c-ares/docs/ares_parse_txt_reply.3

.\"
.\" Copyright 1998 by the Massachusetts Institute of Technology.
.\" SPDX-License-Identifier: MIT
.\"
.TH ARES_PARSE_TXT_REPLY 3 "27 October 2009"
.SH NAME
ares_parse_txt_reply \- Parse a reply to a DNS query of type TXT
.SH SYNOPSIS
.nf
#include <ares.h>

int ares_parse_txt_reply(const unsigned char* \fIabuf\fP, int \fIalen\fP,
                         struct ares_txt_reply **\fItxt_out\fP);

int ares_parse_txt_reply_ext(const unsigned char* \fIabuf\fP, int \fIalen\fP,
                             struct ares_txt_ext **\fItxt_out\fP);
.fi
.SH DESCRIPTION
The \fIares_parse_txt_reply(3)\fP and \fIares_parse_txt_reply_ext(3)\fP
functions parse the response to a query of type TXT into a linked list (one
element per sub-string) of
.IR "struct ares_txt_reply" " (" "struct ares_txt_ext" ")"
The parameters
.I abuf
and
.I alen
give the contents of the response.  The result is stored in allocated
memory and a pointer to it stored into the variable pointed to by
.IR txt_out .
It is the caller's responsibility to free the resulting
.IR txt_out
structure when it is no longer needed using the function
\fBares_free_data(3)\fP.

The structure 
.I ares_txt_reply
contains the following fields:
.nf
struct ares_txt_reply {
  struct ares_txt_reply  *next;
  unsigned int  length;
  unsigned char *txt;
};
.fi

The structure
.I ares_txt_ext
contains the following fields:
.nf
struct ares_txt_ext {
  struct ares_txt_ext  *next;
  unsigned int  length;
  unsigned char *txt;
  unsigned char record_start;
};
.fi
The
.I record_start
field in
.I struct ares_txt_ext
is 1 if this structure is a start of a TXT record, and 0 if the structure is a
continuation of a previous record. The linked list of the
.I struct ares_txt_ext
will have at least one item with
.I record_start
equal to 1, and may have some items with
.I record_start
equal to 0 between them.

These sequences of
.I struct ares_txt_ext
(starting from the item with
.I record_start
equal to 1, and ending right before the record start item) may be treated as
either components of a single TXT record or as a multi-parted TXT record,
depending on particular use case.
.SH RETURN VALUES
.BR "ares_parse_txt_reply" " (" "ares_parse_txt_reply_ext" ")"
can return any of the following values:
.TP 15
.B ARES_SUCCESS
The response was successfully parsed.
.TP 15
.B ARES_EBADRESP
The response was malformatted.
.TP 15
.B ARES_ENODATA
The response did not contain an answer to the query.
.TP 15
.B ARES_ENOMEM
Memory was exhausted.
.SH AVAILABILITY
This function was first introduced in c-ares version 1.7.0.
.SH SEE ALSO
.BR ares_query (3)
.BR ares_free_data (3)