trusty (3) BIO_get_mem_ptr.3ssl.gz

NAME

       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

SYNOPSIS

        #include <openssl/bio.h>

        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);

DESCRIPTION

       BIO_s_mem() 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() and BIO_puts().

       If the BIO_CLOSE flag is set when a memory BIO is freed then the underlying BUF_MEM structure is also
       freed.

       Calling BIO_reset() 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() is true if no data is in the BIO.

       BIO_ctrl_pending() returns the number of bytes currently stored.

       BIO_set_mem_eof_return() sets the behaviour of memory BIO b when 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 v
       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.

       BIO_get_mem_data() sets pp to a pointer to the start of the memory BIOs data and returns the total amount
       of data available. It is implemented as a macro.

       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_CLOSE or BIO_NOCLOSE.  It is a macro.

       BIO_get_mem_ptr() places the underlying BUF_MEM structure in pp. It is a macro.

       BIO_new_mem_buf() creates a memory BIO using len bytes of data at buf, 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 not copied first, so the supplied area of memory must be unchanged until the BIO is freed.

NOTES

       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.

BUGS

       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 its contents.

       The copying operation should not occur after every small read of a large BIO to improve efficiency.

EXAMPLE

       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";
        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);
        BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */
        BIO_free(mem);

SEE ALSO

       TBA