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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.

  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. 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 much 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.

RESTRICTIONS
  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.

  To improve efficiency, the copying operation should not occur after every
  small read of a large BIO.

EXAMPLES
  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

Index for Section 3

Alphabetical listing for B

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