234 lines
7.7 KiB
C++
234 lines
7.7 KiB
C++
// © 2016 and later: Unicode, Inc. and others.
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// License & terms of use: http://www.unicode.org/copyright.html
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/*
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**********************************************************************
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* Copyright (c) 2003-2011, International Business Machines
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* Corporation and others. All Rights Reserved.
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**********************************************************************
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* Author: Alan Liu
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* Created: September 24 2003
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* Since: ICU 2.8
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**********************************************************************
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*/
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#ifndef _RULEITER_H_
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#define _RULEITER_H_
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#include "unicode/uobject.h"
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U_NAMESPACE_BEGIN
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class UnicodeString;
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class ParsePosition;
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class SymbolTable;
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/**
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* An iterator that returns 32-bit code points. This class is deliberately
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* <em>not</em> related to any of the ICU character iterator classes
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* in order to minimize complexity.
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* @author Alan Liu
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* @since ICU 2.8
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*/
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class RuleCharacterIterator : public UMemory {
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// TODO: Ideas for later. (Do not implement if not needed, lest the
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// code coverage numbers go down due to unused methods.)
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// 1. Add a copy constructor, operator==() method.
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// 2. Rather than return DONE, throw an exception if the end
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// is reached -- this is an alternate usage model, probably not useful.
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private:
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/**
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* Text being iterated.
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*/
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const UnicodeString& text;
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/**
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* Position of iterator.
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*/
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ParsePosition& pos;
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/**
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* Symbol table used to parse and dereference variables. May be 0.
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*/
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const SymbolTable* sym;
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/**
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* Current variable expansion, or 0 if none.
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*/
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const UnicodeString* buf;
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/**
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* Position within buf. Meaningless if buf == 0.
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*/
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int32_t bufPos;
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public:
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/**
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* Value returned when there are no more characters to iterate.
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*/
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static constexpr int32_t DONE = -1;
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/**
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* Bitmask option to enable parsing of variable names. If (options &
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* PARSE_VARIABLES) != 0, then an embedded variable will be expanded to
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* its value. Variables are parsed using the SymbolTable API.
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*/
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static constexpr int32_t PARSE_VARIABLES = 1;
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/**
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* Bitmask option to enable parsing of escape sequences. If (options &
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* PARSE_ESCAPES) != 0, then an embedded escape sequence will be expanded
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* to its value. Escapes are parsed using Utility.unescapeAt().
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*/
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static constexpr int32_t PARSE_ESCAPES = 2;
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/**
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* Bitmask option to enable skipping of whitespace. If (options &
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* SKIP_WHITESPACE) != 0, then Pattern_White_Space characters will be silently
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* skipped, as if they were not present in the input.
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*/
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static constexpr int32_t SKIP_WHITESPACE = 4;
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/**
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* Constructs an iterator over the given text, starting at the given
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* position.
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* @param text the text to be iterated
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* @param sym the symbol table, or null if there is none. If sym is null,
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* then variables will not be dereferenced, even if the PARSE_VARIABLES
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* option is set.
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* @param pos upon input, the index of the next character to return. If a
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* variable has been dereferenced, then pos will <em>not</em> increment as
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* characters of the variable value are iterated.
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*/
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RuleCharacterIterator(const UnicodeString& text, const SymbolTable* sym,
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ParsePosition& pos);
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/**
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* Returns true if this iterator has no more characters to return.
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*/
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UBool atEnd() const;
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/**
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* Returns the next character using the given options, or DONE if there
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* are no more characters, and advance the position to the next
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* character.
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* @param options one or more of the following options, bitwise-OR-ed
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* together: PARSE_VARIABLES, PARSE_ESCAPES, SKIP_WHITESPACE.
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* @param isEscaped output parameter set to true if the character
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* was escaped
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* @param ec input-output error code. An error will only be set by
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* this routing if options includes PARSE_VARIABLES and an unknown
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* variable name is seen, or if options includes PARSE_ESCAPES and
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* an invalid escape sequence is seen.
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* @return the current 32-bit code point, or DONE
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*/
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UChar32 next(int32_t options, UBool& isEscaped, UErrorCode& ec);
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/**
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* Returns true if this iterator is currently within a variable expansion.
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*/
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inline UBool inVariable() const;
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/**
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* An opaque object representing the position of a RuleCharacterIterator.
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*/
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struct Pos : public UMemory {
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private:
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const UnicodeString* buf;
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int32_t pos;
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int32_t bufPos;
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friend class RuleCharacterIterator;
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};
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/**
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* Sets an object which, when later passed to setPos(), will
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* restore this iterator's position. Usage idiom:
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*
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* RuleCharacterIterator iterator = ...;
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* RuleCharacterIterator::Pos pos;
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* iterator.getPos(pos);
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* for (;;) {
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* iterator.getPos(pos);
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* int c = iterator.next(...);
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* ...
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* }
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* iterator.setPos(pos);
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*
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* @param p a position object to be set to this iterator's
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* current position.
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*/
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void getPos(Pos& p) const;
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/**
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* Restores this iterator to the position it had when getPos()
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* set the given object.
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* @param p a position object previously set by getPos()
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*/
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void setPos(const Pos& p);
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/**
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* Skips ahead past any ignored characters, as indicated by the given
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* options. This is useful in conjunction with the lookahead() method.
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*
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* Currently, this only has an effect for SKIP_WHITESPACE.
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* @param options one or more of the following options, bitwise-OR-ed
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* together: PARSE_VARIABLES, PARSE_ESCAPES, SKIP_WHITESPACE.
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*/
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void skipIgnored(int32_t options);
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/**
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* Returns a string containing the remainder of the characters to be
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* returned by this iterator, without any option processing. If the
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* iterator is currently within a variable expansion, this will only
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* extend to the end of the variable expansion. This method is provided
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* so that iterators may interoperate with string-based APIs. The typical
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* sequence of calls is to call skipIgnored(), then call lookahead(), then
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* parse the string returned by lookahead(), then call jumpahead() to
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* resynchronize the iterator.
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* @param result a string to receive the characters to be returned
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* by future calls to next()
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* @param maxLookAhead The maximum to copy into the result.
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* @return a reference to result
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*/
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UnicodeString& lookahead(UnicodeString& result, int32_t maxLookAhead = -1) const;
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/**
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* Advances the position by the given number of 16-bit code units.
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* This is useful in conjunction with the lookahead() method.
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* @param count the number of 16-bit code units to jump over
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*/
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void jumpahead(int32_t count);
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/**
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* Returns a string representation of this object, consisting of the
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* characters being iterated, with a '|' marking the current position.
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* Position within an expanded variable is <em>not</em> indicated.
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* @param result output parameter to receive a string
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* representation of this object
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*/
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// UnicodeString& toString(UnicodeString& result) const;
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private:
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/**
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* Returns the current 32-bit code point without parsing escapes, parsing
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* variables, or skipping whitespace.
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* @return the current 32-bit code point
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*/
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UChar32 _current() const;
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/**
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* Advances the position by the given amount.
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* @param count the number of 16-bit code units to advance past
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*/
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void _advance(int32_t count);
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};
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inline UBool RuleCharacterIterator::inVariable() const {
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return buf != nullptr;
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}
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U_NAMESPACE_END
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#endif // _RULEITER_H_
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//eof
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