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| 132 | .\" ======================================================================== |
| 133 | .\" |
| 134 | .IX Title "BIO_read 3" |
| 135 | .TH BIO_read 3 "2009-01-11" "0.9.8j" "OpenSSL" |
| 136 | .\" For nroff, turn off justification. Always turn off hyphenation; it makes |
| 137 | .\" way too many mistakes in technical documents. |
| 138 | .if n .ad l |
| 139 | .nh |
| 140 | .SH "NAME" |
| 141 | BIO_read, BIO_write, BIO_gets, BIO_puts \- BIO I/O functions |
| 142 | .SH "SYNOPSIS" |
| 143 | .IX Header "SYNOPSIS" |
| 144 | .Vb 1 |
| 145 | \& #include <openssl/bio.h> |
| 146 | \& |
| 147 | \& int BIO_read(BIO *b, void *buf, int len); |
| 148 | \& int BIO_gets(BIO *b,char *buf, int size); |
| 149 | \& int BIO_write(BIO *b, const void *buf, int len); |
| 150 | \& int BIO_puts(BIO *b,const char *buf); |
| 151 | .Ve |
| 152 | .SH "DESCRIPTION" |
| 153 | .IX Header "DESCRIPTION" |
| 154 | \&\fIBIO_read()\fR attempts to read \fBlen\fR bytes from \s-1BIO\s0 \fBb\fR and places |
| 155 | the data in \fBbuf\fR. |
| 156 | .PP |
| 157 | \&\fIBIO_gets()\fR performs the BIOs \*(L"gets\*(R" operation and places the data |
| 158 | in \fBbuf\fR. Usually this operation will attempt to read a line of data |
| 159 | from the \s-1BIO\s0 of maximum length \fBlen\fR. There are exceptions to this |
| 160 | however, for example \fIBIO_gets()\fR on a digest \s-1BIO\s0 will calculate and |
| 161 | return the digest and other BIOs may not support \fIBIO_gets()\fR at all. |
| 162 | .PP |
| 163 | \&\fIBIO_write()\fR attempts to write \fBlen\fR bytes from \fBbuf\fR to \s-1BIO\s0 \fBb\fR. |
| 164 | .PP |
| 165 | \&\fIBIO_puts()\fR attempts to write a null terminated string \fBbuf\fR to \s-1BIO\s0 \fBb\fR |
| 166 | .SH "RETURN VALUES" |
| 167 | .IX Header "RETURN VALUES" |
| 168 | All these functions return either the amount of data successfully read or |
| 169 | written (if the return value is positive) or that no data was successfully |
| 170 | read or written if the result is 0 or \-1. If the return value is \-2 then |
| 171 | the operation is not implemented in the specific \s-1BIO\s0 type. |
| 172 | .SH "NOTES" |
| 173 | .IX Header "NOTES" |
| 174 | A 0 or \-1 return is not necessarily an indication of an error. In |
| 175 | particular when the source/sink is non-blocking or of a certain type |
| 176 | it may merely be an indication that no data is currently available and that |
| 177 | the application should retry the operation later. |
| 178 | .PP |
| 179 | One technique sometimes used with blocking sockets is to use a system call |
| 180 | (such as \fIselect()\fR, \fIpoll()\fR or equivalent) to determine when data is available |
| 181 | and then call \fIread()\fR to read the data. The equivalent with BIOs (that is call |
| 182 | \&\fIselect()\fR on the underlying I/O structure and then call \fIBIO_read()\fR to |
| 183 | read the data) should \fBnot\fR be used because a single call to \fIBIO_read()\fR |
| 184 | can cause several reads (and writes in the case of \s-1SSL\s0 BIOs) on the underlying |
| 185 | I/O structure and may block as a result. Instead \fIselect()\fR (or equivalent) |
| 186 | should be combined with non blocking I/O so successive reads will request |
| 187 | a retry instead of blocking. |
| 188 | .PP |
| 189 | See \fIBIO_should_retry\fR\|(3) for details of how to |
| 190 | determine the cause of a retry and other I/O issues. |
| 191 | .PP |
| 192 | If the \fIBIO_gets()\fR function is not supported by a \s-1BIO\s0 then it possible to |
| 193 | work around this by adding a buffering \s-1BIO\s0 \fIBIO_f_buffer\fR\|(3) |
| 194 | to the chain. |
| 195 | .SH "SEE ALSO" |
| 196 | .IX Header "SEE ALSO" |
| 197 | \&\fIBIO_should_retry\fR\|(3) |
| 198 | .PP |
| 199 | \&\s-1TBA\s0 |