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- =pod
- =head1 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
- =head1 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);
- =head1 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<b> when it is
- empty. If the B<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 B<v> is non
- zero then it will return B<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 B<v> should be set to a negative value, typically -1.
- BIO_get_mem_data() sets B<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 B<bm> and sets the
- close flag to B<c>, that is B<c> should be either BIO_CLOSE or BIO_NOCLOSE.
- It is a macro.
- BIO_get_mem_ptr() places the underlying BUF_MEM structure in B<pp>. It is
- a macro.
- BIO_new_mem_buf() creates a memory BIO using B<len> bytes of data at B<buf>,
- if B<len> is -1 then the B<buf> is assumed to be null terminated and its
- length is determined by B<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 B<not> copied
- first, so the supplied area of memory must be unchanged until the BIO is freed.
- =head1 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.
- =head1 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.
- =head1 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);
-
- =head1 SEE ALSO
- TBA
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