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65 lines
1.2 KiB
C
65 lines
1.2 KiB
C
/*
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* percent.c - Take percentage of a number
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*
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* Copyright (C) 2006 Theodore Ts'o <tytso@mit.edu>
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*
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* This file can be redistributed under the terms of the GNU Library General
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* Public License
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*/
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#include "e2p.h"
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#include <stdlib.h>
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/*
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* We work really hard to calculate this accurately, while avoiding
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* an overflow. "Is there a hyphen in anal-retentive?" :-)
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*/
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unsigned int e2p_percent(int percent, unsigned int base)
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{
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unsigned int mask = ~((1 << (sizeof(unsigned int) - 1) * 8) - 1);
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if (!percent)
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return 0;
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if (100 % percent == 0)
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return base / (100 / percent);
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if (mask & base)
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return (base / 100) * percent;
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return base * percent / 100;
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}
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#ifdef DEBUG
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#include <unistd.h>
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#include <stdio.h>
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main(int argc, char **argv)
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{
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unsigned int base;
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int percent;
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char *p;
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int log_block_size = 0;
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if (argc != 3) {
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fprintf(stderr, "Usage: %s percent base\n", argv[0]);
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exit(1);
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}
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percent = strtoul(argv[1], &p, 0);
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if (p[0] && p[1]) {
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fprintf(stderr, "Bad percent: %s\n", argv[1]);
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exit(1);
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}
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base = strtoul(argv[2], &p, 0);
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if (p[0] && p[1]) {
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fprintf(stderr, "Bad base: %s\n", argv[2]);
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exit(1);
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}
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printf("%d percent of %u is %u.\n", percent, base,
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e2p_percent(percent, base));
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exit(0);
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}
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#endif
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