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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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/*
 *******************************************************************************
 * (C) Copyright IBM Corp. 1996-2005 - All Rights Reserved                     *
 *                                                                             *
 * The original version of this source code and documentation is copyrighted   *
 * and owned by IBM, These materials are provided under terms of a License     *
 * Agreement between IBM and Sun. This technology is protected by multiple     *
 * US and International patents. This notice and attribution to IBM may not    *
 * to removed.                                                                 *
 *******************************************************************************
 */

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);
}