/*
* Copyright (c) 2005, 2006, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
*******************************************************************************
* (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 sun.text.normalizer;
/**
* <p>Standalone utility class providing UTF16 character conversions and
* indexing conversions.</p>
* <p>Code that uses strings alone rarely need modification.
* By design, UTF-16 does not allow overlap, so searching for strings is a safe
* operation. Similarly, concatenation is always safe. Substringing is safe if
* the start and end are both on UTF-32 boundaries. In normal code, the values
* for start and end are on those boundaries, since they arose from operations
* like searching. If not, the nearest UTF-32 boundaries can be determined
* using <code>bounds()</code>.</p>
* <strong>Examples:</strong>
* <p>The following examples illustrate use of some of these methods.
* <pre>
* // iteration forwards: Original
* for (int i = 0; i < s.length(); ++i) {
* char ch = s.charAt(i);
* doSomethingWith(ch);
* }
*
* // iteration forwards: Changes for UTF-32
* int ch;
* for (int i = 0; i < s.length(); i+=UTF16.getCharCount(ch)) {
* ch = UTF16.charAt(s,i);
* doSomethingWith(ch);
* }
*
* // iteration backwards: Original
* for (int i = s.length() -1; i >= 0; --i) {
* char ch = s.charAt(i);
* doSomethingWith(ch);
* }
*
* // iteration backwards: Changes for UTF-32
* int ch;
* for (int i = s.length() -1; i > 0; i-=UTF16.getCharCount(ch)) {
* ch = UTF16.charAt(s,i);
* doSomethingWith(ch);
* }
* </pre>
* <strong>Notes:</strong>
* <ul>
* <li>
* <strong>Naming:</strong> For clarity, High and Low surrogates are called
* <code>Lead</code> and <code>Trail</code> in the API, which gives a better
* sense of their ordering in a string. <code>offset16</code> and
* <code>offset32</code> are used to distinguish offsets to UTF-16
* boundaries vs offsets to UTF-32 boundaries. <code>int char32</code> is
* used to contain UTF-32 characters, as opposed to <code>char16</code>,
* which is a UTF-16 code unit.
* </li>
* <li>
* <strong>Roundtripping Offsets:</strong> You can always roundtrip from a
* UTF-32 offset to a UTF-16 offset and back. Because of the difference in
* structure, you can roundtrip from a UTF-16 offset to a UTF-32 offset and
* back if and only if <code>bounds(string, offset16) != TRAIL</code>.
* </li>
* <li>
* <strong>Exceptions:</strong> The error checking will throw an exception
* if indices are out of bounds. Other than than that, all methods will
* behave reasonably, even if unmatched surrogates or out-of-bounds UTF-32
* values are present. <code>UCharacter.isLegal()</code> can be used to check
* for validity if desired.
* </li>
* <li>
* <strong>Unmatched Surrogates:</strong> If the string contains unmatched
* surrogates, then these are counted as one UTF-32 value. This matches
* their iteration behavior, which is vital. It also matches common display
* practice as missing glyphs (see the Unicode Standard Section 5.4, 5.5).
* </li>
* <li>
* <strong>Optimization:</strong> The method implementations may need
* optimization if the compiler doesn't fold static final methods. Since
* surrogate pairs will form an exceeding small percentage of all the text
* in the world, the singleton case should always be optimized for.
* </li>
* </ul>
* @author Mark Davis, with help from Markus Scherer
* @stable ICU 2.1
*/
public final class UTF16
{
// public variables ---------------------------------------------------
/**
* The lowest Unicode code point value.
* @stable ICU 2.1
*/
public static final int CODEPOINT_MIN_VALUE = 0;
/**
* The highest Unicode code point value (scalar value) according to the
* Unicode Standard.
