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

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  2.\" Copyright (C) 2000, 2001, 2003 Internet Software Consortium.
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 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