|BIO_S_MEM(3)||Library Functions Manual||BIO_S_MEM(3)|
const BIO_METHOD *
BUF_MEM *bm, int c);
BIO_new_mem_buf(const void *buf,
BIO_s_mem() returns the memory BIO method function.
A memory BIO is a source/sink BIO which uses memory for its I/O. Data written to a memory BIO is stored in a BUF_MEM structure which is extended as appropriate to accommodate the stored data.
Any data written to a memory BIO can be recalled by reading from it. Unless the memory BIO is read only, any data read from it is deleted from the BIO.
BIO_CLOSE flag is set when a memory
BIO is freed, the underlying
BUF_MEM structure is
Calling BIO_reset(3) on a read/write memory BIO clears any data in it. On a read only BIO it restores the BIO to its original state and the read only data can be read again.
BIO_eof(3) is true if no data is in the BIO.
BIO_ctrl_pending(3) returns the number of bytes currently stored.
BIO_set_mem_eof_return() sets the
behaviour of memory BIO b when it is empty. If
v is zero, then an empty memory BIO will return EOF:
it will return zero and
BIO_should_retry() will be
false. If v is non-zero then it will return
v when it is empty and it will set the read retry
BIO_read_retry() is true. To avoid ambiguity
with a normal positive return value v should be set to
a negative value, typically -1.
*pp to a pointer to the start of the memory BIO's data
and returns the total amount of data available. It is implemented as a
BIO_set_mem_buf() sets the internal
BUF_MEM structure to bm and sets the close flag to
c. That is, c should be either
BIO_set_mem_buf() is a macro.
BIO_get_mem_ptr() places the underlying
BUF_MEM structure in *pp. It is
BIO_new_mem_buf() creates a memory BIO
using len bytes of data at buf.
If len is -1, then buf is
assumed to be NUL terminated and its length is determined by
strlen(3). The BIO is set to a read only
state and as a result cannot be written to. This is useful when some data
needs to be made available from a static area of memory in the form of a
BIO. The supplied data is read directly from the supplied buffer: it is
not copied first, so the supplied area of memory must be
unchanged until the BIO is freed.
Writes to memory BIOs will always succeed if memory is available: their size can grow indefinitely.
Every read from a read/write memory BIO will remove the data just read with an internal copy operation. If a BIO contains a lot of data and it is read in small chunks, the operation can be very slow. The use of a read only memory BIO avoids this problem. If the BIO must be read/write then adding a buffering BIO to the chain will speed up the process.
BIO_s_mem() returns a pointer to a static object.
BIO_get_mem_ptr() return 1 on success or a value
less than or equal to 0 if an error occurred.
BIO_new_mem_buf() returns a newly
allocated BIO object on success or
NULL on error.
BIO *mem = BIO_new(BIO_s_mem()); BIO_puts(mem, "Hello World\n");
Create a read only memory BIO:
char data = "Hello World"; BIO *mem; mem = BIO_new_mem_buf(data, -1);
Extract the BUF_MEM structure from a memory BIO and then free up the BIO:
BUF_MEM *bptr; BIO_get_mem_ptr(mem, &bptr); /* Make sure BIO_free() leaves BUF_MEM alone. */ BIO_set_close(mem, BIO_NOCLOSE); BIO_free(mem);
BIO_s_mem() first appeared in SSLeay 0.6.0.
BIO_get_mem_ptr() first appeared in SSLeay 0.6.5. These functions have been available since OpenBSD 2.4.
BIO_get_mem_data() first appeared in SSLeay 0.9.1
and have been available since OpenBSD 2.6.
BIO_new_mem_buf() first appeared in
OpenSSL 0.9.5 and has been available since OpenBSD
There should be a way to "rewind" a read/write BIO without destroying its contents.
The copying operation should not occur after every small read of a large BIO to improve efficiency.
|May 12, 2018||OpenBSD-current|