/*
 * pdp10-extint.c
 * Copyright (C) 2013-2015  Mikael Pettersson
 *
 * This file is part of pdp10-tools.
 *
 * pdp10-tools is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * pdp10-tools is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with pdp10-tools.  If not, see <http://www.gnu.org/licenses/>.
 */
/*
 * Provide types and procedures for converting 18 and 36-bit integers
 * to and from arrays of 9-bit bytes (nonets).  Use these together with
 * pdp10_fread() and pdp10_fwrite() to convert 18 and 36-bit integers
 * between host-level and file-level binary representations.
 */
#include "pdp10-extint.h"

/*
 * The behaviour of the PDP10's byte pointers implies a big-endian storage model,
 * as does the layout of its 72-bit long integers.
 */

void pdp10_uint18_to_ext(pdp10_uint18_t val, struct pdp10_ext_uint18 *ext)
{
    ext->nonet[0] = (val >> 9) & 0x1FF;
    ext->nonet[1] = val & 0x1FF;
}

pdp10_uint18_t pdp10_uint18_from_ext(const struct pdp10_ext_uint18 *ext)
{
    return
	((pdp10_uint18_t)(ext->nonet[0] & 0x1FF) << 9)
	| (ext->nonet[1] & 0x1FF);
}

void pdp10_uint36_to_ext(pdp10_uint36_t val, struct pdp10_ext_uint36 *ext)
{
    ext->nonet[0] = (val >> 27) & 0x1FF;
    ext->nonet[1] = (val >> 18) & 0x1FF;
    ext->nonet[2] = (val >> 9) & 0x1FF;
    ext->nonet[3] = val & 0x1FF;
}

pdp10_uint36_t pdp10_uint36_from_ext(const struct pdp10_ext_uint36 *ext)
{
    return
	((pdp10_uint36_t)(ext->nonet[0] & 0x1FF) << 27)
	| ((pdp10_uint36_t)(ext->nonet[1] & 0x1FF) << 18)
	| ((pdp10_uint36_t)(ext->nonet[2] & 0x1FF) << 9)
	| (ext->nonet[3] & 0x1FF);
}