Back to index...

	/*
	* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code 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
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	/*
	* (C) Copyright IBM Corp. 1999-2003 - All Rights Reserved
	*
	* The original version of this source code and documentation is
	* copyrighted and owned by IBM. These materials are provided
	* under terms of a License Agreement between IBM and Sun.
	* This technology is protected by multiple US and International
	* patents. This notice and attribution to IBM may not be removed.
	*/

	package java.text;

	import sun.text.bidi.BidiBase;

	/**
	* This class implements the Unicode Bidirectional Algorithm.
	* <p>
	* A Bidi object provides information on the bidirectional reordering of the text
	* used to create it. This is required, for example, to properly display Arabic
	* or Hebrew text. These languages are inherently mixed directional, as they order
	* numbers from left-to-right while ordering most other text from right-to-left.
	* <p>
	* Once created, a Bidi object can be queried to see if the text it represents is
	* all left-to-right or all right-to-left. Such objects are very lightweight and
	* this text is relatively easy to process.
	* <p>
	* If there are multiple runs of text, information about the runs can be accessed
	* by indexing to get the start, limit, and level of a run. The level represents
	* both the direction and the 'nesting level' of a directional run. Odd levels
	* are right-to-left, while even levels are left-to-right. So for example level
	* 0 represents left-to-right text, while level 1 represents right-to-left text, and
	* level 2 represents left-to-right text embedded in a right-to-left run.
	*
	* @since 1.4
	*/
	public final class Bidi {

	/** Constant indicating base direction is left-to-right. */
	public static final int DIRECTION_LEFT_TO_RIGHT = 0;

	/** Constant indicating base direction is right-to-left. */
	public static final int DIRECTION_RIGHT_TO_LEFT = 1;

	/**
	* Constant indicating that the base direction depends on the first strong
	* directional character in the text according to the Unicode
	* Bidirectional Algorithm. If no strong directional character is present,
	* the base direction is left-to-right.
	*/
	public static final int DIRECTION_DEFAULT_LEFT_TO_RIGHT = -2;

	/**
	* Constant indicating that the base direction depends on the first strong
	* directional character in the text according to the Unicode
	* Bidirectional Algorithm. If no strong directional character is present,
	* the base direction is right-to-left.
	*/
	public static final int DIRECTION_DEFAULT_RIGHT_TO_LEFT = -1;

	private BidiBase bidiBase;

	/**
	* Create Bidi from the given paragraph of text and base direction.
	* @param paragraph a paragraph of text
	* @param flags a collection of flags that control the algorithm. The
	* algorithm understands the flags DIRECTION_LEFT_TO_RIGHT, DIRECTION_RIGHT_TO_LEFT,
	* DIRECTION_DEFAULT_LEFT_TO_RIGHT, and DIRECTION_DEFAULT_RIGHT_TO_LEFT.
	* Other values are reserved.
	*/
	public Bidi(String paragraph, int flags) {
	if (paragraph == null) {
	throw new IllegalArgumentException("paragraph is null");
	}

	bidiBase = new BidiBase(paragraph.toCharArray(), 0, null, 0, paragraph.length(), flags);
	}

	/**
	* Create Bidi from the given paragraph of text.
	* <p>
	* The RUN_DIRECTION attribute in the text, if present, determines the base
	* direction (left-to-right or right-to-left). If not present, the base
	* direction is computes using the Unicode Bidirectional Algorithm, defaulting to left-to-right
	* if there are no strong directional characters in the text. This attribute, if
	* present, must be applied to all the text in the paragraph.
	* <p>
	* The BIDI_EMBEDDING attribute in the text, if present, represents embedding level
	* information. Negative values from -1 to -62 indicate overrides at the absolute value
	* of the level. Positive values from 1 to 62 indicate embeddings. Where values are
	* zero or not defined, the base embedding level as determined by the base direction
	* is assumed.
	* <p>
	* The NUMERIC_SHAPING attribute in the text, if present, converts European digits to
	* other decimal digits before running the bidi algorithm. This attribute, if present,
	* must be applied to all the text in the paragraph.
	*
	* @param paragraph a paragraph of text with optional character and paragraph attribute information
	*
	* @see java.awt.font.TextAttribute#BIDI_EMBEDDING
	* @see java.awt.font.TextAttribute#NUMERIC_SHAPING
	* @see java.awt.font.TextAttribute#RUN_DIRECTION
	*/
	public Bidi(AttributedCharacterIterator paragraph) {
	if (paragraph == null) {
	throw new IllegalArgumentException("paragraph is null");
	}

