Rietveld Code Review Tool
Help | Bug tracker | Discussion group | Source code | Sign in
(223)

Delta Between Two Patch Sets: ssh/buffer.go

Issue 6207051: code review 6207051: go.crypto/ssh: introduce a circular buffer for chanReader (Closed)
Left Patch Set: diff -r d59e35c8940f https://code.google.com/p/go.crypto Created 11 years, 10 months ago
Right Patch Set: diff -r d59e35c8940f https://code.google.com/p/go.crypto Created 11 years, 10 months ago
Left:
Right:
Use n/p to move between diff chunks; N/P to move between comments. Please Sign in to add in-line comments.
Jump to:
Right: Side by side diff | Download
« no previous file with change/comment | « no previous file | ssh/buffer_test.go » ('j') | no next file with change/comment »
Toggle Intra-line Diffs ('i') | Expand Comments ('e') | Collapse Comments ('c') | Show Comments Hide Comments ('s')
LEFTRIGHT
(no file at all)
1 // Copyright 2012 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4
5 package ssh
6
7 import (
8 "io"
9 "sync"
10 )
11
12 // buffer provides a linked list buffer for data exchange
13 // between producer and consumer. Theoretically the buffer is
14 // of unlimited capacity as it does no allocation of its own.
15 type buffer struct {
16 // protects concurrent access to head, tail and closed
17 *sync.Cond
18
19 head *element // the buffer that will be read first
20 tail *element // the buffer that will be read last
21
22 closed bool
23 }
24
25 // An element represents a single link in a linked list.
26 type element struct {
27 buf []byte
28 next *element
29 }
30
31 // newBuffer returns an empty buffer that is not closed.
32 func newBuffer() *buffer {
33 e := new(element)
34 b := &buffer{
35 Cond: newCond(),
36 head: e,
37 tail: e,
38 }
39 return b
40 }
41
42 // write makes buf available for Read to receive.
43 // buf must not be modified after the call to write.
44 func (b *buffer) write(buf []byte) {
45 b.Cond.L.Lock()
46 defer b.Cond.L.Unlock()
47 e := &element{buf: buf}
48 b.tail.next = e
49 b.tail = e
50 b.Cond.Signal()
51 }
52
53 // eof closes the buffer. Reads from the buffer once all·
54 // the data has been consumed will receive os.EOF.
55 func (b *buffer) eof() error {
56 b.Cond.L.Lock()
57 defer b.Cond.L.Unlock()
58 b.closed = true
59 b.Cond.Signal()
60 return nil
61 }
62
63 // Read reads data from the internal buffer in buf.·
64 // Reads will block if no data is available, or until
65 // the buffer is closed.
66 func (b *buffer) Read(buf []byte) (n int, err error) {
67 b.Cond.L.Lock()
68 defer b.Cond.L.Unlock()
69 for len(buf) > 0 {
70 // if there is data in b.head, copy it
71 if len(b.head.buf) > 0 {
72 r := copy(buf, b.head.buf)
73 buf, b.head.buf = buf[r:], b.head.buf[r:]
74 n += r
75 continue
76 }
77 // if there is a next buffer, make it the head
78 if len(b.head.buf) == 0 && b.head != b.tail {
79 b.head = b.head.next
80 continue
81 }
82 // if at least one byte has been copied, return
83 if n > 0 {
84 break
85 }
86 // if nothing was read, and there is nothing outstanding
87 // check to see if the buffer is closed.
88 if b.closed {
89 err = io.EOF
90 break
91 }
92 // out of buffers, wait for producer
93 b.Cond.Wait()
94 }
95 return
96 }
LEFTRIGHT
« no previous file | ssh/buffer_test.go » ('j') | Toggle Intra-line Diffs ('i') | Expand Comments ('e') | Collapse Comments ('c') | Toggle Comments ('s')

Powered by Google App Engine
RSS Feeds Recent Issues | This issue
This is Rietveld f62528b