icuSources/common/unicode/rep.h

   1 /*
   2 **************************************************************************
   3 * Copyright (C) 1999-2012, International Business Machines Corporation and
   4 * others. All Rights Reserved.
   5 **************************************************************************
   6 *   Date        Name        Description
   7 *   11/17/99    aliu        Creation.  Ported from java.  Modified to
   8 *                           match current UnicodeString API.  Forced
   9 *                           to use name "handleReplaceBetween" because
  10 *                           of existing methods in UnicodeString.
  11 **************************************************************************
  12 */
  13
  14 #ifndef REP_H
  15 #define REP_H
  16
  17 #include "unicode/uobject.h"
  18
  19 /**
  20  * \file
  21  * \brief C++ API: Replaceable String
  22  */
  23
  24 U_NAMESPACE_BEGIN
  25
  26 class UnicodeString;
  27
  28 /**
  29  * <code>Replaceable</code> is an abstract base class representing a
  30  * string of characters that supports the replacement of a range of
  31  * itself with a new string of characters.  It is used by APIs that
  32  * change a piece of text while retaining metadata.  Metadata is data
  33  * other than the Unicode characters returned by char32At().  One
  34  * example of metadata is style attributes; another is an edit
  35  * history, marking each character with an author and revision number.
  36  *
  37  * <p>An implicit aspect of the <code>Replaceable</code> API is that
  38  * during a replace operation, new characters take on the metadata of
  39  * the old characters.  For example, if the string "the <b>bold</b>
  40  * font" has range (4, 8) replaced with "strong", then it becomes "the
  41  * <b>strong</b> font".
  42  *
  43  * <p><code>Replaceable</code> specifies ranges using a start
  44  * offset and a limit offset.  The range of characters thus specified
  45  * includes the characters at offset start..limit-1.  That is, the
  46  * start offset is inclusive, and the limit offset is exclusive.
  47  *
  48  * <p><code>Replaceable</code> also includes API to access characters
  49  * in the string: <code>length()</code>, <code>charAt()</code>,
  50  * <code>char32At()</code>, and <code>extractBetween()</code>.
  51  *
  52  * <p>For a subclass to support metadata, typical behavior of
  53  * <code>replace()</code> is the following:
  54  * <ul>
  55  *   <li>Set the metadata of the new text to the metadata of the first
  56  *   character replaced</li>
  57  *   <li>If no characters are replaced, use the metadata of the
  58  *   previous character</li>
  59  *   <li>If there is no previous character (i.e. start == 0), use the
  60  *   following character</li>
  61  *   <li>If there is no following character (i.e. the replaceable was
  62  *   empty), use default metadata.<br>
  63  *   <li>If the code point U+FFFF is seen, it should be interpreted as
  64  *   a special marker having no metadata<li>
  65  *   </li>
  66  * </ul>
  67  * If this is not the behavior, the subclass should document any differences.
  68  * @author Alan Liu
  69  * @stable ICU 2.0
  70  */
  71 class U_COMMON_API Replaceable : public UObject {
  72
  73 public:
  74     /**
  75      * Destructor.
  76      * @stable ICU 2.0
  77      */
  78     virtual ~Replaceable();
  79
  80     /**
  81      * Returns the number of 16-bit code units in the text.
  82      * @return number of 16-bit code units in text
  83      * @stable ICU 1.8
  84      */
  85     inline int32_t length() const;
  86
  87     /**
  88      * Returns the 16-bit code unit at the given offset into the text.
  89      * @param offset an integer between 0 and <code>length()</code>-1
  90      * inclusive
  91      * @return 16-bit code unit of text at given offset
  92      * @stable ICU 1.8
  93      */
  94     inline UChar charAt(int32_t offset) const;
  95
  96     /**
  97      * Returns the 32-bit code point at the given 16-bit offset into
  98      * the text.  This assumes the text is stored as 16-bit code units
  99      * with surrogate pairs intermixed.  If the offset of a leading or
 100      * trailing code unit of a surrogate pair is given, return the
 101      * code point of the surrogate pair.
 102      *
 103      * @param offset an integer between 0 and <code>length()</code>-1
 104      * inclusive
 105      * @return 32-bit code point of text at given offset
 106      * @stable ICU 1.8
 107      */
 108     inline UChar32 char32At(int32_t offset) const;
 109
 110     /**
 111      * Copies characters in the range [<tt>start</tt>, <tt>limit</tt>)
 112      * into the UnicodeString <tt>target</tt>.
 113      * @param start offset of first character which will be copied
 114      * @param limit offset immediately following the last character to
 115      * be copied
 116      * @param target UnicodeString into which to copy characters.
 117      * @return A reference to <TT>target</TT>
 118      * @stable ICU 2.1
 119      */
 120     virtual void extractBetween(int32_t start,
 121                                 int32_t limit,
 122                                 UnicodeString& target) const = 0;
 123
 124     /**
 125      * Replaces a substring of this object with the given text.  If the
 126      * characters being replaced have metadata, the new characters
 127      * that replace them should be given the same metadata.
