435c0d9fc8
This PR switches the Nomad repository from using govendor to Go modules for managing dependencies. Aspects of the Nomad workflow remain pretty much the same. The usual Makefile targets should continue to work as they always did. The API submodule simply defers to the parent Nomad version on the repository, keeping the semantics of API versioning that currently exists.
98 lines
2.1 KiB
Go
98 lines
2.1 KiB
Go
// Copyright 2012 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package ssh
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import (
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"io"
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"sync"
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)
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// buffer provides a linked list buffer for data exchange
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// between producer and consumer. Theoretically the buffer is
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// of unlimited capacity as it does no allocation of its own.
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type buffer struct {
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// protects concurrent access to head, tail and closed
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*sync.Cond
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head *element // the buffer that will be read first
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tail *element // the buffer that will be read last
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closed bool
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}
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// An element represents a single link in a linked list.
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type element struct {
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buf []byte
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next *element
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}
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// newBuffer returns an empty buffer that is not closed.
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func newBuffer() *buffer {
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e := new(element)
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b := &buffer{
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Cond: newCond(),
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head: e,
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tail: e,
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}
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return b
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}
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// write makes buf available for Read to receive.
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// buf must not be modified after the call to write.
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func (b *buffer) write(buf []byte) {
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b.Cond.L.Lock()
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e := &element{buf: buf}
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b.tail.next = e
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b.tail = e
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b.Cond.Signal()
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b.Cond.L.Unlock()
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}
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// eof closes the buffer. Reads from the buffer once all
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// the data has been consumed will receive io.EOF.
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func (b *buffer) eof() {
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b.Cond.L.Lock()
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b.closed = true
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b.Cond.Signal()
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b.Cond.L.Unlock()
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}
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// Read reads data from the internal buffer in buf. Reads will block
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// if no data is available, or until the buffer is closed.
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func (b *buffer) Read(buf []byte) (n int, err error) {
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b.Cond.L.Lock()
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defer b.Cond.L.Unlock()
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for len(buf) > 0 {
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// if there is data in b.head, copy it
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if len(b.head.buf) > 0 {
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r := copy(buf, b.head.buf)
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buf, b.head.buf = buf[r:], b.head.buf[r:]
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n += r
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continue
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}
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// if there is a next buffer, make it the head
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if len(b.head.buf) == 0 && b.head != b.tail {
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b.head = b.head.next
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continue
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}
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// if at least one byte has been copied, return
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if n > 0 {
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break
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}
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// if nothing was read, and there is nothing outstanding
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// check to see if the buffer is closed.
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if b.closed {
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err = io.EOF
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break
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}
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// out of buffers, wait for producer
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b.Cond.Wait()
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}
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return
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}
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