Victor Chang | 7322950 | 2020-09-17 13:39:19 +0100 | [diff] [blame] | 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 | |
| 18 | U_NAMESPACE_BEGIN |
| 19 | |
| 20 | class UnicodeString; |
| 21 | class ParsePosition; |
| 22 | class 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 | */ |
| 31 | class 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 | |
| 39 | private: |
| 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 | |
| 65 | public: |
| 66 | /** |
| 67 | * Value returned when there are no more characters to iterate. |
| 68 | */ |
| 69 | enum { 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 | enum { 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 | enum { 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 | enum { 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 deferenced, 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. |
Victor Chang | ce4bf3c | 2021-01-19 16:34:24 +0000 | [diff] [blame] | 117 | * @param isEscaped output parameter set to true if the character |
Victor Chang | 7322950 | 2020-09-17 13:39:19 +0100 | [diff] [blame] | 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 | |
| 211 | private: |
| 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 | |
| 226 | inline UBool RuleCharacterIterator::inVariable() const { |
| 227 | return buf != 0; |
| 228 | } |
| 229 | |
| 230 | U_NAMESPACE_END |
| 231 | |
| 232 | #endif // _RULEITER_H_ |
| 233 | //eof |