| package com.ibm.text; |
| |
| import java.util.Dictionary; |
| |
| /** |
| * A transliteration rule used by |
| * <code>RuleBasedTransliterator</code>. |
| * <code>TransliterationRule</code> is an immutable object. |
| * |
| * <p>A rule consists of an input pattern and an output string. When |
| * the input pattern is matched, the output string is emitted. The |
| * input pattern consists of zero or more characters which are matched |
| * exactly (the key) and optional context. Context must match if it |
| * is specified. Context may be specified before the key, after the |
| * key, or both. The key, preceding context, and following context |
| * may contain variables. Variables represent a set of Unicode |
| * characters, such as the letters <i>a</i> through <i>z</i>. |
| * Variables are detected by looking up each character in a supplied |
| * variable list to see if it has been so defined. |
| * |
| * <p>Copyright © IBM Corporation 1999. All rights reserved. |
| * |
| * @author Alan Liu |
| * @version $RCSfile: TransliterationRule.java,v $ $Revision: 1.7 $ $Date: 2000/01/11 04:12:06 $ |
| * |
| * $Log: TransliterationRule.java,v $ |
| * Revision 1.7 2000/01/11 04:12:06 Alan |
| * Cleanup, embellish comments |
| * |
| * Revision 1.6 2000/01/11 02:25:03 Alan |
| * Rewrite UnicodeSet and RBT parsers for better performance and new syntax |
| * |
| * Revision 1.5 2000/01/04 21:43:57 Alan |
| * Add rule indexing, and move masking check to TransliterationRuleSet. |
| * |
| * Revision 1.4 1999/12/22 01:40:54 Alan |
| * Consolidate rule pattern anteContext, key, and postContext into one string. |
| * |
| * Revision 1.3 1999/12/22 01:05:54 Alan |
| * Improve masking checking; turn it off by default, for better performance |
| * |
| * Revision 1.2 1999/12/21 23:58:44 Alan |
| * Detect a>x masking a>y |
| * |
| */ |
| class TransliterationRule { |
| /** |
| * Constant returned by <code>getMatchDegree()</code> indicating a mismatch |
| * between the text and this rule. One or more characters of the context or |
| * key do not match the text. |
| * @see #getMatchDegree |
| */ |
| public static final int MISMATCH = 0; |
| |
| /** |
| * Constant returned by <code>getMatchDegree()</code> indicating a partial |
| * match between the text and this rule. All characters of the text match |
| * the corresponding context or key, but more characters are required for a |
| * complete match. There are some key or context characters at the end of |
| * the pattern that remain unmatched because the text isn't long enough. |
| * @see #getMatchDegree |
| */ |
| public static final int PARTIAL_MATCH = 1; |
| |
| /** |
| * Constant returned by <code>getMatchDegree()</code> indicating a complete |
| * match between the text and this rule. The text matches all context and |
| * key characters. |
| * @see #getMatchDegree |
| */ |
| public static final int FULL_MATCH = 2; |
| |
| /** |
| * The string that must be matched, consisting of the anteContext, key, |
| * and postContext, concatenated together, in that order. Some components |
| * may be empty (zero length). |
| * @see anteContextLength |
| * @see keyLength |
| */ |
| private String pattern; |
| |
| /** |
| * The string that is emitted if the key, anteContext, and postContext |
| * are matched. |
| */ |
| private String output; |
| |
| /** |
| * The length of the string that must match before the key. If |
| * zero, then there is no matching requirement before the key. |
| * Substring [0,anteContextLength) of pattern is the anteContext. |
| */ |
| private int anteContextLength; |
| |
| /** |
| * The length of the key. Substring [anteContextLength, |
| * anteContextLength + keyLength) is the key. |
| */ |
| private int keyLength; |
| |
| /** |
| * The position of the cursor after emitting the output string, from 0 to |
| * output.length(). For most rules with no special cursor specification, |
| * the cursorPos is output.length(). |
| */ |
| private int cursorPos; |
| |
| private static final String COPYRIGHT = |
| "\u00A9 IBM Corporation 1999. All rights reserved."; |
| |
| /** |
| * Construct a new rule with the given input, output text, and other |
| * attributes. A cursor position may be specified for the output text. |
| * @param input input string, including key and optional ante and |
| * post context |
| * @param anteContextPos offset into input to end of ante context, or -1 if |
| * none. Must be <= input.length() if not -1. |
| * @param postContextPos offset into input to start of post context, or -1 |
| * if none. Must be <= input.length() if not -1, and must be >= |
| * anteContextPos. |
| * @param output output string |
| * @param cursorPos offset into output at which cursor is located, or -1 if |
| * none. If less than zero, then the cursor is placed after the |
| * <code>output</code>; that is, -1 is equivalent to |
| * <code>output.length()</code>. If greater than |
| * <code>output.length()</code> then an exception is thrown. |
