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/contrib/bind9/lib/lwres/man/lwres_context.3

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  1.\" Copyright (C) 2004, 2005, 2007, 2012 Internet Systems Consortium, Inc. ("ISC")
  2.\" Copyright (C) 2000, 2001, 2003 Internet Software Consortium.
  3.\" 
  4.\" Permission to use, copy, modify, and/or distribute this software for any
  5.\" purpose with or without fee is hereby granted, provided that the above
  6.\" copyright notice and this permission notice appear in all copies.
  7.\" 
  8.\" THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
  9.\" REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 10.\" AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 11.\" INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 12.\" LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 13.\" OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 14.\" PERFORMANCE OF THIS SOFTWARE.
 15.\"
 16.\" $Id$
 17.\"
 18.hy 0
 19.ad l
 20.\"     Title: lwres_context
 21.\"    Author: 
 22.\" Generator: DocBook XSL Stylesheets v1.71.1 <http://docbook.sf.net/>
 23.\"      Date: Jun 30, 2000
 24.\"    Manual: BIND9
 25.\"    Source: BIND9
 26.\"
 27.TH "LWRES_CONTEXT" "3" "Jun 30, 2000" "BIND9" "BIND9"
 28.\" disable hyphenation
 29.nh
 30.\" disable justification (adjust text to left margin only)
 31.ad l
 32.SH "NAME"
 33lwres_context_create, lwres_context_destroy, lwres_context_nextserial, lwres_context_initserial, lwres_context_freemem, lwres_context_allocmem, lwres_context_sendrecv \- lightweight resolver context management
 34.SH "SYNOPSIS"
 35.nf
 36#include <lwres/lwres.h>
 37.fi
 38.HP 36
 39.BI "lwres_result_t lwres_context_create(lwres_context_t\ **" "contextp" ", void\ *" "arg" ", lwres_malloc_t\ " "malloc_function" ", lwres_free_t\ " "free_function" ");"
 40.HP 37
 41.BI "lwres_result_t lwres_context_destroy(lwres_context_t\ **" "contextp" ");"
 42.HP 30
 43.BI "void lwres_context_initserial(lwres_context_t\ *" "ctx" ", lwres_uint32_t\ " "serial" ");"
 44.HP 40
 45.BI "lwres_uint32_t lwres_context_nextserial(lwres_context_t\ *" "ctx" ");"
 46.HP 27
 47.BI "void lwres_context_freemem(lwres_context_t\ *" "ctx" ", void\ *" "mem" ", size_t\ " "len" ");"
 48.HP 28
 49.BI "void lwres_context_allocmem(lwres_context_t\ *" "ctx" ", size_t\ " "len" ");"
 50.HP 30
 51.BI "void * lwres_context_sendrecv(lwres_context_t\ *" "ctx" ", void\ *" "sendbase" ", int\ " "sendlen" ", void\ *" "recvbase" ", int\ " "recvlen" ", int\ *" "recvd_len" ");"
 52.SH "DESCRIPTION"
 53.PP
 54\fBlwres_context_create()\fR
 55creates a
 56\fBlwres_context_t\fR
 57structure for use in lightweight resolver operations. It holds a socket and other data needed for communicating with a resolver daemon. The new
 58\fBlwres_context_t\fR
 59is returned through
 60\fIcontextp\fR, a pointer to a
 61\fBlwres_context_t\fR
 62pointer. This
 63\fBlwres_context_t\fR
 64pointer must initially be NULL, and is modified to point to the newly created
 65\fBlwres_context_t\fR.
 66.PP
 67When the lightweight resolver needs to perform dynamic memory allocation, it will call
 68\fImalloc_function\fR
 69to allocate memory and
 70\fIfree_function\fR
 71to free it. If
 72\fImalloc_function\fR
 73and
 74\fIfree_function\fR
 75are NULL, memory is allocated using
 76\fBmalloc\fR(3). and
 77\fBfree\fR(3). It is not permitted to have a NULL
 78\fImalloc_function\fR
 79and a non\-NULL
 80\fIfree_function\fR
 81or vice versa.
 82\fIarg\fR
 83is passed as the first parameter to the memory allocation functions. If
 84\fImalloc_function\fR
 85and
 86\fIfree_function\fR
 87are NULL,
 88\fIarg\fR
 89is unused and should be passed as NULL.
 90.PP
 91Once memory for the structure has been allocated, it is initialized using
 92\fBlwres_conf_init\fR(3)
 93and returned via
 94\fI*contextp\fR.
 95.PP
 96\fBlwres_context_destroy()\fR
 97destroys a
 98\fBlwres_context_t\fR, closing its socket.
 99\fIcontextp\fR
100is 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.
101.PP
102The 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
103\fBlwres_context_initserial()\fR
104and
105\fBlwres_context_nextserial()\fR.
106\fBlwres_context_initserial()\fR
107sets the serial number for context
108\fI*ctx\fR
109to
110\fIserial\fR.
111\fBlwres_context_nextserial()\fR
112increments the serial number and returns the previous value.
113.PP
114Memory for a lightweight resolver context is allocated and freed using
115\fBlwres_context_allocmem()\fR
116and
117\fBlwres_context_freemem()\fR. These use whatever allocations were defined when the context was created with
118\fBlwres_context_create()\fR.
119\fBlwres_context_allocmem()\fR
120allocates
121\fIlen\fR
122bytes of memory and if successful returns a pointer to the allocated storage.
123\fBlwres_context_freemem()\fR
124frees
125\fIlen\fR
126bytes of space starting at location
127\fImem\fR.
128.PP
129\fBlwres_context_sendrecv()\fR
130performs I/O for the context
131\fIctx\fR. Data are read and written from the context's socket. It writes data from
132\fIsendbase\fR
133\(em typically a lightweight resolver query packet \(em and waits for a reply which is copied to the receive buffer at
134\fIrecvbase\fR. The number of bytes that were written to this receive buffer is returned in
135\fI*recvd_len\fR.
136.SH "RETURN VALUES"
137.PP
138\fBlwres_context_create()\fR
139returns
140\fBLWRES_R_NOMEMORY\fR
141if memory for the
142\fBstruct lwres_context\fR
143could not be allocated,
144\fBLWRES_R_SUCCESS\fR
145otherwise.
146.PP
147Successful calls to the memory allocator
148\fBlwres_context_allocmem()\fR
149return a pointer to the start of the allocated space. It returns NULL if memory could not be allocated.
150.PP
151\fBLWRES_R_SUCCESS\fR
152is returned when
153\fBlwres_context_sendrecv()\fR
154completes successfully.
155\fBLWRES_R_IOERROR\fR
156is returned if an I/O error occurs and
157\fBLWRES_R_TIMEOUT\fR
158is returned if
159\fBlwres_context_sendrecv()\fR
160times out waiting for a response.
161.SH "SEE ALSO"
162.PP
163\fBlwres_conf_init\fR(3),
164\fBmalloc\fR(3),
165\fBfree\fR(3).
166.SH "COPYRIGHT"
167Copyright \(co 2004, 2005, 2007, 2012 Internet Systems Consortium, Inc. ("ISC")
168.br
169Copyright \(co 2000, 2001, 2003 Internet Software Consortium.
170.br