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  man pages->NetBSD man pages -> BIO_s_mem (3)              



NAME    [Toc]    [Back]

       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

LIBRARY    [Toc]    [Back]

       libcrypto, -lcrypto

SYNOPSIS    [Toc]    [Back]

        #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    [Toc]    [Back]

       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

       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    [Toc]    [Back]

       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 lots 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

BUGS    [Toc]    [Back]

       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    [Toc]    [Back]

       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 */

SEE ALSO    [Toc]    [Back]


2001-04-12                    0.9.6g                 BIO_s_mem(3)
[ Back ]
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