339 lines
14 KiB
C++
339 lines
14 KiB
C++
/*
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**********************************************************************
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* Copyright (C) 1999, International Business Machines
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* Corporation and others. All Rights Reserved.
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**********************************************************************
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* Date Name Description
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* 11/17/99 aliu Creation.
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**********************************************************************
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*/
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#ifndef RBT_H
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#define RBT_H
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#include "unicode/translit.h"
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#include "unicode/utypes.h"
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class TransliterationRuleData;
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/**
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* A transliterator that reads a set of rules in order to determine how to perform
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* translations. Rules are stored in resource bundles indexed by name. Rules are separated by
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* semicolons (';'). To include a literal semicolon, prefix it with a backslash ('\;').
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* Whitespace, as defined by <code>Character.isWhitespace()</code>, is ignored. If the first
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* non-blank character on a line is '#', the entire line is ignored as a comment. </p>
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*
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* <p>Each set of rules consists of two groups, one forward, and one reverse. This is a
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* convention that is not enforced; rules for one direction may be omitted, with the result
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* that translations in that direction will not modify the source text. </p>
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*
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* <p><b>Rule syntax</b> </p>
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*
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* <p>Rule statements take one of the following forms:
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*
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* <dl>
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* <dt><code>alefmadda=\u0622</code></dt>
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* <dd><strong>Variable definition.</strong> The name on the left is assigned the character or
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* expression on the right. Names may not contain any special characters (see list below).
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* Duplicate names (including duplicates of simple variables or category names) cause an
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* exception to be thrown. If the right hand side consists of one character, then the
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* variable stands for that character. In this example, after this statement, instances of
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* the left hand name surrounded by braces, "<code>{alefmadda}</code>", will be
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* replaced by the Unicode character U+0622. If the right hand side is longer than one
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* character, then it is interpreted as a character category expression; see below for
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* details.</dd>
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* <dt> </dt>
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* <dt><code>softvowel=[eiyEIY]</code></dt>
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* <dd><strong>Category definition.</strong> The name on the left is assigned to stand for a
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* set of characters. The same rules for names of simple variables apply. After this
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* statement, the left hand variable will be interpreted as indicating a set of characters in
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* appropriate contexts. The pattern syntax defining sets of characters is defined by {@link
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* UnicodeSet}. Examples of valid patterns are:<table>
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* <tr valign="top">
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* <td nowrap><code>[abc]</code></td>
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* <td>The set containing the characters 'a', 'b', and 'c'.</td>
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* </tr>
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* <tr valign="top">
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* <td nowrap><code>[^abc]</code></td>
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* <td>The set of all characters <em>except</em> 'a', 'b', and 'c'.</td>
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* </tr>
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* <tr valign="top">
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* <td nowrap><code>[A-Z]</code></td>
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* <td>The set of all characters from 'A' to 'Z' in Unicode order.</td>
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* </tr>
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* <tr valign="top">
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* <td nowrap><code>[:Lu:]</code></td>
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* <td>The set of Unicode uppercase letters. See <a href="http://www.unicode.org">www.unicode.org</a>
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* for a complete list of categories and their two-letter codes.</td>
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* </tr>
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* <tr valign="top">
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* <td nowrap><code>[^a-z[:Lu:][:Ll:]]</code></td>
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* <td>The set of all characters <em>except</em> 'a' through 'z' and uppercase or lowercase
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* letters.</td>
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* </tr>
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* </table>
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* <p>See {@link UnicodeSet} for more documentation and examples. </p>
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* </dd>
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* <dt><code>ai>{alefmadda}</code></dt>
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* <dd><strong>Forward translation rule.</strong> This rule states that the string on the left
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* will be changed to the string on the right when performing forward transliteration.</dd>
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* <dt> </dt>
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* <dt><code>ai<{alefmadda}</code></dt>
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* <dd><strong>Reverse translation rule.</strong> This rule states that the string on the right
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* will be changed to the string on the left when performing reverse transliteration.</dd>
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* </dl>
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*
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* <dl>
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* <dt><code>ai<>{alefmadda}</code></dt>
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* <dd><strong>Bidirectional translation rule.</strong> This rule states that the string on the
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* right will be changed to the string on the left when performing forward transliteration,
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* and vice versa when performing reverse transliteration.</dd>
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* </dl>
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*
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* <p>Forward and reverse translation rules consist of a <em>match pattern</em> and an <em>output
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* string</em>. The match pattern consists of literal characters, optionally preceded by
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* context, and optionally followed by context. Context characters, like literal pattern
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* characters, must be matched in the text being transliterated. However, unlike literal
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* pattern characters, they are not replaced by the output text. For example, the pattern
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* "<code>(abc)def</code>" indicates the characters "<code>def</code>"
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* must be preceded by "<code>abc</code>" for a successful match. If there is a
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* successful match, "<code>def</code>" will be replaced, but not "<code>abc</code>".
