1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
|
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<meta http-equiv="Content-Language" content="en" />
<title>skalibs: the allreadwrite library interface</title>
<meta name="Description" content="skalibs: the allreadwrite library interface" />
<meta name="Keywords" content="skalibs c unix allreadwrite library libstddjb" />
<!-- <link rel="stylesheet" type="text/css" href="//skarnet.org/default.css" /> -->
</head>
<body>
<p>
<a href="index.html">libstddjb</a><br />
<a href="../libskarnet.html">libskarnet</a><br />
<a href="../index.html">skalibs</a><br />
<a href="//skarnet.org/software/">Software</a><br />
<a href="//skarnet.org/">skarnet.org</a>
</p>
<h1> The <tt>allreadwrite</tt> library interface </h1>
<p>
The following functions are declared in the <tt>skalibs/allreadwrite.h</tt> header,
and implemented in the <tt>libskarnet.a</tt> or <tt>libskarnet.so</tt> library.
</p>
<h2> General information </h2>
<p>
<tt>allreadwrite</tt> is a set of IO function helpers. It's the
basis for safe reading and writing, either in blocking or in
non-blocking mode. The <a href="buffer.html">buffer</a> interface
relies heavily on <tt>allreadwrite</tt>.
</p>
<p>
Unless the IO you need is very simple, you generally should not
be using the <tt>allreadwrite</tt> functions directly; you should
use higher-level APIs such as <a href="buffer.html">buffer</a> and
<a href="bufalloc.html">bufalloc</a>.
</p>
<h2> Function types </h2>
<p>
<code> typedef ssize_t iofunc_t (int fd, char *buf, size_t len) </code> <br />
This is the simplified type of IO functions such as
<a href="http://www.opengroup.org/onlinepubs/9699919799/functions/read.html">read()</a>
and
<a href="http://www.opengroup.org/onlinepubs/9699919799/functions/write.html">write()</a>.
</p>
<p>
<code> typedef size_t alliofunc_t (int fd, char *buf, size_t len) </code> <br />
This is the type of an IO operation that expects <em>all</em> of its
<em>len</em> bytes to be sent or received, and that will loop around a
lower-level IO function until either <em>len</em> bytes have been
transmitted or an error has occurred. The return value is the actual
number of transmitted bytes; if this value is lesser than <em>len</em>,
it means that an error has occurred and <tt>errno</tt> is set.
</p>
<h2> Functions </h2>
<p>
<code> ssize_t sanitize_read (ssize_t r) </code> <br />
Reading functions such as <tt>read()</tt> and <tt>fd_read</tt> return
a positive number when they succeed, -1 when they fail, and 0 when they
read an EOF. No data available on the descriptor when reading in
non-blocking mode is treated as a failure: -1 EWOULDBLOCK. But sometimes
(namely, in asynchronous IO loops) it's preferrable to handle EOF as an
exception condition and EWOULDBLOCK as a normal condition.
<tt>sanitize_read()</tt>, when applied to the result of a basic reading
function, returns 0 if <em>r</em> is -1 and errno is EWOULDBLOCK (or
EAGAIN). If <em>r</em> is zero, it returns -1 EPIPE. Else it returns <em>r</em>.
</p>
<p>
(No system reading function can ever set errno to EPIPE, and the
semantics are appropriate, so EPIPE is a good candidate to signal EOF
on reading.)
</p>
<p>
<code> size_t allreadwrite (iofunc_t *f, int fd, char *s, size_t len) </code> <br />
*<em>f</em> must be a basic reading or writing function such as
<tt>fd_read</tt> or <tt>fd_write</tt>. <tt>allreadwrite()</tt> performs
*<em>f</em> on <em>fd</em>, <em>s</em> and <em>len</em> until <em>len</em>
bytes have been read or written, or until an error occurs. It returns the
total number of handled bytes, and sets errno if this number is not
<em>len</em>. <tt>allreadwrite</tt> may block if <em>fd</em> is in
blocking mode; if <em>fd</em> is in non-blocking mode, it might
set errno to EWOULDBLOCK or EAGAIN.
</p>
<p>
<code> ssize_t fd_read (int fd, char *s, size_t len) </code> <br />
<a href="safewrappers.html">Safe wrapper</a> around the
<a href="http://www.opengroup.org/onlinepubs/9699919799/functions/read.html">read()</a>
function.
</p>
<p>
<code> ssize_t fd_write (int fd, char const *s, size_t len) </code> <br />
<a href="safewrappers.html">Safe wrapper</a> around the
<a href="http://www.opengroup.org/onlinepubs/9699919799/functions/write.html">write()</a>
function.
</p>
<p>
<code> ssize_t fd_recv (int fd, char *s, size_t len, unsigned int flags) </code> <br />
<a href="safewrappers.html">Safe wrapper</a> around the
<a href="http://www.opengroup.org/onlinepubs/9699919799/functions/recv.html">recv()</a>
function.
</p>
<p>
<code> ssize_t fd_send (int fd, char const *s, size_t len, unsigned int flags) </code> <br />
<a href="safewrappers.html">Safe wrapper</a> around the
<a href="http://www.opengroup.org/onlinepubs/9699919799/functions/send.html">send()</a>
function.
</p>
<p>
<code> size_t allread (int fd, char *s, size_t len) </code> <br />
Equivalent to <code> allreadwrite(&fd_read, fd, s, len) </code>: attempts
to read <em>len</em> bytes from <em>fd</em> into <em>s</em>, looping around
<tt>fd_read()</tt> if necessary, until either <em>len</em> bytes are read or
an error occurs. EOF is reported as EPIPE.
</p>
<p>
<code> size_t allwrite (int fd, char const *s, size_t len) </code> <br />
Equivalent to <code> allreadwrite((iofunc_t *)&fd_write, fd, s, len) </code>:
attempts to write <em>len</em> bytes from <em>s</em> to <em>fd</em>, looping
around <tt>fd_write()</tt> if necessary, until either <em>len</em> bytes are
written or an error occurs.
</p>
</body>
</html>
|
