usr/src/lib/libcmdutils/common/nicenum.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  24  * Copyright 2017 Jason king
  25  */
  26
  27 #include <stdio.h>
  28 #include <string.h>
  29 #include <sys/types.h>
  30 #include <sys/debug.h>
  31 #include "libcmdutils.h"
  32
  33 /* The largest suffix that can fit, aka an exabyte (2^60 / 10^18) */
  34 #define INDEX_MAX       (6)
  35
  36 /* Verify INDEX_MAX fits */
  37 CTASSERT(INDEX_MAX * 10 < sizeof (uint64_t) * 8);
  38
  39 void
  40 nicenum_scale(uint64_t n, size_t units, char *buf, size_t buflen,
  41     uint32_t flags)
  42 {
  43         uint64_t divamt = 1024;
  44         uint64_t divisor = 1;
  45         int index = 0;
  46         int rc = 0;
  47         char u;
  48
  49         if (units == 0)
  50                 units = 1;
  51
  52         if (n > 0) {
  53                 n *= units;
  54                 if (n < units)
  55                         goto overflow;
  56         }
  57
  58         if (flags & NN_DIVISOR_1000)
  59                 divamt = 1000;
  60
  61         /*
  62          * This tries to find the suffix S(n) such that
  63          * S(n) <= n < S(n+1), where S(n) = 2^(n*10) | 10^(3*n)
  64          * (i.e. 1024/1000, 1,048,576/1,000,000, etc).  Stop once S(n)
  65          * is the largest prefix supported (i.e. don't bother computing
  66          * and checking S(n+1).  Since INDEX_MAX should be the largest
  67          * suffix that fits (currently an exabyte), S(INDEX_MAX + 1) is
  68          * never checked as it would overflow.
  69          */
  70         while (index < INDEX_MAX) {
  71                 uint64_t newdiv = divisor * divamt;
  72
  73                 /* CTASSERT() guarantee these never trip */
  74                 VERIFY3U(newdiv, >=, divamt);
  75                 VERIFY3U(newdiv, >=, divisor);
  76
  77                 if (n < newdiv)
  78                         break;
  79
  80                 divisor = newdiv;
  81                 index++;
  82         }
  83
  84         u = " KMGTPE"[index];
  85
  86         if (index == 0) {
  87                 rc = snprintf(buf, buflen, "%llu", n);
  88         } else if (n % divisor == 0) {
  89                 /*
  90                  * If this is an even multiple of the base, always display
  91                  * without any decimal precision.
  92                  */
  93                 rc = snprintf(buf, buflen, "%llu%c", n / divisor, u);
  94         } else {
  95                 /*
  96                  * We want to choose a precision that reflects the best choice
  97                  * for fitting in 5 characters.  This can get rather tricky
  98                  * when we have numbers that are very close to an order of
  99                  * magnitude.  For example, when displaying 10239 (which is
 100                  * really 9.999K), we want only a single place of precision
 101                  * for 10.0K.  We could develop some complex heuristics for
 102                  * this, but it's much easier just to try each combination
 103                  * in turn.
 104                  */
 105                 int i;
 106                 for (i = 2; i >= 0; i--) {
 107                         if ((rc = snprintf(buf, buflen, "%.*f%c", i,
 108                             (double)n / divisor, u)) <= 5)
 109                                 break;
 110                 }
 111         }
 112
 113         if (rc + 1 > buflen || rc < 0)
 114                 goto overflow;
 115
 116         return;
 117
 118 overflow:
 119         /* prefer a more verbose message if possible */
 120         if (buflen > 10)
 121                 (void) strlcpy(buf, "<overflow>", buflen);
 122         else
 123                 (void) strlcpy(buf, "??", buflen);
 124 }
 125
 126 void
 127 nicenum(uint64_t num, char *buf, size_t buflen)
 128 {
 129         nicenum_scale(num, 1, buf, buflen, 0);
 130 }