| package com.ibm.text; |
| |
| import java.util.*; |
| import java.text.MessageFormat; |
| |
| /** |
| * <code>Transliterator</code> is an abstract class that |
| * transliterates text from one format to another. The most common |
| * kind of transliterator is a script, or alphabet, transliterator. |
| * For example, a Russian to Latin transliterator changes Russian text |
| * written in Cyrillic characters to phonetically equivalent Latin |
| * characters. It does not <em>translate</em> Russian to English! |
| * Transliteration, unlike translation, operates on characters, without |
| * reference to the meanings of words and sentences. |
| * |
| * <p>Although script conversion is its most common use, a |
| * transliterator can actually perform a more general class of tasks. |
| * In fact, <code>Transliterator</code> defines a very general API |
| * which specifies only that a segment of the input text is replaced |
| * by new text. The particulars of this conversion are determined |
| * entirely by subclasses of <code>Transliterator</code>. |
| * |
| * <p><b>Transliterators are stateless</b> |
| * |
| * <p><code>Transliterator</code> objects are <em>stateless</em>; they |
| * retain no information between calls to |
| * <code>transliterate()</code>. As a result, threads may share |
| * transliterators without synchronizing them. This might seem to |
| * limit the complexity of the transliteration operation. In |
| * practice, subclasses perform complex transliterations by delaying |
| * the replacement of text until it is known that no other |
| * replacements are possible. In other words, although the |
| * <code>Transliterator</code> objects are stateless, the source text |
| * itself embodies all the needed information, and delayed operation |
| * allows arbitrary complexity. |
| * |
| * <p><b>Batch transliteration</b> |
| * |
| * <p>The simplest way to perform transliteration is all at once, on a |
| * string of existing text. This is referred to as <em>batch</em> |
| * transliteration. For example, given a string <code>input</code> |
| * and a transliterator <code>t</code>, the call |
| * |
| * <blockquote><code>String result = t.transliterate(input); |
| * </code></blockquote> |
| * |
| * will transliterate it and return the result. Other methods allow |
| * the client to specify a substring to be transliterated and to use |
| * {@link Replaceable} objects instead of strings, in order to |
| * preserve out-of-band information (such as text styles). |
| * |
| * <p><b>Keyboard transliteration</b> |
| * |
| * <p>Somewhat more involved is <em>keyboard</em>, or incremental |
| * transliteration. This is the transliteration of text that is |
| * arriving from some source (typically the user's keyboard) one |
| * character at a time, or in some other piecemeal fashion. |
| * |
| * <p>In keyboard transliteration, a <code>Replaceable</code> buffer |
| * stores the text. As text is inserted, as much as possible is |
| * transliterated on the fly. This means a GUI that displays the |
| * contents of the buffer may show text being modified as each new |
| * character arrives. |
| * |
| * <p>Consider the simple <code>RuleBasedTransliterator</code>: |
| * |
| * <blockquote><code> |
| * th>{theta}<br> |
| * t>{tau} |
| * </code></blockquote> |
| * |
| * When the user types 't', nothing will happen, since the |
| * transliterator is waiting to see if the next character is 'h'. To |
| * remedy this, we introduce the notion of a cursor, marked by a '|' |
| * in the output string: |
| * |
| * <blockquote><code> |
| * t>|{tau}<br> |
| * {tau}h>{theta} |
| * </code></blockquote> |
| * |
| * Now when the user types 't', tau appears, and if the next character |
| * is 'h', the tau changes to a theta. This is accomplished by |
| * maintaining a cursor position (independent of the insertion point, |
| * and invisible in the GUI) across calls to |
| * <code>keyboardTransliterate()</code>. Typically, the cursor will |
| * be coincident with the insertion point, but in a case like the one |
| * above, it will precede the insertion point. |
| * |
| * <p>Keyboard transliteration methods maintain a set of three indices |
| * that are updated with each call to |
| * <code>keyboardTransliterate()</code>, including the cursor, start, |
| * and limit. Since these indices are changed by the method, they are |
| * passed in an <code>int[]</code> array. The <code>START</code> index |
| * marks the beginning of the substring that the transliterator will |