* @stable ICU 2.1
*/
public static final int CODEPOINT_MAX_VALUE = 0x10ffff;
/**
* The minimum value for Supplementary code points
* @stable ICU 2.1
*/
public static final int SUPPLEMENTARY_MIN_VALUE = 0x10000;
/**
* Lead surrogate minimum value
* @stable ICU 2.1
*/
public static final int LEAD_SURROGATE_MIN_VALUE = 0xD800;
/**
* Trail surrogate minimum value
* @stable ICU 2.1
*/
public static final int TRAIL_SURROGATE_MIN_VALUE = 0xDC00;
/**
* Lead surrogate maximum value
* @stable ICU 2.1
*/
public static final int LEAD_SURROGATE_MAX_VALUE = 0xDBFF;
/**
* Trail surrogate maximum value
* @stable ICU 2.1
*/
public static final int TRAIL_SURROGATE_MAX_VALUE = 0xDFFF;
/**
* Surrogate minimum value
* @stable ICU 2.1
*/
public static final int SURROGATE_MIN_VALUE = LEAD_SURROGATE_MIN_VALUE;
// public method ------------------------------------------------------
/**
* Extract a single UTF-32 value from a string.
* Used when iterating forwards or backwards (with
* <code>UTF16.getCharCount()</code>, as well as random access. If a
* validity check is required, use
* <code><a href="../lang/UCharacter.html#isLegal(char)">
* UCharacter.isLegal()</a></code> on the return value.
* If the char retrieved is part of a surrogate pair, its supplementary
* character will be returned. If a complete supplementary character is
* not found the incomplete character will be returned
* @param source array of UTF-16 chars
* @param offset16 UTF-16 offset to the start of the character.
* @return UTF-32 value for the UTF-32 value that contains the char at
* offset16. The boundaries of that codepoint are the same as in
* <code>bounds32()</code>.
* @exception IndexOutOfBoundsException thrown if offset16 is out of
* bounds.
* @stable ICU 2.1
*/
public static int charAt(String source, int offset16)
{
if (offset16 < 0 || offset16 >= source.length()) {
throw new StringIndexOutOfBoundsException(offset16);
}
char single = source.charAt(offset16);
if (single < LEAD_SURROGATE_MIN_VALUE ||
single > TRAIL_SURROGATE_MAX_VALUE) {
return single;
}
// Convert the UTF-16 surrogate pair if necessary.
// For simplicity in usage, and because the frequency of pairs is
// low, look both directions.
if (single <= LEAD_SURROGATE_MAX_VALUE) {
++ offset16;
if (source.length() != offset16) {
char trail = source.charAt(offset16);
if (trail >= TRAIL_SURROGATE_MIN_VALUE &&
trail <= TRAIL_SURROGATE_MAX_VALUE) {
return UCharacterProperty.getRawSupplementary(single,
trail);
}
}
}
else
{
-- offset16;
if (offset16 >= 0) {
// single is a trail surrogate so
char lead = source.charAt(offset16);
if (lead >= LEAD_SURROGATE_MIN_VALUE &&
lead <= LEAD_SURROGATE_MAX_VALUE) {
return UCharacterProperty.getRawSupplementary(lead,
single);
}
}
}
return single; // return unmatched surrogate
}
/**
* Extract a single UTF-32 value from a substring.
* Used when iterating forwards or backwards (with
* <code>UTF16.getCharCount()</code>, as well as random access. If a
* validity check is required, use
* <code><a href="../lang/UCharacter.html#isLegal(char)">UCharacter.isLegal()
* </a></code> on the return value.
* If the char retrieved is part of a surrogate pair, its supplementary
* character will be returned. If a complete supplementary character is
* not found the incomplete character will be returned
* @param source array of UTF-16 chars
* @param start offset to substring in the source array for analyzing
* @param limit offset to substring in the source array for analyzing
* @param offset16 UTF-16 offset relative to start
* @return UTF-32 value for the UTF-32 value that contains the char at
* offset16. The boundaries of that codepoint are the same as in
* <code>bounds32()</code>.
* @exception IndexOutOfBoundsException thrown if offset16 is not within
* the range of start and limit.
* @stable ICU 2.1
*/
public static int charAt(char source[], int start, int limit,
int offset16)
{
offset16 += start;
if (offset16 < start || offset16 >= limit) {
throw new ArrayIndexOutOfBoundsException(offset16);
}
char single = source[offset16];
if (!isSurrogate(single)) {
return single;
}
// Convert the UTF-16 surrogate pair if necessary.
