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package javax.print.attribute;

import java.io.Serializable;

/**
 * Class ResolutionSyntax is an abstract base class providing the common
 * implementation of all attributes denoting a printer resolution.
 * <P>
 * A resolution attribute's value consists of two items, the cross feed
 * direction resolution and the feed direction resolution. A resolution
 * attribute may be constructed by supplying the two values and indicating the
 * units in which the values are measured. Methods are provided to return a
 * resolution attribute's values, indicating the units in which the values are
 * to be returned. The two most common resolution units are dots per inch (dpi)
 * and dots per centimeter (dpcm), and exported constants {@link #DPI
 * <CODE>DPI</CODE>} and {@link #DPCM <CODE>DPCM</CODE>} are provided for
 * indicating those units.
 * <P>
 * Once constructed, a resolution attribute's value is immutable.
 * <P>
 * <B>Design</B>
 * <P>
 * A resolution attribute's cross feed direction resolution and feed direction
 * resolution values are stored internally using units of dots per 100 inches
 * (dphi). Storing the values in dphi rather than, say, metric units allows
 * precise integer arithmetic conversions between dpi and dphi and between dpcm
 * and dphi: 1 dpi = 100 dphi, 1 dpcm = 254 dphi. Thus, the values can be stored
 * into and retrieved back from a resolution attribute in either units with no
 * loss of precision. This would not be guaranteed if a floating point
 * representation were used. However, roundoff error will in general occur if a
 * resolution attribute's values are created in one units and retrieved in
 * different units; for example, 600 dpi will be rounded to 236 dpcm, whereas
 * the true value (to five figures) is 236.22 dpcm.
 * <P>
 * Storing the values internally in common units of dphi lets two resolution
 * attributes be compared without regard to the units in which they were
 * created; for example, 300 dpcm will compare equal to 762 dpi, as they both
 * are stored as 76200 dphi. In particular, a lookup service can
 * match resolution attributes based on equality of their serialized
 * representations regardless of the units in which they were created. Again,
 * using integers for internal storage allows precise equality comparisons to be
 * done, which would not be guaranteed if a floating point representation were
 * used.
 * <P>
 * The exported constant {@link #DPI <CODE>DPI</CODE>} is actually the
 * conversion factor by which to multiply a value in dpi to get the value in
 * dphi. Likewise, the exported constant {@link #DPCM <CODE>DPCM</CODE>} is the
 * conversion factor by which to multiply a value in dpcm to get the value in
 * dphi. A client can specify a resolution value in units other than dpi or dpcm
 * by supplying its own conversion factor. However, since the internal units of
 * dphi was chosen with supporting only the external units of dpi and dpcm in
 * mind, there is no guarantee that the conversion factor for the client's units
 * will be an exact integer. If the conversion factor isn't an exact integer,
 * resolution values in the client's units won't be stored precisely.
 * <P>
 *
 * @author  David Mendenhall
 * @author  Alan Kaminsky
 */
public abstract class ResolutionSyntax implements Serializable, Cloneable {

    private static final long serialVersionUID = 2706743076526672017L;

    /**
     * Cross feed direction resolution in units of dots per 100 inches (dphi).
     * @serial
     */
    private int crossFeedResolution;

    /**
     * Feed direction resolution in units of dots per 100 inches (dphi).
     * @serial
     */
    private int feedResolution;

    /**
     * Value to indicate units of dots per inch (dpi). It is actually the
     * conversion factor by which to multiply dpi to yield dphi (100).
     */
    public static final int DPI = 100;

    /**
     * Value to indicate units of dots per centimeter (dpcm). It is actually
     * the conversion factor by which to multiply dpcm to yield dphi (254).
     */
    public static final int DPCM = 254;


