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[/] [zipcpu/] [trunk/] [sim/] [verilator/] [byteswap.cpp] - Blame information for rev 204

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1 204 dgisselq
////////////////////////////////////////////////////////////////////////////////
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//
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// Filename:    byteswap.cpp
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//
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// Project:     Zip CPU -- a small, lightweight, RISC CPU soft core
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//
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// Purpose:     To convert between little endian and big endian byte orders,
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//              and to handle conversions between character strings and
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//      bit-endian words made from those characters.
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//
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//
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// Creator:     Dan Gisselquist, Ph.D.
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//              Gisselquist Technology, LLC
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//
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////////////////////////////////////////////////////////////////////////////////
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//
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// Copyright (C) 2015-2016, Gisselquist Technology, LLC
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//
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// This program is free software (firmware): you can redistribute it and/or
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// modify it under the terms of  the GNU General Public License as published
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// by the Free Software Foundation, either version 3 of the License, or (at
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// your option) any later version.
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//
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// This program is distributed in the hope that it will be useful, but WITHOUT
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// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
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// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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// for more details.
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//
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// You should have received a copy of the GNU General Public License along
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// with this program.  (It's in the $(ROOT)/doc directory.  Run make with no
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// target there if the PDF file isn't present.)  If not, see
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// <http://www.gnu.org/licenses/> for a copy.
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//
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// License:     GPL, v3, as defined and found on www.gnu.org,
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//              http://www.gnu.org/licenses/gpl.html
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//
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//
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////////////////////////////////////////////////////////////////////////////////
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//
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//
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#include <stdint.h>
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#include "byteswap.h"
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/*
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 * byteswap
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 *
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 * Given a big (or little) endian word, return a little (or big) endian word.
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 */
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uint32_t
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byteswap(uint32_t v) {
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        uint32_t        r = 0;
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        r = (v & 0x0ff);
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        r <<= 8; v >>= 8;
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        r |= (v & 0x0ff);
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        r <<= 8; v >>= 8;
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        r |= (v & 0x0ff);
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        r <<= 8; v >>= 8;
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        r |= (v & 0x0ff);
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        return r;
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}
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/*
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 * byteswapbuf
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 *
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 * To swap from the byte order of every 32-bit word in the given buffer.
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 */
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void
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byteswapbuf(int ln, uint32_t *buf) {
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        for(int i=0; i<ln; i++)
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                buf[i] = byteswap(buf[i]);
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}
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/*
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 * buildword
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 *
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 * Given a pointer within an array of characters, build a 32-bit big-endian
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 * word from those characters.  Does not require the character pointer to be
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 * aligned.
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 */
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uint32_t
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buildword(const unsigned char *p) {
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        uint32_t        r = 0;
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        r  = (*p++); r <<= 8;
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        r |= (*p++); r <<= 8;
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        r |= (*p++); r <<= 8;
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        r |= (*p  );
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        return r;
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}
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/*
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 * buildswap
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 *
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 * Same as buildword, except that we build a little endian word from the
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 * characters given to us.  Hence the first character is the low order octet
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 * of the word.
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 */
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uint32_t
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buildswap(const unsigned char *p) {
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        uint32_t        r = 0;
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        r  = p[3]; r <<= 8;
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        r |= p[2]; r <<= 8;
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        r |= p[1]; r <<= 8;
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        r |= p[0];
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        return r;
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}
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