| * look at. It is advanced as text becomes committed (but it is not |
| * the committed index; that's the <code>CURSOR</code>). The |
| * <code>CURSOR</code> index, described above, marks the point at |
| * which the transliterator last stopped, either because it reached |
| * the end, or because it required more characters to disambiguate |
| * between possible inputs. The <code>CURSOR</code> can also be |
| * explicitly set by rules in a <code>RuleBasedTransliterator</code>. |
| * Any characters before the <code>CURSOR</code> index are frozen; |
| * future keyboard transliteration calls within this input sequence |
| * will not change them. New text is inserted at the |
| * <code>LIMIT</code> index, which marks the end of the substring that |
| * the transliterator looks at. |
| * |
| * <p>Because keyboard transliteration assumes that more characters |
| * are to arrive, it is conservative in its operation. It only |
| * transliterates when it can do so unambiguously. Otherwise it waits |
| * for more characters to arrive. When the client code knows that no |
| * more characters are forthcoming, perhaps because the user has |
| * performed some input termination operation, then it should call |
| * <code>finishKeyboardTransliteration()</code> to complete any |
| * pending transliterations. |
| * |
| * <p><b>Inverses</b> |
| * |
| * <p>Pairs of transliterators may be inverses of one another. For |
| * example, if transliterator <b>A</b> transliterates characters by |
| * incrementing their Unicode value (so "abc" -> "def"), and |
| * transliterator <b>B</b> decrements character values, then <b>A</b> |
| * is an inverse of <b>B</b> and vice versa. If we compose <b>A</b> |
| * with <b>B</b> in a compound transliterator, the result is the |
| * indentity transliterator, that is, a transliterator that does not |
| * change its input text. |
| * |
| * The <code>Transliterator</code> method <code>getInverse()</code> |
| * returns a transliterator's inverse, if one exists, or |
| * <code>null</code> otherwise. However, the result of |
| * <code>getInverse()</code> usually will <em>not</em> be a true |
| * mathematical inverse. This is because true inverse transliterators |
| * are difficult to formulate. For example, consider two |
| * transliterators: <b>AB</b>, which transliterates the character 'A' |
| * to 'B', and <b>BA</b>, which transliterates 'B' to 'A'. It might |
| * seem that these are exact inverses, since |
| * |
| * <blockquote>"A" x <b>AB</b> -> "B"<br> |
| * "B" x <b>BA</b> -> "A"</blockquote> |
| * |
| * where 'x' represents transliteration. However, |
| * |
| * <blockquote>"ABCD" x <b>AB</b> -> "BBCD"<br> |
| * "BBCD" x <b>BA</b> -> "AACD"</blockquote> |
| * |
| * so <b>AB</b> composed with <b>BA</b> is not the |
| * identity. Nonetheless, <b>BA</b> may be usefully considered to be |
| * <b>AB</b>'s inverse, and it is on this basis that |
| * <b>AB</b><code>.getInverse()</code> could legitimately return |
| * <b>BA</b>. |
| * |
| * <p><b>IDs and display names</b> |
| * |
| * <p>A transliterator is designated by a short identifier string or |
| * <em>ID</em>. IDs follow the format <em>source-destination</em>, |
| * where <em>source</em> describes the entity being replaced, and |
| * <em>destination</em> describes the entity replacing |
| * <em>source</em>. The entities may be the names of scripts, |
| * particular sequences of characters, or whatever else it is that the |
| * transliterator converts to or from. For example, a transliterator |
| * from Russian to Latin might be named "Russian-Latin". A |
| * transliterator from keyboard escape sequences to Latin-1 characters |
| * might be named "KeyboardEscape-Latin1". By convention, system |
| * entity names are in English, with the initial letters of words |
| * capitalized; user entity names may follow any format so long as |
| * they do not contain dashes. |
| * |
| * <p>In addition to programmatic IDs, transliterator objects have |
| * display names for presentation in user interfaces, returned by |
| * {@link #getDisplayName}. |
| * |
| * <p><b>Factory methods and registration</b> |
| * |
| * <p>In general, client code should use the factory method |
| * <code>getInstance()</code> to obtain an instance of a |
| * transliterator given its ID. Valid IDs may be enumerated using |
| * <code>getAvailableIDs()</code>. Since transliterators are |
| * stateless, multiple calls to <code>getInstance()</code> with the |
| * same ID will return the same object. |
| * |
| * <p>In addition to the system transliterators registered at startup, |
