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133 .\" ========================================================================
135 .IX Title "BIO_S_MEM 3"
136 .TH BIO_S_MEM 3 "2019-02-26" "1.1.1b" "OpenSSL"
137 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
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142 BIO_s_secmem, BIO_s_mem, BIO_set_mem_eof_return, BIO_get_mem_data, BIO_set_mem_buf, BIO_get_mem_ptr, BIO_new_mem_buf \- memory BIO
144 .IX Header "SYNOPSIS"
146 \& #include <openssl/bio.h>
148 \& const BIO_METHOD *BIO_s_mem(void);
149 \& const BIO_METHOD *BIO_s_secmem(void);
151 \& BIO_set_mem_eof_return(BIO *b, int v)
152 \& long BIO_get_mem_data(BIO *b, char **pp)
153 \& BIO_set_mem_buf(BIO *b, BUF_MEM *bm, int c)
154 \& BIO_get_mem_ptr(BIO *b, BUF_MEM **pp)
156 \& BIO *BIO_new_mem_buf(const void *buf, int len);
159 .IX Header "DESCRIPTION"
160 \&\fBBIO_s_mem()\fR returns the memory \s-1BIO\s0 method function.
162 A memory \s-1BIO\s0 is a source/sink \s-1BIO\s0 which uses memory for its I/O. Data
163 written to a memory \s-1BIO\s0 is stored in a \s-1BUF_MEM\s0 structure which is extended
164 as appropriate to accommodate the stored data.
166 \&\fBBIO_s_secmem()\fR is like \fBBIO_s_mem()\fR except that the secure heap is used
169 Any data written to a memory \s-1BIO\s0 can be recalled by reading from it.
170 Unless the memory \s-1BIO\s0 is read only any data read from it is deleted from
173 Memory BIOs support \fBBIO_gets()\fR and \fBBIO_puts()\fR.
175 If the \s-1BIO_CLOSE\s0 flag is set when a memory \s-1BIO\s0 is freed then the underlying
176 \&\s-1BUF_MEM\s0 structure is also freed.
178 Calling \fBBIO_reset()\fR on a read write memory \s-1BIO\s0 clears any data in it if the
179 flag \s-1BIO_FLAGS_NONCLEAR_RST\s0 is not set. On a read only \s-1BIO\s0 or if the flag
180 \&\s-1BIO_FLAGS_NONCLEAR_RST\s0 is set it restores the \s-1BIO\s0 to its original state and
181 the data can be read again.
183 \&\fBBIO_eof()\fR is true if no data is in the \s-1BIO.\s0
185 \&\fBBIO_ctrl_pending()\fR returns the number of bytes currently stored.
187 \&\fBBIO_set_mem_eof_return()\fR sets the behaviour of memory \s-1BIO\s0 \fBb\fR when it is
188 empty. If the \fBv\fR is zero then an empty memory \s-1BIO\s0 will return \s-1EOF\s0 (that is
189 it will return zero and BIO_should_retry(b) will be false. If \fBv\fR is non
190 zero then it will return \fBv\fR when it is empty and it will set the read retry
191 flag (that is BIO_read_retry(b) is true). To avoid ambiguity with a normal
192 positive return value \fBv\fR should be set to a negative value, typically \-1.
194 \&\fBBIO_get_mem_data()\fR sets *\fBpp\fR to a pointer to the start of the memory BIOs data
195 and returns the total amount of data available. It is implemented as a macro.
197 \&\fBBIO_set_mem_buf()\fR sets the internal \s-1BUF_MEM\s0 structure to \fBbm\fR and sets the
198 close flag to \fBc\fR, that is \fBc\fR should be either \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE.\s0
201 \&\fBBIO_get_mem_ptr()\fR places the underlying \s-1BUF_MEM\s0 structure in *\fBpp\fR. It is
204 \&\fBBIO_new_mem_buf()\fR creates a memory \s-1BIO\s0 using \fBlen\fR bytes of data at \fBbuf\fR,
205 if \fBlen\fR is \-1 then the \fBbuf\fR is assumed to be nul terminated and its
206 length is determined by \fBstrlen\fR. The \s-1BIO\s0 is set to a read only state and
207 as a result cannot be written to. This is useful when some data needs to be
208 made available from a static area of memory in the form of a \s-1BIO.\s0 The
209 supplied data is read directly from the supplied buffer: it is \fBnot\fR copied
210 first, so the supplied area of memory must be unchanged until the \s-1BIO\s0 is freed.
213 Writes to memory BIOs will always succeed if memory is available: that is
214 their size can grow indefinitely.
216 Every read from a read write memory \s-1BIO\s0 will remove the data just read with
217 an internal copy operation, if a \s-1BIO\s0 contains a lot of data and it is
218 read in small chunks the operation can be very slow. The use of a read only
219 memory \s-1BIO\s0 avoids this problem. If the \s-1BIO\s0 must be read write then adding
220 a buffering \s-1BIO\s0 to the chain will speed up the process.
222 Calling \fBBIO_set_mem_buf()\fR on a \s-1BIO\s0 created with \fBBIO_new_secmem()\fR will
223 give undefined results, including perhaps a program crash.
226 There should be an option to set the maximum size of a memory \s-1BIO.\s0
229 Create a memory \s-1BIO\s0 and write some data to it:
232 \& BIO *mem = BIO_new(BIO_s_mem());
234 \& BIO_puts(mem, "Hello World\en");
237 Create a read only memory \s-1BIO:\s0
240 \& char data[] = "Hello World";
241 \& BIO *mem = BIO_new_mem_buf(data, \-1);
244 Extract the \s-1BUF_MEM\s0 structure from a memory \s-1BIO\s0 and then free up the \s-1BIO:\s0
249 \& BIO_get_mem_ptr(mem, &bptr);
250 \& BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */
254 .IX Header "RETURN VALUES"
255 \&\fBBIO_s_mem()\fR and \fBBIO_s_secmem()\fR return a valid memory \fB\s-1BIO_METHOD\s0\fR structure.
257 \&\fBBIO_set_mem_eof_return()\fR, \fBBIO_get_mem_data()\fR, \fBBIO_set_mem_buf()\fR and \fBBIO_get_mem_ptr()\fR
258 return 1 on success or a value which is less than or equal to 0 if an error occurred.
260 \&\fBBIO_new_mem_buf()\fR returns a valid \fB\s-1BIO\s0\fR structure on success or \s-1NULL\s0 on error.
262 .IX Header "COPYRIGHT"
263 Copyright 2000\-2018 The OpenSSL Project Authors. All Rights Reserved.
265 Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use
266 this file except in compliance with the License. You can obtain a copy
267 in the file \s-1LICENSE\s0 in the source distribution or at
268 <https://www.openssl.org/source/license.html>.