.TH RQ_SYMBOL 3 2022-07-07 "LCRQ" "Librecast Programmer's Manual"
.SH NAME
rq_symbol \- generate RaptorQ encoding symbol
.SH SYNOPSIS
.nf
.B #include <lcrq.h>
.PP
.BI "int rq_symbol(rq_t *" rq ", rq_pid_t *" pid ", uint8_t *" sym ", int " flags ");"
.fi
.PP
Compile and link with \fI\-llcrq\fP.
.SH DESCRIPTION
Generates a RaptorQ encoding symbol ready for sending.
.PP
Before calling
.B rq_symbol()
the intermediate symbols must first be created with a call to \fBrq_encode\fP(3).
.PP
.I rq
must be a pointer to valid
.B rq_t
context
.PP
.I pid
will be set to the FEC payload ID as per Section 3.2 of RFC6330:
.PP
.EX
0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     SBN       |               Encoding Symbol ID              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
.EE
.PP
SBN (Source Block Number) is an 8 bit unsigned integer. The Encoding Symbol ID
(ESI) is a 24 bit unsigned integer in network byte order.
.PP
On success,
.I sym
will be a pointer to the encoding symbol.
.PP
.I flags
can be set to:
.TP
.BR RQ_RAND
Generate a random repair symbol instead of returning the next ESI.
.LP
.SH RETURN VALUE
Returns a pointer to the encoded symbol.
.SH ERRORS
None.
.SH SEE ALSO
.BR rq_init (3),
.BR rq_free (3),
.BR rq_encode (3),
.BR rq_decode (3),
.BR rq_query (3),
.BR lcrq (7),
.BR errno (3)