// For simplicity in usage, and because the frequency of pairs is
// low, look both directions.
if (single <= LEAD_SURROGATE_MAX_VALUE) {
offset16 ++;
if (offset16 >= limit) {
return single;
}
char trail = source[offset16];
if (isTrailSurrogate(trail)) {
return UCharacterProperty.getRawSupplementary(single, trail);
}
}
else { // isTrailSurrogate(single), so
if (offset16 == start) {
return single;
}
offset16 --;
char lead = source[offset16];
if (isLeadSurrogate(lead))
return UCharacterProperty.getRawSupplementary(lead, single);
}
return single; // return unmatched surrogate
}
/**
* Determines how many chars this char32 requires.
* If a validity check is required, use <code>
* <a href="../lang/UCharacter.html#isLegal(char)">isLegal()</a></code> on
* char32 before calling.
* @param char32 the input codepoint.
* @return 2 if is in supplementary space, otherwise 1.
* @stable ICU 2.1
*/
public static int getCharCount(int char32)
{
if (char32 < SUPPLEMENTARY_MIN_VALUE) {
return 1;
}
return 2;
}
/**
* Determines whether the code value is a surrogate.
* @param char16 the input character.
* @return true iff the input character is a surrogate.
* @stable ICU 2.1
*/
public static boolean isSurrogate(char char16)
{
return LEAD_SURROGATE_MIN_VALUE <= char16 &&
char16 <= TRAIL_SURROGATE_MAX_VALUE;
}
/**
* Determines whether the character is a trail surrogate.
* @param char16 the input character.
* @return true iff the input character is a trail surrogate.
* @stable ICU 2.1
*/
public static boolean isTrailSurrogate(char char16)
{
return (TRAIL_SURROGATE_MIN_VALUE <= char16 &&
char16 <= TRAIL_SURROGATE_MAX_VALUE);
}
/**
* Determines whether the character is a lead surrogate.
* @param char16 the input character.
* @return true iff the input character is a lead surrogate
* @stable ICU 2.1
*/
public static boolean isLeadSurrogate(char char16)
{
return LEAD_SURROGATE_MIN_VALUE <= char16 &&
char16 <= LEAD_SURROGATE_MAX_VALUE;
}
/**
* Returns the lead surrogate.
* If a validity check is required, use
* <code><a href="../lang/UCharacter.html#isLegal(char)">isLegal()</a></code>
* on char32 before calling.
* @param char32 the input character.
* @return lead surrogate if the getCharCount(ch) is 2; <br>
* and 0 otherwise (note: 0 is not a valid lead surrogate).
* @stable ICU 2.1
*/
public static char getLeadSurrogate(int char32)
{
if (char32 >= SUPPLEMENTARY_MIN_VALUE) {
return (char)(LEAD_SURROGATE_OFFSET_ +
(char32 >> LEAD_SURROGATE_SHIFT_));
}
return 0;
}
/**
* Returns the trail surrogate.
* If a validity check is required, use
* <code><a href="../lang/UCharacter.html#isLegal(char)">isLegal()</a></code>
* on char32 before calling.
* @param char32 the input character.
* @return the trail surrogate if the getCharCount(ch) is 2; <br>otherwise
* the character itself
* @stable ICU 2.1
*/
public static char getTrailSurrogate(int char32)
{
if (char32 >= SUPPLEMENTARY_MIN_VALUE) {
return (char)(TRAIL_SURROGATE_MIN_VALUE +
(char32 & TRAIL_SURROGATE_MASK_));
}
return (char)char32;
}
/**
* Convenience method corresponding to String.valueOf(char). Returns a one
* or two char string containing the UTF-32 value in UTF16 format. If a
* validity check is required, use
* <code><a href="../lang/UCharacter.html#isLegal(char)">isLegal()</a></code>
* on char32 before calling.
* @param char32 the input character.
* @return string value of char32 in UTF16 format
* @exception IllegalArgumentException thrown if char32 is a invalid
* codepoint.
* @stable ICU 2.1
*/
public static String valueOf(int char32)
{
if (char32 < CODEPOINT_MIN_VALUE || char32 > CODEPOINT_MAX_VALUE) {
throw new IllegalArgumentException("Illegal codepoint");
}
return toString(char32);
}
/**
* Append a single UTF-32 value to the end of a StringBuffer.