| * user transliterators may be registered by calling |
| * <code>registerInstance()</code> at run time. To register a |
| * transliterator subclass without instantiating it (until it is |
| * needed), users may call <code>registerClass()</code>. |
| * |
| * <p><b>Subclassing</b> |
| * |
| * <p>Subclasses must implement the abstract |
| * <code>transliterate()</code> method. They should also override the |
| * <code>transliterate()</code> method taking a <code>String</code> |
| * and <code>StringBuffer</code> if the performance of these methods |
| * can be improved over the performance obtained by the default |
| * implementations in this class. Subclasses must also implement |
| * <code>handleKeyboardTransliterate()</code>. |
| * |
| * <p>Copyright © IBM Corporation 1999. All rights reserved. |
| * |
| * @author Alan Liu |
| * @version $RCSfile: Transliterator.java,v $ $Revision: 1.6 $ $Date: 2000/01/06 17:38:25 $ |
| */ |
| public abstract class Transliterator { |
| /** |
| * In the <code>keyboardTransliterate()</code> |
| * <code>index[]</code> array, the beginning index, inclusive |
| * @see #keyboardTransliterate |
| */ |
| public static final int START = 0; |
| |
| /** |
| * In the <code>keyboardTransliterate()</code> |
| * <code>index[]</code> array, the ending index, exclusive |
| * @see #keyboardTransliterate |
| */ |
| public static final int LIMIT = 1; |
| |
| /** |
| * In the <code>keyboardTransliterate()</code> |
| * <code>index[]</code> array, the next character to be considered |
| * for transliteration |
| * @see #keyboardTransliterate |
| */ |
| public static final int CURSOR = 2; |
| |
| /** |
| * Programmatic name, e.g., "Latin-Arabic". |
| */ |
| private String ID; |
| |
| /** |
| * This transliterator's filter. Any character for which |
| * <tt>filter.isIn()</tt> returns <tt>false</tt> will not be |
| * altered by this transliterator. If <tt>filter</tt> is |
| * <tt>null</tt> then no filtering is applied. |
| */ |
| private UnicodeFilter filter; |
| |
| /** |
| * Dictionary of known transliterators. Keys are <code>String</code> |
| * names, values are one of the following: |
| * |
| * <ul><li><code>Transliterator</code> objects |
| * |
| * <li><code>Class</code> objects. Such objects must represent |
| * subclasses of <code>Transliterator</code>, and must satisfy the |
| * constraints described in <code>registerClass()</code> |
| * |
| * <li><code>RULE_BASED_PLACEHOLDER</code>, in which case the ID |
| * will have its first '-' removed and be appended to |
| * RB_RULE_BASED_PREFIX to form a resource bundle name from which |
| * the RB_RULE key is looked up to obtain the rule. |
| * |
| * <li><code>REVERSE_RULE_BASED_PLACEHOLDER</code>. Like |
| * <code>RULE_BASED_PLACEHOLDER</code>, except the entity names in |
| * the ID are reversed, and the argument |
| * RuleBasedTransliterator.REVERSE is pased to the |
| * RuleBasedTransliterator constructor. |
| * </ul> |
| */ |
| private static Hashtable cache; |
| |
| /** |
| * Internal object used to stand for instances of |
| * <code>RuleBasedTransliterator</code> that have not been |
| * constructed yet in the <code>cache</code>. When a |
| * <code>getInstance()</code> call retrieves this object, it is |
| * replaced by the actual <code>RuleBasedTransliterator</code>. |
| * This allows <code>Transliterator</code> to delay instantiation |
| * of such transliterators until they are needed. |
| */ |
| private static final Object RULE_BASED_PLACEHOLDER = new Object(); |
| |
| /** |
| * Internal object used to stand for instances of |
| * <code>RuleBasedTransliterator</code> that have not been |
| * constructed yet in the <code>cache</code>. These instances are |
| * constructed with an argument |
| * <code>RuleBasedTransliterator.REVERSE</code>. |
| */ |
| private static final Object REVERSE_RULE_BASED_PLACEHOLDER = new Object(); |
| |
| /** |
| * Prefix for resource bundle key for the display name for a |
| * transliterator. The ID is appended to this to form the key. |
| * The resource bundle value should be a String. |
| */ |
| private static final String RB_DISPLAY_NAME_PREFIX = "%Translit%%"; |
| |
| /** |
| * Prefix for resource bundle key for the display name for a |
| * transliterator SCRIPT. The ID is appended to this to form the key. |
| * The resource bundle value should be a String. |
| */ |
| private static final String RB_SCRIPT_DISPLAY_NAME_PREFIX = "%Translit%"; |
| |
| /** |
| * Resource bundle key for display name pattern. |
