对于Reader比较麻烦需要记住以下：
When Read encounters an error or end-of-file condition after successfully reading n > 0 bytes, it returns the number of bytes read. It may return the (non-nil) error from the same call or return the error (and n == 0) from a subsequent call
对于Write比较简单需要记住一下：
Write writes len(p) bytes from p to the underlying data stream. It returns the number of bytes written from p (0 <= n <= len(p)) and any error encountered that caused the write to stop early. Write must return a non-nil error if it returns n < len(p). Write must not modify the slice data, even temporarily.
对于ByteReader：就是一个字节一个字节的读
buio是对io的上层封装，他处理了一些常规错误情况等，另外读取支持读取到遇到某个字节为止，等等，还有一些其他很常用的功能。
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