* If a validity check is required, use
* <code><a href="../lang/UCharacter.html#isLegal(char)">isLegal()</a></code>
* on char32 before calling.
* @param target the buffer to append to
* @param char32 value to append.
* @return the updated StringBuffer
* @exception IllegalArgumentException thrown when char32 does not lie
* within the range of the Unicode codepoints
* @stable ICU 2.1
*/
public static StringBuffer append(StringBuffer target, int char32)
{
// Check for irregular values
if (char32 < CODEPOINT_MIN_VALUE || char32 > CODEPOINT_MAX_VALUE) {
throw new IllegalArgumentException("Illegal codepoint: " + Integer.toHexString(char32));
}
// Write the UTF-16 values
if (char32 >= SUPPLEMENTARY_MIN_VALUE)
{
target.append(getLeadSurrogate(char32));
target.append(getTrailSurrogate(char32));
}
else {
target.append((char)char32);
}
return target;
}
//// for StringPrep
/**
* Shifts offset16 by the argument number of codepoints within a subarray.
* @param source char array
* @param start position of the subarray to be performed on
* @param limit position of the subarray to be performed on
* @param offset16 UTF16 position to shift relative to start
* @param shift32 number of codepoints to shift
* @return new shifted offset16 relative to start
* @exception IndexOutOfBoundsException if the new offset16 is out of
* bounds with respect to the subarray or the subarray bounds
* are out of range.
* @stable ICU 2.1
*/
public static int moveCodePointOffset(char source[], int start, int limit,
int offset16, int shift32)
{
int size = source.length;
int count;
char ch;
int result = offset16 + start;
if (start<0 || limit<start) {
throw new StringIndexOutOfBoundsException(start);
}
if (limit>size) {
throw new StringIndexOutOfBoundsException(limit);
}
if (offset16<0 || result>limit) {
throw new StringIndexOutOfBoundsException(offset16);
}
if (shift32 > 0 ) {
if (shift32 + result > size) {
throw new StringIndexOutOfBoundsException(result);
}
count = shift32;
while (result < limit && count > 0)
{
ch = source[result];
if (isLeadSurrogate(ch) && (result+1 < limit) &&
isTrailSurrogate(source[result+1])) {
result ++;
}
count --;
result ++;
}
} else {
if (result + shift32 < start) {
throw new StringIndexOutOfBoundsException(result);
}
for (count=-shift32; count>0; count--) {
result--;
if (result<start) {
break;
}
ch = source[result];
if (isTrailSurrogate(ch) && result>start && isLeadSurrogate(source[result-1])) {
result--;
}
}
}
if (count != 0) {
throw new StringIndexOutOfBoundsException(shift32);
}
result -= start;
return result;
}
// private data members -------------------------------------------------
/**
* Shift value for lead surrogate to form a supplementary character.
*/
private static final int LEAD_SURROGATE_SHIFT_ = 10;
/**
* Mask to retrieve the significant value from a trail surrogate.
*/
private static final int TRAIL_SURROGATE_MASK_ = 0x3FF;
/**
* Value that all lead surrogate starts with
*/
private static final int LEAD_SURROGATE_OFFSET_ =
LEAD_SURROGATE_MIN_VALUE -
(SUPPLEMENTARY_MIN_VALUE
>> LEAD_SURROGATE_SHIFT_);
// private methods ------------------------------------------------------
/**
* <p>Converts argument code point and returns a String object representing
* the code point's value in UTF16 format.</p>
* <p>This method does not check for the validity of the codepoint, the
* results are not guaranteed if a invalid codepoint is passed as
* argument.</p>
* <p>The result is a string whose length is 1 for non-supplementary code
* points, 2 otherwise.</p>
* @param ch code point
* @return string representation of the code point
*/
private static String toString(int ch)
{
if (ch < SUPPLEMENTARY_MIN_VALUE) {
return String.valueOf((char)ch);
}
StringBuffer result = new StringBuffer();
result.append(getLeadSurrogate(ch));
result.append(getTrailSurrogate(ch));
return result.toString();
}
}