New file. The interface is inspired

by the human_readable function that was in du.c, but it's pretty
much rewritten from scratch.

lib/human.c

@@ -0,0 +1,204 @@
+/* human.c -- print human readable file size
+   Copyright (C) 1996, 1997 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+/* Originally contributed by lm@sgi.com;
+   --si and large file support added by eggert@twinsun.com.  */
+
+#include <config.h>
+
+#if HAVE_INTTYPES_H
+# include <inttypes.h>
+#endif
+
+#include <sys/types.h>
+#include <stdio.h>
+
+#if HAVE_LIMITS_H
+# include <limits.h>
+#endif
+
+#ifndef CHAR_BIT
+#define CHAR_BIT 8
+#endif
+
+#include "human.h"
+
+static const char suffixes[] = 
+{
+  0,	/* not used */
+  'k',	/* kilo */
+  'M',	/* Mega */
+  'G',	/* Giga */
+  'T',	/* Tera */
+  'P',	/* Peta */
+  'E',	/* Exa */
+  'Z',	/* Zetta */
+  'Y'	/* Yotta */
+};
+
+/* Convert N to a human readable format in BUF.
+   
+   N is expressed in units of FROM_UNITS; use units of TO_UNITS in the
+   output number.  FROM_UNITS and TO_UNITS must be positive, and one must
+   be a multiple of the other.
+   
+   If BASE is nonzero, use a format like "127k" if possible,
+   using powers of BASE; otherwise, use ordinary decimal format.
+   Normally BASE is either 1000 or 1024; it must be at least 2.
+   Most people visually process strings of 3-4 digits effectively,
+   but longer strings of digits are more prone to misinterpretation.
+   Hence, converting to an abbreviated form usually improves readability.
+   Use a suffix indicating which power is being used.
+   For example, assuming BASE is 1024, 8500 would be converted to 8.3k,
+   133456345 to 127M, 56990456345 to 53G, and so on.  Numbers smaller
+   than BASE aren't modified.  */
+
+char *
+human_readable (n, buf, from_units, to_units, base)
+     uintmax_t n;
+     char *buf;
+     int from_units;
+     int to_units;
+     int base;
+{
+  uintmax_t amt;
+  int tenths;
+  int power;
+  char *p;
+
+  /* 0 means adjusted N == AMT.TENTHS;
+     1 means AMT.TENTHS < adjusted N < AMT.TENTHS + 0.05;
+     2 means adjusted N == AMT.TENTHS + 0.05;
+     3 means AMT.TENTHS + 0.05 < adjusted N < AMT.TENTHS + 0.1.  */
+  int rounding;
+
+  p = buf + LONGEST_HUMAN_READABLE;
+  *p = '\0';
+   
+
+  /* Adjust AMT out of FROM_UNITS units and into TO_UNITS units.  */
+   
+  if (to_units <= from_units)
+    {
+      int multiplier = from_units / to_units;
+      amt = n * multiplier;
+      tenths = rounding = 0;
+
+      if (amt / multiplier != n)
+	{
+	  /* Overflow occurred during multiplication.  We should use
+	     multiple precision arithmetic here, but we'll be lazy and
+	     resort to floating point.  This can yield answers that
+	     are slightly off.  In practice it is quite rare to
+	     overflow uintmax_t, so this is good enough for now.  */
+
+	  double damt = n * (double) multiplier;
+
+	  if (! base)
+	    sprintf (buf, "%.0f", damt);
+	  else
+	    {
+	      double e = 1;
+	      power = 0;
+
+	      do
+		{
+		  e *= base;
+		  power++;
+		}
+	      while (e * base <= amt && power < sizeof suffixes - 1);
+
+	      damt /= e;
+
+	      sprintf (buf, "%.1f%c", damt, suffixes[power]);
+	      if (4 < strlen (buf))
+		sprintf (buf, "%.0f%c", damt, suffixes[power]);
+	    }
+
+	  return buf;
+	}
+    }
+  else
+    {
+      int divisor = to_units / from_units;
+      int r10 = (n % divisor) * 10;
+      int r2 = (r10 % divisor) * 2;
+      amt = n / divisor;
+      tenths = r10 / divisor;
+      rounding = r2 < divisor ? 0 < r2 : 2 + (divisor < r2);
+    }
+
+   
+  /* Use power of BASE notation if adjusted AMT is large enough.  */
+
+  if (base && base <= amt)
+    {
+      power = 0;
+
+      do
+	{
+	  int r10 = (amt % base) * 10 + tenths;
+	  int r2 = (r10 % base) * 2 + (rounding >> 1);
+	  amt /= base;
+	  tenths = r10 / base;
+	  rounding = (r2 < base
+		      ? 0 < r2 + rounding
+		      : 2 + (base < r2 + rounding));
+	  power++;
+	}
+      while (base <= amt && power < sizeof suffixes - 1);
+
+      *--p = suffixes[power];
+
+      if (amt < 10)
+	{
+	  tenths += 2 < rounding + (tenths & 1);
+
+	  if (tenths == 10)
+	    {
+	      amt++;
+	      tenths = 0;
+	    }
+
+	  if (amt < 10)
+	    {
+	      *--p = '0' + tenths;
+	      *--p = '.';
+	      tenths = 0;
+	    }
+	}
+    }
+   
+  if (5 < tenths + (2 < rounding + (amt & 1)))
+    {
+      amt++;
+
+      if (amt == base && power < sizeof suffixes - 1)
+	{
+	  *p = suffixes[power + 1];
+	  *--p = '0';
+	  *--p = '.';
+	  amt = 1;
+	}
+    }
+
+  do
+    *--p = '0' + (int) (amt % 10);
+  while ((amt /= 10) != 0);
+
+  return p;
+}

lib/human.h

@@ -0,0 +1,19 @@
+#ifndef HUMAN_H_
+# define HUMAN_H_ 1
+
+/* A conservative bound on the maximum length of a human-readable string.
+   The output can be the product of the largest uintmax_t and the largest int,
+   so add their sizes before converting to a bound on digits.  */
+#define LONGEST_HUMAN_READABLE ((sizeof (uintmax_t) + sizeof (int)) * CHAR_BIT / 3)
+
+#ifndef __P
+# if defined (__GNUC__) || (defined (__STDC__) && __STDC__)
+#  define __P(args) args
+# else
+#  define __P(args) ()
+# endif  /* GCC.  */
+#endif  /* Not __P.  */
+
+char *human_readable __P ((uintmax_t, char *, int, int, int));
+
+#endif /* HUMAN_H_ */