| * The resource bundle value should be a String forming a |
| * MessageFormat pattern, e.g.: |
| * "{0,choice,0#|1#{1} Transliterator|2#{1} to {2} Transliterator}". |
| */ |
| private static final String RB_DISPLAY_NAME_PATTERN = "TransliteratorNamePattern"; |
| |
| /** |
| * Resource bundle key for the list of RuleBasedTransliterator IDs. |
| * The resource bundle value should be a String[] with each element |
| * being a valid ID. The ID will be appended to RB_RULE_BASED_PREFIX |
| * to obtain the class name in which the RB_RULE key will be sought. |
| */ |
| private static final String RB_RULE_BASED_IDS = "RuleBasedTransliteratorIDs"; |
| |
| /** |
| * Resource bundle containing display name keys and the |
| * RB_RULE_BASED_IDS array. |
| * |
| * <p>If we ever integrate this with the Sun JDK, the resource bundle |
| * root will change to java.text.resources.LocaleElements |
| */ |
| private static final String RB_LOCALE_ELEMENTS = |
| "com.ibm.text.resources.LocaleElements"; |
| |
| /** |
| * Prefix for resource bundle containing RuleBasedTransliterator |
| * RB_RULE string. The ID is munged to remove the first '-' then appended |
| * to this String to obtain the class name. |
| */ |
| private static final String RB_RULE_BASED_PREFIX = |
| "com.ibm.text.resources.TransliterationRule$"; |
| |
| /** |
| * Resource bundle key for the RuleBasedTransliterator rule. |
| */ |
| private static final String RB_RULE = "Rule"; |
| |
| private static final String COPYRIGHT = |
| "\u00A9 IBM Corporation 1999. All rights reserved."; |
| |
| /** |
| * Default constructor. |
| * @param ID the string identifier for this transliterator |
| * @param filter the filter. Any character for which |
| * <tt>filter.isIn()</tt> returns <tt>false</tt> will not be |
| * altered by this transliterator. If <tt>filter</tt> is |
| * <tt>null</tt> then no filtering is applied. |
| */ |
| protected Transliterator(String ID, UnicodeFilter filter) { |
| if (ID == null) { |
| throw new NullPointerException(); |
| } |
| this.ID = ID; |
| this.filter = filter; |
| } |
| |
| /** |
| * Transliterates the segment of a string that begins at the |
| * character at offset <code>start</code> and extends to the |
| * character at offset <code>limit - 1</code>, with optional |
| * filtering. A default implementaion is provided here; |
| * subclasses should provide a more efficient implementation if |
| * possible. |
| * @param text the string to be transliterated |
| * @param start the beginning index, inclusive; <code>0 <= start |
| * <= limit</code>. |
| * @param limit the ending index, exclusive; <code>start <= limit |
| * <= text.length()</code>. |
| * @param result buffer to receive the transliterated text; previous |
| * contents are discarded |
| */ |
| public void transliterate(String text, int start, int limit, |
| StringBuffer result) { |
| /* This is a default implementation that should be replaced by |
| * a more efficient subclass implementation if possible. |
| */ |
| result.setLength(0); |
| result.append(text.substring(start, limit)); |
| transliterate(new ReplaceableString(result), |
| 0, result.length()); |
| } |
| |
| /** |
| * Transliterates a segment of a string, with optional filtering. |
| * Subclasses must override this abstract method. |
| * |
| * @param text the string to be transliterated |
| * @param start the beginning index, inclusive; <code>0 <= start |
| * <= limit</code>. |
| * @param limit the ending index, exclusive; <code>start <= limit |
| * <= text.length()</code>. |
| * @param filter the filter. Any character for which |
| * <tt>filter.isIn()</tt> returns <tt>false</tt> will not be |
| * altered by this transliterator. If <tt>filter</tt> is |
| * <tt>null</tt> then no filtering is applied. |
| * @return The new limit index. The text previously occupying <code>[start, |
| * limit)</code> has been transliterated, possibly to a string of a different |
| * length, at <code>[start, </code><em>new-limit</em><code>)</code>, where |
| * <em>new-limit</em> is the return value. |
| */ |
| public abstract int transliterate(Replaceable text, int start, int limit); |
| |
| /** |
| * Transliterates an entire string. Convenience method. |
| * @param text the string to be transliterated |
| * @param result buffer to receive the transliterated text; previous |
| * contents are discarded |
| */ |
| public final void transliterate(String text, StringBuffer result) { |
| transliterate(text, 0, text.length(), result); |
| } |
| |
| /** |
| * Transliterate an entire string and returns the result. Convenience method. |
