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[dragonfly.git] / secure / lib / libcrypto / man / BIO_s_mem.3
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80.\" If the F register is turned on, we'll generate
81.\" index entries out stderr for the following things:
82.\" TH Title
83.\" SH Header
84.\" Sh Subsection
85.\" Ip Item
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87.\" Of course, you have to process the output yourself
88.\" in some meaninful fashion.
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96.TH BIO_s_mem 3 "0.9.7d" "2/Sep/2004" "OpenSSL"
97.UC
98.if n .hy 0
984263bc 99.if n .na
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188.\}
189.rm #[ #] #H #V #F C
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190.SH "NAME"
191BIO_s_mem, BIO_set_mem_eof_return, BIO_get_mem_data, BIO_set_mem_buf,
74dab6c2 192BIO_get_mem_ptr, BIO_new_mem_buf \- memory BIO
984263bc 193.SH "SYNOPSIS"
74dab6c2 194.PP
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195.Vb 1
196\& #include <openssl/bio.h>
197.Ve
198.Vb 1
199\& BIO_METHOD * BIO_s_mem(void);
200.Ve
201.Vb 4
202\& BIO_set_mem_eof_return(BIO *b,int v)
203\& long BIO_get_mem_data(BIO *b, char **pp)
204\& BIO_set_mem_buf(BIO *b,BUF_MEM *bm,int c)
205\& BIO_get_mem_ptr(BIO *b,BUF_MEM **pp)
206.Ve
207.Vb 1
208\& BIO *BIO_new_mem_buf(void *buf, int len);
209.Ve
210.SH "DESCRIPTION"
74dab6c2 211\fIBIO_s_mem()\fR return the memory BIO method function.
984263bc 212.PP
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213A memory BIO is a source/sink BIO which uses memory for its I/O. Data
214written to a memory BIO is stored in a BUF_MEM structure which is extended
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215as appropriate to accommodate the stored data.
216.PP
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217Any data written to a memory BIO can be recalled by reading from it.
218Unless the memory BIO is read only any data read from it is deleted from
219the BIO.
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220.PP
221Memory BIOs support \fIBIO_gets()\fR and \fIBIO_puts()\fR.
222.PP
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223If the BIO_CLOSE flag is set when a memory BIO is freed then the underlying
224BUF_MEM structure is also freed.
984263bc 225.PP
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226Calling \fIBIO_reset()\fR on a read write memory BIO clears any data in it. On a
227read only BIO it restores the BIO to its original state and the read only
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228data can be read again.
229.PP
74dab6c2 230\fIBIO_eof()\fR is true if no data is in the BIO.
984263bc 231.PP
74dab6c2 232\fIBIO_ctrl_pending()\fR returns the number of bytes currently stored.
984263bc 233.PP
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234\fIBIO_set_mem_eof_return()\fR sets the behaviour of memory BIO \fBb\fR when it is
235empty. If the \fBv\fR is zero then an empty memory BIO will return EOF (that is
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236it will return zero and \fIBIO_should_retry\fR\|(b) will be false. If \fBv\fR is non
237zero then it will return \fBv\fR when it is empty and it will set the read retry
238flag (that is \fIBIO_read_retry\fR\|(b) is true). To avoid ambiguity with a normal
239positive return value \fBv\fR should be set to a negative value, typically \-1.
240.PP
74dab6c2 241\fIBIO_get_mem_data()\fR sets \fBpp\fR to a pointer to the start of the memory BIOs data
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242and returns the total amount of data available. It is implemented as a macro.
243.PP
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244\fIBIO_set_mem_buf()\fR sets the internal BUF_MEM structure to \fBbm\fR and sets the
245close flag to \fBc\fR, that is \fBc\fR should be either BIO_CLOSE or BIO_NOCLOSE.
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246It is a macro.
247.PP
74dab6c2 248\fIBIO_get_mem_ptr()\fR places the underlying BUF_MEM structure in \fBpp\fR. It is
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249a macro.
250.PP
74dab6c2 251\fIBIO_new_mem_buf()\fR creates a memory BIO using \fBlen\fR bytes of data at \fBbuf\fR,
984263bc 252if \fBlen\fR is \-1 then the \fBbuf\fR is assumed to be null terminated and its
74dab6c2 253length is determined by \fBstrlen\fR. The BIO is set to a read only state and
984263bc 254as a result cannot be written to. This is useful when some data needs to be
74dab6c2 255made available from a static area of memory in the form of a BIO. The
984263bc 256supplied data is read directly from the supplied buffer: it is \fBnot\fR copied
74dab6c2 257first, so the supplied area of memory must be unchanged until the BIO is freed.
984263bc 258.SH "NOTES"
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259Writes to memory BIOs will always succeed if memory is available: that is
260their size can grow indefinitely.
261.PP
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262Every read from a read write memory BIO will remove the data just read with
263an internal copy operation, if a BIO contains a lots of data and it is
984263bc 264read in small chunks the operation can be very slow. The use of a read only
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265memory BIO avoids this problem. If the BIO must be read write then adding
266a buffering BIO to the chain will speed up the process.
984263bc 267.SH "BUGS"
74dab6c2 268There should be an option to set the maximum size of a memory BIO.
984263bc 269.PP
74dab6c2 270There should be a way to \*(L"rewind\*(R" a read write BIO without destroying
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271its contents.
272.PP
74dab6c2 273The copying operation should not occur after every small read of a large BIO
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274to improve efficiency.
275.SH "EXAMPLE"
74dab6c2 276Create a memory BIO and write some data to it:
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277.PP
278.Vb 2
279\& BIO *mem = BIO_new(BIO_s_mem());
74dab6c2 280\& BIO_puts(mem, "Hello World\en");
984263bc 281.Ve
74dab6c2 282Create a read only memory BIO:
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283.PP
284.Vb 3
285\& char data[] = "Hello World";
286\& BIO *mem;
287\& mem = BIO_new_mem_buf(data, -1);
288.Ve
74dab6c2 289Extract the BUF_MEM structure from a memory BIO and then free up the BIO:
984263bc 290.PP
74dab6c2 291.Vb 5
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292\& BUF_MEM *bptr;
293\& BIO_get_mem_ptr(mem, &bptr);
294\& BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */
295\& BIO_free(mem);
74dab6c2 296\&
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297.Ve
298.SH "SEE ALSO"
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299TBA
300
301.rn }` ''
302.IX Title "BIO_s_mem 3"
303.IX Name "BIO_s_mem, BIO_set_mem_eof_return, BIO_get_mem_data, BIO_set_mem_buf,
304BIO_get_mem_ptr, BIO_new_mem_buf - memory BIO"
305
306.IX Header "NAME"
307
308.IX Header "SYNOPSIS"
309
310.IX Header "DESCRIPTION"
311
312.IX Header "NOTES"
313
314.IX Header "BUGS"
315
316.IX Header "EXAMPLE"
317
984263bc 318.IX Header "SEE ALSO"
74dab6c2 319