	bidiBase = new BidiBase(0, 0);
	bidiBase.setPara(paragraph);
	}

	/**
	* Create Bidi from the given text, embedding, and direction information.
	* The embeddings array may be null. If present, the values represent embedding level
	* information. Negative values from -1 to -61 indicate overrides at the absolute value
	* of the level. Positive values from 1 to 61 indicate embeddings. Where values are
	* zero, the base embedding level as determined by the base direction is assumed.
	* @param text an array containing the paragraph of text to process.
	* @param textStart the index into the text array of the start of the paragraph.
	* @param embeddings an array containing embedding values for each character in the paragraph.
	* This can be null, in which case it is assumed that there is no external embedding information.
	* @param embStart the index into the embedding array of the start of the paragraph.
	* @param paragraphLength the length of the paragraph in the text and embeddings arrays.
	* @param flags a collection of flags that control the algorithm. The
	* algorithm understands the flags DIRECTION_LEFT_TO_RIGHT, DIRECTION_RIGHT_TO_LEFT,
	* DIRECTION_DEFAULT_LEFT_TO_RIGHT, and DIRECTION_DEFAULT_RIGHT_TO_LEFT.
	* Other values are reserved.
	*/
	public Bidi(char[] text, int textStart, byte[] embeddings, int embStart, int paragraphLength, int flags) {
	if (text == null) {
	throw new IllegalArgumentException("text is null");
	}
	if (paragraphLength < 0) {
	throw new IllegalArgumentException("bad length: " + paragraphLength);
	}
	if (textStart < 0 \|\| paragraphLength > text.length - textStart) {
	throw new IllegalArgumentException("bad range: " + textStart +
	" length: " + paragraphLength +
	" for text of length: " + text.length);
	}
	if (embeddings != null && (embStart < 0 \|\| paragraphLength > embeddings.length - embStart)) {
	throw new IllegalArgumentException("bad range: " + embStart +
	" length: " + paragraphLength +
	" for embeddings of length: " + text.length);
	}

	bidiBase = new BidiBase(text, textStart, embeddings, embStart, paragraphLength, flags);
	}

	/**
	* Create a Bidi object representing the bidi information on a line of text within
	* the paragraph represented by the current Bidi. This call is not required if the
	* entire paragraph fits on one line.
	*
	* @param lineStart the offset from the start of the paragraph to the start of the line.
	* @param lineLimit the offset from the start of the paragraph to the limit of the line.
	* @return a {@code Bidi} object
	*/
	public Bidi createLineBidi(int lineStart, int lineLimit) {
	AttributedString astr = new AttributedString("");
	Bidi newBidi = new Bidi(astr.getIterator());

	return bidiBase.setLine(this, bidiBase, newBidi, newBidi.bidiBase,lineStart, lineLimit);
	}

	/**
	* Return true if the line is not left-to-right or right-to-left. This means it either has mixed runs of left-to-right
	* and right-to-left text, or the base direction differs from the direction of the only run of text.
	*
	* @return true if the line is not left-to-right or right-to-left.
	*/
	public boolean isMixed() {
	return bidiBase.isMixed();
	}

	/**
	* Return true if the line is all left-to-right text and the base direction is left-to-right.
	*
	* @return true if the line is all left-to-right text and the base direction is left-to-right
	*/
	public boolean isLeftToRight() {
	return bidiBase.isLeftToRight();
	}

