Subversion Repositories zipcpu

////////////////////////////////////////////////////////////////////////////////

//

// Filename:    byteswap.cpp

//

// Project:     Zip CPU -- a small, lightweight, RISC CPU soft core

//

// Purpose:     To convert between little endian and big endian byte orders,

//              and to handle conversions between character strings and

//      bit-endian words made from those characters.

//

//

// Creator:     Dan Gisselquist, Ph.D.

//              Gisselquist Technology, LLC

//

////////////////////////////////////////////////////////////////////////////////

//

// Copyright (C) 2015-2016, Gisselquist Technology, LLC

//

// This program is free software (firmware): 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.

//

// This program is distributed in the hope that it will be useful, but WITHOUT

// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY 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 this program.  (It's in the $(ROOT)/doc directory.  Run make with no

// target there if the PDF file isn't present.)  If not, see

// <http://www.gnu.org/licenses/> for a copy.

//

// License:     GPL, v3, as defined and found on www.gnu.org,

//              http://www.gnu.org/licenses/gpl.html

//

//

////////////////////////////////////////////////////////////////////////////////

//

//

#include <stdint.h>

#include "byteswap.h"

/*

 * byteswap

 *

 * Given a big (or little) endian word, return a little (or big) endian word.

 */

uint32_t

byteswap(uint32_t v) {

        uint32_t        r = 0;

        r = (v & 0x0ff);

        r <<= 8; v >>= 8;

        r |= (v & 0x0ff);

        r <<= 8; v >>= 8;

        r |= (v & 0x0ff);

        r <<= 8; v >>= 8;

        r |= (v & 0x0ff);

        return r;

}

/*

 * byteswapbuf

 *

 * To swap from the byte order of every 32-bit word in the given buffer.

 */

void

byteswapbuf(int ln, uint32_t *buf) {

        for(int i=0; i<ln; i++)

                buf[i] = byteswap(buf[i]);

}

/*

 * buildword

 *

 * Given a pointer within an array of characters, build a 32-bit big-endian

 * word from those characters.  Does not require the character pointer to be

 * aligned.

 */

uint32_t

buildword(const unsigned char *p) {

        uint32_t        r = 0;

        r  = (*p++); r <<= 8;

        r |= (*p++); r <<= 8;

        r |= (*p++); r <<= 8;

        r |= (*p  );

        return r;

}

/*

 * buildswap

 *

 * Same as buildword, except that we build a little endian word from the

 * characters given to us.  Hence the first character is the low order octet

 * of the word.

 */

uint32_t

buildswap(const unsigned char *p) {

        uint32_t        r = 0;

        r  = p[3]; r <<= 8;

        r |= p[2]; r <<= 8;

        r |= p[1]; r <<= 8;

        r |= p[0];

        return r;

}