| * |
| * @param text the string to be transliterated |
| * @return The transliterated text |
| */ |
| public final String transliterate(String text) { |
| StringBuffer result = new StringBuffer(); |
| transliterate(text, 0, text.length(), result); |
| return result.toString(); |
| } |
| |
| /** |
| * Transliterates an entire string in place. Convenience method. |
| * @param text the string to be transliterated |
| */ |
| public final void transliterate(Replaceable text) { |
| transliterate(text, 0, text.length()); |
| } |
| |
| /** |
| * Transliterates the portion of the text buffer that can be |
| * transliterated unambiguosly after new text has been inserted, |
| * typically as a result of a keyboard event. The new text in |
| * <code>insertion</code> will be inserted into <code>text</code> |
| * at <code>index[LIMIT]</code>, advancing |
| * <code>index[LIMIT]</code> by <code>insertion.length()</code>. |
| * Then the transliterator will try to transliterate characters of |
| * <code>text</code> between <code>index[CURSOR]</code> and |
| * <code>index[LIMIT]</code>. Characters before |
| * <code>index[CURSOR]</code> will not be changed. |
| * |
| * <p>Upon return, values in <code>index[]</code> will be updated. |
| * <code>index[START]</code> will be advanced to the first |
| * character that future calls to this method will read. |
| * <code>index[CURSOR]</code> and <code>index[LIMIT]</code> will |
| * be adjusted to delimit the range of text that future calls to |
| * this method may change. |
| * |
| * <p>Typical usage of this method begins with an initial call |
| * with <code>index[START]</code> and <code>index[LIMIT]</code> |
| * set to indicate the portion of <code>text</code> to be |
| * transliterated, and <code>index[CURSOR] == index[START]</code>. |
| * Thereafter, <code>index[]</code> can be used without |
| * modification in future calls, provided that all changes to |
| * <code>text</code> are made via this method. |
| * |
| * <p>This method assumes that future calls may be made that will |
| * insert new text into the buffer. As a result, it only performs |
| * unambiguous transliterations. After the last call to this |
| * method, there may be untransliterated text that is waiting for |
| * more input to resolve an ambiguity. In order to perform these |
| * pending transliterations, clients should call {@link |
| * #finishKeyboardTransliteration} after the last call to this |
| * method has been made. |
| * |
| * @param text the buffer holding transliterated and untransliterated text |
| * @param index an array of three integers. |
| * |
| * <ul><li><code>index[START]</code>: the beginning index, |
| * inclusive; <code>0 <= index[START] <= index[LIMIT]</code>. |
| * |
| * <li><code>index[LIMIT]</code>: the ending index, exclusive; |
| * <code>index[START] <= index[LIMIT] <= text.length()</code>. |
| * <code>insertion</code> is inserted at |
| * <code>index[LIMIT]</code>. |
| * |
| * <li><code>index[CURSOR]</code>: the next character to be |
| * considered for transliteration; <code>index[START] <= |
| * index[CURSOR] <= index[LIMIT]</code>. Characters before |
| * <code>index[CURSOR]</code> will not be changed by future calls |
| * to this method.</ul> |
| * |
| * @param insertion text to be inserted and possibly |
| * transliterated into the translation buffer at |
| * <code>index[LIMIT]</code>. If <code>null</code> then no text |
| * is inserted. |
| * @see #START |
| * @see #LIMIT |
| * @see #CURSOR |
| * @see #handleKeyboardTransliterate |
| * @exception IllegalArgumentException if <code>index[]</code> |
| * is invalid |
| */ |
| public final void keyboardTransliterate(Replaceable text, int[] index, |
| String insertion) { |
| if (index.length < 3 || |
| index[START] < 0 || |
| index[LIMIT] > text.length() || |
| index[CURSOR] < index[START] || |
| index[CURSOR] > index[LIMIT]) { |
| throw new IllegalArgumentException("Invalid index array"); |
| } |
| |
| int originalStart = index[START]; |
| if (insertion != null) { |
| text.replace(index[LIMIT], index[LIMIT], insertion); |
| index[LIMIT] += insertion.length(); |
| } |
| |
| handleKeyboardTransliterate(text, index); |
| |
| index[START] = Math.max(index[CURSOR] - getMaximumContextLength(), |
| originalStart); |
| } |
| |
| /** |
| * Transliterates the portion of the text buffer that can be |
| * transliterated unambiguosly after a new character has been |
| * inserted, typically as a result of a keyboard event. This is a |
| * convenience method; see {@link |
