/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