Update build for OpenSSL-0.9.8j upgrade.
[dragonfly.git] / secure / lib / libcrypto / man / BIO_s_mem.3
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132.\" ========================================================================
133.\"
134.IX Title "BIO_s_mem 3"
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135.TH BIO_s_mem 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
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140.SH "NAME"
141BIO_s_mem, BIO_set_mem_eof_return, BIO_get_mem_data, BIO_set_mem_buf,
74dab6c2 142BIO_get_mem_ptr, BIO_new_mem_buf \- memory BIO
984263bc 143.SH "SYNOPSIS"
8b0cefbb 144.IX Header "SYNOPSIS"
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145.Vb 1
146\& #include <openssl/bio.h>
e257b235 147\&
984263bc 148\& BIO_METHOD * BIO_s_mem(void);
e257b235 149\&
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150\& BIO_set_mem_eof_return(BIO *b,int v)
151\& long BIO_get_mem_data(BIO *b, char **pp)
152\& BIO_set_mem_buf(BIO *b,BUF_MEM *bm,int c)
153\& BIO_get_mem_ptr(BIO *b,BUF_MEM **pp)
e257b235 154\&
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155\& BIO *BIO_new_mem_buf(void *buf, int len);
156.Ve
157.SH "DESCRIPTION"
8b0cefbb 158.IX Header "DESCRIPTION"
e257b235 159\&\fIBIO_s_mem()\fR return the memory \s-1BIO\s0 method function.
984263bc 160.PP
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161A memory \s-1BIO\s0 is a source/sink \s-1BIO\s0 which uses memory for its I/O. Data
162written to a memory \s-1BIO\s0 is stored in a \s-1BUF_MEM\s0 structure which is extended
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163as appropriate to accommodate the stored data.
164.PP
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165Any data written to a memory \s-1BIO\s0 can be recalled by reading from it.
166Unless the memory \s-1BIO\s0 is read only any data read from it is deleted from
167the \s-1BIO\s0.
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168.PP
169Memory BIOs support \fIBIO_gets()\fR and \fIBIO_puts()\fR.
170.PP
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171If the \s-1BIO_CLOSE\s0 flag is set when a memory \s-1BIO\s0 is freed then the underlying
172\&\s-1BUF_MEM\s0 structure is also freed.
984263bc 173.PP
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174Calling \fIBIO_reset()\fR on a read write memory \s-1BIO\s0 clears any data in it. On a
175read only \s-1BIO\s0 it restores the \s-1BIO\s0 to its original state and the read only
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176data can be read again.
177.PP
8b0cefbb 178\&\fIBIO_eof()\fR is true if no data is in the \s-1BIO\s0.
984263bc 179.PP
8b0cefbb 180\&\fIBIO_ctrl_pending()\fR returns the number of bytes currently stored.
984263bc 181.PP
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182\&\fIBIO_set_mem_eof_return()\fR sets the behaviour of memory \s-1BIO\s0 \fBb\fR when it is
183empty. If the \fBv\fR is zero then an empty memory \s-1BIO\s0 will return \s-1EOF\s0 (that is
184it will return zero and BIO_should_retry(b) will be false. If \fBv\fR is non
984263bc 185zero then it will return \fBv\fR when it is empty and it will set the read retry
8b0cefbb 186flag (that is BIO_read_retry(b) is true). To avoid ambiguity with a normal
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187positive return value \fBv\fR should be set to a negative value, typically \-1.
188.PP
8b0cefbb 189\&\fIBIO_get_mem_data()\fR sets \fBpp\fR to a pointer to the start of the memory BIOs data
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190and returns the total amount of data available. It is implemented as a macro.
191.PP
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192\&\fIBIO_set_mem_buf()\fR sets the internal \s-1BUF_MEM\s0 structure to \fBbm\fR and sets the
193close flag to \fBc\fR, that is \fBc\fR should be either \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE\s0.
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194It is a macro.
195.PP
8b0cefbb 196\&\fIBIO_get_mem_ptr()\fR places the underlying \s-1BUF_MEM\s0 structure in \fBpp\fR. It is
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197a macro.
198.PP
8b0cefbb 199\&\fIBIO_new_mem_buf()\fR creates a memory \s-1BIO\s0 using \fBlen\fR bytes of data at \fBbuf\fR,
984263bc 200if \fBlen\fR is \-1 then the \fBbuf\fR is assumed to be null terminated and its
8b0cefbb 201length is determined by \fBstrlen\fR. The \s-1BIO\s0 is set to a read only state and
984263bc 202as a result cannot be written to. This is useful when some data needs to be
8b0cefbb 203made available from a static area of memory in the form of a \s-1BIO\s0. The
984263bc 204supplied data is read directly from the supplied buffer: it is \fBnot\fR copied
8b0cefbb 205first, so the supplied area of memory must be unchanged until the \s-1BIO\s0 is freed.
984263bc 206.SH "NOTES"
8b0cefbb 207.IX Header "NOTES"
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208Writes to memory BIOs will always succeed if memory is available: that is
209their size can grow indefinitely.
210.PP
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211Every read from a read write memory \s-1BIO\s0 will remove the data just read with
212an internal copy operation, if a \s-1BIO\s0 contains a lots of data and it is
984263bc 213read in small chunks the operation can be very slow. The use of a read only
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214memory \s-1BIO\s0 avoids this problem. If the \s-1BIO\s0 must be read write then adding
215a buffering \s-1BIO\s0 to the chain will speed up the process.
984263bc 216.SH "BUGS"
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217.IX Header "BUGS"
218There should be an option to set the maximum size of a memory \s-1BIO\s0.
984263bc 219.PP
8b0cefbb 220There should be a way to \*(L"rewind\*(R" a read write \s-1BIO\s0 without destroying
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221its contents.
222.PP
8b0cefbb 223The copying operation should not occur after every small read of a large \s-1BIO\s0
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224to improve efficiency.
225.SH "EXAMPLE"
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226.IX Header "EXAMPLE"
227Create a memory \s-1BIO\s0 and write some data to it:
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228.PP
229.Vb 2
230\& BIO *mem = BIO_new(BIO_s_mem());
8b0cefbb 231\& BIO_puts(mem, "Hello World\en");
984263bc 232.Ve
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233.PP
234Create a read only memory \s-1BIO:\s0
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235.PP
236.Vb 3
237\& char data[] = "Hello World";
238\& BIO *mem;
e257b235 239\& mem = BIO_new_mem_buf(data, \-1);
984263bc 240.Ve
984263bc 241.PP
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242Extract the \s-1BUF_MEM\s0 structure from a memory \s-1BIO\s0 and then free up the \s-1BIO:\s0
243.PP
244.Vb 4
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245\& BUF_MEM *bptr;
246\& BIO_get_mem_ptr(mem, &bptr);
247\& BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */
248\& BIO_free(mem);
249.Ve
250.SH "SEE ALSO"
251.IX Header "SEE ALSO"
8b0cefbb 252\&\s-1TBA\s0