.\" Copyright (C) 2004, 2005, 2007, 2012 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,
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.\" OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
.\" PERFORMANCE OF THIS SOFTWARE.
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.\" $Id$
.\"
.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, 2012 Internet Systems Consortium, Inc. ("ISC")
.br
Copyright \(co 2000, 2001, 2003 Internet Software Consortium.
.br