| */ |
| public TransliterationRule(String input, |
| int anteContextPos, int postContextPos, |
| String output, |
| int cursorPos) { |
| // Do range checks only when warranted to save time |
| if (anteContextPos < 0) { |
| anteContextLength = 0; |
| } else { |
| if (anteContextPos > input.length()) { |
| throw new IllegalArgumentException("Invalid ante context"); |
| } |
| anteContextLength = anteContextPos; |
| } |
| if (postContextPos < 0) { |
| keyLength = input.length() - anteContextLength; |
| } else { |
| if (postContextPos < anteContextLength || |
| postContextPos > input.length()) { |
| throw new IllegalArgumentException("Invalid post context"); |
| } |
| keyLength = postContextPos - anteContextLength; |
| } |
| if (cursorPos < 0) { |
| this.cursorPos = output.length(); |
| } else { |
| if (cursorPos > input.length()) { |
| throw new IllegalArgumentException("Invalid cursor position"); |
| } |
| this.cursorPos = cursorPos; |
| } |
| pattern = input; |
| this.output = output; |
| } |
| |
| /** |
| * Return the length of the key. Equivalent to <code>getKey().length()</code>. |
| * @return the length of the match key. |
| */ |
| public int getKeyLength() { |
| return keyLength; |
| } |
| |
| /** |
| * Return the output string. |
| * @return the output string. |
| */ |
| public String getOutput() { |
| return output; |
| } |
| |
| /** |
| * Return the position of the cursor within the output string. |
| * @return a value from 0 to <code>getOutput().length()</code>, inclusive. |
| */ |
| public int getCursorPos() { |
| return cursorPos; |
| } |
| |
| /** |
| * Return the preceding context length. This method is needed to |
| * support the <code>Transliterator</code> method |
| * <code>getMaximumContextLength()</code>. |
| */ |
| public int getAnteContextLength() { |
| return anteContextLength; |
| } |
| |
| /** |
| * Internal method. Returns 8-bit index value for this rule. |
| * This is the low byte of the first character of the key, |
| * unless the first character of the key is a set. If it's a |
| * set, or otherwise can match multiple keys, the index value is -1. |
| */ |
| final int getIndexValue(Dictionary variables) { |
| if (anteContextLength == pattern.length()) { |
| // A pattern with just ante context {such as foo)>bar} can |
| // match any key. |
| return -1; |
| } |
| char c = pattern.charAt(anteContextLength); |
| return variables.get(new Character(c)) == null ? (c & 0xFF) : -1; |
| } |
| |
| /** |
| * Internal method. Returns true if this rule matches the given |
| * index value. The index value is an 8-bit integer, 0..255, |
| * representing the low byte of the first character of the key. |
| * It matches this rule if it matches the first character of the |
| * key, or if the first character of the key is a set, and the set |
| * contains any character with a low byte equal to the index |
| * value. If the rule contains only ante context, as in foo)>bar, |
| * then it will match any key. |
| */ |
| final boolean matchesIndexValue(int v, Dictionary variables) { |
| if (anteContextLength == pattern.length()) { |
| // A pattern with just ante context {such as foo)>bar} can |
| // match any key. |
| return true; |
| } |
| char c = pattern.charAt(anteContextLength); |
| UnicodeSet set = (UnicodeSet) variables.get(new Character(c)); |
| return set == null ? (c & 0xFF) == v : set.containsIndexValue(v); |
| } |
| |
| /** |
| * Return true if this rule masks another rule. If r1 masks r2 then |
| * r1 matches any input string that r2 matches. If r1 masks r2 and r2 masks |
| * r1 then r1 == r2. Examples: "a>x" masks "ab>y". "a>x" masks "a[b]>y". |
| * "[c]a>x" masks "[dc]a>y". |
| */ |
| public boolean masks(TransliterationRule r2) { |
| /* Rule r1 masks rule r2 if the string formed of the |
| * antecontext, key, and postcontext overlaps in the following |
| * way: |
| * |
| * r1: aakkkpppp |
| * r2: aaakkkkkpppp |
| * ^ |
| * |
| * The strings must be aligned at the first character of the |
| * key. The length of r1 to the left of the alignment point |
| * must be <= the length of r2 to the left; ditto for the |
| * right. The characters of r1 must equal (or be a superset |
| * of) the corresponding characters of r2. The superset |
| * operation should be performed to check for UnicodeSet |
| * masking. |
| */ |
| |
| /* LIMITATION of the current mask algorithm: Some rule |
| * maskings are currently not detected. For example, |
| * "{Lu}]a>x" masks "A]a>y". To detect these sorts of masking, |
| * we need a subset operator on UnicodeSet objects, which we |
| * currently do not have. This can be added later. |
| */ |
| |
| int left = anteContextLength; |
| int left2 = r2.anteContextLength; |
| int right = pattern.length() - left; |
| int right2 = r2.pattern.length() - left2; |
| return left <= left2 && right <= right2 && |
| r2.pattern.substring(left2 - left).startsWith(pattern); |
| } |
| |
| /** |
| * Return a string representation of this object. |
