问题描述

我想比较两个二进制文件.其中一个已经存储在服务器上，并在我最初存储时在数据库中预先计算了 CRC32.

I want to compare two binary files. One of them is already stored on the server with a pre-calculated CRC32 in the database from when I stored it originally.

我知道如果CRC不同，那么文件肯定不同.但是，如果 CRC 相同，我不知道文件是否相同.因此，我正在寻找一种比较两种流的有效方法:一个来自发布的文件，另一个来自文件系统.

I know that if the CRC is different, then the files are definitely different. However, if the CRC is the same, I don't know that the files are. So, I'm looking for a nice efficient way of comparing the two streams: one from the posted file and one from the file system.

我不是流方面的专家，但我很清楚，就内存使用而言，我很容易在这里自爆.

I'm not an expert on streams, but I'm well aware that I could easily shoot myself in the foot here as far as memory usage is concerned.

推荐答案

static bool FileEquals(string fileName1, string fileName2)
{
    // Check the file size and CRC equality here.. if they are equal...    
    using (var file1 = new FileStream(fileName1, FileMode.Open))
        using (var file2 = new FileStream(fileName2, FileMode.Open))
            return FileStreamEquals(file1, file2);
}

static bool FileStreamEquals(Stream stream1, Stream stream2)
{
    const int bufferSize = 2048;
    byte[] buffer1 = new byte[bufferSize]; //buffer size
    byte[] buffer2 = new byte[bufferSize];
    while (true) {
        int count1 = stream1.Read(buffer1, 0, bufferSize);
        int count2 = stream2.Read(buffer2, 0, bufferSize);

        if (count1 != count2)
            return false;

        if (count1 == 0)
            return true;

        // You might replace the following with an efficient "memcmp"
        if (!buffer1.Take(count1).SequenceEqual(buffer2.Take(count2)))
            return false;
    }
}

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