| * #keyboardTransliterate(Replaceable, int[], String)} for details. |
| * @param text the buffer holding transliterated and |
| * untransliterated text |
| * @param index an array of three integers. See {@link |
| * #keyboardTransliterate(Replaceable, int[], String)}. |
| * @param insertion text to be inserted and possibly |
| * transliterated into the translation buffer at |
| * <code>index[LIMIT]</code>. |
| * @see #keyboardTransliterate(Replaceable, int[], String) |
| */ |
| public final void keyboardTransliterate(Replaceable text, int[] index, |
| char insertion) { |
| keyboardTransliterate(text, index, String.valueOf(insertion)); |
| } |
| |
| /** |
| * Transliterates the portion of the text buffer that can be |
| * transliterated unambiguosly. This is a convenience method; see |
| * {@link #keyboardTransliterate(Replaceable, int[], String)} for |
| * details. |
| * @param text the buffer holding transliterated and |
| * untransliterated text |
| * @param index an array of three integers. See {@link |
| * #keyboardTransliterate(Replaceable, int[], String)}. |
| * @see #keyboardTransliterate(Replaceable, int[], String) |
| */ |
| public final void keyboardTransliterate(Replaceable text, int[] index) { |
| keyboardTransliterate(text, index, null); |
| } |
| |
| /** |
| * Finishes any pending transliterations that were waiting for |
| * more characters. Clients should call this method as the last |
| * call after a sequence of one or more calls to |
| * <code>keyboardTransliterate()</code>. |
| * @param text the buffer holding transliterated and |
| * untransliterated text. |
| * @param index the array of indices previously passed to {@link |
| * #keyboardTransliterate} |
| */ |
| public final void finishKeyboardTransliteration(Replaceable text, |
| int[] index) { |
| transliterate(text, index[START], index[LIMIT]); |
| } |
| |
| /** |
| * Abstract method that concrete subclasses define to implement |
| * keyboard transliteration. This method should transliterate all |
| * characters between <code>index[CURSOR]</code> and |
| * <code>index[LIMIT]</code> that can be unambiguously |
| * transliterated, regardless of future insertions of text at |
| * <code>index[LIMIT]</code>. <code>index[CURSOR]</code> should |
| * be advanced past committed characters (those that will not |
| * change in future calls to this method). |
| * <code>index[LIMIT]</code> should be updated to reflect text |
| * replacements that shorten or lengthen the text between |
| * <code>index[CURSOR]</code> and <code>index[LIMIT]</code>. Upon |
| * return, neither <code>index[CURSOR]</code> nor |
| * <code>index[LIMIT]</code> should be less than the initial value |
| * of <code>index[CURSOR]</code>. <code>index[START]</code> |
| * should <em>not</em> be changed. |
| * |
| * @param text the buffer holding transliterated and |
| * untransliterated text |
| * @param index an array of three integers. See {@link |
| * #keyboardTransliterate(Replaceable, int[], String)}. |
| * @see #keyboardTransliterate |
| */ |
| protected abstract void handleKeyboardTransliterate(Replaceable text, |
| int[] index); |
| |
| /** |
| * Returns the length of the longest context required by this transliterator. |
| * This is <em>preceding</em> context. The default implementation supplied |
| * by <code>Transliterator</code> returns zero; subclasses |
| * that use preceding context should override this method to return the |
| * correct value. For example, if a transliterator translates "ddd" (where |
| * d is any digit) to "555" when preceded by "(ddd)", then the preceding |
| * context length is 5, the length of "(ddd)". |
| * |
| * @return The maximum number of preceding context characters this |
| * transliterator needs to examine |
| */ |
| protected int getMaximumContextLength() { |
| return 0; |
| } |
| |
| /** |
| * Returns a programmatic identifier for this transliterator. |
| * If this identifier is passed to <code>getInstance()</code>, it |
| * will return this object, if it has been registered. |
| * @see #registerInstance |
| * @see #registerClass |
| * @see #getAvailableIDs |
| */ |
| public final String getID() { |
| return ID; |
| } |
| |
| /** |
| * Returns a name for this transliterator that is appropriate for |
| * display to the user in the default locale. See {@link |
| * #getDisplayName(Locale)} for details. |
| */ |
| public final static String getDisplayName(String ID) { |
| return getDisplayName(ID, Locale.getDefault()); |
| } |
| |
| /** |
| * Returns a name for this transliterator that is appropriate for |
