我可以使用C#序列化以自定义格式读取二进制文件吗? [英] Can I use C# Serialization to read a binary file in custom format?

问题描述

我有一个自定义二进制文件，我想将其读入C#程序.

I have a custom binary file which I want to read into my C# program.

有几种不同的格式，其中一些是MSB在先，某些是LSB在前，还有一些变量的顺序不同.

There are several different formats, some MSB first, some LSB first and some with the variables in different orders.

目前，我有一个可以读取正确数量的字节的类，一次读取一个.

Currently, I have a class which reads the right number of bytes, one at a time.

这非常慢，因此我希望尽我所能提高性能.

It is very slow and so I am looking to improve performance any way I can.

序列化性能可能会更好吗?如果是这样，我描述过的场景是否有可能?是否可以针对大/小尾数格式自定义BinaryFormatter?

Is serialization likely to perform better? If so, is this possible with the scenario I have decsribed? Is it possible to customise the BinaryFormatter for big/little-endian format?

谢谢.

推荐答案

使用BinaryFormatter无法做到这一点-它将期望对象周围有其他元数据/填充.您必须手动从Stream或类似地通过二进制读取器读取.

You can't do that with BinaryFormatter - it will expect additional meta-data/padding around object. You would have to read manually either from a Stream or similarly via a binary reader.

已经完成了一些非常相似的代码，我将编写自己的读取器，该读取器位于流的顶部，并具有以下方法:ReadInt32LittleEndian，ReadInt32BigEndian(例如您需要的所有内容)-并使用shift(<</>>)组合字节.但是重要我将使用后备缓冲区来减少对底层流的调用量(即使使用缓冲区，这也可能会慢得令人无法接受).

Having done some very similar code, I would write my own reader that sits on top of a stream, with methods like: ReadInt32LittleEndian, ReadInt32BigEndian (etc for everything you need) - and use shift (<< / >>) to assemble the bytes. But importantly I would use a backing buffer to reduce the amount of calls to the underlying stream (even with a buffer, this can be unacceptably slow).

让我介绍一下protobuf-net上执行此操作的一些代码...特别是

Let me refer you to some code from protobuf-net that does this... in particular ProtoReader, taking an example:

    /// <summary>
    /// Reads an unsigned 32-bit integer from the stream; supported wire-types: Variant, Fixed32, Fixed64
    /// </summary>
    public uint ReadUInt32()
    {
        switch (wireType)
        {
            case WireType.Variant:
                return ReadUInt32Variant(false);
            case WireType.Fixed32:
                if (available < 4) Ensure(4, true);
                position += 4;
                available -= 4;
                return ((uint)ioBuffer[ioIndex++])
                    | (((uint)ioBuffer[ioIndex++]) << 8)
                    | (((uint)ioBuffer[ioIndex++]) << 16)
                    | (((uint)ioBuffer[ioIndex++]) << 24);
            case WireType.Fixed64:
                ulong val = ReadUInt64();
                checked { return (uint)val; }
            default:
                throw CreateException();
        }
    }

(这里wireType 广泛用作字节序等的指示符，但这并不重要)

(here wireType broadly acts as an indicater of endianness etc, but that isn't important)

查看Fixed32实现:

• Ensure确保后备缓冲区中至少还有4个字节(如果需要，可获取更多字节)
• 我们增加一些计数器，以便我们可以跟踪逻辑缓冲区中的位置
• 我们从缓冲区读取数据

• The Ensure makes sure that we have at least 4 more bytes in our backing buffer (fetching more if we desire)
• we increment some counters so we can track our position in the logical buffer
• we read the data from the buffer

如果您有格式的阅读器，反序列化应该容易得多.

One you have a reader for your format, deserialization should be much easier.

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