1 /* 2 * percent.c - Take percentage of a number 3 * 4 * Copyright (C) 2006 Theodore Ts'o <tytso (at) mit.edu> 5 * 6 * %Begin-Header% 7 * This file may be redistributed under the terms of the GNU Library 8 * General Public License, version 2. 9 * %End-Header% 10 */ 11 12 #include "e2p.h" 13 14 #include <stdlib.h> 15 16 /* 17 * We work really hard to calculate this accurately, while avoiding 18 * an overflow. "Is there a hyphen in anal-retentive?" :-) 19 */ 20 unsigned int e2p_percent(int percent, unsigned int base) 21 { 22 unsigned int mask = ~((1 << (sizeof(unsigned int) - 1) * 8) - 1); 23 24 if (!percent) 25 return 0; 26 if (100 % percent == 0) 27 return base / (100 / percent); 28 if (mask & base) 29 return (base / 100) * percent; 30 return base * percent / 100; 31 } 32 33 #ifdef DEBUG 34 #include <unistd.h> 35 #include <stdio.h> 36 37 main(int argc, char **argv) 38 { 39 unsigned int base; 40 int percent; 41 char *p; 42 int log_block_size = 0; 43 44 if (argc != 3) { 45 fprintf(stderr, "Usage: %s percent base\n", argv[0]); 46 exit(1); 47 } 48 49 percent = strtoul(argv[1], &p, 0); 50 if (p[0] && p[1]) { 51 fprintf(stderr, "Bad percent: %s\n", argv[1]); 52 exit(1); 53 } 54 55 base = strtoul(argv[2], &p, 0); 56 if (p[0] && p[1]) { 57 fprintf(stderr, "Bad base: %s\n", argv[2]); 58 exit(1); 59 } 60 61 printf("%d percent of %u is %u.\n", percent, base, 62 e2p_percent(percent, base)); 63 64 exit(0); 65 } 66 #endif 67
