1 files changed, 173 insertions, 0 deletions
diff --git a/src/vendor/golang.org/x/net/quic/pipe.go b/src/vendor/golang.org/x/net/quic/pipe.go
new file mode 100644
index 0000000000..2ae651ea3e
--- /dev/null
+++ b/src/vendor/golang.org/x/net/quic/pipe.go
@@ -0,0 +1,173 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package quic
+
+import (
+	"sync"
+)
+
+// A pipe is a byte buffer used in implementing streams.
+//
+// A pipe contains a window of stream data.
+// Random access reads and writes are supported within the window.
+// Writing past the end of the window extends it.
+// Data may be discarded from the start of the pipe, advancing the window.
+type pipe struct {
+	start int64    // stream position of first stored byte
+	end   int64    // stream position just past the last stored byte
+	head  *pipebuf // if non-nil, then head.off + len(head.b) > start
+	tail  *pipebuf // if non-nil, then tail.off + len(tail.b) == end
+}
+
+type pipebuf struct {
+	off  int64 // stream position of b[0]
+	b    []byte
+	next *pipebuf
+}
+
+func (pb *pipebuf) end() int64 {
+	return pb.off + int64(len(pb.b))
+}
+
+var pipebufPool = sync.Pool{
+	New: func() any {
+		return &pipebuf{
+			b: make([]byte, 4096),
+		}
+	},
+}
+
+func newPipebuf() *pipebuf {
+	return pipebufPool.Get().(*pipebuf)
+}
+
+func (b *pipebuf) recycle() {
+	b.off = 0
+	b.next = nil
+	pipebufPool.Put(b)
+}
+
+// writeAt writes len(b) bytes to the pipe at offset off.
+//
+// Writes to offsets before p.start are discarded.
+// Writes to offsets after p.end extend the pipe window.
+func (p *pipe) writeAt(b []byte, off int64) {
+	end := off + int64(len(b))
+	if end > p.end {
+		p.end = end
+	} else if end <= p.start {
+		return
+	}
+
+	if off < p.start {
+		// Discard the portion of b which falls before p.start.
+		trim := p.start - off
+		b = b[trim:]
+		off = p.start
+	}
+
+	if p.head == nil {
+		p.head = newPipebuf()
+		p.head.off = p.start
+		p.tail = p.head
+	}
+	pb := p.head
+	if off >= p.tail.off {
+		// Common case: Writing past the end of the pipe.
+		pb = p.tail
+	}
+	for {
+		pboff := off - pb.off
+		if pboff < int64(len(pb.b)) {
+			n := copy(pb.b[pboff:], b)
+			if n == len(b) {
+				return
+			}
+			off += int64(n)
+			b = b[n:]
+		}
+		if pb.next == nil {
+			pb.next = newPipebuf()
+			pb.next.off = pb.off + int64(len(pb.b))
+			p.tail = pb.next
+		}
+		pb = pb.next
+	}
+}
+
+// copy copies len(b) bytes into b starting from off.
+// The pipe must contain [off, off+len(b)).
+func (p *pipe) copy(off int64, b []byte) {
+	dst := b[:0]
+	p.read(off, len(b), func(c []byte) error {
+		dst = append(dst, c...)
+		return nil
+	})
+}
+
+// read calls f with the data in [off, off+n)
+// The data may be provided sequentially across multiple calls to f.
+// Note that read (unlike an io.Reader) does not consume the read data.
+func (p *pipe) read(off int64, n int, f func([]byte) error) error {
+	if off < p.start {
+		panic("invalid read range")
+	}
+	for pb := p.head; pb != nil && n > 0; pb = pb.next {
+		if off >= pb.end() {
+			continue
+		}
+		b := pb.b[off-pb.off:]
+		if len(b) > n {
+			b = b[:n]
+		}
+		off += int64(len(b))
+		n -= len(b)
+		if err := f(b); err != nil {
+			return err
+		}
+	}
+	if n > 0 {
+		panic("invalid read range")
+	}
+	return nil
+}
+
+// peek returns a reference to up to n bytes of internal data buffer, starting at p.start.
+// The returned slice is valid until the next call to discardBefore.
+// The length of the returned slice will be in the range [0,n].
+func (p *pipe) peek(n int64) []byte {
+	pb := p.head
+	if pb == nil {
+		return nil
+	}
+	b := pb.b[p.start-pb.off:]
+	return b[:min(int64(len(b)), n)]
+}
+
+// availableBuffer returns the available contiguous, allocated buffer space
+// following the pipe window.
+//
+// This is used by the stream write fast path, which makes multiple writes into the pipe buffer
+// without a lock, and then adjusts p.end at a later time with a lock held.
+func (p *pipe) availableBuffer() []byte {
+	if p.tail == nil {
+		return nil
+	}
+	return p.tail.b[p.end-p.tail.off:]
+}
+
+// discardBefore discards all data prior to off.
+func (p *pipe) discardBefore(off int64) {
+	for p.head != nil && p.head.end() < off {
+		head := p.head
+		p.head = p.head.next
+		head.recycle()
+	}
+	if p.head == nil {
+		p.tail = nil
+	}
+	p.start = off
+	p.end = max(p.end, off)
+}