Method Slice

nocopy_linkbuffer.go:376–425

Slice returns a new LinkBuffer, which is a zero-copy slice of this LinkBuffer, and only holds the ability of Reader. Slice will automatically execute a Release.

(n int)

//
// Slice will automatically execute a Release.
func (b *UnsafeLinkBuffer) Slice(n int) (r Reader, err error) {
	if n <= 0 {
		return NewLinkBuffer(0), nil
	}
	// check whether enough or not.
	if b.Len() < n {
		return r, fmt.Errorf("link buffer readv[%d] not enough", n)
	}
	b.recalLen(-n) // re-cal length

	// just use for range
	p := new(LinkBuffer)
	p.length = int64(n)

	defer func() {
		// set to read-only
		p.flush = p.flush.next
		p.write = p.flush
	}()

	// single node
	if b.isSingleNode(n) {
		b.read.setFlag(flagReadExposed)
		node := b.read.Refer(n)
		p.head, p.read, p.flush = node, node, node
		return p, nil
	}
	// multiple nodes
	l := b.read.Len()
	b.read.setFlag(flagReadExposed)
	node := b.read.Refer(l)
	b.read = b.read.next

	p.head, p.read, p.flush = node, node, node
	for ack := n - l; ack > 0; ack = ack - l {
		l = b.read.Len()
		if l >= ack {
			b.read.setFlag(flagReadExposed)
			p.flush.next = b.read.Refer(ack)
			p.flush = p.flush.next
			break
		} else if l > 0 {
			b.read.setFlag(flagReadExposed)
			p.flush.next = b.read.Refer(l)
			p.flush = p.flush.next
		}
		b.read = b.read.next
	}
	return p, b.Release()
}

// ------------------------------------------ implement zero-copy writer ------------------------------------------