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d7b9c76c DSH |
1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
c952780c | 5 | BIO_s_secmem, |
8eec1389 RL |
6 | BIO_s_mem, BIO_set_mem_eof_return, BIO_get_mem_data, BIO_set_mem_buf, |
7 | BIO_get_mem_ptr, BIO_new_mem_buf - memory BIO | |
d7b9c76c DSH |
8 | |
9 | =head1 SYNOPSIS | |
10 | ||
11 | #include <openssl/bio.h> | |
12 | ||
e9b77246 BB |
13 | const BIO_METHOD *BIO_s_mem(void); |
14 | const BIO_METHOD *BIO_s_secmem(void); | |
d7b9c76c | 15 | |
aebb9aac | 16 | BIO_set_mem_eof_return(BIO *b, int v) |
d7b9c76c | 17 | long BIO_get_mem_data(BIO *b, char **pp) |
aebb9aac RS |
18 | BIO_set_mem_buf(BIO *b, BUF_MEM *bm, int c) |
19 | BIO_get_mem_ptr(BIO *b, BUF_MEM **pp) | |
d7b9c76c | 20 | |
8ab31975 | 21 | BIO *BIO_new_mem_buf(const void *buf, int len); |
d7b9c76c DSH |
22 | |
23 | =head1 DESCRIPTION | |
24 | ||
1f13ad31 | 25 | BIO_s_mem() returns the memory BIO method function. |
d7b9c76c DSH |
26 | |
27 | A memory BIO is a source/sink BIO which uses memory for its I/O. Data | |
28 | written to a memory BIO is stored in a BUF_MEM structure which is extended | |
29 | as appropriate to accommodate the stored data. | |
30 | ||
74924dcb RS |
31 | BIO_s_secmem() is like BIO_s_mem() except that the secure heap is used |
32 | for buffer storage. | |
33 | ||
d7b9c76c DSH |
34 | Any data written to a memory BIO can be recalled by reading from it. |
35 | Unless the memory BIO is read only any data read from it is deleted from | |
36 | the BIO. | |
37 | ||
38 | Memory BIOs support BIO_gets() and BIO_puts(). | |
39 | ||
40 | If the BIO_CLOSE flag is set when a memory BIO is freed then the underlying | |
41 | BUF_MEM structure is also freed. | |
42 | ||
9fe9d046 KM |
43 | Calling BIO_reset() on a read write memory BIO clears any data in it if the |
44 | flag BIO_FLAGS_NONCLEAR_RST is not set. On a read only BIO or if the flag | |
1bc74519 | 45 | BIO_FLAGS_NONCLEAR_RST is set it restores the BIO to its original state and |
9fe9d046 | 46 | the data can be read again. |
d7b9c76c DSH |
47 | |
48 | BIO_eof() is true if no data is in the BIO. | |
49 | ||
50 | BIO_ctrl_pending() returns the number of bytes currently stored. | |
51 | ||
acb5b343 | 52 | BIO_set_mem_eof_return() sets the behaviour of memory BIO B<b> when it is |
d7b9c76c DSH |
53 | empty. If the B<v> is zero then an empty memory BIO will return EOF (that is |
54 | it will return zero and BIO_should_retry(b) will be false. If B<v> is non | |
55 | zero then it will return B<v> when it is empty and it will set the read retry | |
56 | flag (that is BIO_read_retry(b) is true). To avoid ambiguity with a normal | |
57 | positive return value B<v> should be set to a negative value, typically -1. | |
58 | ||
36359cec | 59 | BIO_get_mem_data() sets *B<pp> to a pointer to the start of the memory BIOs data |
d7b9c76c DSH |
60 | and returns the total amount of data available. It is implemented as a macro. |
61 | ||
62 | BIO_set_mem_buf() sets the internal BUF_MEM structure to B<bm> and sets the | |
63 | close flag to B<c>, that is B<c> should be either BIO_CLOSE or BIO_NOCLOSE. | |
64 | It is a macro. | |
65 | ||