| * display to the user in the given locale. This name is taken |
| * from the locale resource data in the standard manner of the |
| * <code>java.text</code> package. |
| * |
| * <p>If no localized names exist in the system resource bundles, |
| * a name is synthesized using a localized |
| * <code>MessageFormat</code> pattern from the resource data. The |
| * arguments to this pattern are an integer followed by one or two |
| * strings. The integer is the number of strings, either 1 or 2. |
| * The strings are formed by splitting the ID for this |
| * transliterator at the first '-'. If there is no '-', then the |
| * entire ID forms the only string. |
| * @param inLocale the Locale in which the display name should be |
| * localized. |
| * @see java.text.MessageFormat |
| */ |
| public static String getDisplayName(String ID, Locale inLocale) { |
| ResourceBundle bundle = ResourceBundle.getBundle( |
| RB_LOCALE_ELEMENTS, inLocale); |
| |
| // Use display name for the entire transliterator, if it |
| // exists. |
| try { |
| return bundle.getString(RB_DISPLAY_NAME_PREFIX + ID); |
| } catch (MissingResourceException e) {} |
| |
| try { |
| // Construct the formatter first; if getString() fails |
| // we'll exit the try block |
| MessageFormat format = new MessageFormat( |
| bundle.getString(RB_DISPLAY_NAME_PATTERN)); |
| // Construct the argument array |
| int i = ID.indexOf('-'); |
| Object[] args = (i < 0) |
| ? new Object[] { new Integer(1), ID } |
| : new Object[] { new Integer(2), ID.substring(0, i), |
| ID.substring(i+1) }; |
| |
| // Use display names for the scripts, if they exist |
| for (int j=1; j<=((i<0)?1:2); ++j) { |
| try { |
| args[j] = bundle.getString(RB_SCRIPT_DISPLAY_NAME_PREFIX + |
| (String) args[j]); |
| } catch (MissingResourceException e) {} |
| } |
| |
| // Format it using the pattern in the resource |
| return format.format(args); |
| } catch (MissingResourceException e2) {} |
| |
| // We should not reach this point unless there is something |
| // wrong with the build or the RB_DISPLAY_NAME_PATTERN has |
| // been deleted from the root RB_LOCALE_ELEMENTS resource. |
| throw new RuntimeException(); |
| } |
| |
| /** |
| * Returns the filter used by this transliterator, or <tt>null</tt> |
| * if this transliterator uses no filter. |
| */ |
| public UnicodeFilter getFilter() { |
| return filter; |
| } |
| |
| /** |
| * Changes the filter used by this transliterator. If the filter |
| * is set to <tt>null</tt> then no filtering will occur. |
| * |
| * <p>Callers must take care if a transliterator is in use by |
| * multiple threads. The filter should not be changed by one |
| * thread while another thread may be transliterating. |
| */ |
| public void setFilter(UnicodeFilter filter) { |
| this.filter = filter; |
| } |
| |
| /** |
| * Returns this transliterator's inverse. See the class |
| * documentation for details. This implementation simply inverts |
| * the two entities in the ID and attempts to retrieve the |
| * resulting transliterator. That is, if <code>getID()</code> |
| * returns "A-B", then this method will return the result of |
| * <code>getInstance("B-A")</code>, or <code>null</code> if that |
| * call fails. |
| * |
| * <p>This method does not take filtering into account. The |
| * returned transliterator will have no filter. |
| * |
| * <p>Subclasses with knowledge of their inverse may wish to |
| * override this method. |
| * |
| * @return a transliterator that is an inverse, not necessarily |
| * exact, of this transliterator, or <code>null</code> if no such |
| * transliterator is registered. |
| * @see #registerInstance |
| */ |
| public Transliterator getInverse() { |
| int i = ID.indexOf('-'); |
| if (i >= 0) { |
| String inverseID = ID.substring(i+1) + '-' + ID.substring(0, i); |
| return internalGetInstance(inverseID); |
| } |
| return null; |
| } |
| |
| /** |
| * Returns a <code>Transliterator</code> object given its ID. |
| * The ID must be either a system transliterator ID or a ID registered |
| * using <code>registerInstance()</code>. |
| * |
| * @param ID a valid ID, as enumerated by <code>getAvailableIDs()</code> |
| * @return A <code>Transliterator</code> object with the given ID |
| * @exception IllegalArgumentException if the given ID is invalid. |
| * @see #registerInstance |
| * @see #getAvailableIDs |
| * @see #getID |
| */ |
| public static Transliterator getInstance(String ID) { |
| Transliterator t = internalGetInstance(ID); |
| if (t != null) { |
| return t; |
