277 lines
10 KiB
C++
277 lines
10 KiB
C++
/*
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* Copyright (C) {1999-2001}, International Business Machines 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_RULE_H
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#define RBT_RULE_H
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#include "unicode/unistr.h"
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#include "unicode/utrans.h"
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#include "unicode/unimatch.h"
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U_NAMESPACE_BEGIN
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class Replaceable;
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class TransliterationRuleData;
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class StringMatcher;
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class UnicodeFunctor;
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/**
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* A transliteration rule used by
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* <code>RuleBasedTransliterator</code>.
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* <code>TransliterationRule</code> is an immutable object.
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*
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* <p>A rule consists of an input pattern and an output string. When
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* the input pattern is matched, the output string is emitted. The
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* input pattern consists of zero or more characters which are matched
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* exactly (the key) and optional context. Context must match if it
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* is specified. Context may be specified before the key, after the
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* key, or both. The key, preceding context, and following context
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* may contain variables. Variables represent a set of Unicode
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* characters, such as the letters <i>a</i> through <i>z</i>.
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* Variables are detected by looking up each character in a supplied
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* variable list to see if it has been so defined.
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*
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* <p>A rule may contain segments in its input string and segment
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* references in its output string. A segment is a substring of the
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* input pattern, indicated by an offset and limit. The segment may
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* be in the preceding or following context. It may not span a
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* context boundary. A segment reference is a special character in
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* the output string that causes a segment of the input string (not
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* the input pattern) to be copied to the output string. The range of
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* special characters that represent segment references is defined by
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* RuleBasedTransliterator.Data.
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*
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* @author Alan Liu
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*/
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class TransliterationRule {
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private:
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// TODO Eliminate the pattern and keyLength data members. They
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// are used only by masks() and getIndexValue() which are called
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// only during build time, not during run-time. Perhaps these
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// methods and pattern/keyLength can be isolated into a separate
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// object.
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/**
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* The match that must occur before the key, or null if there is no
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* preceding context.
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*/
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StringMatcher *anteContext;
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/**
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* The matcher object for the key. If null, then the key is empty.
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*/
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StringMatcher *key;
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/**
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* The match that must occur after the key, or null if there is no
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* following context.
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*/
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StringMatcher *postContext;
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/**
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* The object that performs the replacement if the key,
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* anteContext, and postContext are matched. Never null.
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*/
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UnicodeFunctor* output;
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/**
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* The string that must be matched, consisting of the anteContext, key,
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* and postContext, concatenated together, in that order. Some components
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* may be empty (zero length).
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* @see anteContextLength
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* @see keyLength
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*/
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UnicodeString pattern;
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/**
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* An array of matcher objects corresponding to the input pattern
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* segments. If there are no segments this is null. N.B. This is
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* a UnicodeMatcher for generality, but in practice it is always a
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* StringMatcher. In the future we may generalize this, but for
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* now we sometimes cast down to StringMatcher.
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*
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* The array is owned, but the pointers within it are not.
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*/
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UnicodeFunctor** segments;
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/**
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* The number of elements in segments[] or zero if segments is NULL.
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*/
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int32_t segmentsCount;
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/**
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* The length of the string that must match before the key. If
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* zero, then there is no matching requirement before the key.
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* Substring [0,anteContextLength) of pattern is the anteContext.
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*/
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int32_t anteContextLength;
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/**
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* The length of the key. Substring [anteContextLength,
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* anteContextLength + keyLength) is the key.
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*/
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int32_t keyLength;
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/**
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* Miscellaneous attributes.
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*/
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int8_t flags;
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/**
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* Flag attributes.
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*/
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enum {
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ANCHOR_START = 1,
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ANCHOR_END = 2
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};
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/**
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* An alias pointer to the data for this rule. The data provides
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* lookup services for matchers and segments.
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*/
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const TransliterationRuleData* data;
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public:
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/**
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* Construct a new rule with the given input, output text, and other
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* attributes. A cursor position may be specified for the output text.
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* @param input input string, including key and optional ante and
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* post context
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* @param anteContextPos offset into input to end of ante context, or -1 if
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* none. Must be <= input.length() if not -1.
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* @param postContextPos offset into input to start of post context, or -1
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* if none. Must be <= input.length() if not -1, and must be >=
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* anteContextPos.
