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131 .IX Title "BIO_S_MEM 3"
132 .TH BIO_S_MEM 3 "2018-09-11" "1.1.1" "OpenSSL"
133 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
134 .\" way too many mistakes in technical documents.
138 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
140 .IX Header "SYNOPSIS"
142 \& #include <openssl/bio.h>
144 \& const BIO_METHOD *BIO_s_mem(void);
145 \& const BIO_METHOD *BIO_s_secmem(void);
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)
152 \& BIO *BIO_new_mem_buf(const void *buf, int len);
155 .IX Header "DESCRIPTION"
156 \&\fIBIO_s_mem()\fR returns the memory \s-1BIO\s0 method function.
158 A memory \s-1BIO\s0 is a source/sink \s-1BIO\s0 which uses memory for its I/O. Data
159 written to a memory \s-1BIO\s0 is stored in a \s-1BUF_MEM\s0 structure which is extended
160 as appropriate to accommodate the stored data.
162 \&\fIBIO_s_secmem()\fR is like \fIBIO_s_mem()\fR except that the secure heap is used
165 Any data written to a memory \s-1BIO\s0 can be recalled by reading from it.
166 Unless the memory \s-1BIO\s0 is read only any data read from it is deleted from
169 Memory BIOs support \fIBIO_gets()\fR and \fIBIO_puts()\fR.
171 If 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.
174 Calling \fIBIO_reset()\fR on a read write memory \s-1BIO\s0 clears any data in it if the
175 flag \s-1BIO_FLAGS_NONCLEAR_RST\s0 is not set. On a read only \s-1BIO\s0 or if the flag
176 \&\s-1BIO_FLAGS_NONCLEAR_RST\s0 is set it restores the \s-1BIO\s0 to its original state and
177 the data can be read again.
179 \&\fIBIO_eof()\fR is true if no data is in the \s-1BIO.\s0
181 \&\fIBIO_ctrl_pending()\fR returns the number of bytes currently stored.
183 \&\fIBIO_set_mem_eof_return()\fR sets the behaviour of memory \s-1BIO\s0 \fBb\fR when it is
184 empty. If the \fBv\fR is zero then an empty memory \s-1BIO\s0 will return \s-1EOF\s0 (that is
185 it will return zero and BIO_should_retry(b) will be false. If \fBv\fR is non
186 zero then it will return \fBv\fR when it is empty and it will set the read retry
187 flag (that is BIO_read_retry(b) is true). To avoid ambiguity with a normal
188 positive return value \fBv\fR should be set to a negative value, typically \-1.
190 \&\fIBIO_get_mem_data()\fR sets *\fBpp\fR to a pointer to the start of the memory BIOs data
191 and returns the total amount of data available. It is implemented as a macro.
193 \&\fIBIO_set_mem_buf()\fR sets the internal \s-1BUF_MEM\s0 structure to \fBbm\fR and sets the
194 close flag to \fBc\fR, that is \fBc\fR should be either \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE.\s0
197 \&\fIBIO_get_mem_ptr()\fR places the underlying \s-1BUF_MEM\s0 structure in *\fBpp\fR. It is
200 \&\fIBIO_new_mem_buf()\fR creates a memory \s-1BIO\s0 using \fBlen\fR bytes of data at \fBbuf\fR,
201 if \fBlen\fR is \-1 then the \fBbuf\fR is assumed to be nul terminated and its
202 length is determined by \fBstrlen\fR. The \s-1BIO\s0 is set to a read only state and
203 as a result cannot be written to. This is useful when some data needs to be
204 made available from a static area of memory in the form of a \s-1BIO.\s0 The
205 supplied data is read directly from the supplied buffer: it is \fBnot\fR copied
206 first, so the supplied area of memory must be unchanged until the \s-1BIO\s0 is freed.
209 Writes to memory BIOs will always succeed if memory is available: that is
210 their size can grow indefinitely.
212 Every read from a read write memory \s-1BIO\s0 will remove the data just read with
213 an internal copy operation, if a \s-1BIO\s0 contains a lot of data and it is
214 read in small chunks the operation can be very slow. The use of a read only
215 memory \s-1BIO\s0 avoids this problem. If the \s-1BIO\s0 must be read write then adding
216 a buffering \s-1BIO\s0 to the chain will speed up the process.
218 Calling \fIBIO_set_mem_buf()\fR on a \s-1BIO\s0 created with \fIBIO_new_secmem()\fR will
219 give undefined results, including perhaps a program crash.
222 There should be an option to set the maximum size of a memory \s-1BIO.\s0
225 Create a memory \s-1BIO\s0 and write some data to it:
228 \& BIO *mem = BIO_new(BIO_s_mem());
230 \& BIO_puts(mem, "Hello World\en");
233 Create a read only memory \s-1BIO:\s0
236 \& char data[] = "Hello World";
237 \& BIO *mem = BIO_new_mem_buf(data, \-1);
240 Extract the \s-1BUF_MEM\s0 structure from a memory \s-1BIO\s0 and then free up the \s-1BIO:\s0
245 \& BIO_get_mem_ptr(mem, &bptr);
246 \& BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */
250 .IX Header "RETURN VALUES"
251 \&\fIBIO_s_mem()\fR and \fIBIO_s_secmem()\fR return a valid memory \fB\s-1BIO_METHOD\s0\fR structure.
253 \&\fIBIO_set_mem_eof_return()\fR, \fIBIO_get_mem_data()\fR, \fIBIO_set_mem_buf()\fR and \fIBIO_get_mem_ptr()\fR
254 return 1 on success or a value which is less than or equal to 0 if an error occurred.
256 \&\fIBIO_new_mem_buf()\fR returns a valid \fB\s-1BIO\s0\fR structure on success or \s-1NULL\s0 on error.
258 .IX Header "COPYRIGHT"
259 Copyright 2000\-2018 The OpenSSL Project Authors. All Rights Reserved.
261 Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use
262 this file except in compliance with the License. You can obtain a copy
263 in the file \s-1LICENSE\s0 in the source distribution or at
264 <https://www.openssl.org/source/license.html>.