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
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
|
.\" Automatically generated by Pod::Man version 1.15
.\" Wed Feb 19 16:42:44 2003
.\"
.\" Standard preamble:
.\" ======================================================================
.de Sh \" Subsection heading
.br
.if t .Sp
.ne 5
.PP
\fB\\$1\fR
.PP
..
.de Sp \" Vertical space (when we can't use .PP)
.if t .sp .5v
.if n .sp
..
.de Ip \" List item
.br
.ie \\n(.$>=3 .ne \\$3
.el .ne 3
.IP "\\$1" \\$2
..
.de Vb \" Begin verbatim text
.ft CW
.nf
.ne \\$1
..
.de Ve \" End verbatim text
.ft R
.fi
..
.\" Set up some character translations and predefined strings. \*(-- will
.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
.\" double quote, and \*(R" will give a right double quote. | will give a
.\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used
.\" to do unbreakable dashes and therefore won't be available. \*(C` and
.\" \*(C' expand to `' in nroff, nothing in troff, for use with C<>
.tr \(*W-|\(bv\*(Tr
.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
.ie n \{\
. ds -- \(*W-
. ds PI pi
. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
. if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
. ds L" ""
. ds R" ""
. ds C` ""
. ds C' ""
'br\}
.el\{\
. ds -- \|\(em\|
. ds PI \(*p
. ds L" ``
. ds R" ''
'br\}
.\"
.\" If the F register is turned on, we'll generate index entries on stderr
.\" for titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and
.\" index entries marked with X<> in POD. Of course, you'll have to process
.\" the output yourself in some meaningful fashion.
.if \nF \{\
. de IX
. tm Index:\\$1\t\\n%\t"\\$2"
..
. nr % 0
. rr F
.\}
.\"
.\" For nroff, turn off justification. Always turn off hyphenation; it
.\" makes way too many mistakes in technical documents.
.hy 0
.if n .na
.\"
.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
.\" Fear. Run. Save yourself. No user-serviceable parts.
.bd B 3
. \" fudge factors for nroff and troff
.if n \{\
. ds #H 0
. ds #V .8m
. ds #F .3m
. ds #[ \f1
. ds #] \fP
.\}
.if t \{\
. ds #H ((1u-(\\\\n(.fu%2u))*.13m)
. ds #V .6m
. ds #F 0
. ds #[ \&
. ds #] \&
.\}
. \" simple accents for nroff and troff
.if n \{\
. ds ' \&
. ds ` \&
. ds ^ \&
. ds , \&
. ds ~ ~
. ds /
.\}
.if t \{\
. ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
. ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
. ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
. ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
. ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
. ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
.\}
. \" troff and (daisy-wheel) nroff accents
.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
.ds 8 \h'\*(#H'\(*b\h'-\*(#H'
.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
.ds ae a\h'-(\w'a'u*4/10)'e
.ds Ae A\h'-(\w'A'u*4/10)'E
. \" corrections for vroff
.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
. \" for low resolution devices (crt and lpr)
.if \n(.H>23 .if \n(.V>19 \
\{\
. ds : e
. ds 8 ss
. ds o a
. ds d- d\h'-1'\(ga
. ds D- D\h'-1'\(hy
. ds th \o'bp'
. ds Th \o'LP'
. ds ae ae
. ds Ae AE
.\}
.rm #[ #] #H #V #F C
.\" ======================================================================
.\"
.IX Title "BIO_read 3"
.TH BIO_read 3 "0.9.7a" "2003-02-19" "OpenSSL"
.UC
.SH "NAME"
BIO_read, BIO_write, BIO_gets, BIO_puts \- \s-1BIO\s0 I/O functions
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/bio.h>
.Ve
.Vb 4
\& int BIO_read(BIO *b, void *buf, int len);
\& int BIO_gets(BIO *b,char *buf, int size);
\& int BIO_write(BIO *b, const void *buf, int len);
\& int BIO_puts(BIO *b,const char *buf);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fIBIO_read()\fR attempts to read \fBlen\fR bytes from \s-1BIO\s0 \fBb\fR and places
the data in \fBbuf\fR.
.PP
\&\fIBIO_gets()\fR performs the BIOs \*(L"gets\*(R" operation and places the data
in \fBbuf\fR. Usually this operation will attempt to read a line of data
from the \s-1BIO\s0 of maximum length \fBlen\fR. There are exceptions to this
however, for example \fIBIO_gets()\fR on a digest \s-1BIO\s0 will calculate and
return the digest and other BIOs may not support \fIBIO_gets()\fR at all.
.PP
\&\fIBIO_write()\fR attempts to write \fBlen\fR bytes from \fBbuf\fR to \s-1BIO\s0 \fBb\fR.
.PP
\&\fIBIO_puts()\fR attempts to write a null terminated string \fBbuf\fR to \s-1BIO\s0 \fBb\fR
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
All these functions return either the amount of data successfully read or
written (if the return value is positive) or that no data was successfully
read or written if the result is 0 or \-1. If the return value is \-2 then
the operation is not implemented in the specific \s-1BIO\s0 type.
.SH "NOTES"
.IX Header "NOTES"
A 0 or \-1 return is not necessarily an indication of an error. In
particular when the source/sink is non-blocking or of a certain type
it may merely be an indication that no data is currently available and that
the application should retry the operation later.
.PP
One technique sometimes used with blocking sockets is to use a system call
(such as \fIselect()\fR, \fIpoll()\fR or equivalent) to determine when data is available
and then call \fIread()\fR to read the data. The equivalent with BIOs (that is call
\&\fIselect()\fR on the underlying I/O structure and then call \fIBIO_read()\fR to
read the data) should \fBnot\fR be used because a single call to \fIBIO_read()\fR
can cause several reads (and writes in the case of \s-1SSL\s0 BIOs) on the underlying
I/O structure and may block as a result. Instead \fIselect()\fR (or equivalent)
should be combined with non blocking I/O so successive reads will request
a retry instead of blocking.
.PP
See BIO_should_retry(3) for details of how to
determine the cause of a retry and other I/O issues.
.PP
If the \fIBIO_gets()\fR function is not supported by a \s-1BIO\s0 then it possible to
work around this by adding a buffering \s-1BIO\s0 BIO_f_buffer(3)
to the chain.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
BIO_should_retry(3)
.PP
\&\s-1TBA\s0
|
