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/*
* Copyright (C) 2013 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*/
package com.aerospike.client.util;
import static java.lang.Character.MAX_SURROGATE;
import static java.lang.Character.MIN_SURROGATE;
import com.aerospike.client.AerospikeException;
/**
* Low-level, high-performance utility methods related to the {@linkplain Charsets#UTF_8 UTF-8}
* character encoding. UTF-8 is defined in section D92 of The Unicode Standard Core
* Specification, Chapter 3.
*
* The variant of UTF-8 implemented by this class is the restricted definition of UTF-8
* introduced in Unicode 3.1. One implication of this is that it rejects "non-shortest form" byte sequences,
* even though the JDK decoder may accept them.
*
* @author Martin Buchholz
* @author Clément Roux
* @since 16.0
*/
public final class Utf8 {
/**
* Returns the number of bytes in the UTF-8-encoded form of {@code sequence}. For a string, this
* method is equivalent to {@code string.getBytes(UTF_8).length}, but is more efficient in both
* time and space.
*
* @throws IllegalArgumentException if {@code sequence} contains ill-formed UTF-16 (unpaired
* surrogates)
*/
public static int encodedLength(CharSequence sequence) {
// Warning to maintainers: this implementation is highly optimized.
int utf16Length = sequence.length();
int utf8Length = utf16Length;
int i = 0;
// This loop optimizes for pure ASCII.
while (i < utf16Length && sequence.charAt(i) < 0x80) {
i++;
}
// This loop optimizes for chars less than 0x800.
for (; i < utf16Length; i++) {
char c = sequence.charAt(i);
if (c < 0x800) {
utf8Length += ((0x7f - c) >>> 31); // branch free!
} else {
utf8Length += encodedLengthGeneral(sequence, i);
break;
}
}
if (utf8Length < utf16Length) {
// Necessary and sufficient condition for overflow because of maximum 3x expansion
throw new AerospikeException("UTF-8 length does not fit in int: " + (utf8Length + (1L << 32)));
}
return utf8Length;
}
private static int encodedLengthGeneral(CharSequence sequence, int start) {
int utf16Length = sequence.length();
int utf8Length = 0;
for (int i = start; i < utf16Length; i++) {
char c = sequence.charAt(i);
if (c < 0x800) {
utf8Length += (0x7f - c) >>> 31; // branch free!
} else {
utf8Length += 2;
// jdk7+: if (Character.isSurrogate(c)) {
if (MIN_SURROGATE <= c && c <= MAX_SURROGATE) {
// Check that we have a well-formed surrogate pair.
if (Character.codePointAt(sequence, i) == c) {
throw new AerospikeException("Unpaired surrogate at index " + i);
}
i++;
}
}
}
return utf8Length;
}
}