// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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package com.google.protobuf;
import static com.google.protobuf.UnsafeUtil.addressOffset;
import static com.google.protobuf.UnsafeUtil.hasUnsafeArrayOperations;
import static com.google.protobuf.UnsafeUtil.hasUnsafeByteBufferOperations;
import static java.lang.Character.MAX_SURROGATE;
import static java.lang.Character.MIN_HIGH_SURROGATE;
import static java.lang.Character.MIN_LOW_SURROGATE;
import static java.lang.Character.MIN_SUPPLEMENTARY_CODE_POINT;
import static java.lang.Character.MIN_SURROGATE;
import static java.lang.Character.isSurrogatePair;
import static java.lang.Character.toCodePoint;
import java.nio.ByteBuffer;
/**
* A set of low-level, high-performance static utility methods related to the UTF-8 character
* encoding. This class has no dependencies outside of the core JDK libraries.
*
* <p>There are several variants of UTF-8. The one implemented by this class is the restricted
* definition of UTF-8 introduced in Unicode 3.1, which mandates the rejection of "overlong" byte
* sequences as well as rejection of 3-byte surrogate codepoint byte sequences. Note that the UTF-8
* decoder included in Oracle's JDK has been modified to also reject "overlong" byte sequences, but
* (as of 2011) still accepts 3-byte surrogate codepoint byte sequences.
*
* <p>The byte sequences considered valid by this class are exactly those that can be roundtrip
* converted to Strings and back to bytes using the UTF-8 charset, without loss:
*
* <pre>{@code
* Arrays.equals(bytes, new String(bytes, Internal.UTF_8).getBytes(Internal.UTF_8))
* }</pre>
*
* <p>See the Unicode Standard,</br> Table 3-6. <em>UTF-8 Bit Distribution</em>,</br> Table 3-7.
* <em>Well Formed UTF-8 Byte Sequences</em>.
*
* <p>This class supports decoding of partial byte sequences, so that the bytes in a complete UTF-8
* byte sequences can be stored in multiple segments. Methods typically return {@link #MALFORMED} if
* the partial byte sequence is definitely not well-formed, {@link #COMPLETE} if it is well-formed
* in the absence of additional input, or if the byte sequence apparently terminated in the middle
* of a character, an opaque integer "state" value containing enough information to decode the
* character when passed to a subsequent invocation of a partial decoding method.
*
* @author martinrb@google.com (Martin Buchholz)
*/
// TODO(nathanmittler): Copy changes in this class back to Guava
final class Utf8 {
/**
* UTF-8 is a runtime hot spot so we attempt to provide heavily optimized implementations
* depending on what is available on the platform. The processor is the platform-optimized
* delegate for which all methods are delegated directly to.
*/
private static final Processor processor =
(UnsafeProcessor.isAvailable() && !Android.isOnAndroidDevice())
? new UnsafeProcessor()
: new SafeProcessor();
/**
* A mask used when performing unsafe reads to determine if a long value contains any non-ASCII
* characters (i.e. any byte >= 0x80).
*/
private static final long ASCII_MASK_LONG = 0x8080808080808080L;
/**
* Maximum number of bytes per Java UTF-16 char in UTF-8.
*
* @see java.nio.charset.CharsetEncoder#maxBytesPerChar()
*/
static final int MAX_BYTES_PER_CHAR = 3;
/**
* State value indicating that the byte sequence is well-formed and complete (no further bytes are
* needed to complete a character).
*/
public static final int COMPLETE = 0;
/** State value indicating that the byte sequence is definitely not well-formed. */
public static final int MALFORMED = -1;
/**
* Used by {@code Unsafe} UTF-8 string validation logic to determine the minimum string length
* above which to employ an optimized algorithm for counting ASCII characters. The reason for this
* threshold is that for small strings, the optimization may not be beneficial or may even
* negatively impact performance since it requires additional logic to avoid unaligned reads (when
* calling {@code Unsafe.getLong}). This threshold guarantees that even if the initial offset is
* unaligned, we're guaranteed to make at least one call to {@code Unsafe.getLong()} which
* provides a performance improvement that entirely subsumes the cost of the additional logic.
*/
private static final int UNSAFE_COUNT_ASCII_THRESHOLD = 16;
// Other state values include the partial bytes of the incomplete
// character to be decoded in the simplest way: we pack the bytes
// into the state int in little-endian order. For example:
//
// int state = byte1 ^ (byte2 << 8) ^ (byte3 << 16);
//
// Such a state is unpacked thus (note the ~ operation for byte2 to
// undo byte1's sign-extension bits):
//
// int byte1 = (byte) state;
// int byte2 = (byte) ~(state >> 8);
// int byte3 = (byte) (state >> 16);
//
// We cannot store a zero byte in the state because it would be
// indistinguishable from the absence of a byte. But we don't need
// to, because partial bytes must always be negative. When building
// a state, we ensure that byte1 is negative and subsequent bytes
// are valid trailing bytes.
/**
* Returns {@code true} if the given byte array is a well-formed UTF-8 byte sequence.
*
* <p>This is a convenience method, equivalent to a call to {@code isValidUtf8(bytes, 0,
* bytes.length)}.
*/
public static boolean isValidUtf8(byte[] bytes) {
return processor.isValidUtf8(bytes, 0, bytes.length);
}
/**
* Returns {@code true} if the given byte array slice is a well-formed UTF-8 byte sequence. The
* range of bytes to be checked extends from index {@code index}, inclusive, to {@code limit},
* exclusive.
*
* <p>This is a convenience method, equivalent to {@code partialIsValidUtf8(bytes, index, limit)
* == Utf8.COMPLETE}.
*/
public static boolean isValidUtf8(byte[] bytes, int index, int limit) {
return processor.isValidUtf8(bytes, index, limit);
}
/**
* Tells whether the given byte array slice is a well-formed, malformed, or incomplete UTF-8 byte
* sequence. The range of bytes to be checked extends from index {@code index}, inclusive, to
* {@code limit}, exclusive.
*
* @param state either {@link Utf8#COMPLETE} (if this is the initial decoding operation) or the
* value returned from a call to a partial decoding method for the previous bytes
* @return {@link #MALFORMED} if the partial byte sequence is definitely not well-formed, {@link
* #COMPLETE} if it is well-formed (no additional input needed), or if the byte sequence is
* "incomplete", i.e. apparently terminated in the middle of a character, an opaque integer
* "state" value containing enough information to decode the character when passed to a
* subsequent invocation of a partial decoding method.
*/
public static int partialIsValidUtf8(int state, byte[] bytes, int index, int limit) {
return processor.partialIsValidUtf8(state, bytes, index, limit);
}
private static int incompleteStateFor(int byte1) {
return (byte1 > (byte) 0xF4) ? MALFORMED : byte1;
}
private static int incompleteStateFor(int byte1, int byte2) {
return (byte1 > (byte) 0xF4 || byte2 > (byte) 0xBF) ? MALFORMED : byte1 ^ (byte2 << 8);
}
private static int incompleteStateFor(int byte1, int byte2, int byte3) {
return (byte1 > (byte) 0xF4 || byte2 > (byte) 0xBF || byte3 > (byte) 0xBF)
? MALFORMED
: byte1 ^ (byte2 << 8) ^ (byte3 << 16);
}
private static int incompleteStateFor(byte[] bytes, int index, int limit) {
int byte1 = bytes[index - 1];
switch (limit - index) {
case 0:
return incompleteStateFor(byte1);
case 1:
return incompleteStateFor(byte1, bytes[index]);
case 2:
return incompleteStateFor(byte1, bytes[index], bytes[index + 1]);
default:
throw new AssertionError();
}
}
private static int incompleteStateFor(
final ByteBuffer buffer, final int byte1, final int index, final int remaining) {
switch (remaining) {
case 0:
return incompleteStateFor(byte1);
case 1:
return incompleteStateFor(byte1, buffer.get(index));
case 2:
return incompleteStateFor(byte1, buffer.get(index), buffer.get(index + 1));
default:
throw new AssertionError();
}
}
// These UTF-8 handling methods are copied from Guava's Utf8 class with a modification to throw
// a protocol buffer local exception. This exception is then caught in CodedOutputStream so it can
// fallback to more lenient behavior.
static class UnpairedSurrogateException extends IllegalArgumentException {
UnpairedSurrogateException(int index, int length) {
super("Unpaired surrogate at index " + index + " of " + length);
}
}
/**
* 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)
*/
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 IllegalArgumentException(
"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 (Character.MIN_SURROGATE <= c && c <= Character.MAX_SURROGATE) {
// Check that we have a well-formed surrogate pair.
int cp = Character.codePointAt(sequence, i);
if (cp < MIN_SUPPLEMENTARY_CODE_POINT) {
throw new UnpairedSurrogateException(i, utf16Length);
}
i++;
}
}
}
return utf8Length;
}
static int encode(CharSequence in, byte[] out, int offset, int length) {
return processor.encodeUtf8(in, out, offset, length);
}
// End Guava UTF-8 methods.
/**
* Determines if the given {@link ByteBuffer} is a valid UTF-8 string.
*
* <p>Selects an optimal algorithm based on the type of {@link ByteBuffer} (i.e. heap or direct)
* and the capabilities of the platform.
*
* @param buffer the buffer to check.
