c# - 使用自定义 Read() 和 Write() 功能装饰 FileStream

Question

我正在尝试用 CaesarStream 类装饰 Stream 类，它基本上将凯撒密码应用于 Read 和 Write 操作。我已经很容易地覆盖了 Write 方法，但是 Read 让我很头疼。据我了解，我需要调用底层 FileStream 的 Read 方法并以某种方式修改它，但是我如何让它读取值同时添加一个数字每个字节，类似于我在 Write() 方法中所做的？这对我来说更难，因为 Read 的返回值只是读取的字节数，而不是实际读取的项目。

public class CaesarStream : Stream
{
    private int _offset;
    private FileStream _stream;

    public CaesarStream(FileStream stream, int offset)
    {
        _offset = offset;
        _stream = stream;
    }
    public override int Read(byte[] array, int offset, int count)
    {
        //I imagine i need to call 
        //_stream.Read(array, offset, count);
        //and modify the array, but how do i make my stream return it afterwards?
        //I have no access to the underlying private FileStream fields so I'm clueless
    }
    public override void Write(byte[] buffer, int offset, int count)
    {
        byte[] changedBytes = new byte[buffer.Length];

        int index = 0;
        foreach (byte b in buffer)
        {
            changedBytes[index] = (byte) (b + (byte) _offset);
            index++;
        }

        _stream.Write(changedBytes, offset, count);
    }
}

PS 我知道我还应该检查读/写的字节数并继续读/写直到完成，但我还没有做到这一点。我想先完成阅读部分。

Answer 1

根据 Eugene 的建议，我设法让它按预期工作，这里是代码以防有人想看它:

public class CaesarStream : Stream
{
    private int _offset;
    private FileStream _stream;


    public CaesarStream(FileStream stream, int offset)
    {
        _offset = offset;
        _stream = stream;
    }

    public override int Read(byte[] array, int offset, int count)
    {
        int retValue = _stream.Read(array, offset, count);

        for (int a = 0; a < array.Length; a++)
        {
            array[a] = (byte) (array[a] - (byte) _offset);
        }

        return retValue;
    }

    public override void Write(byte[] buffer, int offset, int count)
    {
        byte[] changedBytes = new byte[buffer.Length];

        int index = 0;
        foreach (byte b in buffer)
        {
            changedBytes[index] = (byte) (b + (byte) _offset);
            index++;
        }

        _stream.Write(changedBytes, offset, count);
    }
}