.\"	$OpenBSD: SSL_CTX_set_read_ahead.3,v 1.4 2018/03/27 17:35:50 schwarze Exp $
.\"	OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
.\"
.\" This file was written by Matt Caswell <matt@openssl.org>.
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.Dd $Mdocdate: March 27 2018 $
.Dt SSL_CTX_SET_READ_AHEAD 3
.Os
.Sh NAME
.Nm SSL_CTX_set_read_ahead ,
.Nm SSL_CTX_get_read_ahead ,
.Nm SSL_set_read_ahead ,
.Nm SSL_get_read_ahead ,
.Nm SSL_CTX_get_default_read_ahead
.Nd manage whether to read as many input bytes as possible
.Sh SYNOPSIS
.In openssl/ssl.h
.Ft void
.Fo SSL_CTX_set_read_ahead
.Fa "SSL_CTX *ctx"
.Fa "int yes"
.Fc
.Ft long
.Fo SSL_CTX_get_read_ahead
.Fa "SSL_CTX *ctx"
.Fc
.Ft void
.Fo SSL_set_read_ahead
.Fa "SSL *s"
.Fa "int yes"
.Fc
.Ft long
.Fo SSL_get_read_ahead
.Fa "const SSL *s"
.Fc
.Ft long
.Fo SSL_CTX_get_default_read_ahead
.Fa "SSL_CTX *ctx"
.Fc
.Sh DESCRIPTION
.Fn SSL_CTX_set_read_ahead
and
.Fn SSL_set_read_ahead
set whether as many input bytes as possible are read for non-blocking
reads.
For example if
.Ar x
bytes are currently required by OpenSSL, but
.Ar y
bytes are available from the underlying BIO (where
.Ar y No > Ar x ) ,
then OpenSSL will read all
.Ar y
bytes into its buffer (provided that the buffer is large enough) if
reading ahead is on, or
.Ar x
bytes otherwise.
The parameter
.Fa yes
should be 0 to ensure reading ahead is off, or non zero otherwise.
.Pp
.Fn SSL_CTX_get_read_ahead
and
.Fn SSL_get_read_ahead
indicate whether reading ahead is set or not.
.Pp
.Fn SSL_CTX_get_default_read_ahead
is identical to
.Fn SSL_CTX_get_read_ahead .
.Pp
These functions are implemented as macros.
.Pp
These functions have no effect when used with DTLS.
.Sh RETURN VALUES
.Fn SSL_CTX_get_read_ahead
and
.Fn SSL_get_read_ahead
return 0 if reading ahead is off or non-zero otherwise,
except that the return values are undefined for DTLS.
.Sh SEE ALSO
.Xr ssl 3 ,
.Xr SSL_pending 3
.Sh HISTORY
.Fn SSL_set_read_ahead
and
.Fn SSL_get_read_ahead
appeared in SSLeay 0.4 or earlier and have been available since
.Ox 2.4 .
.Pp
.Fn SSL_CTX_set_read_ahead ,
.Fn SSL_CTX_get_read_ahead ,
and
.Fn SSL_CTX_get_default_read_ahead
first appeared in OpenSSL 0.9.2b and have been available since
.Ox 2.6 .
.Sh CAVEATS
Switching read ahead on can impact the behaviour of the
.Xr SSL_pending 3
function.