* @see Utf8#isValidUtf8(byte[], int, int)
*/
static boolean isValidUtf8(ByteBuffer buffer) {
return processor.isValidUtf8(buffer, buffer.position(), buffer.remaining());
}
/**
* Determines if the given {@link ByteBuffer} is a partially valid UTF-8 string.
*
* <p>Selects an optimal algorithm based on the type of {@link ByteBuffer} (i.e. heap or direct)
* and the capabilities of the platform.
*
* @param buffer the buffer to check.
* @see Utf8#partialIsValidUtf8(int, byte[], int, int)
*/
static int partialIsValidUtf8(int state, ByteBuffer buffer, int index, int limit) {
return processor.partialIsValidUtf8(state, buffer, index, limit);
}
/**
* Decodes the given UTF-8 portion of the {@link ByteBuffer} into a {@link String}.
*
* @throws InvalidProtocolBufferException if the input is not valid UTF-8.
*/
static String decodeUtf8(ByteBuffer buffer, int index, int size)
throws InvalidProtocolBufferException {
return processor.decodeUtf8(buffer, index, size);
}
/**
* Decodes the given UTF-8 encoded byte array slice into a {@link String}.
*
* @throws InvalidProtocolBufferException if the input is not valid UTF-8.
*/
static String decodeUtf8(byte[] bytes, int index, int size)
throws InvalidProtocolBufferException {
return processor.decodeUtf8(bytes, index, size);
}
/**
* Encodes the given characters to the target {@link ByteBuffer} using UTF-8 encoding.
*
* <p>Selects an optimal algorithm based on the type of {@link ByteBuffer} (i.e. heap or direct)
* and the capabilities of the platform.
*
* @param in the source string to be encoded
* @param out the target buffer to receive the encoded string.
* @see Utf8#encode(CharSequence, byte[], int, int)
*/
static void encodeUtf8(CharSequence in, ByteBuffer out) {
processor.encodeUtf8(in, out);
}
/**
* Counts (approximately) the number of consecutive ASCII characters in the given buffer. The byte
* order of the {@link ByteBuffer} does not matter, so performance can be improved if native byte
* order is used (i.e. no byte-swapping in {@link ByteBuffer#getLong(int)}).
*
* @param buffer the buffer to be scanned for ASCII chars
* @param index the starting index of the scan
* @param limit the limit within buffer for the scan
* @return the number of ASCII characters found. The stopping position will be at or before the
* first non-ASCII byte.
*/
private static int estimateConsecutiveAscii(ByteBuffer buffer, int index, int limit) {
int i = index;
final int lim = limit - 7;
// This simple loop stops when we encounter a byte >= 0x80 (i.e. non-ASCII).
// To speed things up further, we're reading longs instead of bytes so we use a mask to
// determine if any byte in the current long is non-ASCII.
for (; i < lim && (buffer.getLong(i) & ASCII_MASK_LONG) == 0; i += 8) {}
return i - index;
}
/** A processor of UTF-8 strings, providing methods for checking validity and encoding. */
// TODO(nathanmittler): Add support for Memory/MemoryBlock on Android.
abstract static class Processor {
/**
* Returns {@code true} if the given byte array slice is a well-formed UTF-8 byte sequence. The
* range of bytes to be checked extends from index {@code index}, inclusive, to {@code limit},
* exclusive.
*
* <p>This is a convenience method, equivalent to {@code partialIsValidUtf8(bytes, index, limit)
* == Utf8.COMPLETE}.
*/
final boolean isValidUtf8(byte[] bytes, int index, int limit) {
return partialIsValidUtf8(COMPLETE, bytes, index, limit) == COMPLETE;
}
/**
* Tells whether the given byte array slice is a well-formed, malformed, or incomplete UTF-8
* byte sequence. The range of bytes to be checked extends from index {@code index}, inclusive,
* to {@code limit}, exclusive.
*
* @param state either {@link Utf8#COMPLETE} (if this is the initial decoding operation) or the
* value returned from a call to a partial decoding method for the previous bytes
* @return {@link #MALFORMED} if the partial byte sequence is definitely not well-formed, {@link
* #COMPLETE} if it is well-formed (no additional input needed), or if the byte sequence is
* "incomplete", i.e. apparently terminated in the middle of a character, an opaque integer
* "state" value containing enough information to decode the character when passed to a
* subsequent invocation of a partial decoding method.
*/
abstract int partialIsValidUtf8(int state, byte[] bytes, int index, int limit);
/**
* Returns {@code true} if the given portion of the {@link ByteBuffer} is a well-formed UTF-8
* byte sequence. The range of bytes to be checked extends from index {@code index}, inclusive,
* to {@code limit}, exclusive.
*
* <p>This is a convenience method, equivalent to {@code partialIsValidUtf8(bytes, index, limit)
* == Utf8.COMPLETE}.
*/
final boolean isValidUtf8(ByteBuffer buffer, int index, int limit) {
return partialIsValidUtf8(COMPLETE, buffer, index, limit) == COMPLETE;
}
/**
* Indicates whether or not the given buffer contains a valid UTF-8 string.
*
* @param buffer the buffer to check.
* @return {@code true} if the given buffer contains a valid UTF-8 string.
*/
final int partialIsValidUtf8(
final int state, final ByteBuffer buffer, int index, final int limit) {
if (buffer.hasArray()) {
final int offset = buffer.arrayOffset();
return partialIsValidUtf8(state, buffer.array(), offset + index, offset + limit);
} else if (buffer.isDirect()) {
return partialIsValidUtf8Direct(state, buffer, index, limit);
}
return partialIsValidUtf8Default(state, buffer, index, limit);
}
/** Performs validation for direct {@link ByteBuffer} instances. */
abstract int partialIsValidUtf8Direct(
final int state, final ByteBuffer buffer, int index, final int limit);
/**
* Performs validation for {@link ByteBuffer} instances using the {@link ByteBuffer} API rather
* than potentially faster approaches. This first completes validation for the current character
* (provided by {@code state}) and then finishes validation for the sequence.
*/
final int partialIsValidUtf8Default(
final int state, final ByteBuffer buffer, int index, final int limit) {
if (state != COMPLETE) {
// The previous decoding operation was incomplete (or malformed).
// We look for a well-formed sequence consisting of bytes from
// the previous decoding operation (stored in state) together
// with bytes from the array slice.
//
// We expect such "straddler characters" to be rare.
if (index >= limit) { // No bytes? No progress.
return state;
}
byte byte1 = (byte) state;
// byte1 is never ASCII.
if (byte1 < (byte) 0xE0) {
// two-byte form
// Simultaneously checks for illegal trailing-byte in
// leading position and overlong 2-byte form.
if (byte1 < (byte) 0xC2
// byte2 trailing-byte test
|| buffer.get(index++) > (byte) 0xBF) {
return MALFORMED;
}
} else if (byte1 < (byte) 0xF0) {
// three-byte form
// Get byte2 from saved state or array
byte byte2 = (byte) ~(state >> 8);
if (byte2 == 0) {
byte2 = buffer.get(index++);
if (index >= limit) {
return incompleteStateFor(byte1, byte2);
}
}
if (byte2 > (byte) 0xBF
// overlong? 5 most significant bits must not all be zero
|| (byte1 == (byte) 0xE0 && byte2 < (byte) 0xA0)
// illegal surrogate codepoint?
|| (byte1 == (byte) 0xED && byte2 >= (byte) 0xA0)
// byte3 trailing-byte test
|| buffer.get(index++) > (byte) 0xBF) {
return MALFORMED;
}
} else {
// four-byte form
// Get byte2 and byte3 from saved state or array
byte byte2 = (byte) ~(state >> 8);
byte byte3 = 0;
if (byte2 == 0) {
byte2 = buffer.get(index++);
if (index >= limit) {
return incompleteStateFor(byte1, byte2);
}
} else {
byte3 = (byte) (state >> 16);
}
if (byte3 == 0) {
byte3 = buffer.get(index++);
if (index >= limit) {
return incompleteStateFor(byte1, byte2, byte3);
}
}
// If we were called with state == MALFORMED, then byte1 is 0xFF,
// which never occurs in well-formed UTF-8, and so we will return
// MALFORMED again below.
if (byte2 > (byte) 0xBF
// Check that 1 <= plane <= 16. Tricky optimized form of:
// if (byte1 > (byte) 0xF4 ||
// byte1 == (byte) 0xF0 && byte2 < (byte) 0x90 ||
// byte1 == (byte) 0xF4 && byte2 > (byte) 0x8F)
|| (((byte1 << 28) + (byte2 - (byte) 0x90)) >> 30) != 0
// byte3 trailing-byte test
|| byte3 > (byte) 0xBF
// byte4 trailing-byte test
|| buffer.get(index++) > (byte) 0xBF) {
return MALFORMED;
}
}
}
// Finish validation for the sequence.
return partialIsValidUtf8(buffer, index, limit);
}
/**
* Performs validation for {@link ByteBuffer} instances using the {@link ByteBuffer} API rather
* than potentially faster approaches.
*/
private static int partialIsValidUtf8(final ByteBuffer buffer, int index, final int limit) {
index += estimateConsecutiveAscii(buffer, index, limit);
for (; ; ) {
// Optimize for interior runs of ASCII bytes.
// TODO(nathanmittler): Consider checking 8 bytes at a time after some threshold?
