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Java: Pulling in protobuf's faster UTF-8 encoder. (google#5035)
* Pulling in protobuf's faster UTF-8 encoder. * Remove Utf8 unsafe code.
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| /* | ||
| * Copyright 2014 Google Inc. All rights reserved. | ||
| * | ||
| * 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. | ||
| */ | ||
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| package com.google.flatbuffers; | ||
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| import java.nio.ByteBuffer; | ||
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| 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; | ||
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| public abstract class Utf8 { | ||
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| /** | ||
| * 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 abstract int encodedLength(CharSequence sequence); | ||
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| /** | ||
| * 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. | ||
| */ | ||
| public abstract void encodeUtf8(CharSequence in, ByteBuffer out); | ||
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| /** | ||
| * Decodes the given UTF-8 portion of the {@link ByteBuffer} into a {@link String}. | ||
| * | ||
| * @throws IllegalArgumentException if the input is not valid UTF-8. | ||
| */ | ||
| public abstract String decodeUtf8(ByteBuffer buffer, int offset, int length); | ||
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| private static Utf8 DEFAULT; | ||
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| /** | ||
| * Get the default UTF-8 processor. | ||
| * @return the default processor | ||
| */ | ||
| public static Utf8 getDefault() { | ||
| if (DEFAULT == null) { | ||
| DEFAULT = new Utf8Safe(); | ||
| } | ||
| return DEFAULT; | ||
| } | ||
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| /** | ||
| * Set the default instance of the UTF-8 processor. | ||
| * @param instance the new instance to use | ||
| */ | ||
| public static void setDefault(Utf8 instance) { | ||
| DEFAULT = instance; | ||
| } | ||
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| /** | ||
| * 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. | ||
| */ | ||
| static class DecodeUtil { | ||
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| /** | ||
| * Returns whether this is a single-byte codepoint (i.e., ASCII) with the form '0XXXXXXX'. | ||
| */ | ||
| static boolean isOneByte(byte b) { | ||
| return b >= 0; | ||
| } | ||
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| /** | ||
| * Returns whether this is a two-byte codepoint with the form '10XXXXXX'. | ||
| */ | ||
| static boolean isTwoBytes(byte b) { | ||
| return b < (byte) 0xE0; | ||
| } | ||
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| /** | ||
| * Returns whether this is a three-byte codepoint with the form '110XXXXX'. | ||
| */ | ||
| static boolean isThreeBytes(byte b) { | ||
| return b < (byte) 0xF0; | ||
| } | ||
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| static void handleOneByte(byte byte1, char[] resultArr, int resultPos) { | ||
| resultArr[resultPos] = (char) byte1; | ||
| } | ||
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| static void handleTwoBytes( | ||
| byte byte1, byte byte2, char[] resultArr, int resultPos) | ||
| throws IllegalArgumentException { | ||
| // Simultaneously checks for illegal trailing-byte in leading position (<= '11000000') and | ||
| // overlong 2-byte, '11000001'. | ||
| if (byte1 < (byte) 0xC2 | ||
| || isNotTrailingByte(byte2)) { | ||
| throw new IllegalArgumentException("Invalid UTF-8"); | ||
| } | ||
| resultArr[resultPos] = (char) (((byte1 & 0x1F) << 6) | trailingByteValue(byte2)); | ||
| } | ||
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| static void handleThreeBytes( | ||
| byte byte1, byte byte2, byte byte3, char[] resultArr, int resultPos) | ||
| throws IllegalArgumentException { | ||
| 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 new IllegalArgumentException("Invalid UTF-8"); | ||
| } | ||
| resultArr[resultPos] = (char) | ||
| (((byte1 & 0x0F) << 12) | (trailingByteValue(byte2) << 6) | trailingByteValue(byte3)); | ||
| } | ||
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| static void handleFourBytes( | ||
| byte byte1, byte byte2, byte byte3, byte byte4, char[] resultArr, int resultPos) | ||
| throws IllegalArgumentException{ | ||
| 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 new IllegalArgumentException("Invalid UTF-8"); | ||
| } | ||
| int codepoint = ((byte1 & 0x07) << 18) | ||
| | (trailingByteValue(byte2) << 12) | ||
| | (trailingByteValue(byte3) << 6) | ||
| | trailingByteValue(byte4); | ||
| resultArr[resultPos] = DecodeUtil.highSurrogate(codepoint); | ||
| resultArr[resultPos + 1] = DecodeUtil.lowSurrogate(codepoint); | ||
| } | ||
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| /** | ||
| * Returns whether the byte is not a valid continuation of the form '10XXXXXX'. | ||
| */ | ||
| private static boolean isNotTrailingByte(byte b) { | ||
| return b > (byte) 0xBF; | ||
| } | ||
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| /** | ||
| * Returns the actual value of the trailing byte (removes the prefix '10') for composition. | ||
| */ | ||
| private static int trailingByteValue(byte b) { | ||
| return b & 0x3F; | ||
| } | ||
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| private static char highSurrogate(int codePoint) { | ||
| return (char) ((MIN_HIGH_SURROGATE - (MIN_SUPPLEMENTARY_CODE_POINT >>> 10)) | ||
| + (codePoint >>> 10)); | ||
| } | ||
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| private static char lowSurrogate(int codePoint) { | ||
| return (char) (MIN_LOW_SURROGATE + (codePoint & 0x3ff)); | ||
| } | ||
| } | ||
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| // These UTF-8 handling methods are copied from Guava's Utf8Unsafe 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); | ||
| } | ||
| } | ||
| } |
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