 128      *
 129      * <p>Subclasses must ensure that if the text between start and
 130      * limit is equal to the replacement text, that replace has no
 131      * effect. That is, any metadata
 132      * should be unaffected. In addition, subclasses are encouraged to
 133      * check for initial and trailing identical characters, and make a
 134      * smaller replacement if possible. This will preserve as much
 135      * metadata as possible.
 136      * @param start the beginning index, inclusive; <code>0 <= start
 137      * <= limit</code>.
 138      * @param limit the ending index, exclusive; <code>start <= limit
 139      * <= length()</code>.
 140      * @param text the text to replace characters <code>start</code>
 141      * to <code>limit - 1</code>
 142      * @stable ICU 2.0
 143      */
 144     virtual void handleReplaceBetween(int32_t start,
 145                                       int32_t limit,
 146                                       const UnicodeString& text) = 0;
 147     // Note: All other methods in this class take the names of
 148     // existing UnicodeString methods.  This method is the exception.
 149     // It is named differently because all replace methods of
 150     // UnicodeString return a UnicodeString&.  The 'between' is
 151     // required in order to conform to the UnicodeString naming
 152     // convention; API taking start/length are named <operation>, and
 153     // those taking start/limit are named <operationBetween>.  The
 154     // 'handle' is added because 'replaceBetween' and
 155     // 'doReplaceBetween' are already taken.
 156
 157     /**
 158      * Copies a substring of this object, retaining metadata.
 159      * This method is used to duplicate or reorder substrings.
 160      * The destination index must not overlap the source range.
 161      *
 162      * @param start the beginning index, inclusive; <code>0 <= start <=
 163      * limit</code>.
 164      * @param limit the ending index, exclusive; <code>start <= limit <=
 165      * length()</code>.
 166      * @param dest the destination index.  The characters from
 167      * <code>start..limit-1</code> will be copied to <code>dest</code>.
 168      * Implementations of this method may assume that <code>dest <= start ||
 169      * dest >= limit</code>.
 170      * @stable ICU 2.0
 171      */
 172     virtual void copy(int32_t start, int32_t limit, int32_t dest) = 0;
 173
 174     /**
 175      * Returns true if this object contains metadata.  If a
 176      * Replaceable object has metadata, calls to the Replaceable API
 177      * must be made so as to preserve metadata.  If it does not, calls
 178      * to the Replaceable API may be optimized to improve performance.
 179      * The default implementation returns true.
 180      * @return true if this object contains metadata
 181      * @stable ICU 2.2
 182      */
 183     virtual UBool hasMetaData() const;
 184
 185     /**
 186      * Clone this object, an instance of a subclass of Replaceable.
 187      * Clones can be used concurrently in multiple threads.
 188      * If a subclass does not implement clone(), or if an error occurs,
 189      * then NULL is returned.
 190      * The clone functions in all subclasses return a pointer to a Replaceable
 191      * because some compilers do not support covariant (same-as-this)
 192      * return types; cast to the appropriate subclass if necessary.
 193      * The caller must delete the clone.
 194      *
 195      * @return a clone of this object
 196      *
 197      * @see getDynamicClassID
 198      * @stable ICU 2.6
 199      */
 200     virtual Replaceable *clone() const;
 201
 202 protected:
 203
 204     /**
 205      * Default constructor.
 206      * @stable ICU 2.4
 207      */
 208     inline Replaceable();
 209
 210     /*
 211      * Assignment operator not declared. The compiler will provide one
 212      * which does nothing since this class does not contain any data members.
 213      * API/code coverage may show the assignment operator as present and
 214      * untested - ignore.
 215      * Subclasses need this assignment operator if they use compiler-provided
 216      * assignment operators of their own. An alternative to not declaring one
 217      * here would be to declare and empty-implement a protected or public one.
 218     Replaceable &Replaceable::operator=(const Replaceable &);
 219      */
 220
 221     /**
 222      * Virtual version of length().
 223      * @stable ICU 2.4
 224      */
 225     virtual int32_t getLength() const = 0;
 226
 227     /**
 228      * Virtual version of charAt().
 229      * @stable ICU 2.4
 230      */
 231     virtual UChar getCharAt(int32_t offset) const = 0;
 232
 233     /**
 234      * Virtual version of char32At().
 235      * @stable ICU 2.4
 236      */
 237     virtual UChar32 getChar32At(int32_t offset) const = 0;
 238 };
 239
 240 inline Replaceable::Replaceable() {}
 241
 242 inline int32_t
 243 Replaceable::length() const {
 244     return getLength();
 245 }
 246
 247 inline UChar
 248 Replaceable::charAt(int32_t offset) const {
 249     return getCharAt(offset);
 250 }
 251
 252 inline UChar32
 253 Replaceable::char32At(int32_t offset) const {
 254     return getChar32At(offset);
 255 }
 256
 257 // There is no rep.cpp, see unistr.cpp for Replaceable function implementations.
 258
 259 U_NAMESPACE_END
 260
 261 #endif