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.\" $OpenBSD: BUF_MEM_new.3,v 1.4 2016/11/06 15:52:50 jmc Exp $
.\"
.Dd $Mdocdate: November 6 2016 $
.Dt BUF_MEM_NEW 3
.Os
.Sh NAME
.Nm BUF_MEM_new ,
.Nm BUF_MEM_free ,
.Nm BUF_MEM_grow ,
.Nm BUF_strdup
.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 char *
.Fo BUF_strdup
.Fa "const char *str"
.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
.Dq 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.
.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_strdup
copies a NUL terminated string into a block of allocated memory and
returns a pointer to the allocated block.
Unlike the system
.Xr strdup 3
function,
.Fn BUF_strdup
will accept a
.Dv NULL
argument and will return
.Dv NULL
in that case.
Its use in new programs is discouraged.
.Pp
The memory allocated from
.Fn BUF_strdup
should be freed up using the
.Xr free 3
function.
.Sh RETURN VALUES
.Fn BUF_MEM_new
returns the buffer or
.Dv NULL
on error.
.Pp
.Fn BUF_MEM_grow
returns zero on error or the new size (i.e.
.Fa len ) .
.Sh SEE ALSO
.Xr bio 3
.Sh HISTORY
.Fn BUF_MEM_new ,
.Fn BUF_MEM_free
and
.Fn BUF_MEM_grow
are available in all versions of SSLeay and OpenSSL.
.Fn BUF_strdup
was added in SSLeay 0.8.
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