BIO_s_mem(3)

     BIO_s_mem(3)           0.9.6h (2000-09-16)           BIO_s_mem(3)

     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.

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     BIO_s_mem(3)           0.9.6h (2000-09-16)           BIO_s_mem(3)

          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 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 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:

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     BIO_s_mem(3)           0.9.6h (2000-09-16)           BIO_s_mem(3)

           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

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