36359cec | 66 | BIO_get_mem_ptr() places the underlying BUF_MEM structure in *B<pp>. It is |
d7b9c76c DSH |
67 | a macro. |
68 | ||
69 | BIO_new_mem_buf() creates a memory BIO using B<len> bytes of data at B<buf>, | |
8ab31975 | 70 | if B<len> is -1 then the B<buf> is assumed to be nul terminated and its |
d7b9c76c DSH |
71 | length is determined by B<strlen>. The BIO is set to a read only state and |
72 | as a result cannot be written to. This is useful when some data needs to be | |
73 | made available from a static area of memory in the form of a BIO. The | |
74 | supplied data is read directly from the supplied buffer: it is B<not> copied | |
75 | first, so the supplied area of memory must be unchanged until the BIO is freed. | |
76 | ||
77 | =head1 NOTES | |
78 | ||
79 | Writes to memory BIOs will always succeed if memory is available: that is | |
80 | their size can grow indefinitely. | |
81 | ||
82 | Every read from a read write memory BIO will remove the data just read with | |
8711efb4 | 83 | an internal copy operation, if a BIO contains a lot of data and it is |
d7b9c76c DSH |
84 | read in small chunks the operation can be very slow. The use of a read only |
85 | memory BIO avoids this problem. If the BIO must be read write then adding | |
86 | a buffering BIO to the chain will speed up the process. | |
87 | ||
74924dcb RS |
88 | Calling BIO_set_mem_buf() on a BIO created with BIO_new_secmem() will |
89 | give undefined results, including perhaps a program crash. | |
90 | ||
d7b9c76c DSH |
91 | =head1 BUGS |
92 | ||
93 | There should be an option to set the maximum size of a memory BIO. | |
94 | ||
d7b9c76c DSH |
95 | =head1 EXAMPLE |
96 | ||
97 | Create a memory BIO and write some data to it: | |
98 | ||
99 | BIO *mem = BIO_new(BIO_s_mem()); | |
e9b77246 | 100 | |
1bc74519 | 101 | BIO_puts(mem, "Hello World\n"); |
d7b9c76c DSH |
102 | |
103 | Create a read only memory BIO: | |
104 | ||
105 | char data[] = "Hello World"; | |
e9b77246 | 106 | BIO *mem = BIO_new_mem_buf(data, -1); |
d7b9c76c DSH |
107 | |
108 | Extract the BUF_MEM structure from a memory BIO and then free up the BIO: | |
109 | ||
110 | BUF_MEM *bptr; | |
e9b77246 | 111 | |
d7b9c76c DSH |
112 | BIO_get_mem_ptr(mem, &bptr); |
113 | BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */ | |
114 | BIO_free(mem); | |
1bc74519 | 115 | |
1f13ad31 PY |
116 | =head1 RETURN VALUES |
117 | ||
118 | BIO_s_mem() and BIO_s_secmem() return a valid memory B<BIO_METHOD> structure. | |
119 | ||
120 | BIO_set_mem_eof_return(), BIO_get_mem_data(), BIO_set_mem_buf() and BIO_get_mem_ptr() | |
121 | return 1 on success or a value which is less than or equal to 0 if an error occurred. | |
122 | ||
123 | BIO_new_mem_buf() returns a valid B<BIO> structure on success or NULL on error. | |
124 | ||
e2f92610 RS |
125 | =head1 COPYRIGHT |
126 | ||
61f805c1 | 127 | Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved. |
e2f92610 RS |
128 | |
129 | Licensed under the OpenSSL license (the "License"). You may not use | |
130 | this file except in compliance with the License. You can obtain a copy | |
131 | in the file LICENSE in the source distribution or at | |
132 | L<https://www.openssl.org/source/license.html>. | |
133 | ||
134 | =cut |