/*	$OpenBSD: fmt_scaled.c,v 1.19 2020/10/12 22:08:34 deraadt Exp $	*/

/*
 * Copyright (c) 2001, 2002, 2003 Ian F. Darwin.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * fmt_scaled: Format numbers scaled for human comprehension
 * scan_scaled: Scan numbers in this format.
 *
 * "Human-readable" output uses 4 digits max, and puts a unit suffix at
 * the end.  Makes output compact and easy-to-read esp. on huge disks.
 * Formatting code was originally in OpenBSD "df", converted to library routine.
 * Scanning code written for OpenBSD libutil.
 */

#include "compat.h"

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <ctype.h>
#include <limits.h>

typedef enum {
	NONE = 0, KILO = 1, MEGA = 2, GIGA = 3, TERA = 4, PETA = 5, EXA = 6
} unit_type;

/* These three arrays MUST be in sync!  XXX make a struct */
static const unit_type units[] = { NONE, KILO, MEGA, GIGA, TERA, PETA, EXA };
static const char scale_chars[] = "BKMGTPE";
static const long long scale_factors[] = {
	1LL,
	1024LL,
	1024LL*1024,
	1024LL*1024*1024,
	1024LL*1024*1024*1024,
	1024LL*1024*1024*1024*1024,
	1024LL*1024*1024*1024*1024*1024,
};
#define	SCALE_LENGTH (sizeof(units)/sizeof(units[0]))

#define MAX_DIGITS (SCALE_LENGTH * 3)	/* XXX strlen(sprintf("%lld", -1)? */

/* Format the given "number" into human-readable form in "result".
 * Result must point to an allocated buffer of length FMT_SCALED_STRSIZE.
 * Return 0 on success, -1 and errno set if error.
 */
int
fmt_scaled(long long number, char *result)
{
	long long abval, fract = 0;
	unsigned int i;
	unit_type unit = NONE;

	/* Not every negative long long has a positive representation. */
	if (number == LLONG_MIN) {
		errno = ERANGE;
		return -1;
	}

	abval = llabs(number);

	/* Also check for numbers that are just too darned big to format. */
	if (abval / 1024 >= scale_factors[SCALE_LENGTH-1]) {
		errno = ERANGE;
		return -1;
	}

	/* scale whole part; get unscaled fraction */
	for (i = 0; i < SCALE_LENGTH; i++) {
		if (abval/1024 < scale_factors[i]) {
			unit = units[i];
			fract = (i == 0) ? 0 : abval % scale_factors[i];
			number /= scale_factors[i];
			if (i > 0)
				fract /= scale_factors[i - 1];
			break;
		}
	}

	fract = (10 * fract + 512) / 1024;
	/* if the result would be >= 10, round main number */
	if (fract >= 10) {
		if (number >= 0)
			number++;
		else
			number--;
		fract = 0;
	} else if (fract < 0) {
		/* shouldn't happen */
		fract = 0;
	}

	if (number == 0)
		strlcpy(result, "0B", FMT_SCALED_STRSIZE);
	else if (unit == NONE || number >= 100 || number <= -100) {
		if (fract >= 5) {
			if (number >= 0)
				number++;
			else
				number--;
		}
		(void)snprintf(result, FMT_SCALED_STRSIZE, "%lld%c",
			number, scale_chars[unit]);
	} else
		(void)snprintf(result, FMT_SCALED_STRSIZE, "%lld.%1lld%c",
			number, fract, scale_chars[unit]);

	return 0;
}

#ifdef	MAIN
/*
 * This is the original version of the program in the man page.
 * Copy-and-paste whatever you need from it.
 */
int
main(int argc, char **argv)
{
	char *cinput = "1.5K", buf[FMT_SCALED_STRSIZE];
	long long ninput = 10483892, result;

	if (scan_scaled(cinput, &result) == 0)
		printf("\"%s\" -> %lld\n", cinput, result);
	else
		perror(cinput);

	if (fmt_scaled(ninput, buf) == 0)
		printf("%lld -> \"%s\"\n", ninput, buf);
	else
		fprintf(stderr, "%lld invalid (%s)\n", ninput, strerror(errno));

	return 0;
}
#endif