1// © 2016 and later: Unicode, Inc. and others.
2// License & terms of use: http://www.unicode.org/copyright.html
3/*
4**********************************************************************
5* Copyright (c) 2003-2011, International Business Machines
6* Corporation and others. All Rights Reserved.
7**********************************************************************
8* Author: Alan Liu
9* Created: September 24 2003
10* Since: ICU 2.8
11**********************************************************************
12*/
13#ifndef _RULEITER_H_
14#define _RULEITER_H_
15
16#include "unicode/uobject.h"
17
18U_NAMESPACE_BEGIN
19
20class UnicodeString;
21class ParsePosition;
22class SymbolTable;
23
24/**
25 * An iterator that returns 32-bit code points. This class is deliberately
26 * <em>not</em> related to any of the ICU character iterator classes
27 * in order to minimize complexity.
28 * @author Alan Liu
29 * @since ICU 2.8
30 */
31class RuleCharacterIterator : public UMemory {
32
33 // TODO: Ideas for later. (Do not implement if not needed, lest the
34 // code coverage numbers go down due to unused methods.)
35 // 1. Add a copy constructor, operator==() method.
36 // 2. Rather than return DONE, throw an exception if the end
37 // is reached -- this is an alternate usage model, probably not useful.
38
39private:
40 /**
41 * Text being iterated.
42 */
43 const UnicodeString& text;
44
45 /**
46 * Position of iterator.
47 */
48 ParsePosition& pos;
49
50 /**
51 * Symbol table used to parse and dereference variables. May be 0.
52 */
53 const SymbolTable* sym;
54
55 /**
56 * Current variable expansion, or 0 if none.
57 */
58 const UnicodeString* buf;
59
60 /**
61 * Position within buf. Meaningless if buf == 0.
62 */
63 int32_t bufPos;
64
65public:
66 /**
67 * Value returned when there are no more characters to iterate.
68 */
69 static constexpr int32_t DONE = -1;
70
71 /**
72 * Bitmask option to enable parsing of variable names. If (options &
73 * PARSE_VARIABLES) != 0, then an embedded variable will be expanded to
74 * its value. Variables are parsed using the SymbolTable API.
75 */
76 static constexpr int32_t PARSE_VARIABLES = 1;
77
78 /**
79 * Bitmask option to enable parsing of escape sequences. If (options &
80 * PARSE_ESCAPES) != 0, then an embedded escape sequence will be expanded
81 * to its value. Escapes are parsed using Utility.unescapeAt().
82 */
83 static constexpr int32_t PARSE_ESCAPES = 2;
84
85 /**
86 * Bitmask option to enable skipping of whitespace. If (options &
87 * SKIP_WHITESPACE) != 0, then Pattern_White_Space characters will be silently
88 * skipped, as if they were not present in the input.
89 */
90 static constexpr int32_t SKIP_WHITESPACE = 4;
91
92 /**
93 * Constructs an iterator over the given text, starting at the given
94 * position.
95 * @param text the text to be iterated
96 * @param sym the symbol table, or null if there is none. If sym is null,
97 * then variables will not be dereferenced, even if the PARSE_VARIABLES
98 * option is set.
99 * @param pos upon input, the index of the next character to return. If a
100 * variable has been dereferenced, then pos will <em>not</em> increment as
101 * characters of the variable value are iterated.
102 */
103 RuleCharacterIterator(const UnicodeString& text, const SymbolTable* sym,
104 ParsePosition& pos);
105
106 /**
107 * Returns true if this iterator has no more characters to return.
108 */
109 UBool atEnd() const;
110
111 /**
112 * Returns the next character using the given options, or DONE if there
113 * are no more characters, and advance the position to the next
114 * character.
115 * @param options one or more of the following options, bitwise-OR-ed
116 * together: PARSE_VARIABLES, PARSE_ESCAPES, SKIP_WHITESPACE.
