- update OpenSSL to 0.9.8
[dragonfly.git] / secure / lib / libcrypto / man / BIO_s_mem.3
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129.\" ========================================================================
130.\"
131.IX Title "BIO_s_mem 3"
a561f9ff 132.TH BIO_s_mem 3 "2005-07-06" "0.9.8" "OpenSSL"
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133.SH "NAME"
134BIO_s_mem, BIO_set_mem_eof_return, BIO_get_mem_data, BIO_set_mem_buf,
74dab6c2 135BIO_get_mem_ptr, BIO_new_mem_buf \- memory BIO
984263bc 136.SH "SYNOPSIS"
8b0cefbb 137.IX Header "SYNOPSIS"
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138.Vb 1
139\& #include <openssl/bio.h>
140.Ve
8b0cefbb 141.PP
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142.Vb 1
143\& BIO_METHOD * BIO_s_mem(void);
144.Ve
8b0cefbb 145.PP
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146.Vb 4
147\& BIO_set_mem_eof_return(BIO *b,int v)
148\& long BIO_get_mem_data(BIO *b, char **pp)
149\& BIO_set_mem_buf(BIO *b,BUF_MEM *bm,int c)
150\& BIO_get_mem_ptr(BIO *b,BUF_MEM **pp)
151.Ve
8b0cefbb 152.PP
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153.Vb 1
154\& BIO *BIO_new_mem_buf(void *buf, int len);
155.Ve
156.SH "DESCRIPTION"
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157.IX Header "DESCRIPTION"
158\&\fIBIO_s_mem()\fR return the memory \s-1BIO\s0 method function.
984263bc 159.PP
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160A memory \s-1BIO\s0 is a source/sink \s-1BIO\s0 which uses memory for its I/O. Data
161written to a memory \s-1BIO\s0 is stored in a \s-1BUF_MEM\s0 structure which is extended
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162as appropriate to accommodate the stored data.
163.PP
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164Any data written to a memory \s-1BIO\s0 can be recalled by reading from it.
165Unless the memory \s-1BIO\s0 is read only any data read from it is deleted from
166the \s-1BIO\s0.
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167.PP
168Memory BIOs support \fIBIO_gets()\fR and \fIBIO_puts()\fR.
169.PP
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170If the \s-1BIO_CLOSE\s0 flag is set when a memory \s-1BIO\s0 is freed then the underlying
171\&\s-1BUF_MEM\s0 structure is also freed.
984263bc 172.PP
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173Calling \fIBIO_reset()\fR on a read write memory \s-1BIO\s0 clears any data in it. On a
174read only \s-1BIO\s0 it restores the \s-1BIO\s0 to its original state and the read only
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175data can be read again.
176.PP
8b0cefbb 177\&\fIBIO_eof()\fR is true if no data is in the \s-1BIO\s0.
984263bc 178.PP
8b0cefbb 179\&\fIBIO_ctrl_pending()\fR returns the number of bytes currently stored.
984263bc 180.PP
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181\&\fIBIO_set_mem_eof_return()\fR sets the behaviour of memory \s-1BIO\s0 \fBb\fR when it is
182empty. If the \fBv\fR is zero then an empty memory \s-1BIO\s0 will return \s-1EOF\s0 (that is
183it will return zero and BIO_should_retry(b) will be false. If \fBv\fR is non
984263bc 184zero then it will return \fBv\fR when it is empty and it will set the read retry
8b0cefbb 185flag (that is BIO_read_retry(b) is true). To avoid ambiguity with a normal
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186positive return value \fBv\fR should be set to a negative value, typically \-1.
187.PP
8b0cefbb 188\&\fIBIO_get_mem_data()\fR sets \fBpp\fR to a pointer to the start of the memory BIOs data
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189and returns the total amount of data available. It is implemented as a macro.
190.PP
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191\&\fIBIO_set_mem_buf()\fR sets the internal \s-1BUF_MEM\s0 structure to \fBbm\fR and sets the
192close flag to \fBc\fR, that is \fBc\fR should be either \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE\s0.
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193It is a macro.
194.PP
8b0cefbb 195\&\fIBIO_get_mem_ptr()\fR places the underlying \s-1BUF_MEM\s0 structure in \fBpp\fR. It is
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196a macro.
197.PP
8b0cefbb 198\&\fIBIO_new_mem_buf()\fR creates a memory \s-1BIO\s0 using \fBlen\fR bytes of data at \fBbuf\fR,
984263bc 199if \fBlen\fR is \-1 then the \fBbuf\fR is assumed to be null terminated and its
8b0cefbb 200length is determined by \fBstrlen\fR. The \s-1BIO\s0 is set to a read only state and
984263bc 201as a result cannot be written to. This is useful when some data needs to be
8b0cefbb 202made available from a static area of memory in the form of a \s-1BIO\s0. The
984263bc 203supplied data is read directly from the supplied buffer: it is \fBnot\fR copied
8b0cefbb 204first, so the supplied area of memory must be unchanged until the \s-1BIO\s0 is freed.
984263bc 205.SH "NOTES"
8b0cefbb 206.IX Header "NOTES"
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207Writes to memory BIOs will always succeed if memory is available: that is
208their size can grow indefinitely.
209.PP
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210Every read from a read write memory \s-1BIO\s0 will remove the data just read with
211an internal copy operation, if a \s-1BIO\s0 contains a lots of data and it is
984263bc 212read in small chunks the operation can be very slow. The use of a read only
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213memory \s-1BIO\s0 avoids this problem. If the \s-1BIO\s0 must be read write then adding
214a buffering \s-1BIO\s0 to the chain will speed up the process.
984263bc 215.SH "BUGS"
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216.IX Header "BUGS"
217There should be an option to set the maximum size of a memory \s-1BIO\s0.
984263bc 218.PP
8b0cefbb 219There should be a way to \*(L"rewind\*(R" a read write \s-1BIO\s0 without destroying
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220its contents.
221.PP
8b0cefbb 222The copying operation should not occur after every small read of a large \s-1BIO\s0
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223to improve efficiency.
224.SH "EXAMPLE"
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225.IX Header "EXAMPLE"
226Create a memory \s-1BIO\s0 and write some data to it:
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227.PP
228.Vb 2
229\& BIO *mem = BIO_new(BIO_s_mem());
8b0cefbb 230\& BIO_puts(mem, "Hello World\en");
984263bc 231.Ve
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232.PP
233Create a read only memory \s-1BIO:\s0
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234.PP
235.Vb 3
236\& char data[] = "Hello World";
237\& BIO *mem;
238\& mem = BIO_new_mem_buf(data, -1);
239.Ve
984263bc 240.PP
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241Extract the \s-1BUF_MEM\s0 structure from a memory \s-1BIO\s0 and then free up the \s-1BIO:\s0
242.PP
243.Vb 4
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244\& BUF_MEM *bptr;
245\& BIO_get_mem_ptr(mem, &bptr);
246\& BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */
247\& BIO_free(mem);
248.Ve
249.SH "SEE ALSO"
250.IX Header "SEE ALSO"
8b0cefbb 251\&\s-1TBA\s0