	/**
	* Return true if the line is all right-to-left text, and the base direction is right-to-left.
	* @return true if the line is all right-to-left text, and the base direction is right-to-left
	*/
	public boolean isRightToLeft() {
	return bidiBase.isRightToLeft();
	}

	/**
	* Return the length of text in the line.
	* @return the length of text in the line
	*/
	public int getLength() {
	return bidiBase.getLength();
	}

	/**
	* Return true if the base direction is left-to-right.
	* @return true if the base direction is left-to-right
	*/
	public boolean baseIsLeftToRight() {
	return bidiBase.baseIsLeftToRight();
	}

	/**
	* Return the base level (0 if left-to-right, 1 if right-to-left).
	* @return the base level
	*/
	public int getBaseLevel() {
	return bidiBase.getParaLevel();
	}

	/**
	* Return the resolved level of the character at offset. If offset is
	* {@literal <} 0 or ≥ the length of the line, return the base direction
	* level.
	*
	* @param offset the index of the character for which to return the level
	* @return the resolved level of the character at offset
	*/
	public int getLevelAt(int offset) {
	return bidiBase.getLevelAt(offset);
	}

	/**
	* Return the number of level runs.
	* @return the number of level runs
	*/
	public int getRunCount() {
	return bidiBase.countRuns();
	}

	/**
	* Return the level of the nth logical run in this line.
	* @param run the index of the run, between 0 and <code>getRunCount()</code>
	* @return the level of the run
	*/
	public int getRunLevel(int run) {
	return bidiBase.getRunLevel(run);
	}

	/**
	* Return the index of the character at the start of the nth logical run in this line, as
	* an offset from the start of the line.
	* @param run the index of the run, between 0 and <code>getRunCount()</code>
	* @return the start of the run
	*/
	public int getRunStart(int run) {
	return bidiBase.getRunStart(run);
	}

	/**
	* Return the index of the character past the end of the nth logical run in this line, as
	* an offset from the start of the line. For example, this will return the length
	* of the line for the last run on the line.
	* @param run the index of the run, between 0 and <code>getRunCount()</code>
	* @return limit the limit of the run
	*/
	public int getRunLimit(int run) {
	return bidiBase.getRunLimit(run);
	}

	/**
	* Return true if the specified text requires bidi analysis. If this returns false,
	* the text will display left-to-right. Clients can then avoid constructing a Bidi object.
	* Text in the Arabic Presentation Forms area of Unicode is presumed to already be shaped
	* and ordered for display, and so will not cause this function to return true.
	*
	* @param text the text containing the characters to test
	* @param start the start of the range of characters to test
	* @param limit the limit of the range of characters to test
	* @return true if the range of characters requires bidi analysis
	*/
	public static boolean requiresBidi(char[] text, int start, int limit) {
	return BidiBase.requiresBidi(text, start, limit);
	}

	/**
	* Reorder the objects in the array into visual order based on their levels.
	* This is a utility function to use when you have a collection of objects
	* representing runs of text in logical order, each run containing text
	* at a single level. The elements at <code>index</code> from
	* <code>objectStart</code> up to <code>objectStart + count</code>
	* in the objects array will be reordered into visual order assuming
	* each run of text has the level indicated by the corresponding element
	* in the levels array (at <code>index - objectStart + levelStart</code>).
	*
	* @param levels an array representing the bidi level of each object
	* @param levelStart the start position in the levels array
	* @param objects the array of objects to be reordered into visual order
	* @param objectStart the start position in the objects array
	* @param count the number of objects to reorder
	*/
	public static void reorderVisually(byte[] levels, int levelStart, Object[] objects, int objectStart, int count) {
	BidiBase.reorderVisually(levels, levelStart, objects, objectStart, count);
	}

	/**
	* Display the bidi internal state, used in debugging.
	*/
	public String toString() {
	return bidiBase.toString();
	}

	}

Back to index...