117 * @param isEscaped output parameter set to true if the character
118 * was escaped
119 * @param ec input-output error code. An error will only be set by
120 * this routing if options includes PARSE_VARIABLES and an unknown
121 * variable name is seen, or if options includes PARSE_ESCAPES and
122 * an invalid escape sequence is seen.
123 * @return the current 32-bit code point, or DONE
124 */
125 UChar32 next(int32_t options, UBool& isEscaped, UErrorCode& ec);
126
127 /**
128 * Returns true if this iterator is currently within a variable expansion.
129 */
130 inline UBool inVariable() const;
131
132 /**
133 * An opaque object representing the position of a RuleCharacterIterator.
134 */
135 struct Pos : public UMemory {
136 private:
137 const UnicodeString* buf;
138 int32_t pos;
139 int32_t bufPos;
140 friend class RuleCharacterIterator;
141 };
142
143 /**
144 * Sets an object which, when later passed to setPos(), will
145 * restore this iterator's position. Usage idiom:
146 *
147 * RuleCharacterIterator iterator = ...;
148 * RuleCharacterIterator::Pos pos;
149 * iterator.getPos(pos);
150 * for (;;) {
151 * iterator.getPos(pos);
152 * int c = iterator.next(...);
153 * ...
154 * }
155 * iterator.setPos(pos);
156 *
157 * @param p a position object to be set to this iterator's
158 * current position.
159 */
160 void getPos(Pos& p) const;
161
162 /**
163 * Restores this iterator to the position it had when getPos()
164 * set the given object.
165 * @param p a position object previously set by getPos()
166 */
167 void setPos(const Pos& p);
168
169 /**
170 * Skips ahead past any ignored characters, as indicated by the given
171 * options. This is useful in conjunction with the lookahead() method.
172 *
173 * Currently, this only has an effect for SKIP_WHITESPACE.
174 * @param options one or more of the following options, bitwise-OR-ed
175 * together: PARSE_VARIABLES, PARSE_ESCAPES, SKIP_WHITESPACE.
176 */
177 void skipIgnored(int32_t options);
178
179 /**
180 * Returns a string containing the remainder of the characters to be
181 * returned by this iterator, without any option processing. If the
182 * iterator is currently within a variable expansion, this will only
183 * extend to the end of the variable expansion. This method is provided
184 * so that iterators may interoperate with string-based APIs. The typical
185 * sequence of calls is to call skipIgnored(), then call lookahead(), then
186 * parse the string returned by lookahead(), then call jumpahead() to
187 * resynchronize the iterator.
188 * @param result a string to receive the characters to be returned
189 * by future calls to next()
190 * @param maxLookAhead The maximum to copy into the result.
191 * @return a reference to result
192 */
193 UnicodeString& lookahead(UnicodeString& result, int32_t maxLookAhead = -1) const;
194
195 /**
196 * Advances the position by the given number of 16-bit code units.
197 * This is useful in conjunction with the lookahead() method.
198 * @param count the number of 16-bit code units to jump over
199 */
200 void jumpahead(int32_t count);
201
202 /**
203 * Returns a string representation of this object, consisting of the
204 * characters being iterated, with a '|' marking the current position.
205 * Position within an expanded variable is <em>not</em> indicated.
206 * @param result output parameter to receive a string
207 * representation of this object
208 */
209// UnicodeString& toString(UnicodeString& result) const;
210
211private:
212 /**
213 * Returns the current 32-bit code point without parsing escapes, parsing
214 * variables, or skipping whitespace.
215 * @return the current 32-bit code point
216 */
217 UChar32 _current() const;
218
219 /**
220 * Advances the position by the given amount.
221 * @param count the number of 16-bit code units to advance past
222 */
223 void _advance(int32_t count);
224};
225
226inline UBool RuleCharacterIterator::inVariable() const {
227 return buf != 0;
228}
229
230U_NAMESPACE_END
231
232#endif // _RULEITER_H_
233//eof
234