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* The initial '<code>(</code>' is optional, so "<code>abc)def</code>" is
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* equivalent to "<code>(abc)def</code>". Another example is "<code>123(456)</code>"
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* (or "<code>123(456</code>") in which the literal pattern "<code>123</code>"
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* must be followed by "<code>456</code>". </p>
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*
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* <p>The output string of a forward or reverse rule consists of characters to replace the
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* literal pattern characters. If the output string contains the character '<code>|</code>',
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* this is taken to indicate the location of the <em>cursor</em> after replacement. The
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* cursor is the point in the text at which the next replacement, if any, will be applied. </p>
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*
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* <p>In addition to being defined in variables, <code>UnicodeSet</code> patterns may be
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* embedded directly into rule strings. Thus, the following two rules are equivalent:</p>
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*
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* <blockquote>
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* <p><code>vowel=[aeiou]; {vowel}>*; # One way to do this<br>
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* [aeiou]>*;
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* #
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* Another way</code></p>
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* </blockquote>
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*
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* <p><b>Example</b> </p>
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*
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* <p>The following example rules illustrate many of the features of the rule language. </p>
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*
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* <table cellpadding="4">
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* <tr valign="top">
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* <td>Rule 1.</td>
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* <td nowrap><code>(abc)def>x|y</code></td>
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* </tr>
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* <tr valign="top">
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* <td>Rule 2.</td>
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* <td nowrap><code>xyz>r</code></td>
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* </tr>
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* <tr valign="top">
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* <td>Rule 3.</td>
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* <td nowrap><code>yz>q</code></td>
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* </tr>
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* </table>
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*
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* <p>Applying these rules to the string "<code>adefabcdefz</code>" yields the
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* following results: </p>
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*
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* <table cellpadding="4">
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* <tr valign="top">
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* <td nowrap><code>|adefabcdefz</code></td>
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* <td>Initial state, no rules match. Advance cursor.</td>
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* </tr>
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* <tr valign="top">
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* <td nowrap><code>a|defabcdefz</code></td>
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* <td>Still no match. Rule 1 does not match because the preceding context is not present.</td>
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* </tr>
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* <tr valign="top">
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* <td nowrap><code>ad|efabcdefz</code></td>
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* <td>Still no match. Keep advancing until there is a match...</td>
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* </tr>
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* <tr valign="top">
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* <td nowrap><code>ade|fabcdefz</code></td>
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* <td>...</td>
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* </tr>
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* <tr valign="top">
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* <td nowrap><code>adef|abcdefz</code></td>
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* <td>...</td>
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* </tr>
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* <tr valign="top">
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* <td nowrap><code>adefa|bcdefz</code></td>
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* <td>...</td>
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* </tr>
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* <tr valign="top">
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* <td nowrap><code>adefab|cdefz</code></td>
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* <td>...</td>
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* </tr>
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* <tr valign="top">
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* <td nowrap><code>adefabc|defz</code></td>
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* <td>Rule 1 matches; replace "<code>def</code>" with "<code>xy</code>"
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* and back up the cursor to before the '<code>y</code>'.</td>
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* </tr>
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* <tr valign="top">
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* <td nowrap><code>adefabcx|yz</code></td>
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* <td>Although "<code>xyz</code>" is present, rule 2 does not match because the
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* cursor is before the '<code>y</code>', not before the '<code>x</code>'. Rule 3 does match.
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* Replace "<code>yz</code>" with "<code>q</code>".</td>
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* </tr>
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* <tr valign="top">
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* <td nowrap><code>adefabcxq|</code></td>
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* <td>The cursor is at the end; transliteration is complete.</td>
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* </tr>
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* </table>
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*
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* <p>The order of rules is significant. If multiple rules may match at some point, the first
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* matching rule is applied. </p>
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*
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* <p>Forward and reverse rules may have an empty output string. Otherwise, an empty left or
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* right hand side of any statement is a syntax error. </p>
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*
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* <p>Single quotes are used to quote the special characters <code>=><{}[]()|</code>.
