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129.\" ========================================================================
130.\"
131.IX Title "BIO_read 3"
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124.\" ========================================================================
125.\"
126.IX Title "BIO_read 3"
|
132.TH BIO_read 3 "2010-03-24" "0.9.8n" "OpenSSL"
| 127.TH BIO_read 3 "2010-11-16" "0.9.8p" "OpenSSL"
128.\" For nroff, turn off justification. Always turn off hyphenation; it makes
129.\" way too many mistakes in technical documents.
130.if n .ad l
131.nh
|
133.SH "NAME"
134BIO_read, BIO_write, BIO_gets, BIO_puts \- BIO I/O functions
135.SH "SYNOPSIS"
136.IX Header "SYNOPSIS"
137.Vb 1
138\& #include <openssl/bio.h>
| 132.SH "NAME"
133BIO_read, BIO_write, BIO_gets, BIO_puts \- BIO I/O functions
134.SH "SYNOPSIS"
135.IX Header "SYNOPSIS"
136.Vb 1
137\& #include <openssl/bio.h>
|
139.Ve
140.PP
141.Vb 4
| 138\&
|
142\& int BIO_read(BIO *b, void *buf, int len);
143\& int BIO_gets(BIO *b,char *buf, int size);
144\& int BIO_write(BIO *b, const void *buf, int len);
145\& int BIO_puts(BIO *b,const char *buf);
146.Ve
147.SH "DESCRIPTION"
148.IX Header "DESCRIPTION"
149\&\fIBIO_read()\fR attempts to read \fBlen\fR bytes from \s-1BIO\s0 \fBb\fR and places
150the data in \fBbuf\fR.
151.PP
152\&\fIBIO_gets()\fR performs the BIOs \*(L"gets\*(R" operation and places the data
153in \fBbuf\fR. Usually this operation will attempt to read a line of data
154from the \s-1BIO\s0 of maximum length \fBlen\fR. There are exceptions to this
155however, for example \fIBIO_gets()\fR on a digest \s-1BIO\s0 will calculate and
156return the digest and other BIOs may not support \fIBIO_gets()\fR at all.
157.PP
158\&\fIBIO_write()\fR attempts to write \fBlen\fR bytes from \fBbuf\fR to \s-1BIO\s0 \fBb\fR.
159.PP
160\&\fIBIO_puts()\fR attempts to write a null terminated string \fBbuf\fR to \s-1BIO\s0 \fBb\fR
161.SH "RETURN VALUES"
162.IX Header "RETURN VALUES"
163All these functions return either the amount of data successfully read or
164written (if the return value is positive) or that no data was successfully
165read or written if the result is 0 or \-1. If the return value is \-2 then
166the operation is not implemented in the specific \s-1BIO\s0 type.
167.SH "NOTES"
168.IX Header "NOTES"
169A 0 or \-1 return is not necessarily an indication of an error. In
170particular when the source/sink is non-blocking or of a certain type
171it may merely be an indication that no data is currently available and that
172the application should retry the operation later.
173.PP
174One technique sometimes used with blocking sockets is to use a system call
175(such as \fIselect()\fR, \fIpoll()\fR or equivalent) to determine when data is available
176and then call \fIread()\fR to read the data. The equivalent with BIOs (that is call
177\&\fIselect()\fR on the underlying I/O structure and then call \fIBIO_read()\fR to
178read the data) should \fBnot\fR be used because a single call to \fIBIO_read()\fR
179can cause several reads (and writes in the case of \s-1SSL\s0 BIOs) on the underlying
180I/O structure and may block as a result. Instead \fIselect()\fR (or equivalent)
181should be combined with non blocking I/O so successive reads will request
182a retry instead of blocking.
183.PP
184See \fIBIO_should_retry\fR\|(3) for details of how to
185determine the cause of a retry and other I/O issues.
186.PP
187If the \fIBIO_gets()\fR function is not supported by a \s-1BIO\s0 then it possible to
188work around this by adding a buffering \s-1BIO\s0 \fIBIO_f_buffer\fR\|(3)
189to the chain.
190.SH "SEE ALSO"
191.IX Header "SEE ALSO"
192\&\fIBIO_should_retry\fR\|(3)
193.PP
194\&\s-1TBA\s0
| 139\& int BIO_read(BIO *b, void *buf, int len);
140\& int BIO_gets(BIO *b,char *buf, int size);
141\& int BIO_write(BIO *b, const void *buf, int len);
142\& int BIO_puts(BIO *b,const char *buf);
143.Ve
144.SH "DESCRIPTION"
145.IX Header "DESCRIPTION"
146\&\fIBIO_read()\fR attempts to read \fBlen\fR bytes from \s-1BIO\s0 \fBb\fR and places
147the data in \fBbuf\fR.
148.PP
149\&\fIBIO_gets()\fR performs the BIOs \*(L"gets\*(R" operation and places the data
150in \fBbuf\fR. Usually this operation will attempt to read a line of data
151from the \s-1BIO\s0 of maximum length \fBlen\fR. There are exceptions to this
152however, for example \fIBIO_gets()\fR on a digest \s-1BIO\s0 will calculate and
153return the digest and other BIOs may not support \fIBIO_gets()\fR at all.
154.PP
155\&\fIBIO_write()\fR attempts to write \fBlen\fR bytes from \fBbuf\fR to \s-1BIO\s0 \fBb\fR.
156.PP
157\&\fIBIO_puts()\fR attempts to write a null terminated string \fBbuf\fR to \s-1BIO\s0 \fBb\fR
158.SH "RETURN VALUES"
159.IX Header "RETURN VALUES"
160All these functions return either the amount of data successfully read or
161written (if the return value is positive) or that no data was successfully
162read or written if the result is 0 or \-1. If the return value is \-2 then
163the operation is not implemented in the specific \s-1BIO\s0 type.
164.SH "NOTES"
165.IX Header "NOTES"
166A 0 or \-1 return is not necessarily an indication of an error. In
167particular when the source/sink is non-blocking or of a certain type
168it may merely be an indication that no data is currently available and that
169the application should retry the operation later.
170.PP
171One technique sometimes used with blocking sockets is to use a system call
172(such as \fIselect()\fR, \fIpoll()\fR or equivalent) to determine when data is available
173and then call \fIread()\fR to read the data. The equivalent with BIOs (that is call
174\&\fIselect()\fR on the underlying I/O structure and then call \fIBIO_read()\fR to
175read the data) should \fBnot\fR be used because a single call to \fIBIO_read()\fR
176can cause several reads (and writes in the case of \s-1SSL\s0 BIOs) on the underlying
177I/O structure and may block as a result. Instead \fIselect()\fR (or equivalent)
178should be combined with non blocking I/O so successive reads will request
179a retry instead of blocking.
180.PP
181See \fIBIO_should_retry\fR\|(3) for details of how to
182determine the cause of a retry and other I/O issues.
183.PP
184If the \fIBIO_gets()\fR function is not supported by a \s-1BIO\s0 then it possible to
185work around this by adding a buffering \s-1BIO\s0 \fIBIO_f_buffer\fR\|(3)
186to the chain.
187.SH "SEE ALSO"
188.IX Header "SEE ALSO"
189\&\fIBIO_should_retry\fR\|(3)
190.PP
191\&\s-1TBA\s0
|