BIO_get_mem_data man page on DragonFly

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BIO_S_MEM(3)		 BSD Library Functions Manual		  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);

     long
     BIO_set_mem_eof_return(BIO *b, int v);

     long
     BIO_get_mem_data(BIO *b, char **pp);

     long
     BIO_set_mem_buf(BIO *b, BUF_MEM *bm, int c);

     long
     BIO_get_mem_ptr(BIO *b, BUF_MEM **pp);

     BIO *
     BIO_new_mem_buf(void *buf, int len);

DESCRIPTION
     BIO_s_mem() returns 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(3) and BIO_puts(3).

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

     Calling BIO_reset(3) 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(3) is true if no data is in the BIO.

     BIO_ctrl_pending(3) returns the number of bytes currently stored.

     BIO_set_mem_eof_return(3) sets the behaviour of memory BIO b when it is
     empty.  If v is zero, then an empty memory BIO will return EOF: It will
     return zero and BIO_should_retry() 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:
     BIO_read_retry() 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 BIO's
     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.
     BIO_set_mem_buf() 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 buf is assumed to be NUL terminated and its length is
     determined by strlen(3).  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 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.

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);
	   /* Make sure BIO_free() leaves BUF_MEM alone. */
	   BIO_set_close(mem, BIO_NOCLOSE);
	   BIO_free(mem);

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.

BSD				March 28, 2024				   BSD
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