// Maybe after seeing a few in a row that are ASCII, go back to fast mode?
int byte1;
do {
if (index >= limit) {
return COMPLETE;
}
} while ((byte1 = buffer.get(index++)) >= 0);
// If we're here byte1 is not ASCII. Only need to handle 2-4 byte forms.
if (byte1 < (byte) 0xE0) {
// Two-byte form (110xxxxx 10xxxxxx)
if (index >= limit) {
// Incomplete sequence
return byte1;
}
// Simultaneously checks for illegal trailing-byte in
// leading position and overlong 2-byte form.
if (byte1 < (byte) 0xC2 || buffer.get(index) > (byte) 0xBF) {
return MALFORMED;
}
index++;
} else if (byte1 < (byte) 0xF0) {
// Three-byte form (1110xxxx 10xxxxxx 10xxxxxx)
if (index >= limit - 1) {
// Incomplete sequence
return incompleteStateFor(buffer, byte1, index, limit - index);
}
final byte byte2 = buffer.get(index++);
if (byte2 > (byte) 0xBF
// overlong? 5 most significant bits must not all be zero
|| (byte1 == (byte) 0xE0 && byte2 < (byte) 0xA0)
// check for illegal surrogate codepoints
|| (byte1 == (byte) 0xED && byte2 >= (byte) 0xA0)
// byte3 trailing-byte test
|| buffer.get(index) > (byte) 0xBF) {
return MALFORMED;
}
index++;
} else {
// Four-byte form (1110xxxx 10xxxxxx 10xxxxxx 10xxxxxx)
if (index >= limit - 2) {
// Incomplete sequence
return incompleteStateFor(buffer, byte1, index, limit - index);
}
// TODO(nathanmittler): Consider using getInt() to improve performance.
final int byte2 = buffer.get(index++);
if (byte2 > (byte) 0xBF
// Check that 1 <= plane <= 16. Tricky optimized form of:
// if (byte1 > (byte) 0xF4 ||
// byte1 == (byte) 0xF0 && byte2 < (byte) 0x90 ||
// byte1 == (byte) 0xF4 && byte2 > (byte) 0x8F)
|| (((byte1 << 28) + (byte2 - (byte) 0x90)) >> 30) != 0
// byte3 trailing-byte test
|| buffer.get(index++) > (byte) 0xBF
// byte4 trailing-byte test
|| buffer.get(index++) > (byte) 0xBF) {
return MALFORMED;
}
}
}
}
/**
* Decodes the given byte array slice into a {@link String}.
*
* @throws InvalidProtocolBufferException if the byte array slice is not valid UTF-8.
*/
abstract String decodeUtf8(byte[] bytes, int index, int size)
throws InvalidProtocolBufferException;
/**
* Decodes the given portion of the {@link ByteBuffer} into a {@link String}.
*
* @throws InvalidProtocolBufferException if the portion of the buffer is not valid UTF-8.
*/
final String decodeUtf8(ByteBuffer buffer, int index, int size)
throws InvalidProtocolBufferException {
if (buffer.hasArray()) {
final int offset = buffer.arrayOffset();
return decodeUtf8(buffer.array(), offset + index, size);
} else if (buffer.isDirect()) {
return decodeUtf8Direct(buffer, index, size);
}
return decodeUtf8Default(buffer, index, size);
}
/** Decodes direct {@link ByteBuffer} instances into {@link String}. */
abstract String decodeUtf8Direct(ByteBuffer buffer, int index, int size)
throws InvalidProtocolBufferException;
/**
* Decodes {@link ByteBuffer} instances using the {@link ByteBuffer} API rather than potentially
* faster approaches.
*/
final String decodeUtf8Default(ByteBuffer buffer, int index, int size)
throws InvalidProtocolBufferException {
// Bitwise OR combines the sign bits so any negative value fails the check.
if ((index | size | buffer.limit() - index - size) < 0) {
throw new ArrayIndexOutOfBoundsException(
String.format("buffer limit=%d, index=%d, limit=%d", buffer.limit(), index, size));
}
int offset = index;
final int limit = offset + size;
// The longest possible resulting String is the same as the number of input bytes, when it is
// all ASCII. For other cases, this over-allocates and we will truncate in the end.
char[] resultArr = new char[size];
int resultPos = 0;
// Optimize for 100% ASCII (Hotspot loves small simple top-level loops like this).
// This simple loop stops when we encounter a byte >= 0x80 (i.e. non-ASCII).
while (offset < limit) {
byte b = buffer.get(offset);
if (!DecodeUtil.isOneByte(b)) {
break;
}
offset++;
DecodeUtil.handleOneByte(b, resultArr, resultPos++);
}
while (offset < limit) {
byte byte1 = buffer.get(offset++);
if (DecodeUtil.isOneByte(byte1)) {
DecodeUtil.handleOneByte(byte1, resultArr, resultPos++);
// It's common for there to be multiple ASCII characters in a run mixed in, so add an
// extra optimized loop to take care of these runs.
while (offset < limit) {
byte b = buffer.get(offset);
if (!DecodeUtil.isOneByte(b)) {
break;
}
offset++;
DecodeUtil.handleOneByte(b, resultArr, resultPos++);
}
} else if (DecodeUtil.isTwoBytes(byte1)) {
if (offset >= limit) {
throw InvalidProtocolBufferException.invalidUtf8();
}
DecodeUtil.handleTwoBytes(
byte1, /* byte2 */ buffer.get(offset++), resultArr, resultPos++);
} else if (DecodeUtil.isThreeBytes(byte1)) {
if (offset >= limit - 1) {
throw InvalidProtocolBufferException.invalidUtf8();
}
DecodeUtil.handleThreeBytes(
byte1,
/* byte2 */ buffer.get(offset++),
/* byte3 */ buffer.get(offset++),
resultArr,
resultPos++);
} else {
if (offset >= limit - 2) {
throw InvalidProtocolBufferException.invalidUtf8();
}
DecodeUtil.handleFourBytes(
byte1,
/* byte2 */ buffer.get(offset++),
/* byte3 */ buffer.get(offset++),
/* byte4 */ buffer.get(offset++),
resultArr,
resultPos++);
// 4-byte case requires two chars.
resultPos++;
}
}
return new String(resultArr, 0, resultPos);
}
/**
* Encodes an input character sequence ({@code in}) to UTF-8 in the target array ({@code out}).
* For a string, this method is similar to
*
* <pre>{@code
* byte[] a = string.getBytes(UTF_8);
* System.arraycopy(a, 0, bytes, offset, a.length);
* return offset + a.length;
* }</pre>
*
* but is more efficient in both time and space. One key difference is that this method requires
* paired surrogates, and therefore does not support chunking. While {@code
* String.getBytes(UTF_8)} replaces unpaired surrogates with the default replacement character,
* this method throws {@link UnpairedSurrogateException}.
*
* <p>To ensure sufficient space in the output buffer, either call {@link #encodedLength} to
* compute the exact amount needed, or leave room for {@code Utf8.MAX_BYTES_PER_CHAR *
* sequence.length()}, which is the largest possible number of bytes that any input can be
* encoded to.
*
* @param in the input character sequence to be encoded
* @param out the target array
* @param offset the starting offset in {@code bytes} to start writing at
* @param length the length of the {@code bytes}, starting from {@code offset}
* @throws UnpairedSurrogateException if {@code sequence} contains ill-formed UTF-16 (unpaired
* surrogates)
* @throws ArrayIndexOutOfBoundsException if {@code sequence} encoded in UTF-8 is longer than
* {@code bytes.length - offset}
* @return the new offset, equivalent to {@code offset + Utf8.encodedLength(sequence)}
*/
abstract int encodeUtf8(CharSequence in, byte[] out, int offset, int length);
/**
* Encodes an input character sequence ({@code in}) to UTF-8 in the target buffer ({@code out}).
* Upon returning from this method, the {@code out} position will point to the position after
* the last encoded byte. This method requires paired surrogates, and therefore does not support
* chunking.
*
* <p>To ensure sufficient space in the output buffer, either call {@link #encodedLength} to
* compute the exact amount needed, or leave room for {@code Utf8.MAX_BYTES_PER_CHAR *
* in.length()}, which is the largest possible number of bytes that any input can be encoded to.
*
* @param in the source character sequence to be encoded
* @param out the target buffer
* @throws UnpairedSurrogateException if {@code in} contains ill-formed UTF-16 (unpaired
* surrogates)
* @throws ArrayIndexOutOfBoundsException if {@code in} encoded in UTF-8 is longer than {@code
* out.remaining()}
*/
final void encodeUtf8(CharSequence in, ByteBuffer out) {
if (out.hasArray()) {
final int offset = out.arrayOffset();
int endIndex = Utf8.encode(in, out.array(), offset + out.position(), out.remaining());
out.position(endIndex - offset);
} else if (out.isDirect()) {
encodeUtf8Direct(in, out);
} else {
encodeUtf8Default(in, out);
}
}
/** Encodes the input character sequence to a direct {@link ByteBuffer} instance. */
abstract void encodeUtf8Direct(CharSequence in, ByteBuffer out);
/**
* Encodes the input character sequence to a {@link ByteBuffer} instance using the {@link
* ByteBuffer} API, rather than potentially faster approaches.