    /**
     * Construct a new resolution attribute from the given items.
     *
     * @param  crossFeedResolution
     *     Cross feed direction resolution.
     * @param  feedResolution
     *     Feed direction resolution.
     * @param units
     *     Unit conversion factor, e.g. {@link #DPI <CODE>DPI</CODE>} or
     * {@link    #DPCM <CODE>DPCM</CODE>}.
     *
     * @exception  IllegalArgumentException
     *     (unchecked exception) Thrown if <CODE>crossFeedResolution</CODE> <
     *     1 or <CODE>feedResolution</CODE> < 1 or <CODE>units</CODE> < 1.
     */
    public ResolutionSyntax(int crossFeedResolution, int feedResolution,
                            int units) {

        if (crossFeedResolution < 1) {
            throw new IllegalArgumentException("crossFeedResolution is < 1");
        }
        if (feedResolution < 1) {
                throw new IllegalArgumentException("feedResolution is < 1");
        }
        if (units < 1) {
                throw new IllegalArgumentException("units is < 1");
        }

        this.crossFeedResolution = crossFeedResolution * units;
        this.feedResolution = feedResolution * units;
    }

    /**
     * Convert a value from dphi to some other units. The result is rounded to
     * the nearest integer.
     *
     * @param  dphi
     *     Value (dphi) to convert.
     * @param  units
     *     Unit conversion factor, e.g. {@link #DPI <CODE>DPI</CODE>} or
     * {@link     #DPCM <CODE>DPCM</CODE>}.
     *
     * @return  The value of <CODE>dphi</CODE> converted to the desired units.
     *
     * @exception  IllegalArgumentException
     *     (unchecked exception) Thrown if <CODE>units</CODE> < 1.
     */
    private static int convertFromDphi(int dphi, int units) {
        if (units < 1) {
            throw new IllegalArgumentException(": units is < 1");
        }
        int round = units / 2;
        return (dphi + round) / units;
    }

    /**
     * Get this resolution attribute's resolution values in the given units.
     * The values are rounded to the nearest integer.
     *
     * @param  units
     *     Unit conversion factor, e.g. {@link #DPI <CODE>DPI</CODE>} or
     * {@link   #DPCM <CODE>DPCM</CODE>}.
     *
     * @return  A two-element array with the cross feed direction resolution
     *          at index 0 and the feed direction resolution at index 1.
     *
     * @exception  IllegalArgumentException
     *     (unchecked exception) Thrown if <CODE>units</CODE> < 1.
     */
    public int[] getResolution(int units) {
        return new int[] { getCrossFeedResolution(units),
                               getFeedResolution(units)
                               };
    }

    /**
     * Returns this resolution attribute's cross feed direction resolution in
     * the given units. The value is rounded to the nearest integer.
     *
     * @param  units
     *     Unit conversion factor, e.g. {@link #DPI <CODE>DPI</CODE>} or
     * {@link  #DPCM <CODE>DPCM</CODE>}.
     *
     * @return  Cross feed direction resolution.
     *
     * @exception  IllegalArgumentException
     *     (unchecked exception) Thrown if <CODE>units</CODE> < 1.
     */
    public int getCrossFeedResolution(int units) {
        return convertFromDphi (crossFeedResolution, units);
    }

    /**
     * Returns this resolution attribute's feed direction resolution in the
     * given units. The value is rounded to the nearest integer.
     *
     * @param  units
     *     Unit conversion factor, e.g. {@link #DPI <CODE>DPI</CODE>} or {@link
     *     #DPCM <CODE>DPCM</CODE>}.
     *
     * @return  Feed direction resolution.
     *
     * @exception  IllegalArgumentException
     *     (unchecked exception) Thrown if <CODE>units</CODE> < 1.
     */
    public int getFeedResolution(int units) {
        return convertFromDphi (feedResolution, units);
    }

