convtbl.c revision 164671
1/* 2 * Copyright (c) 2003, Trent Nelson, <trent@arpa.com>. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. The name of the author may not be used to endorse or promote products 14 * derived from this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 * 28 * $FreeBSD: head/usr.bin/systat/convtbl.c 164671 2006-11-27 15:26:26Z yar $ 29 */ 30 31#include <sys/types.h> 32#include <unistd.h> 33#include "convtbl.h" 34 35struct convtbl convtbl[] = { 36 /* mul, scale, str */ 37 [SC_BYTE] = { BYTE, BYTES, "bytes" }, 38 [SC_KILOBYTE] = { BYTE, KILO, "KB" }, 39 [SC_MEGABYTE] = { BYTE, MEGA, "MB" }, 40 [SC_GIGABYTE] = { BYTE, GIGA, "GB" }, 41 42 [SC_BIT] = { BIT, BITS, "b" }, 43 [SC_KILOBIT] = { BIT, KILO, "Kb" }, 44 [SC_MEGABIT] = { BIT, MEGA, "Mb" }, 45 [SC_GIGABIT] = { BIT, GIGA, "Gb" }, 46 47 [SC_AUTO] = { 0, 0, "" } 48}; 49 50 51static 52struct convtbl * 53get_tbl_ptr(const uintmax_t size, const int scale) 54{ 55 uintmax_t tmp; 56 int idx; 57 58 /* If our index is out of range, default to auto-scaling. */ 59 idx = scale < SC_AUTO ? scale : SC_AUTO; 60 61 if (idx == SC_AUTO) 62 /* 63 * Simple but elegant algorithm. Count how many times 64 * we can shift our size value right by a factor of ten, 65 * incrementing an index each time. We then use the 66 * index as the array index into the conversion table. 67 */ 68 for (tmp = size, idx = SC_KILOBYTE; 69 tmp >= MEGA && idx < SC_GIGABYTE; 70 tmp >>= 10, idx++); 71 72 return (&convtbl[idx]); 73} 74 75double 76convert(const uintmax_t size, const int scale) 77{ 78 struct convtbl *tp; 79 80 tp = get_tbl_ptr(size, scale); 81 return ((double)size * tp->mul / tp->scale); 82 83} 84 85const char * 86get_string(const uintmax_t size, const int scale) 87{ 88 struct convtbl *tp; 89 90 tp = get_tbl_ptr(size, scale); 91 return (tp->str); 92} 93