*/
final void encodeUtf8Default(CharSequence in, ByteBuffer out) {
final int inLength = in.length();
int outIx = out.position();
int inIx = 0;
// Since ByteBuffer.putXXX() already checks boundaries for us, no need to explicitly check
// access. Assume the buffer is big enough and let it handle the out of bounds exception
// if it occurs.
try {
// Designed to take advantage of
// https://wiki.openjdk.java.net/display/HotSpotInternals/RangeCheckElimination
for (char c; inIx < inLength && (c = in.charAt(inIx)) < 0x80; ++inIx) {
out.put(outIx + inIx, (byte) c);
}
if (inIx == inLength) {
// Successfully encoded the entire string.
out.position(outIx + inIx);
return;
}
outIx += inIx;
for (char c; inIx < inLength; ++inIx, ++outIx) {
c = in.charAt(inIx);
if (c < 0x80) {
// One byte (0xxx xxxx)
out.put(outIx, (byte) c);
} else if (c < 0x800) {
// Two bytes (110x xxxx 10xx xxxx)
// Benchmarks show put performs better than putShort here (for HotSpot).
out.put(outIx++, (byte) (0xC0 | (c >>> 6)));
out.put(outIx, (byte) (0x80 | (0x3F & c)));
} else if (c < MIN_SURROGATE || MAX_SURROGATE < c) {
// Three bytes (1110 xxxx 10xx xxxx 10xx xxxx)
// Maximum single-char code point is 0xFFFF, 16 bits.
// Benchmarks show put performs better than putShort here (for HotSpot).
out.put(outIx++, (byte) (0xE0 | (c >>> 12)));
out.put(outIx++, (byte) (0x80 | (0x3F & (c >>> 6))));
out.put(outIx, (byte) (0x80 | (0x3F & c)));
} else {
// Four bytes (1111 xxxx 10xx xxxx 10xx xxxx 10xx xxxx)
// Minimum code point represented by a surrogate pair is 0x10000, 17 bits, four UTF-8
// bytes
final char low;
if (inIx + 1 == inLength || !isSurrogatePair(c, (low = in.charAt(++inIx)))) {
throw new UnpairedSurrogateException(inIx, inLength);
}
// TODO(nathanmittler): Consider using putInt() to improve performance.
int codePoint = toCodePoint(c, low);
out.put(outIx++, (byte) ((0xF << 4) | (codePoint >>> 18)));
out.put(outIx++, (byte) (0x80 | (0x3F & (codePoint >>> 12))));
out.put(outIx++, (byte) (0x80 | (0x3F & (codePoint >>> 6))));
out.put(outIx, (byte) (0x80 | (0x3F & codePoint)));
}
}
// Successfully encoded the entire string.
out.position(outIx);
} catch (IndexOutOfBoundsException e) {
// TODO(nathanmittler): Consider making the API throw IndexOutOfBoundsException instead.
// If we failed in the outer ASCII loop, outIx will not have been updated. In this case,
// use inIx to determine the bad write index.
int badWriteIndex = out.position() + Math.max(inIx, outIx - out.position() + 1);
throw new ArrayIndexOutOfBoundsException(
"Failed writing " + in.charAt(inIx) + " at index " + badWriteIndex);
}
}
}
/** {@link Processor} implementation that does not use any {@code sun.misc.Unsafe} methods. */
static final class SafeProcessor extends Processor {
@Override
int partialIsValidUtf8(int state, byte[] bytes, int index, int limit) {
if (state != COMPLETE) {
// The previous decoding operation was incomplete (or malformed).
// We look for a well-formed sequence consisting of bytes from
// the previous decoding operation (stored in state) together
// with bytes from the array slice.
//
// We expect such "straddler characters" to be rare.
if (index >= limit) { // No bytes? No progress.
return state;
}
int byte1 = (byte) state;
// byte1 is never ASCII.
if (byte1 < (byte) 0xE0) {
// two-byte form
// Simultaneously checks for illegal trailing-byte in
// leading position and overlong 2-byte form.
if (byte1 < (byte) 0xC2
// byte2 trailing-byte test
|| bytes[index++] > (byte) 0xBF) {
return MALFORMED;
}
} else if (byte1 < (byte) 0xF0) {
// three-byte form
// Get byte2 from saved state or array
int byte2 = (byte) ~(state >> 8);
if (byte2 == 0) {
byte2 = bytes[index++];
if (index >= limit) {
return incompleteStateFor(byte1, byte2);
}
}
if (byte2 > (byte) 0xBF
// overlong? 5 most significant bits must not all be zero
|| (byte1 == (byte) 0xE0 && byte2 < (byte) 0xA0)
// illegal surrogate codepoint?
|| (byte1 == (byte) 0xED && byte2 >= (byte) 0xA0)
// byte3 trailing-byte test
|| bytes[index++] > (byte) 0xBF) {
return MALFORMED;
}
} else {
// four-byte form
// Get byte2 and byte3 from saved state or array
int byte2 = (byte) ~(state >> 8);
int byte3 = 0;
if (byte2 == 0) {
byte2 = bytes[index++];
if (index >= limit) {
return incompleteStateFor(byte1, byte2);
}
} else {
byte3 = (byte) (state >> 16);
}
if (byte3 == 0) {
byte3 = bytes[index++];
if (index >= limit) {
return incompleteStateFor(byte1, byte2, byte3);
}
}
// If we were called with state == MALFORMED, then byte1 is 0xFF,
// which never occurs in well-formed UTF-8, and so we will return
// MALFORMED again below.
if (byte2 > (byte) 0xBF
// Check that 1 <= plane <= 16. Tricky optimized form of:
// if (byte1 > (byte) 0xF4 ||
// byte1 == (byte) 0xF0 && byte2 < (byte) 0x90 ||
// byte1 == (byte) 0xF4 && byte2 > (byte) 0x8F)
|| (((byte1 << 28) + (byte2 - (byte) 0x90)) >> 30) != 0
// byte3 trailing-byte test
|| byte3 > (byte) 0xBF
// byte4 trailing-byte test
|| bytes[index++] > (byte) 0xBF) {
return MALFORMED;
}
}
}
return partialIsValidUtf8(bytes, index, limit);
}
@Override
int partialIsValidUtf8Direct(int state, ByteBuffer buffer, int index, int limit) {
// For safe processing, we have to use the ByteBuffer API.
return partialIsValidUtf8Default(state, buffer, index, limit);
}
@Override
String decodeUtf8(byte[] bytes, int index, int size) throws InvalidProtocolBufferException {
// Bitwise OR combines the sign bits so any negative value fails the check.
if ((index | size | bytes.length - index - size) < 0) {
throw new ArrayIndexOutOfBoundsException(
String.format("buffer length=%d, index=%d, size=%d", bytes.length, index, size));
}
int offset = index;
final int limit = offset + size;
// The longest possible resulting String is the same as the number of input bytes, when it is
// all ASCII. For other cases, this over-allocates and we will truncate in the end.
char[] resultArr = new char[size];
int resultPos = 0;
// Optimize for 100% ASCII (Hotspot loves small simple top-level loops like this).
// This simple loop stops when we encounter a byte >= 0x80 (i.e. non-ASCII).
while (offset < limit) {
byte b = bytes[offset];
if (!DecodeUtil.isOneByte(b)) {
break;
}
offset++;
DecodeUtil.handleOneByte(b, resultArr, resultPos++);
}
while (offset < limit) {
byte byte1 = bytes[offset++];
if (DecodeUtil.isOneByte(byte1)) {
DecodeUtil.handleOneByte(byte1, resultArr, resultPos++);
// It's common for there to be multiple ASCII characters in a run mixed in, so add an
// extra optimized loop to take care of these runs.
while (offset < limit) {
byte b = bytes[offset];
if (!DecodeUtil.isOneByte(b)) {
break;
}
offset++;
DecodeUtil.handleOneByte(b, resultArr, resultPos++);
}
} else if (DecodeUtil.isTwoBytes(byte1)) {
if (offset >= limit) {
throw InvalidProtocolBufferException.invalidUtf8();
}
DecodeUtil.handleTwoBytes(byte1, /* byte2 */ bytes[offset++], resultArr, resultPos++);
} else if (DecodeUtil.isThreeBytes(byte1)) {
if (offset >= limit - 1) {
throw InvalidProtocolBufferException.invalidUtf8();
}
DecodeUtil.handleThreeBytes(
byte1,
/* byte2 */ bytes[offset++],
/* byte3 */ bytes[offset++],
resultArr,
resultPos++);
} else {
if (offset >= limit - 2) {
throw InvalidProtocolBufferException.invalidUtf8();
}
DecodeUtil.handleFourBytes(
byte1,
/* byte2 */ bytes[offset++],
/* byte3 */ bytes[offset++],
/* byte4 */ bytes[offset++],
resultArr,
resultPos++);
// 4-byte case requires two chars.
resultPos++;
}
}
return new String(resultArr, 0, resultPos);
}
@Override
String decodeUtf8Direct(ByteBuffer buffer, int index, int size)
throws InvalidProtocolBufferException {
// For safe processing, we have to use the ByteBufferAPI.