| * @return string representation of this object |
| */ |
| public String toString() { |
| return getClass().getName() + '{' |
| + escape((anteContextLength > 0 ? ("(" + pattern.substring(0, anteContextLength) + |
| ") ") : "") |
| + pattern.substring(anteContextLength, anteContextLength + keyLength) |
| + (anteContextLength + keyLength < pattern.length() ? |
| (" (" + pattern.substring(anteContextLength + keyLength) + ")") : "") |
| + " > " |
| + (cursorPos < output.length() |
| ? (output.substring(0, cursorPos) + '|' + output.substring(cursorPos)) |
| : output)) |
| + '}'; |
| } |
| |
| /** |
| * Return true if this rule matches the given text. The text being matched |
| * occupies a virtual buffer consisting of the contents of |
| * <code>result</code> concatenated to a substring of <code>text</code>. |
| * The substring is specified by <code>start</code> and <code>limit</code>. |
| * The value of <code>cursor</code> is an index into this virtual buffer, |
| * from 0 to the length of the buffer. In terms of the parameters, |
| * <code>cursor</code> must be between 0 and <code>result.length() + limit - |
| * start</code>. |
| * @param text the untranslated text |
| * @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 translated text so far |
| * @param cursor position at which to translate next, an offset into result. |
| * If greater than or equal to result.length(), represents offset start + |
| * cursor - result.length() into text. |
| * @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. |
| */ |
| public final boolean matches(String text, int start, int limit, |
| StringBuffer result, int cursor, |
| Dictionary variables, |
| UnicodeFilter filter) { |
| // Match anteContext, key, and postContext |
| return regionMatches(text, start, limit, result, |
| cursor - anteContextLength, |
| pattern, variables, filter); |
| } |
| |
| /** |
| * Return true if this rule matches the given text. |
| * @param text the text, both translated and untranslated |
| * @param start the beginning index, inclusive; <code>0 <= start |
| * <= limit</code>. |
| * @param limit the ending index, exclusive; <code>start <= limit |
| * <= text.length()</code>. |
| * @param cursor position at which to translate next, representing offset |
| * into text. This value must be between <code>start</code> and |
| * <code>limit</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. |
| */ |
| public final boolean matches(Replaceable text, int start, int limit, |
| int cursor, Dictionary variables, |
| UnicodeFilter filter) { |
| // Match anteContext, key, and postContext |
| return regionMatches(text, start, limit, |
| cursor - anteContextLength, |
| pattern, variables, filter); |
| } |
| |
| /** |
| * Return the degree of match between this rule and the given text. The |
| * degree of match may be mismatch, a partial match, or a full match. A |
| * mismatch means at least one character of the text does not match the |
| * context or key. A partial match means some context and key characters |
| * match, but the text is not long enough to match all of them. A full |
| * match means all context and key characters match. |
| * @param text the text, both translated and untranslated |
| * @param start the beginning index, inclusive; <code>0 <= start |
| * <= limit</code>. |
| * @param limit the ending index, exclusive; <code>start <= limit |
| * <= text.length()</code>. |
| * @param cursor position at which to translate next, representing offset |
| * into text. This value must be between <code>start</code> and |
| * <code>limit</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 one of <code>MISMATCH</code>, <code>PARTIAL_MATCH</code>, or |
| * <code>FULL_MATCH</code>. |
| * @see #MISMATCH |
| * @see #PARTIAL_MATCH |
| * @see #FULL_MATCH |
| */ |
| public int getMatchDegree(Replaceable text, int start, int limit, |
| int cursor, Dictionary variables, |
| UnicodeFilter filter) { |
| int len = getRegionMatchLength(text, start, limit, cursor - anteContextLength, |
| pattern, variables, filter); |
| return len < anteContextLength ? MISMATCH : |
| (len < pattern.length() ? PARTIAL_MATCH : FULL_MATCH); |
| } |
| |
| /** |
| * Return true if a template matches the text. The entire length of the |
| * template is compared to the text at the cursor. As in |
| * <code>matches()</code>, the text being matched occupies a virtual buffer |
| * consisting of the contents of <code>result</code> concatenated to a |
| * substring of <code>text</code>. See <code>matches()</code> for details. |
| * @param text the untranslated text |
| * @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 translated text so far |
| * @param cursor position at which to translate next, an offset into result. |
| * If greater than or equal to result.length(), represents offset start + |
| * cursor - result.length() into text. |
| * @param template the text to match against. All characters must match. |
