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 */