Update files for OpenSSL-1.0.0f import.
[dragonfly.git] / secure / lib / libcrypto / man / BIO_s_mem.3
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124.\" ========================================================================
125.\"
126.IX Title "BIO_s_mem 3"
e3261593 127.TH BIO_s_mem 3 "2012-01-04" "1.0.0f" "OpenSSL"
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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
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132.SH "NAME"
133BIO_s_mem, BIO_set_mem_eof_return, BIO_get_mem_data, BIO_set_mem_buf,
74dab6c2 134BIO_get_mem_ptr, BIO_new_mem_buf \- memory BIO
984263bc 135.SH "SYNOPSIS"
8b0cefbb 136.IX Header "SYNOPSIS"
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137.Vb 1
138\& #include <openssl/bio.h>
e257b235 139\&
984263bc 140\& BIO_METHOD * BIO_s_mem(void);
e257b235 141\&
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142\& BIO_set_mem_eof_return(BIO *b,int v)
143\& long BIO_get_mem_data(BIO *b, char **pp)
144\& BIO_set_mem_buf(BIO *b,BUF_MEM *bm,int c)
145\& BIO_get_mem_ptr(BIO *b,BUF_MEM **pp)
e257b235 146\&
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147\& BIO *BIO_new_mem_buf(void *buf, int len);
148.Ve
149.SH "DESCRIPTION"
8b0cefbb 150.IX Header "DESCRIPTION"
e257b235 151\&\fIBIO_s_mem()\fR return the memory \s-1BIO\s0 method function.
984263bc 152.PP
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153A memory \s-1BIO\s0 is a source/sink \s-1BIO\s0 which uses memory for its I/O. Data
154written to a memory \s-1BIO\s0 is stored in a \s-1BUF_MEM\s0 structure which is extended
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155as appropriate to accommodate the stored data.
156.PP
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157Any data written to a memory \s-1BIO\s0 can be recalled by reading from it.
158Unless the memory \s-1BIO\s0 is read only any data read from it is deleted from
159the \s-1BIO\s0.
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160.PP
161Memory BIOs support \fIBIO_gets()\fR and \fIBIO_puts()\fR.
162.PP
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163If the \s-1BIO_CLOSE\s0 flag is set when a memory \s-1BIO\s0 is freed then the underlying
164\&\s-1BUF_MEM\s0 structure is also freed.
984263bc 165.PP
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166Calling \fIBIO_reset()\fR on a read write memory \s-1BIO\s0 clears any data in it. On a
167read only \s-1BIO\s0 it restores the \s-1BIO\s0 to its original state and the read only
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168data can be read again.
169.PP
8b0cefbb 170\&\fIBIO_eof()\fR is true if no data is in the \s-1BIO\s0.
984263bc 171.PP
8b0cefbb 172\&\fIBIO_ctrl_pending()\fR returns the number of bytes currently stored.
984263bc 173.PP
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174\&\fIBIO_set_mem_eof_return()\fR sets the behaviour of memory \s-1BIO\s0 \fBb\fR when it is
175empty. If the \fBv\fR is zero then an empty memory \s-1BIO\s0 will return \s-1EOF\s0 (that is
176it will return zero and BIO_should_retry(b) will be false. If \fBv\fR is non
984263bc 177zero then it will return \fBv\fR when it is empty and it will set the read retry
8b0cefbb 178flag (that is BIO_read_retry(b) is true). To avoid ambiguity with a normal
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179positive return value \fBv\fR should be set to a negative value, typically \-1.
180.PP
8b0cefbb 181\&\fIBIO_get_mem_data()\fR sets \fBpp\fR to a pointer to the start of the memory BIOs data
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182and returns the total amount of data available. It is implemented as a macro.
183.PP
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184\&\fIBIO_set_mem_buf()\fR sets the internal \s-1BUF_MEM\s0 structure to \fBbm\fR and sets the
185close flag to \fBc\fR, that is \fBc\fR should be either \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE\s0.
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186It is a macro.
187.PP
8b0cefbb 188\&\fIBIO_get_mem_ptr()\fR places the underlying \s-1BUF_MEM\s0 structure in \fBpp\fR. It is
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189a macro.
190.PP
8b0cefbb 191\&\fIBIO_new_mem_buf()\fR creates a memory \s-1BIO\s0 using \fBlen\fR bytes of data at \fBbuf\fR,
984263bc 192if \fBlen\fR is \-1 then the \fBbuf\fR is assumed to be null terminated and its
8b0cefbb 193length is determined by \fBstrlen\fR. The \s-1BIO\s0 is set to a read only state and
984263bc 194as a result cannot be written to. This is useful when some data needs to be
8b0cefbb 195made available from a static area of memory in the form of a \s-1BIO\s0. The
984263bc 196supplied data is read directly from the supplied buffer: it is \fBnot\fR copied
8b0cefbb 197first, so the supplied area of memory must be unchanged until the \s-1BIO\s0 is freed.
984263bc 198.SH "NOTES"
8b0cefbb 199.IX Header "NOTES"
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200Writes to memory BIOs will always succeed if memory is available: that is
201their size can grow indefinitely.
202.PP
8b0cefbb 203Every read from a read write memory \s-1BIO\s0 will remove the data just read with
01185282 204an internal copy operation, if a \s-1BIO\s0 contains a lot of data and it is
984263bc 205read in small chunks the operation can be very slow. The use of a read only
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206memory \s-1BIO\s0 avoids this problem. If the \s-1BIO\s0 must be read write then adding
207a buffering \s-1BIO\s0 to the chain will speed up the process.
984263bc 208.SH "BUGS"
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209.IX Header "BUGS"
210There should be an option to set the maximum size of a memory \s-1BIO\s0.
984263bc 211.PP
8b0cefbb 212There should be a way to \*(L"rewind\*(R" a read write \s-1BIO\s0 without destroying
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213its contents.
214.PP
8b0cefbb 215The copying operation should not occur after every small read of a large \s-1BIO\s0
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216to improve efficiency.
217.SH "EXAMPLE"
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218.IX Header "EXAMPLE"
219Create a memory \s-1BIO\s0 and write some data to it:
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220.PP
221.Vb 2
222\& BIO *mem = BIO_new(BIO_s_mem());
8b0cefbb 223\& BIO_puts(mem, "Hello World\en");
984263bc 224.Ve
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225.PP
226Create a read only memory \s-1BIO:\s0
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227.PP
228.Vb 3
229\& char data[] = "Hello World";
230\& BIO *mem;
e257b235 231\& mem = BIO_new_mem_buf(data, \-1);
984263bc 232.Ve
984263bc 233.PP
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234Extract the \s-1BUF_MEM\s0 structure from a memory \s-1BIO\s0 and then free up the \s-1BIO:\s0
235.PP
236.Vb 4
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237\& BUF_MEM *bptr;
238\& BIO_get_mem_ptr(mem, &bptr);
239\& BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */
240\& BIO_free(mem);
241.Ve
242.SH "SEE ALSO"
243.IX Header "SEE ALSO"
8b0cefbb 244\&\s-1TBA\s0