c# - 提高 BinaryReader 的性能

Question

我目前正在编写一个缓存 BaseStream.Position 和 BaseStream.Length 属性的 BinaryReader。这是我目前所拥有的:

public class FastBinaryReader
{
    BinaryReader reader;

    public long Length { get; private set; }
    public long Position { get; private set; }

    public FastBinaryReader(Stream stream)
    {
        reader = new BinaryReader(stream);
        Length = stream.Length;
        Position = 0;
    }

    public void Seek(long newPosition)
    {
        reader.BaseStream.Position = newPosition;
        Position = newPosition;
    }

    public byte[] ReadBytes(int count)
    {
        if (Position + count >= Length)
            Position = Length;
        else
            Position += count;

        return reader.ReadBytes(count);
    }

    public void Close()
    {
        reader.Close();
    }
}

我不想提供 Length 和 Position 属性，而是想创建一个 BaseStream 属性来公开我的 Position 和 Length 属性为 FastBinaryReader.BaseStream.Position 和 FastBinaryReader.BaseStream.Length，这样我现有的代码将保持兼容使用原始的 BinaryReader 类。

我该怎么做？

Answer 1

这是最终实现，如果有人感兴趣的话。将其作为 Stream 对象传递给 BinaryReader，而不是通常的 FileStream 对象，我的机器速度提高了大约 45%，读取 1000 字节 block 时。

请注意，Length 参数仅在读取 时准确，因为 Length 是在开始时读取的并且不会更改。如果您正在编写，它不会随着基础流的长度变化而更新。

public class FastFileStream : FileStream
{
    private long _position;
    private long _length;

    public FastFileStream(string path, FileMode fileMode) : base(path, fileMode)
    {
        _position = base.Position;
        _length = base.Length;
    }

    public override long Length
    {
        get { return _length; }
    }

    public override long Position
    {
        get { return _position; }
        set
        {
            base.Position = value;
            _position = value;
        }
    }

    public override long Seek(long offset, SeekOrigin seekOrigin)
    {
        switch (seekOrigin)
        {
            case SeekOrigin.Begin:
                _position = offset;
                break;
            case SeekOrigin.Current:
                _position += offset;
                break;
            case SeekOrigin.End:
                _position = Length + offset;
                break;
        }
        return base.Seek(offset, seekOrigin);
    }

    public override int Read(byte[] array, int offset, int count)
    {
        _position += count;
        return base.Read(array, offset, count);
    }

    public override int ReadByte()
    {
        _position += 1;
        return base.ReadByte();
    }
}