.\"	$OpenBSD: BUF_MEM_new.3,v 1.18 2023/07/27 06:20:45 tb Exp $
.\"	OpenSSL doc/crypto/buffer.pod 18edda0f Sep 20 03:28:54 2000 +0000
.\"	not merged: 74924dcb, 58e3457a, 21b0fa91, 7644a9ae
.\"	OpenSSL doc/crypto/BUF_MEM_new.pod 53934822 Jun 9 16:39:19 2016 -0400
.\"	not merged: c952780c, 91da5e77
.\"	OpenSSL doc/man3/BUF_MEM_new.pod 498180de Dec 12 15:35:09 2016 +0300
.\"
.\" This file was written by Ralf S. Engelschall <rse@openssl.org>.
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.Dd $Mdocdate: July 27 2023 $
.Dt BUF_MEM_NEW 3
.Os
.Sh NAME
.Nm BUF_MEM_new ,
.Nm BUF_MEM_free ,
.Nm BUF_MEM_grow ,
.Nm BUF_MEM_grow_clean
.Nd simple character arrays structure
.Sh SYNOPSIS
.In openssl/buffer.h
.Ft BUF_MEM *
.Fo BUF_MEM_new
.Fa void
.Fc
.Ft void
.Fo BUF_MEM_free
.Fa "BUF_MEM *a"
.Fc
.Ft int
.Fo BUF_MEM_grow
.Fa "BUF_MEM *str"
.Fa "size_t len"
.Fc
.Ft int
.Fo BUF_MEM_grow_clean
.Fa "BUF_MEM *str"
.Fa "size_t len"
.Fc
.Sh DESCRIPTION
The buffer library handles simple character arrays.
Buffers are used for various purposes in the library, most notably
memory BIOs.
.Pp
The library uses the
.Vt BUF_MEM
structure defined in buffer.h:
.Bd -literal
typedef struct buf_mem_st
{
	size_t length;	/* current number of bytes */
	char *data;
	size_t max;	/* size of buffer */
} BUF_MEM;
.Ed
.Pp
.Fa length
is the current size of the buffer in bytes;
.Fa max
is the amount of memory allocated to the buffer.
There are three functions which handle these and one miscellaneous function.
.Pp
.Fn BUF_MEM_new
allocates a new buffer of zero size.
.Pp
.Fn BUF_MEM_free
frees up an already existing buffer.
The data is zeroed before freeing up in case the buffer contains
sensitive data.
If
.Fa a
is a
.Dv NULL
pointer, no action occurs.
.Pp
.Fn BUF_MEM_grow
changes the size of an already existing buffer to
.Fa len .
Any data already in the buffer is preserved if it increases in size.
.Pp
.Fn BUF_MEM_grow_clean
is similar to
.Fn BUF_MEM_grow ,
but it sets any freed or additionally allocated memory to zero.
.Sh RETURN VALUES
.Fn BUF_MEM_new
returns the buffer or
.Dv NULL
on error.
.Pp
.Fn BUF_MEM_grow
and
.Fn BUF_MEM_grow_clean
return zero on error or the new size (i.e.\&
.Fa len ) .
.Sh SEE ALSO
.Xr BIO_new 3 ,
.Xr BIO_s_mem 3
.Sh HISTORY
.Fn BUF_MEM_new ,
.Fn BUF_MEM_free ,
and
.Fn BUF_MEM_grow
first appeared in SSLeay 0.6.0.
All these functions  have been available since
.Ox 2.4 .
.Pp
.Fn BUF_MEM_grow_clean
first appeared in OpenSSL 0.9.7 and has been available since
.Ox 3.2 .