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ScaledNumberFormat.javaAPI DocExample5242Fri Mar 02 11:02:50 GMT 2001None

ScaledNumberFormat

public class ScaledNumberFormat extends Format
Format numbers scaled for human comprehension. "Human-readable" output uses 3 digits max.--put unit suffixes at the end. Makes output compact and easy-to-read esp. on huge disks. Formatting code was originally in OpenBSD "df", converted to library routine. Scanning code written for OpenBSD libutil by Todd Miller. Rewritten in Java in January, 2001.
author
Ian F. Darwin, ian@darwinsys.com
version
$Id: ScaledNumberFormat.java,v 1.3 2001/03/02 16:02:51 ian Exp $

Fields Summary
static final int
NONE
static final int
KILO
static final int
MEGA
static final int
GIGA
static final int
TERA
static final int
PETA
static final int
EXA
DecimalFormat
df5
DecimalFormat
df6
static char[]
scale_chars
The input scaling factors. All three arrays must be in same order.
int[]
units
The numeric scale values. All three arrays must be in same order.
static long[]
scale_factors
The input scale sizes. All three arrays must be in same order.
static final int
MAX_DIGITS
Constructors Summary
public ScaledNumberFormat()


	  
		df5 = new DecimalFormat("0");
		df5.setMinimumIntegerDigits(5);
		df6 = new DecimalFormat("0");
		df6.setMinimumIntegerDigits(6);
Methods Summary
public java.lang.StringBufferformat(java.lang.Object on, java.lang.StringBuffer sb, java.text.FieldPosition fp)

		long n = 0 /* ((Number)on).getLongValue(); */;
		sb.append(format(n));
		return sb;
public java.lang.Stringformat(double n)
Format a double as a Scaled Numeral; just truncate to a long, and call format(long).

		return format((long)n);
public java.lang.Stringformat(long number)
Format a given long as a Scaled Numeral. This method is the REAL FORMATTING ENGINE.

		long fract = 0;
		int unit = NONE;

		StringBuffer buf = new StringBuffer();

		long abval = Math.abs(number);

		for (int i = 1/*!*/; i < scale_factors.length; i++) {
			if (abval < scale_factors[i]) {
				unit = units[i-1];
				fract = i == 1 ? 0 : abval % scale_factors[i-1];
				number /= scale_factors[i-1];
				break;
			}
		}
		// printf("AFTER: unit %d, number %d, fract %d\n", unit, number, fract);

		if (fract < 0)
			fract = -fract;

		/* scale fraction to one digit (truncate, not round) */
		while (fract>9)
			fract /= 10;

		if (number == 0)
			return "     0B";
		else if (number > 10) {
			buf.append(df6.format(number)).append(scale_chars[unit]);
		} else {
			buf.append(df5.format(number)).append('.").
				append(number>10?0:fract).append(scale_chars[unit]);
		}

		// replace leading zeros with spaces
		for (int i = 0; i < buf.length(); i++) {
			if (buf.charAt(i) == '0")
				buf.setCharAt(i, ' ");
			else
				break;
		}

		return buf.toString();
public java.lang.ObjectparseObject(java.lang.String s, java.text.ParsePosition where)
Parse a generic object, returning an Object


	        
	      
		int i, neg = +1, fract_digits = 0;
		long scale_fact = 1, whole = 0;
		long fpart = 0;

		if (s == null)
			return null;

		char[] b = s.trim().toCharArray();
		int p = 0;	// the index into b; the # of chars we've scanned.
		
		/* Main loop: Scan digits, find sign & decimal point, if present.
		 * We don't allow exponentials, so no e E f F g G etc.
		 * Advance 'p' to end, to get scale factor. *
		 */
		if (b[p] == '-") {
			neg = -1;
			++p;
		} else if (b[p] == '+") {
			/* nothing much to do */
			++p;
		}
		for (; p<b.length && (Character.isDigit(b[p]) || b[p]=='."); ++p) {
			if (b[p] == '.") {
				if (fract_digits>0) {
					throw new NumberFormatException(
					"Number " + s + " has more than one decimal point ");
				}
				fract_digits = 1;
				continue;
			}
			if (fract_digits==0 && p > MAX_DIGITS) {
				throw new IllegalArgumentException("Number too large");
			}
			i = (b[p]) - '0";			// whew! finally a digit we can use
			if (fract_digits > 0) {
				fpart *= 10;
				fpart += i;
				++fract_digits;		// track for later scaling
			} else {
				whole *= 10;
				whole += i;
			}
		}
		/* printf("whole=%qd, fpart %ld, fract_digits %ld\n",
		 *	whole, fpart, fract_digits);
		 */
		whole *= neg;
		fpart *= neg;

		/* If no scale factor given, we're done. fraction is discarded. */
		if (p >= b.length) {
			return new Long(whole);
		}

		/* Validate scale factor, and scale whole and fraction by it. */
		for (i = 0; i < scale_factors.length; i++) {
			if (b[p] == scale_chars[i] ||
				b[p] == Character.toLowerCase(scale_chars[i])) {
				scale_fact = scale_factors[i];
				// scale whole part: easy
				whole *= scale_fact;
				// scale fractional part
				fpart *= scale_fact;
				for (i = 0; i < fract_digits - 1; i++)
					fpart /= 10;
				whole += fpart;
				return new Long(whole);
			}
		}
		throw new IllegalArgumentException("invalid scale factor " + b[p]);