return decodeUtf8Default(buffer, index, size);
}
@Override
int encodeUtf8(CharSequence in, byte[] out, int offset, int length) {
int utf16Length = in.length();
int j = offset;
int i = 0;
int limit = offset + length;
// Designed to take advantage of
// https://wiki.openjdk.java.net/display/HotSpotInternals/RangeCheckElimination
for (char c; i < utf16Length && i + j < limit && (c = in.charAt(i)) < 0x80; i++) {
out[j + i] = (byte) c;
}
if (i == utf16Length) {
return j + utf16Length;
}
j += i;
for (char c; i < utf16Length; i++) {
c = in.charAt(i);
if (c < 0x80 && j < limit) {
out[j++] = (byte) c;
} else if (c < 0x800 && j <= limit - 2) { // 11 bits, two UTF-8 bytes
out[j++] = (byte) ((0xF << 6) | (c >>> 6));
out[j++] = (byte) (0x80 | (0x3F & c));
} else if ((c < Character.MIN_SURROGATE || Character.MAX_SURROGATE < c) && j <= limit - 3) {
// Maximum single-char code point is 0xFFFF, 16 bits, three UTF-8 bytes
out[j++] = (byte) ((0xF << 5) | (c >>> 12));
out[j++] = (byte) (0x80 | (0x3F & (c >>> 6)));
out[j++] = (byte) (0x80 | (0x3F & c));
} else if (j <= limit - 4) {
// Minimum code point represented by a surrogate pair is 0x10000, 17 bits,
// four UTF-8 bytes
final char low;
if (i + 1 == in.length() || !Character.isSurrogatePair(c, (low = in.charAt(++i)))) {
throw new UnpairedSurrogateException((i - 1), utf16Length);
}
int codePoint = Character.toCodePoint(c, low);
out[j++] = (byte) ((0xF << 4) | (codePoint >>> 18));
out[j++] = (byte) (0x80 | (0x3F & (codePoint >>> 12)));
out[j++] = (byte) (0x80 | (0x3F & (codePoint >>> 6)));
out[j++] = (byte) (0x80 | (0x3F & codePoint));
} else {
// If we are surrogates and we're not a surrogate pair, always throw an
// UnpairedSurrogateException instead of an ArrayOutOfBoundsException.
if ((Character.MIN_SURROGATE <= c && c <= Character.MAX_SURROGATE)
&& (i + 1 == in.length() || !Character.isSurrogatePair(c, in.charAt(i + 1)))) {
throw new UnpairedSurrogateException(i, utf16Length);
}
throw new ArrayIndexOutOfBoundsException("Failed writing " + c + " at index " + j);
}
}
return j;
}
@Override
void encodeUtf8Direct(CharSequence in, ByteBuffer out) {
// For safe processing, we have to use the ByteBuffer API.
encodeUtf8Default(in, out);
}
private static int partialIsValidUtf8(byte[] bytes, int index, int limit) {
// Optimize for 100% ASCII (Hotspot loves small simple top-level loops like this).
// This simple loop stops when we encounter a byte >= 0x80 (i.e. non-ASCII).
while (index < limit && bytes[index] >= 0) {
index++;
}
return (index >= limit) ? COMPLETE : partialIsValidUtf8NonAscii(bytes, index, limit);
}
private static int partialIsValidUtf8NonAscii(byte[] bytes, int index, int limit) {
for (; ; ) {
int byte1;
int byte2;
// Optimize for interior runs of ASCII bytes.
do {
if (index >= limit) {
return COMPLETE;
}
} while ((byte1 = bytes[index++]) >= 0);
if (byte1 < (byte) 0xE0) {
// two-byte form
if (index >= limit) {
// Incomplete sequence
return byte1;
}
// Simultaneously checks for illegal trailing-byte in
// leading position and overlong 2-byte form.
if (byte1 < (byte) 0xC2 || bytes[index++] > (byte) 0xBF) {
return MALFORMED;
}
} else if (byte1 < (byte) 0xF0) {
// three-byte form
if (index >= limit - 1) { // incomplete sequence
return incompleteStateFor(bytes, index, limit);
}
if ((byte2 = bytes[index++]) > (byte) 0xBF
// overlong? 5 most significant bits must not all be zero
|| (byte1 == (byte) 0xE0 && byte2 < (byte) 0xA0)
// check for illegal surrogate codepoints
|| (byte1 == (byte) 0xED && byte2 >= (byte) 0xA0)
// byte3 trailing-byte test
|| bytes[index++] > (byte) 0xBF) {
return MALFORMED;
}
} else {
// four-byte form
if (index >= limit - 2) { // incomplete sequence
return incompleteStateFor(bytes, index, limit);
}
if ((byte2 = bytes[index++]) > (byte) 0xBF
// Check that 1 <= plane <= 16. Tricky optimized form of:
// if (byte1 > (byte) 0xF4 ||
// byte1 == (byte) 0xF0 && byte2 < (byte) 0x90 ||
// byte1 == (byte) 0xF4 && byte2 > (byte) 0x8F)
|| (((byte1 << 28) + (byte2 - (byte) 0x90)) >> 30) != 0
// byte3 trailing-byte test
|| bytes[index++] > (byte) 0xBF
// byte4 trailing-byte test
|| bytes[index++] > (byte) 0xBF) {
return MALFORMED;
}
}
}
}
}
/** {@link Processor} that uses {@code sun.misc.Unsafe} where possible to improve performance. */
static final class UnsafeProcessor extends Processor {
/** Indicates whether or not all required unsafe operations are supported on this platform. */
static boolean isAvailable() {
return hasUnsafeArrayOperations() && hasUnsafeByteBufferOperations();
}
@Override
int partialIsValidUtf8(int state, byte[] bytes, final int index, final int limit) {
// Bitwise OR combines the sign bits so any negative value fails the check.
if ((index | limit | bytes.length - limit) < 0) {
throw new ArrayIndexOutOfBoundsException(
String.format("Array length=%d, index=%d, limit=%d", bytes.length, index, limit));
}
long offset = index;
final long offsetLimit = limit;
if (state != COMPLETE) {
// The previous decoding operation was incomplete (or malformed).
// We look for a well-formed sequence consisting of bytes from
// the previous decoding operation (stored in state) together
// with bytes from the array slice.
//
// We expect such "straddler characters" to be rare.
if (offset >= offsetLimit) { // No bytes? No progress.
return state;
}
int byte1 = (byte) state;
// byte1 is never ASCII.
if (byte1 < (byte) 0xE0) {
// two-byte form
// Simultaneously checks for illegal trailing-byte in
// leading position and overlong 2-byte form.
if (byte1 < (byte) 0xC2
// byte2 trailing-byte test
|| UnsafeUtil.getByte(bytes, offset++) > (byte) 0xBF) {
return MALFORMED;
}
} else if (byte1 < (byte) 0xF0) {
// three-byte form
// Get byte2 from saved state or array
int byte2 = (byte) ~(state >> 8);
if (byte2 == 0) {
byte2 = UnsafeUtil.getByte(bytes, offset++);
if (offset >= offsetLimit) {
return incompleteStateFor(byte1, byte2);
}
}
if (byte2 > (byte) 0xBF
// overlong? 5 most significant bits must not all be zero
|| (byte1 == (byte) 0xE0 && byte2 < (byte) 0xA0)
// illegal surrogate codepoint?
|| (byte1 == (byte) 0xED && byte2 >= (byte) 0xA0)
// byte3 trailing-byte test
|| UnsafeUtil.getByte(bytes, offset++) > (byte) 0xBF) {
return MALFORMED;
}
} else {
// four-byte form
// Get byte2 and byte3 from saved state or array
int byte2 = (byte) ~(state >> 8);
int byte3 = 0;
if (byte2 == 0) {
byte2 = UnsafeUtil.getByte(bytes, offset++);
if (offset >= offsetLimit) {
return incompleteStateFor(byte1, byte2);
}
} else {
byte3 = (byte) (state >> 16);
}
if (byte3 == 0) {
byte3 = UnsafeUtil.getByte(bytes, offset++);
if (offset >= offsetLimit) {
return incompleteStateFor(byte1, byte2, byte3);
}
}
// If we were called with state == MALFORMED, then byte1 is 0xFF,
// which never occurs in well-formed UTF-8, and so we will return
// MALFORMED again below.
if (byte2 > (byte) 0xBF
// Check that 1 <= plane <= 16. Tricky optimized form of:
// if (byte1 > (byte) 0xF4 ||
// byte1 == (byte) 0xF0 && byte2 < (byte) 0x90 ||
// byte1 == (byte) 0xF4 && byte2 > (byte) 0x8F)
|| (((byte1 << 28) + (byte2 - (byte) 0x90)) >> 30) != 0
// byte3 trailing-byte test
|| byte3 > (byte) 0xBF
// byte4 trailing-byte test
|| UnsafeUtil.getByte(bytes, offset++) > (byte) 0xBF) {
return MALFORMED;
}
}
}
return partialIsValidUtf8(bytes, offset, (int) (offsetLimit - offset));
}
@Override
int partialIsValidUtf8Direct(
final int state, ByteBuffer buffer, final int index, final int limit) {
// Bitwise OR combines the sign bits so any negative value fails the check.
if ((index | limit | buffer.limit() - limit) < 0) {
throw new ArrayIndexOutOfBoundsException(
String.format("buffer limit=%d, index=%d, limit=%d", buffer.limit(), index, limit));
}
long address = addressOffset(buffer) + index;
final long addressLimit = address + (limit - index);
if (state != COMPLETE) {
// The previous decoding operation was incomplete (or malformed).
