Replaceable is an abstract base class representing a
+ * string of characters that supports the replacement of a range of
+ * itself with a new string of characters. It is used by APIs that
+ * change a piece of text while retaining metadata. Metadata is data
+ * other than the Unicode characters returned by char32At(). One
+ * example of metadata is style attributes; another is an edit
+ * history, marking each character with an author and revision number.
+ *
+ * An implicit aspect of the Replaceable API is that
+ * during a replace operation, new characters take on the metadata of
+ * the old characters. For example, if the string "the bold
+ * font" has range (4, 8) replaced with "strong", then it becomes "the
+ * strong font".
+ *
+ *
Replaceable specifies ranges using a start
+ * offset and a limit offset. The range of characters thus specified
+ * includes the characters at offset start..limit-1. That is, the
+ * start offset is inclusive, and the limit offset is exclusive.
+ *
+ *
Replaceable also includes API to access characters
+ * in the string: length(), charAt(),
+ * char32At(), and extractBetween().
+ *
+ *
For a subclass to support metadata, typical behavior of
+ * replace() is the following:
+ *
length()-1
+ * inclusive
+ * @return 16-bit code unit of text at given offset
+ * @stable ICU 1.8
+ */
+ inline UChar charAt(int32_t offset) const;
+
+ /**
+ * Returns the 32-bit code point at the given 16-bit offset into
+ * the text. This assumes the text is stored as 16-bit code units
+ * with surrogate pairs intermixed. If the offset of a leading or
+ * trailing code unit of a surrogate pair is given, return the
+ * code point of the surrogate pair.
+ *
+ * @param offset an integer between 0 and length()-1
+ * inclusive
+ * @return 32-bit code point of text at given offset
+ * @stable ICU 1.8
+ */
+ inline UChar32 char32At(int32_t offset) const;
+
+ /**
+ * Copies characters in the range [start, limit)
+ * into the UnicodeString target.
+ * @param start offset of first character which will be copied
+ * @param limit offset immediately following the last character to
+ * be copied
+ * @param target UnicodeString into which to copy characters.
+ * @return A reference to target
+ * @stable ICU 2.1
+ */
+ virtual void extractBetween(int32_t start,
+ int32_t limit,
+ UnicodeString& target) const = 0;
+
+ /**
+ * Replaces a substring of this object with the given text. If the
+ * characters being replaced have metadata, the new characters
+ * that replace them should be given the same metadata.
+ *
+ * Subclasses must ensure that if the text between start and
+ * limit is equal to the replacement text, that replace has no
+ * effect. That is, any metadata
+ * should be unaffected. In addition, subclasses are encouraged to
+ * check for initial and trailing identical characters, and make a
+ * smaller replacement if possible. This will preserve as much
+ * metadata as possible.
+ * @param start the beginning index, inclusive; 0 <= start
+ * <= limit.
+ * @param limit the ending index, exclusive; start <= limit
+ * <= length().
+ * @param text the text to replace characters start
+ * to limit - 1
+ * @stable ICU 2.0
+ */
+ virtual void handleReplaceBetween(int32_t start,
+ int32_t limit,
+ const UnicodeString& text) = 0;
+ // Note: All other methods in this class take the names of
+ // existing UnicodeString methods. This method is the exception.
+ // It is named differently because all replace methods of
+ // UnicodeString return a UnicodeString&. The 'between' is
+ // required in order to conform to the UnicodeString naming
+ // convention; API taking start/length are named 0 <= start <=
+ * limit.
+ * @param limit the ending index, exclusive; start <= limit <=
+ * length().
+ * @param dest the destination index. The characters from
+ * start..limit-1 will be copied to dest.
+ * Implementations of this method may assume that dest <= start ||
+ * dest >= limit.
+ * @stable ICU 2.0
+ */
+ virtual void copy(int32_t start, int32_t limit, int32_t dest) = 0;
+
+ /**
+ * Returns true if this object contains metadata. If a
+ * Replaceable object has metadata, calls to the Replaceable API
+ * must be made so as to preserve metadata. If it does not, calls
+ * to the Replaceable API may be optimized to improve performance.
+ * The default implementation returns true.
+ * @return true if this object contains metadata
+ * @stable ICU 2.2
+ */
+ virtual UBool hasMetaData() const;
+
+ /**
+ * Clone this object, an instance of a subclass of Replaceable.
+ * Clones can be used concurrently in multiple threads.
+ * If a subclass does not implement clone(), or if an error occurs,
+ * then NULL is returned.
+ * The clone functions in all subclasses return a pointer to a Replaceable
+ * because some compilers do not support covariant (same-as-this)
+ * return types; cast to the appropriate subclass if necessary.
+ * The caller must delete the clone.
+ *
+ * @return a clone of this object
+ *
+ * @see getDynamicClassID
+ * @stable ICU 2.6
+ */
+ virtual Replaceable *clone() const;
+
+protected:
+
+ /**
+ * Default constructor.
+ * @stable ICU 2.4
+ */
+ inline Replaceable();
+
+ /*
+ * Assignment operator not declared. The compiler will provide one
+ * which does nothing since this class does not contain any data members.
+ * API/code coverage may show the assignment operator as present and
+ * untested - ignore.
+ * Subclasses need this assignment operator if they use compiler-provided
+ * assignment operators of their own. An alternative to not declaring one
+ * here would be to declare and empty-implement a protected or public one.
+ Replaceable &Replaceable::operator=(const Replaceable &);
+ */
+
+ /**
+ * Virtual version of length().
+ * @stable ICU 2.4
+ */
+ virtual int32_t getLength() const = 0;
+
+ /**
+ * Virtual version of charAt().
+ * @stable ICU 2.4
+ */
+ virtual UChar getCharAt(int32_t offset) const = 0;
+
+ /**
+ * Virtual version of char32At().
+ * @stable ICU 2.4
+ */
+ virtual UChar32 getChar32At(int32_t offset) const = 0;
+};
+
+inline Replaceable::Replaceable() {}
+
+inline int32_t
+Replaceable::length() const {
+ return getLength();
+}
+
+inline UChar
+Replaceable::charAt(int32_t offset) const {
+ return getCharAt(offset);
+}
+
+inline UChar32
+Replaceable::char32At(int32_t offset) const {
+ return getChar32At(offset);
+}
+
+// There is no rep.cpp, see unistr.cpp for Replaceable function implementations.
+
+U_NAMESPACE_END
+
+#endif