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* @param output output string
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* @param cursorPosition offset into output at which cursor is located, or -1 if
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* none. If less than zero, then the cursor is placed after the
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* <code>output</code>; that is, -1 is equivalent to
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* <code>output.length()</code>. If greater than
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* <code>output.length()</code> then an exception is thrown.
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* @param cursorOffset an offset to be added to cursorPos to position the
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* cursor either in the ante context, if < 0, or in the post context, if >
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* 0. For example, the rule "abc{def} > | @@@ xyz;" changes "def" to
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* "xyz" and moves the cursor to before "a". It would have a cursorOffset
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* of -3.
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* @param segs array of UnicodeMatcher corresponding to input pattern
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* segments, or null if there are none. The array itself is adopted,
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* but the pointers within it are not.
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* @param segsCount number of elements in segs[]
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* @param anchorStart TRUE if the the rule is anchored on the left to
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* the context start
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* @param anchorEnd TRUE if the rule is anchored on the right to the
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* context limit
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*/
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TransliterationRule(const UnicodeString& input,
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int32_t anteContextPos, int32_t postContextPos,
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const UnicodeString& outputStr,
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int32_t cursorPosition, int32_t cursorOffset,
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UnicodeFunctor** segs,
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int32_t segsCount,
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UBool anchorStart, UBool anchorEnd,
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const TransliterationRuleData* data,
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UErrorCode& status);
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/**
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* Copy constructor.
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*/
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TransliterationRule(TransliterationRule& other);
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/**
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* Destructor.
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*/
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virtual ~TransliterationRule();
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/**
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* Change the data object that this rule belongs to. Used
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* internally by the TransliterationRuleData copy constructor.
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*/
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void setData(const TransliterationRuleData* data);
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/**
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* Return the preceding context length. This method is needed to
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* support the <code>Transliterator</code> method
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* <code>getMaximumContextLength()</code>. Internally, this is
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* implemented as the anteContextLength, optionally plus one if
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* there is a start anchor. The one character anchor gap is
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* needed to make repeated incremental transliteration with
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* anchors work.
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*/
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virtual int32_t getContextLength(void) const;
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/**
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* Internal method. Returns 8-bit index value for this rule.
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* This is the low byte of the first character of the key,
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* unless the first character of the key is a set. If it's a
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* set, or otherwise can match multiple keys, the index value is -1.
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*/
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int16_t getIndexValue() const;
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/**
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* Internal method. Returns true if this rule matches the given
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* index value. The index value is an 8-bit integer, 0..255,
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* representing the low byte of the first character of the key.
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* It matches this rule if it matches the first character of the
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* key, or if the first character of the key is a set, and the set
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* contains any character with a low byte equal to the index
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* value. If the rule contains only ante context, as in foo)>bar,
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* then it will match any key.
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*/
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UBool matchesIndexValue(uint8_t v) const;
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/**
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* Return true if this rule masks another rule. If r1 masks r2 then
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* r1 matches any input string that r2 matches. If r1 masks r2 and r2 masks
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* r1 then r1 == r2. Examples: "a>x" masks "ab>y". "a>x" masks "a[b]>y".
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* "[c]a>x" masks "[dc]a>y".
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*/
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virtual UBool masks(const TransliterationRule& r2) const;
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/**
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* Attempt a match and replacement at the given position. Return
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* the degree of match between this rule and the given text. The
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* degree of match may be mismatch, a partial match, or a full
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* match. A mismatch means at least one character of the text
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* does not match the context or key. A partial match means some
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* context and key characters match, but the text is not long
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* enough to match all of them. A full match means all context
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* and key characters match.
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*
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* If a full match is obtained, perform a replacement, update pos,
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* and return U_MATCH. Otherwise both text and pos are unchanged.
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*
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* @param text the text
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* @param pos the position indices
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* @param incremental if TRUE, test for partial matches that may
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* be completed by additional text inserted at pos.limit.
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* @return one of <code>U_MISMATCH</code>,
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* <code>U_PARTIAL_MATCH</code>, or <code>U_MATCH</code>. If
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* incremental is FALSE then U_PARTIAL_MATCH will not be returned.
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*/
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UMatchDegree matchAndReplace(Replaceable& text,
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UTransPosition& pos,
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UBool incremental) const;
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/**
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* Create a rule string that represents this rule object. Append
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* it to the given string.
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*/
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virtual UnicodeString& toRule(UnicodeString& pat,
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UBool escapeUnprintable) const;
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private:
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friend class StringMatcher;
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};
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U_NAMESPACE_END
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#endif
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