// We look for a well-formed sequence consisting of bytes from
// the previous decoding operation (stored in state) together
// with bytes from the array slice.
//
// We expect such "straddler characters" to be rare.
if (address >= addressLimit) { // No bytes? No progress.
return state;
}
final int byte1 = (byte) state;
// byte1 is never ASCII.
if (byte1 < (byte) 0xE0) {
// two-byte form
// Simultaneously checks for illegal trailing-byte in
// leading position and overlong 2-byte form.
if (byte1 < (byte) 0xC2
// byte2 trailing-byte test
|| UnsafeUtil.getByte(address++) > (byte) 0xBF) {
return MALFORMED;
}
} else if (byte1 < (byte) 0xF0) {
// three-byte form
// Get byte2 from saved state or array
int byte2 = (byte) ~(state >> 8);
if (byte2 == 0) {
byte2 = UnsafeUtil.getByte(address++);
if (address >= addressLimit) {
return incompleteStateFor(byte1, byte2);
}
}
if (byte2 > (byte) 0xBF
// overlong? 5 most significant bits must not all be zero
|| (byte1 == (byte) 0xE0 && byte2 < (byte) 0xA0)
// illegal surrogate codepoint?
|| (byte1 == (byte) 0xED && byte2 >= (byte) 0xA0)
// byte3 trailing-byte test
|| UnsafeUtil.getByte(address++) > (byte) 0xBF) {
return MALFORMED;
}
} else {
// four-byte form
// Get byte2 and byte3 from saved state or array
int byte2 = (byte) ~(state >> 8);
int byte3 = 0;
if (byte2 == 0) {
byte2 = UnsafeUtil.getByte(address++);
if (address >= addressLimit) {
return incompleteStateFor(byte1, byte2);
}
} else {
byte3 = (byte) (state >> 16);
}
if (byte3 == 0) {
byte3 = UnsafeUtil.getByte(address++);
if (address >= addressLimit) {
return incompleteStateFor(byte1, byte2, byte3);
}
}
// If we were called with state == MALFORMED, then byte1 is 0xFF,
// which never occurs in well-formed UTF-8, and so we will return
// MALFORMED again below.
if (byte2 > (byte) 0xBF
// Check that 1 <= plane <= 16. Tricky optimized form of:
// if (byte1 > (byte) 0xF4 ||
// byte1 == (byte) 0xF0 && byte2 < (byte) 0x90 ||
// byte1 == (byte) 0xF4 && byte2 > (byte) 0x8F)
|| (((byte1 << 28) + (byte2 - (byte) 0x90)) >> 30) != 0
// byte3 trailing-byte test
|| byte3 > (byte) 0xBF
// byte4 trailing-byte test
|| UnsafeUtil.getByte(address++) > (byte) 0xBF) {
return MALFORMED;
}
}
}
return partialIsValidUtf8(address, (int) (addressLimit - address));
}
@Override
String decodeUtf8(byte[] bytes, int index, int size) throws InvalidProtocolBufferException {
if ((index | size | bytes.length - index - size) < 0) {
throw new ArrayIndexOutOfBoundsException(
String.format("buffer length=%d, index=%d, size=%d", bytes.length, index, size));
}
int offset = index;
final int limit = offset + size;
// The longest possible resulting String is the same as the number of input bytes, when it is
// all ASCII. For other cases, this over-allocates and we will truncate in the end.
char[] resultArr = new char[size];
int resultPos = 0;
// Optimize for 100% ASCII (Hotspot loves small simple top-level loops like this).
// This simple loop stops when we encounter a byte >= 0x80 (i.e. non-ASCII).
while (offset < limit) {
byte b = UnsafeUtil.getByte(bytes, offset);
if (!DecodeUtil.isOneByte(b)) {
break;
}
offset++;
DecodeUtil.handleOneByte(b, resultArr, resultPos++);
}
while (offset < limit) {
byte byte1 = UnsafeUtil.getByte(bytes, offset++);
if (DecodeUtil.isOneByte(byte1)) {
DecodeUtil.handleOneByte(byte1, resultArr, resultPos++);
// It's common for there to be multiple ASCII characters in a run mixed in, so add an
// extra optimized loop to take care of these runs.
while (offset < limit) {
byte b = UnsafeUtil.getByte(bytes, offset);
if (!DecodeUtil.isOneByte(b)) {
break;
}
offset++;
DecodeUtil.handleOneByte(b, resultArr, resultPos++);
}
} else if (DecodeUtil.isTwoBytes(byte1)) {
if (offset >= limit) {
throw InvalidProtocolBufferException.invalidUtf8();
}
DecodeUtil.handleTwoBytes(
byte1, /* byte2 */ UnsafeUtil.getByte(bytes, offset++), resultArr, resultPos++);
} else if (DecodeUtil.isThreeBytes(byte1)) {
if (offset >= limit - 1) {
throw InvalidProtocolBufferException.invalidUtf8();
}
DecodeUtil.handleThreeBytes(
byte1,
/* byte2 */ UnsafeUtil.getByte(bytes, offset++),
/* byte3 */ UnsafeUtil.getByte(bytes, offset++),
resultArr,
resultPos++);
} else {
if (offset >= limit - 2) {
throw InvalidProtocolBufferException.invalidUtf8();
}
DecodeUtil.handleFourBytes(
byte1,
/* byte2 */ UnsafeUtil.getByte(bytes, offset++),
/* byte3 */ UnsafeUtil.getByte(bytes, offset++),
/* byte4 */ UnsafeUtil.getByte(bytes, offset++),
resultArr,
resultPos++);
// 4-byte case requires two chars.
resultPos++;
}
}
return new String(resultArr, 0, resultPos);
}
@Override
String decodeUtf8Direct(ByteBuffer buffer, int index, int size)
throws InvalidProtocolBufferException {
// Bitwise OR combines the sign bits so any negative value fails the check.
if ((index | size | buffer.limit() - index - size) < 0) {
throw new ArrayIndexOutOfBoundsException(
String.format("buffer limit=%d, index=%d, limit=%d", buffer.limit(), index, size));
}
long address = UnsafeUtil.addressOffset(buffer) + index;
final long addressLimit = address + size;
// The longest possible resulting String is the same as the number of input bytes, when it is
// all ASCII. For other cases, this over-allocates and we will truncate in the end.
char[] resultArr = new char[size];
int resultPos = 0;
// Optimize for 100% ASCII (Hotspot loves small simple top-level loops like this).
// This simple loop stops when we encounter a byte >= 0x80 (i.e. non-ASCII).
while (address < addressLimit) {
byte b = UnsafeUtil.getByte(address);
if (!DecodeUtil.isOneByte(b)) {
break;
}
address++;
DecodeUtil.handleOneByte(b, resultArr, resultPos++);
}
while (address < addressLimit) {
byte byte1 = UnsafeUtil.getByte(address++);
if (DecodeUtil.isOneByte(byte1)) {
DecodeUtil.handleOneByte(byte1, resultArr, resultPos++);
// It's common for there to be multiple ASCII characters in a run mixed in, so add an
// extra optimized loop to take care of these runs.
while (address < addressLimit) {
byte b = UnsafeUtil.getByte(address);
if (!DecodeUtil.isOneByte(b)) {
break;
}
address++;
DecodeUtil.handleOneByte(b, resultArr, resultPos++);
}
} else if (DecodeUtil.isTwoBytes(byte1)) {
if (address >= addressLimit) {
throw InvalidProtocolBufferException.invalidUtf8();
}
DecodeUtil.handleTwoBytes(
byte1, /* byte2 */ UnsafeUtil.getByte(address++), resultArr, resultPos++);
} else if (DecodeUtil.isThreeBytes(byte1)) {
if (address >= addressLimit - 1) {
throw InvalidProtocolBufferException.invalidUtf8();
}
DecodeUtil.handleThreeBytes(
byte1,
/* byte2 */ UnsafeUtil.getByte(address++),
/* byte3 */ UnsafeUtil.getByte(address++),
resultArr,
resultPos++);
} else {
if (address >= addressLimit - 2) {
throw InvalidProtocolBufferException.invalidUtf8();
}
DecodeUtil.handleFourBytes(
byte1,
/* byte2 */ UnsafeUtil.getByte(address++),
/* byte3 */ UnsafeUtil.getByte(address++),
/* byte4 */ UnsafeUtil.getByte(address++),
resultArr,
resultPos++);
// 4-byte case requires two chars.
resultPos++;
}
}
return new String(resultArr, 0, resultPos);
}
@Override
int encodeUtf8(final CharSequence in, final byte[] out, final int offset, final int length) {
long outIx = offset;
final long outLimit = outIx + length;
final int inLimit = in.length();
if (inLimit > length || out.length - length < offset) {
// Not even enough room for an ASCII-encoded string.
throw new ArrayIndexOutOfBoundsException(
"Failed writing " + in.charAt(inLimit - 1) + " at index " + (offset + length));
}
// Designed to take advantage of
// https://wiki.openjdk.java.net/display/HotSpotInternals/RangeCheckElimination
int inIx = 0;
for (char c; inIx < inLimit && (c = in.charAt(inIx)) < 0x80; ++inIx) {
UnsafeUtil.putByte(out, outIx++, (byte) c);
}
if (inIx == inLimit) {
// We're done, it was ASCII encoded.
