1BIO_s_mem(3)                        OpenSSL                       BIO_s_mem(3)
2
3
4

NAME

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
8

SYNOPSIS

10        #include <openssl/bio.h>
11
12        BIO_METHOD *   BIO_s_mem(void);
13
14        BIO_set_mem_eof_return(BIO *b,int v)
15        long BIO_get_mem_data(BIO *b, char **pp)
16        BIO_set_mem_buf(BIO *b,BUF_MEM *bm,int c)
17        BIO_get_mem_ptr(BIO *b,BUF_MEM **pp)
18
19        BIO *BIO_new_mem_buf(const void *buf, int len);
20

DESCRIPTION

22       BIO_s_mem() return the memory BIO method function.
23
24       A memory BIO is a source/sink BIO which uses memory for its I/O. Data
25       written to a memory BIO is stored in a BUF_MEM structure which is
26       extended as appropriate to accommodate the stored data.
27
28       Any data written to a memory BIO can be recalled by reading from it.
29       Unless the memory BIO is read only any data read from it is deleted
30       from the BIO.
31
32       Memory BIOs support BIO_gets() and BIO_puts().
33
34       If the BIO_CLOSE flag is set when a memory BIO is freed then the
35       underlying BUF_MEM structure is also freed.
36
37       Calling BIO_reset() on a read write memory BIO clears any data in it.
38       On a read only BIO it restores the BIO to its original state and the
39       read only data can be read again.
40
41       BIO_eof() is true if no data is in the BIO.
42
43       BIO_ctrl_pending() returns the number of bytes currently stored.
44
45       BIO_set_mem_eof_return() sets the behaviour of memory BIO b when it is
46       empty. If the v is zero then an empty memory BIO will return EOF (that
47       is it will return zero and BIO_should_retry(b) will be false. If v is
48       non zero then it will return v when it is empty and it will set the
49       read retry flag (that is BIO_read_retry(b) is true). To avoid ambiguity
50       with a normal positive return value v should be set to a negative
51       value, typically -1.
52
53       BIO_get_mem_data() sets *pp to a pointer to the start of the memory
54       BIOs data and returns the total amount of data available. It is
55       implemented as a macro.
56
57       BIO_set_mem_buf() sets the internal BUF_MEM structure to bm and sets
58       the close flag to c, that is c should be either BIO_CLOSE or
59       BIO_NOCLOSE.  It is a macro.
60
61       BIO_get_mem_ptr() places the underlying BUF_MEM structure in *pp. It is
62       a macro.
63
64       BIO_new_mem_buf() creates a memory BIO using len bytes of data at buf,
65       if len is -1 then the buf is assumed to be nul terminated and its
66       length is determined by strlen. The BIO is set to a read only state and
67       as a result cannot be written to. This is useful when some data needs
68       to be made available from a static area of memory in the form of a BIO.
69       The supplied data is read directly from the supplied buffer: it is not
70       copied first, so the supplied area of memory must be unchanged until
71       the BIO is freed.
72

NOTES

74       Writes to memory BIOs will always succeed if memory is available: that
75       is their size can grow indefinitely.
76
77       Every read from a read write memory BIO will remove the data just read
78       with an internal copy operation, if a BIO contains a lot of data and it
79       is read in small chunks the operation can be very slow. The use of a
80       read only memory BIO avoids this problem. If the BIO must be read write
81       then adding a buffering BIO to the chain will speed up the process.
82

BUGS

84       There should be an option to set the maximum size of a memory BIO.
85
86       There should be a way to "rewind" a read write BIO without destroying
87       its contents.
88
89       The copying operation should not occur after every small read of a
90       large BIO to improve efficiency.
91

EXAMPLE

93       Create a memory BIO and write some data to it:
94
95        BIO *mem = BIO_new(BIO_s_mem());
96        BIO_puts(mem, "Hello World\n");
97
98       Create a read only memory BIO:
99
100        char data[] = "Hello World";
101        BIO *mem;
102        mem = BIO_new_mem_buf(data, -1);
103
104       Extract the BUF_MEM structure from a memory BIO and then free up the
105       BIO:
106
107        BUF_MEM *bptr;
108        BIO_get_mem_ptr(mem, &bptr);
109        BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */
110        BIO_free(mem);
111

SEE ALSO

113       TBA
114
115
116
1171.0.2o                            2020-08-01                      BIO_s_mem(3)
Impressum