Replaceable.java

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/*
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 * (C) Copyright IBM Corp. 1996-2005 - All Rights Reserved                     *
 *                                                                             *
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 */

package jdk.internal.icu.text;

/**
 * <code>Replaceable</code> is an interface 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.
 *
 * <p>An implicit aspect of the <code>Replaceable</code> API is that
 * during a replace operation, new characters take on the metadata of
 * the old characters.  For example, if the string "the <b>bold</b>
 * font" has range (4, 8) replaced with "strong", then it becomes "the
 * <b>strong</b> font".
 *
 * <p><code>Replaceable</code> 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.
 *
 * <p><code>Replaceable</code> also includes API to access characters
 * in the string: <code>length()</code>, <code>charAt()</code>,
 * <code>char32At()</code>, and <code>extractBetween()</code>.
 *
 * <p>For a subclass to support metadata, typical behavior of
 * <code>replace()</code> is the following:
 * <ul>
 *   <li>Set the metadata of the new text to the metadata of the first
 *   character replaced</li>
 *   <li>If no characters are replaced, use the metadata of the
 *   previous character</li>
 *   <li>If there is no previous character (i.e. start == 0), use the
 *   following character</li>
 *   <li>If there is no following character (i.e. the replaceable was
 *   empty), use default metadata</li>
 *   <li>If the code point U+FFFF is seen, it should be interpreted as
 *   a special marker having no metadata</li>
 * </ul>
 * If this is not the behavior, the subclass should document any differences.
 *
 * <p>Copyright &copy; IBM Corporation 1999.  All rights reserved.
 *
 * @author Alan Liu
 * @stable ICU 2.0
 */
public interface Replaceable {
    /**
     * Returns the number of 16-bit code units in the text.
     * @return number of 16-bit code units in text
     * @stable ICU 2.0
     */
    int length();

    /**
     * Returns the 16-bit code unit at the given offset into the text.
     * @param offset an integer between 0 and <code>length()</code>-1
     * inclusive
     * @return 16-bit code unit of text at given offset
     * @stable ICU 2.0
     */
    char charAt(int offset);

    /**
     * Copies characters from this object into the destination
     * character array.  The first character to be copied is at index
     * <code>srcStart</code>; the last character to be copied is at
     * index <code>srcLimit-1</code> (thus the total number of
     * characters to be copied is <code>srcLimit-srcStart</code>). The
     * characters are copied into the subarray of <code>dst</code>
     * starting at index <code>dstStart</code> and ending at index
     * <code>dstStart + (srcLimit-srcStart) - 1</code>.
     *
     * @param srcStart the beginning index to copy, inclusive;
     *        {@code 0 <= start <= limit}.
     * @param srcLimit the ending index to copy, exclusive;
     *        {@code start <= limit <= length()}.
     * @param dst the destination array.
     * @param dstStart the start offset in the destination array.
     * @stable ICU 2.0
     */
    void getChars(int srcStart, int srcLimit, char dst[], int dstStart);
}