BIO_s_mem, BIO_set_mem_eof_return, BIO_get_mem_data, BIO_set_mem_buf,
BIO_get_mem_ptr, BIO_new_mem_buf - memory BIO
BIO_METHOD * BIO_s_mem(void);
BIO_set_mem_eof_return(BIO *b,int v)
long BIO_get_mem_data(BIO *b, char **pp)
BIO_set_mem_buf(BIO *b,BUF_MEM *bm,int c)
BIO_get_mem_ptr(BIO *b,BUF_MEM **pp)
BIO *BIO_new_mem_buf(void *buf, int len);
return 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.
Memory BIOs support BIO_gets()
If the BIO_CLOSE flag is set when a memory BIO is freed then the underlying
BUF_MEM structure is also freed.
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.
is true if no data is in the BIO.
returns the number of bytes currently stored.
sets the behaviour of memory BIO b
it is empty. If the v
is zero then an empty memory BIO will return EOF
(that is it will return zero and BIO_should_retry(b) will be false. If
is non zero then it will return v
when it is empty and it will
set the read retry flag (that is BIO_read_retry(b) is true). To avoid
ambiguity with a normal positive return value v
should be set to a
negative value, typically -1.
to a pointer to the start of the memory
BIOs data and returns the total amount of data available. It is implemented as
sets the internal BUF_MEM structure to bm
sets the close flag to c
, that is c
should be either BIO_CLOSE
or BIO_NOCLOSE. It is a macro.
places the underlying BUF_MEM structure in pp
It is a macro.
creates a memory BIO using len
bytes of data at
, if len
is -1 then the buf
is assumed to be null
terminated and its length is determined by strlen
. 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
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: that is 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.
There should be an option to set the maximum size of a memory BIO.
There should be a way to "rewind" a read write BIO without destroying
The copying operation should not occur after every small read of a large BIO to
Create a memory BIO and write some data to it:
BIO *mem = BIO_new(BIO_s_mem());
BIO_puts(mem, "Hello World\n");
Create a read only memory BIO:
char data = "Hello World";
mem = BIO_new_mem_buf(data, -1);
Extract the BUF_MEM structure from a memory BIO and then free up the BIO:
BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */