java/text/ChoiceFormat.java

/* ChoiceFormat.java -- Format over a range of numbers
   Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.

This file is part of GNU Classpath.

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it under the terms of the GNU General Public License as published by
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Linking this library statically or dynamically with other modules is
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permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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package java.text;

import java.util.Vector;

/**
 * This class allows a format to be specified based on a range of numbers.
 * To use this class, first specify two lists of formats and range terminators.
 * These lists must be arrays of equal length.  The format of index
 * <code>i</code> will be selected for value <code>X</code> if
 * <code>terminator[i] <= X < limit[i + 1]</code>.  If the value X is not
 * included in any range, then either the first or last format will be
 * used depending on whether the value X falls outside the range.
 * <p>
 * This sounds complicated, but that is because I did a poor job of
 * explaining it.  Consider the following example:
 * <p>
 *
<pre>terminators = { 1, ChoiceFormat.nextDouble(1) }
formats = { "file", "files" }</pre>
 *
 * <p>
 * In this case if the actual number tested is one or less, then the word
 * "file" is used as the format value.  If the number tested is greater than
 * one, then "files" is used.  This allows plurals to be handled
 * gracefully.  Note the use of the method <code>nextDouble</code>.  This
 * method selects the next highest double number than its argument.  This
 * effectively makes any double greater than 1.0 cause the "files" string
 * to be selected.  (Note that all terminator values are specified as
 * doubles.
 * <p>
 * Note that in order for this class to work properly, the range terminator
 * array must be sorted in ascending order and the format string array
 * must be the same length as the terminator array.
 *
 * @author Tom Tromey <tromey@cygnus.com>
 * @author Aaron M. Renn (arenn@urbanophile.com)
 * @date March 9, 1999
 */
/* Written using "Java Class Libraries", 2nd edition, plus online
 * API docs for JDK 1.2 from http://www.javasoft.com.
 * Status:  Believed complete and correct to 1.1.
 */
public class ChoiceFormat extends NumberFormat
{
  /**
   * This method sets new range terminators and format strings for this
   * object based on the specified pattern. This pattern is of the form
   * "term#string|term#string...".  For example "1#Sunday|2#Monday|#Tuesday".
   *
   * @param pattern The pattern of terminators and format strings.
   *
   * @exception IllegalArgumentException If the pattern is not valid
   */
  public void applyPattern (String newPattern)
  {
    // Note: we assume the same kind of quoting rules apply here.
    // This isn't explicitly documented.  But for instance we accept
    // '#' as a literal hash in a format string.
    int index = 0, max = newPattern.length();
    Vector stringVec = new Vector ();
    Vector limitVec = new Vector ();
    StringBuffer buf = new StringBuffer ();

    while (true)
      {
	// Find end of double.
	int dstart = index;
	while (index < max)
	  {
	    char c = newPattern.charAt(index);
	    if (c == '#' || c == '\u2064' || c == '<')
	      break;
	    ++index;
	  }

	if (index == max)
	  throw new IllegalArgumentException ("unexpected end of text");
	Double d = new Double (newPattern.substring(dstart, index));

	if (newPattern.charAt(index) == '<')
	  d = new Double (nextDouble (d.doubleValue()));

	limitVec.addElement(d);

	// Scan text.
	++index;
	buf.setLength(0);
	while (index < max)
	  {
	    char c = newPattern.charAt(index);
	    if (c == '\'' && index < max + 1
		&& newPattern.charAt(index + 1) == '\'')
	      {
		buf.append(c);
		++index;
	      }
	    else if (c == '\'' && index < max + 2)
	      {
		buf.append(newPattern.charAt(index + 1));
		index += 2;
	      }
	    else if (c == '|')
	      break;
	    else
	      buf.append(c);
	    ++index;
	  }

	stringVec.addElement(buf.toString());
	if (index == max)
	  break;
	++index;
      }

    choiceFormats = new String[stringVec.size()];
    stringVec.copyInto(choiceFormats);

    choiceLimits = new double[limitVec.size()];
    for (int i = 0; i < choiceLimits.length; ++i)
      {
	Double d = (Double) limitVec.elementAt(i);
	choiceLimits[i] = d.doubleValue();
      }
  }

  /**
   * This method initializes a new instance of <code>ChoiceFormat</code> that
   * generates its range terminator and format string arrays from the
   * specified pattern.  This pattern is of the form
   * "term#string|term#string...".  For example "1#Sunday|2#Monday|#Tuesday".
   * This is the same pattern type used by the <code>applyPattern</code>
   * method.
   *
   * @param pattern The pattern of terminators and format strings.
   *
   * @exception IllegalArgumentException If the pattern is not valid
   */
  public ChoiceFormat (String newPattern)
  {
    super ();
    applyPattern (newPattern);
  }

  /**
   * This method initializes a new instance of <code>ChoiceFormat</code> that
   * will use the specified range terminators and format strings.
   *
   * @param choiceLimits The array of range terminators
   * @param choiceFormats The array of format strings
   */
  public ChoiceFormat (double[] choiceLimits, String[] choiceFormats)
  {
    super ();
    setChoices (choiceLimits, choiceFormats);
  }

  /**
   * This method tests this object for equality with the specified
   * object.  This will be true if and only if:
   * <ul>
   * <li>The specified object is not <code>null</code>.
   * <li>The specified object is an instance of <code>ChoiceFormat</code>.
   * <li>The termination ranges and format strings are identical to
   *     this object's.
   * </ul>
   *
   * @param obj The object to test for equality against.
   *
   * @return <code>true</code> if the specified object is equal to
   * this one, <code>false</code> otherwise.
   */
  public boolean equals (Object obj)
  {
    if (! (obj instanceof ChoiceFormat))
      return false;
    ChoiceFormat cf = (ChoiceFormat) obj;
    if (choiceLimits.length != cf.choiceLimits.length)
      return false;
    for (int i = choiceLimits.length - 1; i >= 0; --i)
      {
	if (choiceLimits[i] != cf.choiceLimits[i]
	    || !choiceFormats[i].equals(cf.choiceFormats[i]))
	  return false;
      }
    return true;
  }

  /**
   * This method appends the appropriate format string to the specified
   * <code>StringBuffer</code> based on the supplied <code>long</code>
   * argument.
   *
   * @param number The number used for determine (based on the range
   *               terminators) which format string to append.
   * @param sb The <code>StringBuffer</code> to append the format string to.
   * @param status Unused.
   *
   * @return The <code>StringBuffer</code> with the format string appended.
   */
  public StringBuffer format (long num, StringBuffer appendBuf,
			      FieldPosition pos)
  {
    return format ((double) num, appendBuf, pos);
  }

  /**
   * This method appends the appropriate format string to the specified
   * <code>StringBuffer</code> based on the supplied <code>double</code>
   * argument.
   *
   * @param number The number used for determine (based on the range
   *               terminators) which format string to append.
   * @param sb The <code>StringBuffer</code> to append the format string to.
   * @param status Unused.
   *
   * @return The <code>StringBuffer</code> with the format string appended.
   */
  public StringBuffer format (double num, StringBuffer appendBuf,
			      FieldPosition pos)
  {
    if (choiceLimits.length == 0)
      return appendBuf;

    int index = 0;
    if (! Double.isNaN(num) && num >= choiceLimits[0])
      {
	for (; index < choiceLimits.length - 1; ++index)
	  {
	    if (choiceLimits[index] <= num && num < choiceLimits[index + 1])
	      break;
	  }
      }

    return appendBuf.append(choiceFormats[index]);
  }

  /**
   * This method returns the list of format strings in use.
   *
   * @return The list of format objects.
   */
  public Object[] getFormats ()
  {
    return (Object[]) choiceFormats.clone();
  }

  /**
   * This method returns the list of range terminators in use.
   *
   * @return The list of range terminators.
   */
  public double[] getLimits ()
  {
    return (double[]) choiceLimits.clone();
  }

  /**
   * This method returns a hash value for this object
   *
   * @return A hash value for this object.
   */
  public int hashCode ()
  {
    int hash = 0;
    for (int i = 0; i < choiceLimits.length; ++i)
      {
	long v = Double.doubleToLongBits(choiceLimits[i]);
	hash ^= (v ^ (v >>> 32));
	hash ^= choiceFormats[i].hashCode();
      }
    return hash;
  }

  /**
   * This method returns the lowest possible double greater than the
   * specified double.  If the specified double value is equal to
   * <code>Double.NaN</code> then that is the value returned.
   *
   * @param d The specified double
   *
   * @return The lowest double value greater than the specified double.
   */
  public static final double nextDouble (double d)
  {
    return nextDouble (d, true);
  }

  /**
   * This method returns a double that is either the next highest double
   * or next lowest double compared to the specified double depending on the
   * value of the passed boolean parameter.  If the boolean parameter is
   * <code>true</code>, then the lowest possible double greater than the
   * specified double will be returned.  Otherwise the highest possible
   * double less than the specified double will be returned.
   *
   * @param d The specified double
   * @param positive <code>true</code> to return the next highest
   *                 double, <code>false</code> otherwise.
   *
   * @return The next highest or lowest double value.
   */
  public static double nextDouble (double d, boolean next)
  {
    if (Double.isInfinite(d) || Double.isNaN(d))
      return d;

    long bits = Double.doubleToLongBits(d);

    long mantMask = (1L << mantissaBits) - 1;
    long mantissa = bits & mantMask;

    long expMask = (1L << exponentBits) - 1;
    long exponent = (bits >>> mantissaBits) & expMask;

    if (next ^ (bits < 0)) // Increment magnitude
      {
	if (mantissa == (1L << mantissaBits) - 1)
	  {
	    mantissa = 0L;
	    exponent++;

	    // Check for absolute overflow.
	    if (exponent >= (1L << mantissaBits))
	      return (bits > 0) ? Double.POSITIVE_INFINITY
		: Double.NEGATIVE_INFINITY;
	  }
	else
	  mantissa++;
      }
    else // Decrement magnitude
      {
	if (exponent == 0L && mantissa == 0L)
	  {
	    // The only case where there is a change of sign
	    return next ? Double.MIN_VALUE : -Double.MIN_VALUE;
	  }
	else
	  {
	    if (mantissa == 0L)
	      {
		mantissa = (1L << mantissaBits) - 1;
		exponent--;
	      }
	    else
	      mantissa--;
	  }
      }

    long result = bits < 0 ? 1 : 0;
    result = (result << exponentBits) | exponent;
    result = (result << mantissaBits) | mantissa;
    return Double.longBitsToDouble(result);
  }

  /**
   * I'm not sure what this method is really supposed to do, as it is
   * not documented.
   */
  public Number parse (String sourceStr, ParsePosition pos)
  {
    int index = pos.getIndex();
    for (int i = 0; i < choiceLimits.length; ++i)
      {
	if (sourceStr.startsWith(choiceFormats[i], index))
	  {
	    pos.setIndex(index + choiceFormats[i].length());
	    return new Double (choiceLimits[i]);
	  }
      }
    pos.setErrorIndex(index);
    return new Double (Double.NaN);
  }

  /**
   * This method returns the highest possible double less than the
   * specified double.  If the specified double value is equal to
   * <code>Double.NaN</code> then that is the value returned.
   *
   * @param d The specified double
   *
   * @return The highest double value less than the specified double.
   */
  public static final double previousDouble (double d)
  {
    return nextDouble (d, false);
  }

  /**
   * This method sets new range terminators and format strings for this
   * object.
   *
   * @param choiceLimits The new range terminators
   * @param choiceFormats The new choice formats
   */
  public void setChoices (double[] choiceLimits, String[] choiceFormats)
  {
    if (choiceLimits == null || choiceFormats == null)
      throw new NullPointerException ();
    if (choiceLimits.length != choiceFormats.length)
      throw new IllegalArgumentException ();
    this.choiceFormats = (String[]) choiceFormats.clone();
    this.choiceLimits = (double[]) choiceLimits.clone();
  }

  private final void quoteString (StringBuffer dest, String text)
  {
    int max = text.length();
    for (int i = 0; i < max; ++i)
      {
	char c = text.charAt(i);
	if (c == '\'')
	  {
	    dest.append(c);
	    dest.append(c);
	  }
	else if (c == '#' || c == '|' || c == '\u2064' || c == '<')
	  {
	    dest.append('\'');
	    dest.append(c);
	    dest.append('\'');
	  }
	else
	  dest.append(c);
      }
  }

  /**
   * This method returns the range terminator list and format string list
   * as a <code>String</code> suitable for using with the
   * <code>applyPattern</code> method.
   *
   * @return A pattern string for this object
   */
  public String toPattern ()
  {
    StringBuffer result = new StringBuffer ();
    for (int i = 0; i < choiceLimits.length; ++i)
      {
	result.append(choiceLimits[i]);
	result.append('#');
	quoteString (result, choiceFormats[i]);
      }
    return result.toString();
  }

  /**
   * This is the list of format strings.  Note that this variable is
   * specified by the serialization spec of this class.
   */
  private String[] choiceFormats;

  /**
   * This is the list of range terminator values.  Note that this variable is
   * specified by the serialization spec of this class.
   */
  private double[] choiceLimits;

  // Number of mantissa bits in double.
  private static final int mantissaBits = 52;
  // Number of exponent bits in a double.
  private static final int exponentBits = 11;

  private static final long serialVersionUID = 1795184449645032964L;
}