/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2015 K. Isom <coder@kyleisom.net>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * copy of this  software and associated documentation  files (the "Software"),
 * to deal  in the Software  without restriction, including  without limitation
 * the rights  to use,  copy, modify,  merge, publish,  distribute, sublicense,
 * and/or  sell copies  of the  Software,  and to  permit persons  to whom  the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS  PROVIDED "AS IS", WITHOUT WARRANTY OF  ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING  BUT NOT  LIMITED TO  THE WARRANTIES  OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS  OR COPYRIGHT  HOLDERS BE  LIABLE FOR  ANY CLAIM,  DAMAGES OR  OTHER
 * LIABILITY,  WHETHER IN  AN ACTION  OF CONTRACT,  TORT OR  OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */


#include <cassert>
#include <cstdint>
#include <cstring>
#include <iostream>

#include <emsha/emsha.h>


using std::uint8_t;
using std::uint32_t;


namespace emsha {


bool
HashEqual(const uint8_t *a, const uint8_t *b)
{
	uint8_t	res = 0;

	EMSHA_CHECK(a != nullptr, false);
	EMSHA_CHECK(b != nullptr, false);

	for (uint32_t i = 0; i < SHA256_HASH_SIZE; i++) {
		res += a[i] ^ b[i];
	}

	return res == 0;
}


#ifndef EMSHA_NO_HEXSTRING
#ifndef EMSHA_NO_HEXLUT
// If using a lookup table is permitted, then the faster way to do this
// is to use one.
static void
writeHexChar(uint8_t *dest, uint8_t src)
{
	static constexpr uint8_t lut[256][3] = {
		"00", "01", "02", "03", "04", "05", "06", "07",
		"08", "09", "0a", "0b", "0c", "0d", "0e", "0f",
		"10", "11", "12", "13", "14", "15", "16", "17",
		"18", "19", "1a", "1b", "1c", "1d", "1e", "1f",
		"20", "21", "22", "23", "24", "25", "26", "27",
		"28", "29", "2a", "2b", "2c", "2d", "2e", "2f",
		"30", "31", "32", "33", "34", "35", "36", "37",
		"38", "39", "3a", "3b", "3c", "3d", "3e", "3f",
		"40", "41", "42", "43", "44", "45", "46", "47",
		"48", "49", "4a", "4b", "4c", "4d", "4e", "4f",
		"50", "51", "52", "53", "54", "55", "56", "57",
		"58", "59", "5a", "5b", "5c", "5d", "5e", "5f",
		"60", "61", "62", "63", "64", "65", "66", "67",
		"68", "69", "6a", "6b", "6c", "6d", "6e", "6f",
		"70", "71", "72", "73", "74", "75", "76", "77",
		"78", "79", "7a", "7b", "7c", "7d", "7e", "7f",
		"80", "81", "82", "83", "84", "85", "86", "87",
		"88", "89", "8a", "8b", "8c", "8d", "8e", "8f",
		"90", "91", "92", "93", "94", "95", "96", "97",
		"98", "99", "9a", "9b", "9c", "9d", "9e", "9f",
		"a0", "a1", "a2", "a3", "a4", "a5", "a6", "a7",
		"a8", "a9", "aa", "ab", "ac", "ad", "ae", "af",
		"b0", "b1", "b2", "b3", "b4", "b5", "b6", "b7",
		"b8", "b9", "ba", "bb", "bc", "bd", "be", "bf",
		"c0", "c1", "c2", "c3", "c4", "c5", "c6", "c7",
		"c8", "c9", "ca", "cb", "cc", "cd", "ce", "cf",
		"d0", "d1", "d2", "d3", "d4", "d5", "d6", "d7",
		"d8", "d9", "da", "db", "dc", "dd", "de", "df",
		"e0", "e1", "e2", "e3", "e4", "e5", "e6", "e7",
		"e8", "e9", "ea", "eb", "ec", "ed", "ee", "ef",
		"f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7",
		"f8", "f9", "fa", "fb", "fc", "fd", "fe", "ff"
	};

	*dest = lut[src][0];
	*(dest + 1) = lut[src][1];
}


#else	// #ifndef EMSHA_NO_HEXLUT
// If the full lookup table can't be used, e.g. because MSP430-level
// memory constraints, we'll work around this using a small (16-byte)
// lookup table and some bit shifting. On platforms where even this is
// too much, the HexString functionality will just be disabled.
static void
writeHexChar(uint8_t *dest, uint8_t src)
{
	static constexpr uint8_t	lut[] = {
		'0', '1', '2', '3', '4', '5', '6', '7',
		'8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
	};

	*dest = lut[((src & 0xF0) >> 4)];
	*(dest + 1) = lut[(src & 0xF)];
}
#endif // #ifndef EMSHA_NO_HEXLUT


void
HexString(uint8_t *dest, uint8_t *src, uint32_t srclen)
{
	size_t	dp = 0;

	for (uint32_t i = 0; i < srclen; i++) {
		writeHexChar(&dest[dp], src[i]);
		dp += 2;
	}
}
#endif // #ifndef EMSHA_NO_HEXSTRING


} // end of namespace emsha