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* To specify a single quote itself, inside or outside of quotes, use two single quotes in a
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* row. For example, the rule "<code>'>'>o''clock</code>" changes the string
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* "<code>></code>" to the string "<code>o'clock</code>". </p>
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*
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* <p><b>Notes</b> </p>
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*
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* <p>While a RuleBasedTransliterator is being built, it checks that the rules are added in
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* proper order. For example, if the rule "a>x" is followed by the rule
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* "ab>y", then the second rule will throw an exception. The reason is that the
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* second rule can never be triggered, since the first rule always matches anything it
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* matches. In other words, the first rule <em>masks</em> the second rule. </p>
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*
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* @author Alan Liu
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*/
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class U_I18N_API RuleBasedTransliterator : public Transliterator {
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/**
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* The data object is immutable, so we can freely share it with
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* other instances of RBT, as long as we do NOT own this object.
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*/
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TransliterationRuleData* data;
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/**
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* If true, we own the data object and must delete it.
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*/
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bool_t isDataOwned;
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public:
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/**
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* Constructs a new transliterator from the given rules.
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* @param rules rules, separated by ';'
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* @param direction either FORWARD or REVERSE.
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* @exception IllegalArgumentException if rules are malformed
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* or direction is invalid.
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*/
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RuleBasedTransliterator(const UnicodeString& ID,
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const UnicodeString& rules,
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Direction direction,
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UnicodeFilter* adoptedFilter,
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UErrorCode& status);
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/**
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* Covenience constructor with no filter.
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*/
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RuleBasedTransliterator(const UnicodeString& ID,
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const UnicodeString& rules,
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Direction direction,
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UErrorCode& status);
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/**
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* Covenience constructor with no filter and FORWARD direction.
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*/
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RuleBasedTransliterator(const UnicodeString& ID,
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const UnicodeString& rules,
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UErrorCode& status);
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/**
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* Covenience constructor with FORWARD direction.
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*/
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RuleBasedTransliterator(const UnicodeString& ID,
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const UnicodeString& rules,
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UnicodeFilter* adoptedFilter,
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UErrorCode& status);
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RuleBasedTransliterator(const UnicodeString& ID,
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const TransliterationRuleData* theData,
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UnicodeFilter* adoptedFilter = 0);
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RuleBasedTransliterator(const RuleBasedTransliterator&);
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virtual ~RuleBasedTransliterator();
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/**
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* Implement Transliterator API.
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*/
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Transliterator* clone(void) const;
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/**
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* Implements {@link Transliterator#handleTransliterate}.
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*/
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virtual void handleTransliterate(Replaceable& text, Position& offsets,
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bool_t isIncremental) const;
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private:
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void _construct(const UnicodeString& rules,
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Direction direction,
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UErrorCode& status);
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};
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/**
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* Constructs a new transliterator from the given rules.
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* @param rules rules, separated by ';'
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* @param direction either FORWARD or REVERSE.
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* @exception IllegalArgumentException if rules are malformed
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* or direction is invalid.
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*/
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inline RuleBasedTransliterator::RuleBasedTransliterator(
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const UnicodeString& ID,
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const UnicodeString& rules,
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Direction direction,
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UnicodeFilter* adoptedFilter,
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UErrorCode& status) :
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Transliterator(ID, adoptedFilter) {
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_construct(rules, direction, status);
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}
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/**
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* Covenience constructor with no filter.
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*/
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inline RuleBasedTransliterator::RuleBasedTransliterator(
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const UnicodeString& ID,
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const UnicodeString& rules,
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Direction direction,
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UErrorCode& status) :
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Transliterator(ID, 0) {
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_construct(rules, direction, status);
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}
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/**
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* Covenience constructor with no filter and FORWARD direction.
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*/
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inline RuleBasedTransliterator::RuleBasedTransliterator(
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const UnicodeString& ID,
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const UnicodeString& rules,
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UErrorCode& status) :
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Transliterator(ID, 0) {
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_construct(rules, FORWARD, status);
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}
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/**
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* Covenience constructor with FORWARD direction.
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*/
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inline RuleBasedTransliterator::RuleBasedTransliterator(
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const UnicodeString& ID,
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const UnicodeString& rules,
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UnicodeFilter* adoptedFilter,
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UErrorCode& status) :
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Transliterator(ID, adoptedFilter) {
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_construct(rules, FORWARD, status);
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}
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#endif
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