return (int) outIx;
}
for (char c; inIx < inLimit; ++inIx) {
c = in.charAt(inIx);
if (c < 0x80 && outIx < outLimit) {
UnsafeUtil.putByte(out, outIx++, (byte) c);
} else if (c < 0x800 && outIx <= outLimit - 2L) { // 11 bits, two UTF-8 bytes
UnsafeUtil.putByte(out, outIx++, (byte) ((0xF << 6) | (c >>> 6)));
UnsafeUtil.putByte(out, outIx++, (byte) (0x80 | (0x3F & c)));
} else if ((c < MIN_SURROGATE || MAX_SURROGATE < c) && outIx <= outLimit - 3L) {
// Maximum single-char code point is 0xFFFF, 16 bits, three UTF-8 bytes
UnsafeUtil.putByte(out, outIx++, (byte) ((0xF << 5) | (c >>> 12)));
UnsafeUtil.putByte(out, outIx++, (byte) (0x80 | (0x3F & (c >>> 6))));
UnsafeUtil.putByte(out, outIx++, (byte) (0x80 | (0x3F & c)));
} else if (outIx <= outLimit - 4L) {
// Minimum code point represented by a surrogate pair is 0x10000, 17 bits, four UTF-8
// bytes
final char low;
if (inIx + 1 == inLimit || !isSurrogatePair(c, (low = in.charAt(++inIx)))) {
throw new UnpairedSurrogateException((inIx - 1), inLimit);
}
int codePoint = toCodePoint(c, low);
UnsafeUtil.putByte(out, outIx++, (byte) ((0xF << 4) | (codePoint >>> 18)));
UnsafeUtil.putByte(out, outIx++, (byte) (0x80 | (0x3F & (codePoint >>> 12))));
UnsafeUtil.putByte(out, outIx++, (byte) (0x80 | (0x3F & (codePoint >>> 6))));
UnsafeUtil.putByte(out, outIx++, (byte) (0x80 | (0x3F & codePoint)));
} else {
if ((MIN_SURROGATE <= c && c <= MAX_SURROGATE)
&& (inIx + 1 == inLimit || !isSurrogatePair(c, in.charAt(inIx + 1)))) {
// We are surrogates and we're not a surrogate pair.
throw new UnpairedSurrogateException(inIx, inLimit);
}
// Not enough space in the output buffer.
throw new ArrayIndexOutOfBoundsException("Failed writing " + c + " at index " + outIx);
}
}
// All bytes have been encoded.
return (int) outIx;
}
@Override
void encodeUtf8Direct(CharSequence in, ByteBuffer out) {
final long address = addressOffset(out);
long outIx = address + out.position();
final long outLimit = address + out.limit();
final int inLimit = in.length();
if (inLimit > outLimit - outIx) {
// Not even enough room for an ASCII-encoded string.
throw new ArrayIndexOutOfBoundsException(
"Failed writing " + in.charAt(inLimit - 1) + " at index " + out.limit());
}
// Designed to take advantage of
// https://wiki.openjdk.java.net/display/HotSpotInternals/RangeCheckElimination
int inIx = 0;
for (char c; inIx < inLimit && (c = in.charAt(inIx)) < 0x80; ++inIx) {
UnsafeUtil.putByte(outIx++, (byte) c);
}
if (inIx == inLimit) {
// We're done, it was ASCII encoded.
out.position((int) (outIx - address));
return;
}
for (char c; inIx < inLimit; ++inIx) {
c = in.charAt(inIx);
if (c < 0x80 && outIx < outLimit) {
UnsafeUtil.putByte(outIx++, (byte) c);
} else if (c < 0x800 && outIx <= outLimit - 2L) { // 11 bits, two UTF-8 bytes
UnsafeUtil.putByte(outIx++, (byte) ((0xF << 6) | (c >>> 6)));
UnsafeUtil.putByte(outIx++, (byte) (0x80 | (0x3F & c)));
} else if ((c < MIN_SURROGATE || MAX_SURROGATE < c) && outIx <= outLimit - 3L) {
// Maximum single-char code point is 0xFFFF, 16 bits, three UTF-8 bytes
UnsafeUtil.putByte(outIx++, (byte) ((0xF << 5) | (c >>> 12)));
UnsafeUtil.putByte(outIx++, (byte) (0x80 | (0x3F & (c >>> 6))));
UnsafeUtil.putByte(outIx++, (byte) (0x80 | (0x3F & c)));
} else if (outIx <= outLimit - 4L) {
// Minimum code point represented by a surrogate pair is 0x10000, 17 bits, four UTF-8
// bytes
final char low;
if (inIx + 1 == inLimit || !isSurrogatePair(c, (low = in.charAt(++inIx)))) {
throw new UnpairedSurrogateException((inIx - 1), inLimit);
}
int codePoint = toCodePoint(c, low);
UnsafeUtil.putByte(outIx++, (byte) ((0xF << 4) | (codePoint >>> 18)));
UnsafeUtil.putByte(outIx++, (byte) (0x80 | (0x3F & (codePoint >>> 12))));
UnsafeUtil.putByte(outIx++, (byte) (0x80 | (0x3F & (codePoint >>> 6))));
UnsafeUtil.putByte(outIx++, (byte) (0x80 | (0x3F & codePoint)));
} else {
if ((MIN_SURROGATE <= c && c <= MAX_SURROGATE)
&& (inIx + 1 == inLimit || !isSurrogatePair(c, in.charAt(inIx + 1)))) {
// We are surrogates and we're not a surrogate pair.
throw new UnpairedSurrogateException(inIx, inLimit);
}
// Not enough space in the output buffer.
throw new ArrayIndexOutOfBoundsException("Failed writing " + c + " at index " + outIx);
}
}
// All bytes have been encoded.
out.position((int) (outIx - address));
}
/**
* Counts (approximately) the number of consecutive ASCII characters starting from the given
* position, using the most efficient method available to the platform.
*
* @param bytes the array containing the character sequence
* @param offset the offset position of the index (same as index + arrayBaseOffset)
* @param maxChars the maximum number of characters to count
* @return the number of ASCII characters found. The stopping position will be at or before the
* first non-ASCII byte.
*/
private static int unsafeEstimateConsecutiveAscii(
byte[] bytes, long offset, final int maxChars) {
if (maxChars < UNSAFE_COUNT_ASCII_THRESHOLD) {
// Don't bother with small strings.
return 0;
}
for (int i = 0; i < maxChars; i++) {
if (UnsafeUtil.getByte(bytes, offset++) < 0) {
return i;
}
}
return maxChars;
}
/**
* Same as {@link Utf8#estimateConsecutiveAscii(ByteBuffer, int, int)} except that it uses the
* most efficient method available to the platform.
*/
private static int unsafeEstimateConsecutiveAscii(long address, final int maxChars) {
int remaining = maxChars;
if (remaining < UNSAFE_COUNT_ASCII_THRESHOLD) {
// Don't bother with small strings.
return 0;
}
// Read bytes until 8-byte aligned so that we can read longs in the loop below.
// We do this by ANDing the address with 7 to determine the number of bytes that need to
// be read before we're 8-byte aligned.
final int unaligned = 8 - ((int) address & 7);
for (int j = unaligned; j > 0; j--) {
if (UnsafeUtil.getByte(address++) < 0) {
return unaligned - j;
}
}
// This simple loop stops when we encounter a byte >= 0x80 (i.e. non-ASCII).
// To speed things up further, we're reading longs instead of bytes so we use a mask to
// determine if any byte in the current long is non-ASCII.
remaining -= unaligned;
for (;
remaining >= 8 && (UnsafeUtil.getLong(address) & ASCII_MASK_LONG) == 0;
address += 8, remaining -= 8) {}
return maxChars - remaining;
}
private static int partialIsValidUtf8(final byte[] bytes, long offset, int remaining) {
// Skip past ASCII characters as quickly as possible.
final int skipped = unsafeEstimateConsecutiveAscii(bytes, offset, remaining);
remaining -= skipped;
offset += skipped;
for (; ; ) {
// Optimize for interior runs of ASCII bytes.
// TODO(nathanmittler): Consider checking 8 bytes at a time after some threshold?
