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Annotation of src/lib/libutil/strpct.c, Revision 1.3

1.3     ! christos    1: /* $NetBSD: strpct.c,v 1.2 2011/09/02 10:13:44 christos Exp $ */
1.1       christos    2:
                      3: /*-
                      4:  * Copyright (c) 1998 The NetBSD Foundation, Inc.
                      5:  * All rights reserved.
                      6:  *
                      7:  * This code is derived from software contributed to The NetBSD Foundation
                      8:  * by Erik E. Fair
                      9:  *
                     10:  * Redistribution and use in source and binary forms, with or without
                     11:  * modification, are permitted provided that the following conditions
                     12:  * are met:
                     13:  * 1. Redistributions of source code must retain the above copyright
                     14:  *    notice, this list of conditions and the following disclaimer.
                     15:  * 2. Redistributions in binary form must reproduce the above copyright
                     16:  *    notice, this list of conditions and the following disclaimer in the
                     17:  *    documentation and/or other materials provided with the distribution.
                     18:  *
                     19:  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
                     20:  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
                     21:  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
                     22:  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
                     23:  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
                     24:  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
                     25:  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
                     26:  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
                     27:  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
                     28:  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
                     29:  * POSSIBILITY OF SUCH DAMAGE.
                     30:  */
                     31:
                     32: /*
                     33:  * Calculate a percentage without resorting to floating point
                     34:  * and return a pointer to a string
                     35:  *
                     36:  * "digits" is the number of digits past the decimal place you want
                     37:  * (zero being the straight percentage with no decimals)
                     38:  *
                     39:  * Erik E. Fair <fair@clock.org>, May 8, 1997
                     40:  */
                     41:
                     42: #include <sys/cdefs.h>
1.3     ! christos   43: __RCSID("$NetBSD: strpct.c,v 1.2 2011/09/02 10:13:44 christos Exp $");
1.1       christos   44:
                     45: #include <stdint.h>
                     46: #include <locale.h>
                     47: #include <limits.h>
                     48: #include <stdio.h>
                     49: #include <errno.h>
                     50: #include <util.h>
                     51:
                     52: char *
1.3     ! christos   53: strspct(char *buf, size_t bufsiz, intmax_t numerator, intmax_t denominator,
        !            54:     size_t digits)
        !            55: {
        !            56:        int sign;
        !            57:
        !            58:        switch (bufsiz) {
        !            59:        case 1:
        !            60:                *buf = '\0';
        !            61:                /*FALLTHROUGH*/
        !            62:        case 0:
        !            63:                return buf;
        !            64:        default:
        !            65:                break;
        !            66:        }
        !            67:
        !            68:        if (denominator < 0) {
        !            69:                denominator = -denominator;
        !            70:                sign = 1;
        !            71:        } else
        !            72:                sign = 0;
        !            73:
        !            74:        if (numerator < 0) {
        !            75:                numerator = -numerator;
        !            76:                sign++;
        !            77:        }
        !            78:
        !            79:        sign &= 1;
        !            80:        (void)strpct(buf + sign, bufsiz - sign, (uintmax_t)numerator,
        !            81:            (uintmax_t)denominator, digits);
        !            82:        if (sign)
        !            83:                *buf = '-';
        !            84:        return buf;
        !            85: }
        !            86:
        !            87: char *
1.1       christos   88: strpct(char *buf, size_t bufsiz, uintmax_t numerator, uintmax_t denominator,
                     89:     size_t digits)
                     90: {
                     91:        uintmax_t factor, result;
                     92:        size_t u;
                     93:
                     94:        factor = 100;
                     95:        for (u = 0; u < digits; u++) {
                     96:                /* watch out for overflow! */
                     97:                if (factor < (UINTMAX_MAX / 10))
                     98:                        factor *= 10;
                     99:                else
                    100:                        break;
                    101:        }
                    102:
                    103:        /* watch out for overflow! */
                    104:        if (numerator < (UINTMAX_MAX / factor))
                    105:                numerator *= factor;
                    106:        else {
                    107:                /* toss some of the bits of lesser significance */
                    108:                denominator /= factor;
                    109:        }
                    110:
                    111:        if (denominator == 0)
                    112:                denominator = 1;
                    113:
                    114:        result = numerator / denominator;
                    115:
                    116:        if (digits == 0)
                    117:                (void)snprintf(buf, bufsiz, "%ju", result);
                    118:        else {
                    119:                factor /= 100;          /* undo initialization */
                    120:
1.2       christos  121:                (void)snprintf(buf, bufsiz, "%ju%s%0*ju",
1.1       christos  122:                    result / factor, localeconv()->decimal_point, (int)u,
                    123:                    result % factor);
                    124:        }
                    125:
                    126:        return buf;
                    127: }

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