Method Read

internal/transport/readyreader/ready_reader.go:199–243

Read reads data into p. It returns the number of bytes read into p. The bytes are taken from at most one Read on the underlying [ReadyReader], hence n may be less than len(p). If the underlying [ReadyReader] can return a non-zero count with io.EOF, then this Read method can do so as well; see the [i

(p []byte)

// a non-zero count with io.EOF, then this Read method can do so as well; see
// the [io.Reader] docs.
func (b *bufReadyReader) Read(p []byte) (n int, err error) {
	n = len(p)
	if n == 0 {
		if b.buffered() > 0 {
			return 0, nil
		}
		return 0, b.readErr()
	}
	if b.r == b.w {
		if b.err != nil {
			return 0, b.readErr()
		}
		if len(p) >= b.bufSize {
			// Large read, empty buffer.
			// Read directly into p to avoid copy.
			b.constPool.buffer = p
			_, n, b.err = b.rd.ReadOnReady(len(p), &b.constPool)
			return n, b.readErr()
		}
		// One read.
		b.r = 0
		b.w = 0
		b.buf, n, b.err = b.rd.ReadOnReady(b.bufSize, b.pool)
		if n == 0 {
			if b.buf != nil {
				b.pool.Put(b.buf)
				b.buf = nil
			}
			return 0, b.readErr()
		}
		b.w += n
	}

	// copy as much as we can
	// b.buf must be non-nil since b.r != b.w.
	buf := *b.buf
	n = copy(p, buf[b.r:b.w])
	b.r += n
	if b.r == b.w {
		// Consumed entire buffer, release it.
		b.pool.Put(b.buf)
		b.buf = nil
	}
	return n, nil
}

type constBufferPool struct {
	buffer []byte