| } |
| throw new IllegalArgumentException("Unsupported transliterator: " |
| + ID); |
| } |
| |
| /** |
| * Returns a transliterator object given its ID. Unlike getInstance(), |
| * this method returns null if it cannot make use of the given ID. |
| */ |
| private static Transliterator internalGetInstance(String ID) { |
| Object obj = cache.get(ID); |
| RuleBasedTransliterator.Data data = null; |
| |
| if (obj instanceof RuleBasedTransliterator.Data) { |
| data = (RuleBasedTransliterator.Data) obj; |
| // Fall through to construct transliterator from cached Data object. |
| } else if (obj instanceof Class) { |
| try { |
| return (Transliterator) ((Class) obj).newInstance(); |
| } catch (InstantiationException e) { |
| } catch (IllegalAccessException e2) {} |
| } else { |
| synchronized (cache) { |
| boolean isReverse = (obj == REVERSE_RULE_BASED_PLACEHOLDER); |
| String resourceName = RB_RULE_BASED_PREFIX; |
| int i = ID.indexOf('-'); |
| if (i < 0) { |
| resourceName += ID; |
| } else { |
| String IDLeft = ID.substring(0, i); |
| String IDRight = ID.substring(i+1); |
| resourceName += isReverse ? (IDRight + '$' + IDLeft) |
| : (IDLeft + '$' + IDRight); |
| } |
| try { |
| ResourceBundle resource = ResourceBundle.getBundle(resourceName); |
| |
| // We allow the resource bundle to contain either an array |
| // of rules, or a single rule string. |
| String[] ruleArray; |
| try { |
| ruleArray = resource.getStringArray(RB_RULE); |
| } catch (Exception e) { |
| // This is a ClassCastException under JDK 1.1.8 |
| ruleArray = new String[] { resource.getString(RB_RULE) }; |
| } |
| |
| data = RuleBasedTransliterator.parse(ruleArray, |
| isReverse |
| ? RuleBasedTransliterator.REVERSE |
| : RuleBasedTransliterator.FORWARD); |
| |
| cache.put(ID, data); |
| // Fall through to construct transliterator from Data object. |
| } catch (MissingResourceException e) {} |
| } |
| } |
| |
| if (data != null) { |
| return new RuleBasedTransliterator(ID, data, null); |
| } |
| |
| return null; |
| } |
| |
| /** |
| * Registers a subclass of <code>Transliterator</code> with the |
| * system. This subclass must have a public constructor taking no |
| * arguments. When that constructor is called, the resulting |
| * object must return the <code>ID</code> passed to this method if |
| * its <code>getID()</code> method is called. |
| * |
| * @param ID the result of <code>getID()</code> for this |
| * transliterator |
| * @param transClass a subclass of <code>Transliterator</code> |
| * @see #registerInstance |
| * @see #unregister |
| */ |
| public static void registerClass(String ID, Class transClass) { |
| cache.put(ID, transClass); |
| } |
| |
| /** |
| * Unregisters a transliterator or class. This may be either |
| * a system transliterator or a user transliterator or class. |
| * |
| * @param ID the ID of the transliterator or class |
| * @return the <code>Object</code> that was registered with |
| * <code>ID</code>, or <code>null</code> if none was |
| * @see #registerInstance |
| * @see #registerClass |
| */ |
| public static Object unregister(String ID) { |
| return cache.remove(ID); |
| } |
| |
| /** |
| * Returns an enumeration over the programmatic names of registered |
| * <code>Transliterator</code> objects. This includes both system |
| * transliterators and user transliterators registered using |
| * <code>registerInstance()</code>. The enumerated names may be |
| * passed to <code>getInstance()</code>. |
| * |
| * @return An <code>Enumeration</code> over <code>String</code> objects |
| * @see #getInstance |
| * @see #registerInstance |
| */ |
| public static final Enumeration getAvailableIDs() { |
| return cache.keys(); |
| } |
| |
| static { |
| ResourceBundle bundle = ResourceBundle.getBundle(RB_LOCALE_ELEMENTS); |
| |
| try { |
| String[] ruleBasedIDs = bundle.getStringArray(RB_RULE_BASED_IDS); |
| |
| cache = new Hashtable(); |
| |
| for (int i=0; i<ruleBasedIDs.length; ++i) { |
| String ID = ruleBasedIDs[i]; |
| boolean isReverse = (ID.charAt(0) == '*'); |
| if (isReverse) { |
| ID = ID.substring(1); |
| } |
| cache.put(ID, isReverse ? REVERSE_RULE_BASED_PLACEHOLDER |
| : RULE_BASED_PLACEHOLDER); |
| } |
| } catch (MissingResourceException e) {} |
| |
| // Register non-rule-based transliterators |
| registerClass(HexToUnicodeTransliterator._ID, |
| HexToUnicodeTransliterator.class); |
| registerClass(UnicodeToHexTransliterator._ID, |
| UnicodeToHexTransliterator.class); |
| registerClass(NullTransliterator._ID, |
| NullTransliterator.class); |
| } |
| } |