// Maybe after seeing a few in a row that are ASCII, go back to fast mode?
int byte1 = 0;
for (; remaining > 0 && (byte1 = UnsafeUtil.getByte(bytes, offset++)) >= 0; --remaining) {}
if (remaining == 0) {
return COMPLETE;
}
remaining--;
// If we're here byte1 is not ASCII. Only need to handle 2-4 byte forms.
if (byte1 < (byte) 0xE0) {
// Two-byte form (110xxxxx 10xxxxxx)
if (remaining == 0) {
// Incomplete sequence
return byte1;
}
remaining--;
// Simultaneously checks for illegal trailing-byte in
// leading position and overlong 2-byte form.
if (byte1 < (byte) 0xC2 || UnsafeUtil.getByte(bytes, offset++) > (byte) 0xBF) {
return MALFORMED;
}
} else if (byte1 < (byte) 0xF0) {
// Three-byte form (1110xxxx 10xxxxxx 10xxxxxx)
if (remaining < 2) {
// Incomplete sequence
return unsafeIncompleteStateFor(bytes, byte1, offset, remaining);
}
remaining -= 2;
final int byte2;
if ((byte2 = UnsafeUtil.getByte(bytes, offset++)) > (byte) 0xBF
// overlong? 5 most significant bits must not all be zero
|| (byte1 == (byte) 0xE0 && byte2 < (byte) 0xA0)
// check for illegal surrogate codepoints
|| (byte1 == (byte) 0xED && byte2 >= (byte) 0xA0)
// byte3 trailing-byte test
|| UnsafeUtil.getByte(bytes, offset++) > (byte) 0xBF) {
return MALFORMED;
}
} else {
// Four-byte form (1110xxxx 10xxxxxx 10xxxxxx 10xxxxxx)
if (remaining < 3) {
// Incomplete sequence
return unsafeIncompleteStateFor(bytes, byte1, offset, remaining);
}
remaining -= 3;
final int byte2;
if ((byte2 = UnsafeUtil.getByte(bytes, offset++)) > (byte) 0xBF
// Check that 1 <= plane <= 16. Tricky optimized form of:
// if (byte1 > (byte) 0xF4 ||
// byte1 == (byte) 0xF0 && byte2 < (byte) 0x90 ||
// byte1 == (byte) 0xF4 && byte2 > (byte) 0x8F)
|| (((byte1 << 28) + (byte2 - (byte) 0x90)) >> 30) != 0
// byte3 trailing-byte test
|| UnsafeUtil.getByte(bytes, offset++) > (byte) 0xBF
// byte4 trailing-byte test
|| UnsafeUtil.getByte(bytes, offset++) > (byte) 0xBF) {
return MALFORMED;
}
}
}
}
private static int partialIsValidUtf8(long address, int remaining) {
// Skip past ASCII characters as quickly as possible.
final int skipped = unsafeEstimateConsecutiveAscii(address, remaining);
address += skipped;
remaining -= skipped;
for (; ; ) {
// Optimize for interior runs of ASCII bytes.
// TODO(nathanmittler): Consider checking 8 bytes at a time after some threshold?
// Maybe after seeing a few in a row that are ASCII, go back to fast mode?
int byte1 = 0;
for (; remaining > 0 && (byte1 = UnsafeUtil.getByte(address++)) >= 0; --remaining) {}
if (remaining == 0) {
return COMPLETE;
}
remaining--;
if (byte1 < (byte) 0xE0) {
// Two-byte form
if (remaining == 0) {
// Incomplete sequence
return byte1;
}
remaining--;
// Simultaneously checks for illegal trailing-byte in
// leading position and overlong 2-byte form.
if (byte1 < (byte) 0xC2 || UnsafeUtil.getByte(address++) > (byte) 0xBF) {
return MALFORMED;
}
} else if (byte1 < (byte) 0xF0) {
// Three-byte form
if (remaining < 2) {
// Incomplete sequence
return unsafeIncompleteStateFor(address, byte1, remaining);
}
remaining -= 2;
final byte byte2 = UnsafeUtil.getByte(address++);
if (byte2 > (byte) 0xBF
// overlong? 5 most significant bits must not all be zero
|| (byte1 == (byte) 0xE0 && byte2 < (byte) 0xA0)
// check for illegal surrogate codepoints
|| (byte1 == (byte) 0xED && byte2 >= (byte) 0xA0)
// byte3 trailing-byte test
|| UnsafeUtil.getByte(address++) > (byte) 0xBF) {
return MALFORMED;
}
} else {
// Four-byte form
if (remaining < 3) {
// Incomplete sequence
return unsafeIncompleteStateFor(address, byte1, remaining);
}
remaining -= 3;
final byte byte2 = UnsafeUtil.getByte(address++);
if (byte2 > (byte) 0xBF
// Check that 1 <= plane <= 16. Tricky optimized form of:
// if (byte1 > (byte) 0xF4 ||
// byte1 == (byte) 0xF0 && byte2 < (byte) 0x90 ||
// byte1 == (byte) 0xF4 && byte2 > (byte) 0x8F)
|| (((byte1 << 28) + (byte2 - (byte) 0x90)) >> 30) != 0
// byte3 trailing-byte test
|| UnsafeUtil.getByte(address++) > (byte) 0xBF
// byte4 trailing-byte test
|| UnsafeUtil.getByte(address++) > (byte) 0xBF) {
return MALFORMED;
}
}
}
}
private static int unsafeIncompleteStateFor(
byte[] bytes, int byte1, long offset, int remaining) {
switch (remaining) {
case 0:
return incompleteStateFor(byte1);
case 1:
return incompleteStateFor(byte1, UnsafeUtil.getByte(bytes, offset));
case 2:
return incompleteStateFor(
byte1, UnsafeUtil.getByte(bytes, offset), UnsafeUtil.getByte(bytes, offset + 1));
default:
throw new AssertionError();
}
}
private static int unsafeIncompleteStateFor(long address, final int byte1, int remaining) {
switch (remaining) {
case 0:
return incompleteStateFor(byte1);
case 1:
return incompleteStateFor(byte1, UnsafeUtil.getByte(address));
case 2:
return incompleteStateFor(
byte1, UnsafeUtil.getByte(address), UnsafeUtil.getByte(address + 1));
default:
throw new AssertionError();
}
}
}
/**
* Utility methods for decoding bytes into {@link String}. Callers are responsible for extracting
* bytes (possibly using Unsafe methods), and checking remaining bytes. All other UTF-8 validity
* checks and codepoint conversion happen in this class.
*/
private static class DecodeUtil {
/** Returns whether this is a single-byte codepoint (i.e., ASCII) with the form '0XXXXXXX'. */
private static boolean isOneByte(byte b) {
return b >= 0;
}
/** Returns whether this is a two-byte codepoint with the form '10XXXXXX'. */
private static boolean isTwoBytes(byte b) {
return b < (byte) 0xE0;
}
/** Returns whether this is a three-byte codepoint with the form '110XXXXX'. */
private static boolean isThreeBytes(byte b) {
return b < (byte) 0xF0;
}
private static void handleOneByte(byte byte1, char[] resultArr, int resultPos) {
resultArr[resultPos] = (char) byte1;
}
private static void handleTwoBytes(byte byte1, byte byte2, char[] resultArr, int resultPos)
throws InvalidProtocolBufferException {
// Simultaneously checks for illegal trailing-byte in leading position (<= '11000000') and
// overlong 2-byte, '11000001'.
if (byte1 < (byte) 0xC2 || isNotTrailingByte(byte2)) {
throw InvalidProtocolBufferException.invalidUtf8();
}
resultArr[resultPos] = (char) (((byte1 & 0x1F) << 6) | trailingByteValue(byte2));
}
private static void handleThreeBytes(
byte byte1, byte byte2, byte byte3, char[] resultArr, int resultPos)
throws InvalidProtocolBufferException {
if (isNotTrailingByte(byte2)
// overlong? 5 most significant bits must not all be zero
|| (byte1 == (byte) 0xE0 && byte2 < (byte) 0xA0)
// check for illegal surrogate codepoints
|| (byte1 == (byte) 0xED && byte2 >= (byte) 0xA0)
|| isNotTrailingByte(byte3)) {
throw InvalidProtocolBufferException.invalidUtf8();
}
resultArr[resultPos] =
(char)
(((byte1 & 0x0F) << 12) | (trailingByteValue(byte2) << 6) | trailingByteValue(byte3));
}
private static void handleFourBytes(
byte byte1, byte byte2, byte byte3, byte byte4, char[] resultArr, int resultPos)
throws InvalidProtocolBufferException {
if (isNotTrailingByte(byte2)
// Check that 1 <= plane <= 16. Tricky optimized form of:
// valid 4-byte leading byte?
// if (byte1 > (byte) 0xF4 ||
// overlong? 4 most significant bits must not all be zero
// byte1 == (byte) 0xF0 && byte2 < (byte) 0x90 ||
// codepoint larger than the highest code point (U+10FFFF)?
// byte1 == (byte) 0xF4 && byte2 > (byte) 0x8F)
|| (((byte1 << 28) + (byte2 - (byte) 0x90)) >> 30) != 0
|| isNotTrailingByte(byte3)
|| isNotTrailingByte(byte4)) {
throw InvalidProtocolBufferException.invalidUtf8();
}
int codepoint =
((byte1 & 0x07) << 18)
| (trailingByteValue(byte2) << 12)
| (trailingByteValue(byte3) << 6)
| trailingByteValue(byte4);
resultArr[resultPos] = DecodeUtil.highSurrogate(codepoint);
resultArr[resultPos + 1] = DecodeUtil.lowSurrogate(codepoint);
}
/** Returns whether the byte is not a valid continuation of the form '10XXXXXX'. */
private static boolean isNotTrailingByte(byte b) {
return b > (byte) 0xBF;
}
/** Returns the actual value of the trailing byte (removes the prefix '10') for composition. */
private static int trailingByteValue(byte b) {
return b & 0x3F;
}
private static char highSurrogate(int codePoint) {
return (char)
((MIN_HIGH_SURROGATE - (MIN_SUPPLEMENTARY_CODE_POINT >>> 10)) + (codePoint >>> 10));
}
private static char lowSurrogate(int codePoint) {
return (char) (MIN_LOW_SURROGATE + (codePoint & 0x3ff));
}
}
private Utf8() {}
}