io.ReadAtLeast - expect EOF return when buffer is empty in Read function

[ChinW]

Please fill out the following system information before opening an issue:

• OS (e.g. Ubuntu 18.04): macOS 12.5
• Go version (e.g. Go 1.13): Go 1.18
• gnet version (e.g. v1.0.0): v2.1.1

What is your question about gnet?
Please describe your question meticulously.

hi Andy, thanks for your work. I met below issue in io.ReadAtLeast function, wonder if my thought is correct?

1. io.ReadAtLeast

 # from go/src/io/io.go
func ReadAtLeast(r Reader, buf []byte, min int) (n int, err error) {
	if len(buf) < min {
		return 0, ErrShortBuffer
	}
	for n < min && err == nil {
		var nn int
		nn, err = r.Read(buf[n:]) // !! here, if buf is empty, we expect err should be EOF
		n += nn
	}
	if n >= min {
		err = nil
	} else if n > 0 && err == EOF {
		err = ErrUnexpectedEOF
	}
	return
}

2. gnet/connection.go

func (c *conn) Read(p []byte) (n int, err error) {
	if c.inboundBuffer.IsEmpty() {
		n = copy(p, c.buffer)
		c.buffer = c.buffer[n:]
		return n, nil // should this be io.EOF? 
	}
	n, _ = c.inboundBuffer.Read(p)
	if n == len(p) {
		return
	}
	m := copy(p[n:], c.buffer)
	n += m
	c.buffer = c.buffer[m:]
	return
}

Comparing to bytes/buffer.go, it returns EOF in a case where input bytes also empty

func (b *Buffer) Read(p []byte) (n int, err error) {
	b.lastRead = opInvalid
	if b.empty() {
		// Buffer is empty, reset to recover space.
		b.Reset()
		if len(p) == 0 {
			return 0, nil
		} 
		return 0, io.EOF // here
	}
	n = copy(p, b.buf[b.off:])
	b.off += n
	if n > 0 {
		b.lastRead = opRead
	}
	return n, nil
}

[panjf2000]

Sorry for the delay, I've fixed this issue and c.Read([]byte) now is behaving like bytes.Buffer.Read([]byte), please get the latest code and try it on.