    /**
     * Returns a string version of this resolution attribute in the given units.
     * The string takes the form <CODE>"<I>C</I>x<I>F</I> <I>U</I>"</CODE>,
     * where <I>C</I> is the cross feed direction resolution, <I>F</I> is the
     * feed direction resolution, and <I>U</I> is the units name. The values are
     * rounded to the nearest integer.
     *
     * @param  units
     *     Unit conversion factor, e.g. {@link #DPI <CODE>DPI</CODE>} or {@link
     *     #DPCM <CODE>DPCM</CODE>}.
     * @param  unitsName
     *     Units name string, e.g. <CODE>"dpi"</CODE> or <CODE>"dpcm"</CODE>. If
     *     null, no units name is appended to the result.
     *
     * @return  String version of this resolution attribute.
     *
     * @exception  IllegalArgumentException
     *     (unchecked exception) Thrown if <CODE>units</CODE> < 1.
     */
    public String toString(int units, String unitsName) {
        StringBuffer result = new StringBuffer();
        result.append(getCrossFeedResolution (units));
        result.append('x');
        result.append(getFeedResolution (units));
        if (unitsName != null) {
            result.append (' ');
            result.append (unitsName);
        }
        return result.toString();
    }


    /**
     * Determine whether this resolution attribute's value is less than or
     * equal to the given resolution attribute's value. This is true if all
     * of the following conditions are true:
     * <UL>
     * <LI>
     * This attribute's cross feed direction resolution is less than or equal to
     * the <CODE>other</CODE> attribute's cross feed direction resolution.
     * <LI>
     * This attribute's feed direction resolution is less than or equal to the
     * <CODE>other</CODE> attribute's feed direction resolution.
     * </UL>
     *
     * @param  other  Resolution attribute to compare with.
     *
     * @return  True if this resolution attribute is less than or equal to the
     *          <CODE>other</CODE> resolution attribute, false otherwise.
     *
     * @exception  NullPointerException
     *     (unchecked exception) Thrown if <CODE>other</CODE> is null.
     */
    public boolean lessThanOrEquals(ResolutionSyntax other) {
        return (this.crossFeedResolution <= other.crossFeedResolution &&
                this.feedResolution <= other.feedResolution);
    }


    /**
     * Returns whether this resolution attribute is equivalent to the passed in
     * object. To be equivalent, all of the following conditions must be true:
     * <OL TYPE=1>
     * <LI>
     * <CODE>object</CODE> is not null.
     * <LI>
     * <CODE>object</CODE> is an instance of class ResolutionSyntax.
     * <LI>
     * This attribute's cross feed direction resolution is equal to
     * <CODE>object</CODE>'s cross feed direction resolution.
     * <LI>
     * This attribute's feed direction resolution is equal to
     * <CODE>object</CODE>'s feed direction resolution.
     * </OL>
     *
     * @param  object  Object to compare to.
     *
     * @return  True if <CODE>object</CODE> is equivalent to this resolution
     *          attribute, false otherwise.
     */
    public boolean equals(Object object) {

        return(object != null &&
               object instanceof ResolutionSyntax &&
               this.crossFeedResolution ==
               ((ResolutionSyntax) object).crossFeedResolution &&
               this.feedResolution ==
               ((ResolutionSyntax) object).feedResolution);
    }

    /**
     * Returns a hash code value for this resolution attribute.
     */
    public int hashCode() {
        return(((crossFeedResolution & 0x0000FFFF)) |
               ((feedResolution      & 0x0000FFFF) << 16));
    }

    /**
     * Returns a string version of this resolution attribute. The string takes
     * the form <CODE>"<I>C</I>x<I>F</I> dphi"</CODE>, where <I>C</I> is the
     * cross feed direction resolution and <I>F</I> is the feed direction
     * resolution. The values are reported in the internal units of dphi.
     */
    public String toString() {
        StringBuffer result = new StringBuffer();
        result.append(crossFeedResolution);
        result.append('x');
        result.append(feedResolution);
        result.append(" dphi");
        return result.toString();
    }


    /**
     * Returns this resolution attribute's cross feed direction resolution in
     * units of dphi. (For use in a subclass.)
     *
     * @return  Cross feed direction resolution.
     */
    protected int getCrossFeedResolutionDphi() {
        return crossFeedResolution;
    }

    /**
     * Returns this resolution attribute's feed direction resolution in units
     * of dphi. (For use in a subclass.)
     *
     * @return  Feed direction resolution.
     */
    protected int getFeedResolutionDphi() {
        return feedResolution;
    }

}
