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