/*
 * Copyright © 2023-2024 Nick Bowler
 *
 * This program 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.
 *
 * This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#ifndef CDECL99_INTCONV_H_
#define CDECL99_INTCONV_H_

#include <string.h>
#include <stdbool.h>

enum { INTCONV_OCTAL = 8, INTCONV_DECIMAL = 10, INTCONV_HEXADECIMAL = 16 };

/*
 * Multiply *v by base, which must be one of the above enumeration constants,
 * and add digit, updating *v with the result.
 *
 * If the result does not fit in cdecl_uintmax, then 0 is returned.  Otherwise,
 * a non-zero result is returned.
 */
static inline bool intconv_shift(cdecl_uintmax *v, unsigned base, unsigned digit)
{
	cdecl_uintmax old_v = *v;

	if (old_v > (cdecl_uintmax)-1 / base)
		return false;
	old_v *= base;

	return (*v = old_v + digit) >= old_v;
}

/*
 * Assuming d is a hexadecimal digit character (converted to unsigned char),
 * return the corresponding value of that digit (between 0 and 15, inclusive).
 */
static inline unsigned char intconv_digit(unsigned char d)
{
	if (d >= '0' && d <= '9') {
		return d - '0';
	} else {
#if ('A' & 7) == 1 && ('B' & 7) == 2 && ('C' & 7) == 3 \
 && ('a' & 7) == 1 && ('b' & 7) == 2 && ('c' & 7) == 3 \
 && ('D' & 7) == 4 && ('E' & 7) == 5 && ('F' & 7) == 6 \
 && ('d' & 7) == 4 && ('e' & 7) == 5 && ('f' & 7) == 6
		/* EBCDIC or ASCII-like encoding */
		return 9 + (d & 7);
#else
		/* Something else */
		static const char idx[] = "abcdef..ABCDEF";
		return 10 + (((char *)memchr(idx, d, sizeof idx) - idx) & 7);
#endif
	}
}

#endif