library/GSM_RestOctets.ttcn

/**
 * GSM Rest Octets definitions as per 3GPP TS 44.018.
 *
 * (C) 2020 Vadim Yanitskiy <axilirator@gmail.com>
 * All rights reserved.
 *
 * Released under the terms of GNU General Public License, Version 2 or
 * (at your option) any later version.
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

module GSM_RestOctets {

import from General_Types all;
import from Osmocom_Types all;

/* 10.5.2.34 SI 3 Rest Octets */
type record SI3RestOctets {
	SelectionParamsOpt	sel_params,
	PowerOffsetOpt		pwr_offset,
	BIT1			si_2ter_ind,
	BIT1			early_cm_ind,
	SchedIfAndWhere		sched_where,
	GPRSIndicatorOpt	gprs_ind,
	BIT1			umts_early_cm_ind,
	SI2quaterIndicatorOpt	si2_quater_ind,
	BIT1			iu_mode_ind ('1'B) optional,
	SI21IndicatorOpt	si21_ind optional
	/* ... spare padding ... */
} with {
	variant (si_2ter_ind) "CSN.1 L/H"
	variant (early_cm_ind) "CSN.1 L/H"
	variant (umts_early_cm_ind) "CSN.1 L/H"

	/* If Iu mode is not supported in the cell, the Iu Indicator is not sent
	 * within this cell. Iu Indicator is included if and only if GPRS is
	 * not supported, and Iu mode is supported in the cell. */
	variant (iu_mode_ind) "PRESENCE(gprs_ind.presence = '0'B)"
	/* SI21 field is only present if 'WHERE' information is not present. */
	variant (si21_ind) "PRESENCE(sched_where.presence = '0'B)"

	/* The TITAN's RAW encoder generates an octet-aligned octetstring,
	 * so we should make sure that unused bits contain proper padding. */
	variant "PADDING(yes), PADDING_PATTERN('00101011'B)"
};

/* 10.5.2.35 SI 4 Rest Octets (O & S) */
type record SI4RestOctets {
	SelectionParamsOpt	sel_params,
	PowerOffsetOpt		pwr_offset,
	GPRSIndicatorOpt	gprs_ind,
	BIT1			s_presence, // L/H
	/* TODO: optional "Rest Octets S" part */
	bitstring		s optional
} with {
	variant (s_presence) "CSN.1 L/H"
	variant (s) "PRESENCE(s_presence = '1'B)"

	/* The TITAN's RAW encoder generates an octet-aligned octetstring,
	 * so we should make sure that unused bits contain proper padding. */
	variant "PADDING(yes), PADDING_PATTERN('00101011'B)"
};

/* Selection Parameters */
type record SelectionParams {
	boolean			cbq,
	uint6_t			cr_offset,
	uint3_t			temp_offset,
	uint5_t			penalty_time
} with {
	variant (cbq) "FIELDLENGTH(1)"
};

/* Optional Selection Parameters: L | H < Selection Parameters > */
type record SelectionParamsOpt {
	BIT1			presence, // L/H
	SelectionParams		params optional
} with {
	variant (presence) "CSN.1 L/H"
	variant (params) "PRESENCE(presence = '1'B)"
};

/* Optional Power Offset: L | H < Power Offset bit(2) > */
type record PowerOffsetOpt {
	BIT1			presence, // L/H
	uint2_t			offset optional
} with {
	variant (presence) "CSN.1 L/H"
	variant (offset) "PRESENCE(presence = '1'B)"
};

/* Scheduling if and where: L | H < WHERE bit(3) > */
type record SchedIfAndWhere {
	BIT1			presence, // L/H
	uint3_t			where optional
} with {
	variant (presence) "CSN.1 L/H"
	variant (where) "PRESENCE(presence = '1'B)"
};

type record GPRSIndicator {
	uint3_t			ra_colour,
	BIT1			si13_pos
} with { variant "" };

/* Optional GPRS Indicator: L | H < GPRS Indicator > */
type record GPRSIndicatorOpt {
	BIT1			presence, // L/H
	GPRSIndicator		ind optional
} with {
	variant (presence) "CSN.1 L/H"
	variant (ind) "PRESENCE(presence = '1'B)"
};

/* Optional SI2quater Indicator: L | H < SI2quater Indicator > */
type record SI2quaterIndicatorOpt {
	BIT1			presence, // L/H
	BIT1			ind optional
} with {
	variant (presence) "CSN.1 L/H"
	variant (ind) "PRESENCE(presence = '1'B)"
};

/* Optional SI21 Indicator: L | H < SI21 Position > */
type record SI21IndicatorOpt {
	BIT1			presence, // L/H
	BIT1			pos optional
} with {
	variant (presence) "CSN.1 L/H"
	variant (pos) "PRESENCE(presence = '1'B)"
};

external function enc_SI3RestOctets(in SI3RestOctets ro) return octetstring
	with { extension "prototype(convert) encode(RAW)" };
external function dec_SI3RestOctets(in octetstring stream) return SI3RestOctets
	with { extension "prototype(convert) decode(RAW)" };

external function enc_SI4RestOctets(in SI4RestOctets ro) return octetstring
	with { extension "prototype(convert) encode(RAW)" };
external function dec_SI4RestOctets(in octetstring stream) return SI4RestOctets
	with { extension "prototype(convert) decode(RAW)" };


/* Basic templates to be extended in place */
template (value) SI3RestOctets ts_SI3RestOctets := {
	sel_params := {
		presence := CSN1_L,
		params := omit
	},
	pwr_offset := {
		presence := CSN1_L,
		offset := omit
	},
	si_2ter_ind := CSN1_L,
	early_cm_ind := CSN1_L,
	sched_where := {
		presence := CSN1_L,
		where := omit
	},
	gprs_ind := {
		presence := CSN1_L,
		ind := omit
	},
	umts_early_cm_ind := CSN1_L,
	si2_quater_ind := {
		presence := CSN1_L,
		ind := omit
	},
	iu_mode_ind := omit,
	si21_ind := {
		presence := CSN1_L,
		pos := omit
	}
}

template (value) SI4RestOctets ts_SI4RestOctets := {
	sel_params := {
		presence := CSN1_L,
		params := omit
	},
	pwr_offset := {
		presence := CSN1_L,
		offset := omit
	},
	gprs_ind := {
		presence := CSN1_L,
		ind := omit
	},
	s_presence := CSN1_L,
	s := omit
}


} with { encode "RAW"; variant "FIELDORDER(msb)" }