5 BIO_s_mem, BIO_set_mem_eof_return, BIO_get_mem_data, BIO_set_mem_buf,
6 BIO_get_mem_ptr, BIO_new_mem_buf - memory BIO
10 #include <openssl/bio.h>
12 const BIO_METHOD * BIO_s_mem(void);
13 const BIO_METHOD * BIO_s_secmem(void);
15 BIO_set_mem_eof_return(BIO *b,int v)
16 long BIO_get_mem_data(BIO *b, char **pp)
17 BIO_set_mem_buf(BIO *b,BUF_MEM *bm,int c)
18 BIO_get_mem_ptr(BIO *b,BUF_MEM **pp)
20 BIO *BIO_new_mem_buf(const void *buf, int len);
24 BIO_s_mem() return the memory BIO method function.
26 A memory BIO is a source/sink BIO which uses memory for its I/O. Data
27 written to a memory BIO is stored in a BUF_MEM structure which is extended
28 as appropriate to accommodate the stored data.
30 BIO_s_secmem() is like BIO_s_mem() except that the secure heap is used
33 Any data written to a memory BIO can be recalled by reading from it.
34 Unless the memory BIO is read only any data read from it is deleted from
37 Memory BIOs support BIO_gets() and BIO_puts().
39 If the BIO_CLOSE flag is set when a memory BIO is freed then the underlying
40 BUF_MEM structure is also freed.
42 Calling BIO_reset() on a read write memory BIO clears any data in it if the
43 flag BIO_FLAGS_NONCLEAR_RST is not set. On a read only BIO or if the flag
44 BIO_FLAGS_NONCLEAR_RST is set it restores the BIO to its original state and
45 the data can be read again.
47 BIO_eof() is true if no data is in the BIO.
49 BIO_ctrl_pending() returns the number of bytes currently stored.
51 BIO_set_mem_eof_return() sets the behaviour of memory BIO B<b> when it is
52 empty. If the B<v> is zero then an empty memory BIO will return EOF (that is
53 it will return zero and BIO_should_retry(b) will be false. If B<v> is non
54 zero then it will return B<v> when it is empty and it will set the read retry
55 flag (that is BIO_read_retry(b) is true). To avoid ambiguity with a normal
56 positive return value B<v> should be set to a negative value, typically -1.
58 BIO_get_mem_data() sets B<pp> to a pointer to the start of the memory BIOs data
59 and returns the total amount of data available. It is implemented as a macro.
61 BIO_set_mem_buf() sets the internal BUF_MEM structure to B<bm> and sets the
62 close flag to B<c>, that is B<c> should be either BIO_CLOSE or BIO_NOCLOSE.
65 BIO_get_mem_ptr() places the underlying BUF_MEM structure in B<pp>. It is
68 BIO_new_mem_buf() creates a memory BIO using B<len> bytes of data at B<buf>,
69 if B<len> is -1 then the B<buf> is assumed to be nul terminated and its
70 length is determined by B<strlen>. The BIO is set to a read only state and
71 as a result cannot be written to. This is useful when some data needs to be
72 made available from a static area of memory in the form of a BIO. The
73 supplied data is read directly from the supplied buffer: it is B<not> copied
74 first, so the supplied area of memory must be unchanged until the BIO is freed.
78 Writes to memory BIOs will always succeed if memory is available: that is
79 their size can grow indefinitely.
81 Every read from a read write memory BIO will remove the data just read with
82 an internal copy operation, if a BIO contains a lot of data and it is
83 read in small chunks the operation can be very slow. The use of a read only
84 memory BIO avoids this problem. If the BIO must be read write then adding
85 a buffering BIO to the chain will speed up the process.
87 Calling BIO_set_mem_buf() on a BIO created with BIO_new_secmem() will
88 give undefined results, including perhaps a program crash.
92 There should be an option to set the maximum size of a memory BIO.
96 Create a memory BIO and write some data to it:
98 BIO *mem = BIO_new(BIO_s_mem());
99 BIO_puts(mem, "Hello World\n");
101 Create a read only memory BIO:
103 char data[] = "Hello World";
105 mem = BIO_new_mem_buf(data, -1);
107 Extract the BUF_MEM structure from a memory BIO and then free up the BIO:
110 BIO_get_mem_ptr(mem, &bptr);
111 BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */
116 Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
118 Licensed under the OpenSSL license (the "License"). You may not use
119 this file except in compliance with the License. You can obtain a copy
120 in the file LICENSE in the source distribution or at
121 L<https://www.openssl.org/source/license.html>.