance, they're using explicit calls to Close (not in a finally block) on the FileStream instead of using a using statement, and also assuming that a single call to Read will read the whole of a file. Heck, even reading the whole file into a buffer is a bad idea - it would be better to copy a chunk at a time straight into the DeflateStream.

These things suggest to me that it's not worth worrying about this specific odd bit of code (the extra 100 bytes) within that example. Certainly don't regard it as "best practice".

MSDN examples are usually better than this - although there are plenty of other odd ones.

EDIT: Having reread the code and CodeMelt's answer, it does indeed need the extra 100 bytes - but only because ReadAllBytesFromStream is implemented so badly. Here's a better implementation, which always asks the stream to fill the rest of the buffer:

public static int ReadAllBytesFromStream(Stream stream, byte[] buffer) 
{
    int offset = 0;
    int bytesRead;
    while ((bytesRead = stream.Read(buffer, offset, 
                                    buffer.Length-offset)) > 0) 
    {
        offset += bytesRead;
    }
    return offset;
}

(Note that there was no need for both offset and totalCount as they always had the same value.)

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神仙妹妹 2024-07-21 12:10:11

它可以防止 Stream.Read(buffer, offset, 100) 在以下方法中超出其长度，因为流会一直读取，直到什么也读不到。

public static int ReadAllBytesFromStream(Stream stream, byte[] buffer) 
{
// Use this method is used to read all bytes from a stream.
int offset = 0;
int totalCount = 0;
    while (true) 
    {
    // even it reads to the end, but it will still read the next
    // 100 bytes to see if anything has been read.
    int bytesRead = stream.Read(buffer, offset, 100); 
        if ( bytesRead == 0) 
        {
        break; 
        }
offset += bytesRead;
totalCount += bytesRead; 
    }
return totalCount;
}

It prevents stream.Read(buffer, offset, 100) from going over its length within the following method because the stream keeps reading until it reads nothing.

public static int ReadAllBytesFromStream(Stream stream, byte[] buffer) 
{
// Use this method is used to read all bytes from a stream.
int offset = 0;
int totalCount = 0;
    while (true) 
    {
    // even it reads to the end, but it will still read the next
    // 100 bytes to see if anything has been read.
    int bytesRead = stream.Read(buffer, offset, 100); 
        if ( bytesRead == 0) 
        {
        break; 
        }
offset += bytesRead;
totalCount += bytesRead; 
    }
return totalCount;
}

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~没有更多了~