| * @param variables a dictionary of variables mapping <code>Character</code> |
| * to <code>UnicodeSet</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 true if there is a match |
| */ |
| protected static boolean regionMatches(String text, int start, int limit, |
| StringBuffer result, int cursor, |
| String template, |
| Dictionary variables, |
| UnicodeFilter filter) { |
| int rlen = result.length(); |
| if (cursor < 0 |
| || (cursor + template.length()) > (rlen + limit - start)) { |
| return false; |
| } |
| for (int i=0; i<template.length(); ++i, ++cursor) { |
| if (!charMatches(template.charAt(i), |
| cursor < rlen ? result.charAt(cursor) |
| : text.charAt(cursor - rlen + start), |
| variables, filter)) { |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| /** |
| * Return true if a template matches the text. The entire length of the |
| * template is compared to the text at the cursor. |
| * @param text the text, both translated and untranslated |
| * @param start the beginning index, inclusive; <code>0 <= start |
| * <= limit</code>. |
| * @param limit the ending index, exclusive; <code>start <= limit |
| * <= text.length()</code>. |
| * @param cursor position at which to translate next, representing offset |
| * into text. This value must be between <code>start</code> and |
| * <code>limit</code>. |
| * @param template the text to match against. All characters must match. |
| * @param variables a dictionary of variables mapping <code>Character</code> |
| * to <code>UnicodeSet</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 true if there is a match |
| */ |
| protected static boolean regionMatches(Replaceable text, int start, int limit, |
| int cursor, |
| String template, Dictionary variables, |
| UnicodeFilter filter) { |
| if (cursor < start |
| || (cursor + template.length()) > limit) { |
| return false; |
| } |
| for (int i=0; i<template.length(); ++i, ++cursor) { |
| if (!charMatches(template.charAt(i), text.charAt(cursor), |
| variables, filter)) { |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| /** |
| * Return the number of characters of the text that match this rule. If |
| * there is a mismatch, return -1. If the text is not long enough to match |
| * any characters, return 0. |
| * @param text the text, both translated and untranslated |
| * @param start the beginning index, inclusive; <code>0 <= start |
| * <= limit</code>. |
| * @param limit the ending index, exclusive; <code>start <= limit |
| * <= text.length()</code>. |
| * @param cursor position at which to translate next, representing offset |
| * into text. This value must be between <code>start</code> and |
| * <code>limit</code>. |
| * @param template the text to match against. All characters must match. |
| * @param variables a dictionary of variables mapping <code>Character</code> |
| * to <code>UnicodeSet</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 -1 if there is a mismatch, 0 if the text is not long enough to |
| * match any characters, otherwise the number of characters of text that |
| * match this rule. |
| */ |
| protected static int getRegionMatchLength(Replaceable text, int start, |
| int limit, int cursor, |
| String template, |
| Dictionary variables, |
| UnicodeFilter filter) { |
| if (cursor < start) { |
| return -1; |
| } |
| int i; |
| for (i=0; i<template.length() && cursor<limit; ++i, ++cursor) { |
| if (!charMatches(template.charAt(i), text.charAt(cursor), |
| variables, filter)) { |
| return -1; |
| } |
| } |
| return i; |
| } |
| |
| /** |
| * Return true if the given key matches the given text. This method |
| * accounts for the fact that the key character may represent a character |
| * set. Note that the key and text characters may not be interchanged |
| * without altering the results. |
| * @param keyChar a character in the match key |
| * @param textChar a character in the text being transliterated |
| * @param variables a dictionary of variables mapping <code>Character</code> |
| * to <code>UnicodeSet</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. |
| */ |
| protected static final boolean charMatches(char keyChar, char textChar, |
| Dictionary variables, UnicodeFilter filter) { |
| UnicodeSet set = null; |
| return (filter == null || filter.isIn(textChar)) && |
| ((set = (UnicodeSet) variables.get(new Character(keyChar))) |
| == null) ? |
| keyChar == textChar : set.contains(textChar); |
| } |
| |
| /** |
| * Escape non-ASCII characters as Unicode. |
| */ |
| public static final String escape(String s) { |
| StringBuffer buf = new StringBuffer(); |
| for (int i=0; i<s.length(); ++i) { |
| char c = s.charAt(i); |
| if (c >= ' ' && c <= 0x007F) { |
| buf.append(c); |
| } else { |
| buf.append("\\u"); |
| if (c < 0x1000) { |
| buf.append('0'); |
| if (c < 0x100) { |
| buf.append('0'); |
| if (c < 0x10) { |
| buf.append('0'); |
| } |
| } |
| } |
| buf.append(Integer.toHexString(c)); |
| } |
| } |
| return buf.toString(); |
| } |
| } |
