.\" Copyright (C) 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC")
.\" Copyright (C) 2000, 2001, 2003 Internet Software Consortium.
.\" 
.\" Permission to use, copy, modify, and/or distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\" 
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.\" REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
.\" AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
.\" INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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.\" PERFORMANCE OF THIS SOFTWARE.
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.\" $Id: lwres_context.3,v 1.28.214.1 2009/07/11 01:43:32 tbox Exp $
.\"
.hy 0
.ad l
.\"     Title: lwres_context
.\"    Author: 
.\" Generator: DocBook XSL Stylesheets v1.71.1 <http://docbook.sf.net/>
.\"      Date: Jun 30, 2000
.\"    Manual: BIND9
.\"    Source: BIND9
.\"
.TH "LWRES_CONTEXT" "3" "Jun 30, 2000" "BIND9" "BIND9"
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.SH "NAME"
lwres_context_create, lwres_context_destroy, lwres_context_nextserial, lwres_context_initserial, lwres_context_freemem, lwres_context_allocmem, lwres_context_sendrecv \- lightweight resolver context management
.SH "SYNOPSIS"
.nf
#include <lwres/lwres.h>
.fi
.HP 36
.BI "lwres_result_t lwres_context_create(lwres_context_t\ **" "contextp" ", void\ *" "arg" ", lwres_malloc_t\ " "malloc_function" ", lwres_free_t\ " "free_function" ");"
.HP 37
.BI "lwres_result_t lwres_context_destroy(lwres_context_t\ **" "contextp" ");"
.HP 30
.BI "void lwres_context_initserial(lwres_context_t\ *" "ctx" ", lwres_uint32_t\ " "serial" ");"
.HP 40
.BI "lwres_uint32_t lwres_context_nextserial(lwres_context_t\ *" "ctx" ");"
.HP 27
.BI "void lwres_context_freemem(lwres_context_t\ *" "ctx" ", void\ *" "mem" ", size_t\ " "len" ");"
.HP 28
.BI "void lwres_context_allocmem(lwres_context_t\ *" "ctx" ", size_t\ " "len" ");"
.HP 30
.BI "void * lwres_context_sendrecv(lwres_context_t\ *" "ctx" ", void\ *" "sendbase" ", int\ " "sendlen" ", void\ *" "recvbase" ", int\ " "recvlen" ", int\ *" "recvd_len" ");"
.SH "DESCRIPTION"
.PP
\fBlwres_context_create()\fR
creates a
\fBlwres_context_t\fR
structure for use in lightweight resolver operations. It holds a socket and other data needed for communicating with a resolver daemon. The new
\fBlwres_context_t\fR
is returned through
\fIcontextp\fR, a pointer to a
\fBlwres_context_t\fR
pointer. This
\fBlwres_context_t\fR
pointer must initially be NULL, and is modified to point to the newly created
\fBlwres_context_t\fR.
.PP
When the lightweight resolver needs to perform dynamic memory allocation, it will call
\fImalloc_function\fR
to allocate memory and
\fIfree_function\fR
to free it. If
\fImalloc_function\fR
and
\fIfree_function\fR
are NULL, memory is allocated using
\fBmalloc\fR(3). and
\fBfree\fR(3). It is not permitted to have a NULL
\fImalloc_function\fR
and a non\-NULL
\fIfree_function\fR
or vice versa.
\fIarg\fR
is passed as the first parameter to the memory allocation functions. If
\fImalloc_function\fR
and
\fIfree_function\fR
are NULL,
\fIarg\fR
is unused and should be passed as NULL.
.PP
Once memory for the structure has been allocated, it is initialized using
\fBlwres_conf_init\fR(3)
and returned via
\fI*contextp\fR.
.PP
\fBlwres_context_destroy()\fR
destroys a
\fBlwres_context_t\fR, closing its socket.
\fIcontextp\fR
is a pointer to a pointer to the context that is to be destroyed. The pointer will be set to NULL when the context has been destroyed.
.PP
The context holds a serial number that is used to identify resolver request packets and associate responses with the corresponding requests. This serial number is controlled using
\fBlwres_context_initserial()\fR
and
\fBlwres_context_nextserial()\fR.
\fBlwres_context_initserial()\fR
sets the serial number for context
\fI*ctx\fR
to
\fIserial\fR.
\fBlwres_context_nextserial()\fR
increments the serial number and returns the previous value.
.PP
Memory for a lightweight resolver context is allocated and freed using
\fBlwres_context_allocmem()\fR
and
\fBlwres_context_freemem()\fR. These use whatever allocations were defined when the context was created with
\fBlwres_context_create()\fR.
\fBlwres_context_allocmem()\fR
allocates
\fIlen\fR
bytes of memory and if successful returns a pointer to the allocated storage.
\fBlwres_context_freemem()\fR
frees
\fIlen\fR
bytes of space starting at location
\fImem\fR.
.PP
\fBlwres_context_sendrecv()\fR
performs I/O for the context
\fIctx\fR. Data are read and written from the context's socket. It writes data from
\fIsendbase\fR
\(em typically a lightweight resolver query packet \(em and waits for a reply which is copied to the receive buffer at
\fIrecvbase\fR. The number of bytes that were written to this receive buffer is returned in
\fI*recvd_len\fR.
.SH "RETURN VALUES"
.PP
\fBlwres_context_create()\fR
returns
\fBLWRES_R_NOMEMORY\fR
if memory for the
\fBstruct lwres_context\fR
could not be allocated,
\fBLWRES_R_SUCCESS\fR
otherwise.
.PP
Successful calls to the memory allocator
\fBlwres_context_allocmem()\fR
return a pointer to the start of the allocated space. It returns NULL if memory could not be allocated.
.PP
\fBLWRES_R_SUCCESS\fR
is returned when
\fBlwres_context_sendrecv()\fR
completes successfully.
\fBLWRES_R_IOERROR\fR
is returned if an I/O error occurs and
\fBLWRES_R_TIMEOUT\fR
is returned if
\fBlwres_context_sendrecv()\fR
times out waiting for a response.
.SH "SEE ALSO"
.PP
\fBlwres_conf_init\fR(3),
\fBmalloc\fR(3),
\fBfree\fR(3).
.SH "COPYRIGHT"
Copyright \(co 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC")
.br
Copyright \(co 2000, 2001, 2003 Internet Software Consortium.
.br