1 // Protocol Buffers - Google's data interchange format 2 // Copyright 2008 Google Inc. All rights reserved. 3 // http://code.google.com/p/protobuf/ 4 // 5 // Redistribution and use in source and binary forms, with or without 6 // modification, are permitted provided that the following conditions are 7 // met: 8 // 9 // * Redistributions of source code must retain the above copyright 10 // notice, this list of conditions and the following disclaimer. 11 // * Redistributions in binary form must reproduce the above 12 // copyright notice, this list of conditions and the following disclaimer 13 // in the documentation and/or other materials provided with the 14 // distribution. 15 // * Neither the name of Google Inc. nor the names of its 16 // contributors may be used to endorse or promote products derived from 17 // this software without specific prior written permission. 18 // 19 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 31 package com.google.protobuf; 32 33 import java.io.UnsupportedEncodingException; 34 35 /** 36 * The classes contained within are used internally by the Protocol Buffer 37 * library and generated message implementations. They are public only because 38 * those generated messages do not reside in the {@code protobuf} package. 39 * Others should not use this class directly. 40 * 41 * @author kenton@google.com (Kenton Varda) 42 */ 43 public class Internal { 44 /** 45 * Helper called by generated code to construct default values for string 46 * fields. 47 * <p> 48 * The protocol compiler does not actually contain a UTF-8 decoder -- it 49 * just pushes UTF-8-encoded text around without touching it. The one place 50 * where this presents a problem is when generating Java string literals. 51 * Unicode characters in the string literal would normally need to be encoded 52 * using a Unicode escape sequence, which would require decoding them. 53 * To get around this, protoc instead embeds the UTF-8 bytes into the 54 * generated code and leaves it to the runtime library to decode them. 55 * <p> 56 * It gets worse, though. If protoc just generated a byte array, like: 57 * new byte[] {0x12, 0x34, 0x56, 0x78} 58 * Java actually generates *code* which allocates an array and then fills 59 * in each value. This is much less efficient than just embedding the bytes 60 * directly into the bytecode. To get around this, we need another 61 * work-around. String literals are embedded directly, so protoc actually 62 * generates a string literal corresponding to the bytes. The easiest way 63 * to do this is to use the ISO-8859-1 character set, which corresponds to 64 * the first 256 characters of the Unicode range. Protoc can then use 65 * good old CEscape to generate the string. 66 * <p> 67 * So we have a string literal which represents a set of bytes which 68 * represents another string. This function -- stringDefaultValue -- 69 * converts from the generated string to the string we actually want. The 70 * generated code calls this automatically. 71 */ stringDefaultValue(String bytes)72 public static String stringDefaultValue(String bytes) { 73 try { 74 return new String(bytes.getBytes("ISO-8859-1"), "UTF-8"); 75 } catch (UnsupportedEncodingException e) { 76 // This should never happen since all JVMs are required to implement 77 // both of the above character sets. 78 throw new IllegalStateException( 79 "Java VM does not support a standard character set.", e); 80 } 81 } 82 83 /** 84 * Helper called by generated code to construct default values for bytes 85 * fields. 86 * <p> 87 * This is a lot like {@link #stringDefaultValue}, but for bytes fields. 88 * In this case we only need the second of the two hacks -- allowing us to 89 * embed raw bytes as a string literal with ISO-8859-1 encoding. 90 */ bytesDefaultValue(String bytes)91 public static ByteString bytesDefaultValue(String bytes) { 92 try { 93 return ByteString.copyFrom(bytes.getBytes("ISO-8859-1")); 94 } catch (UnsupportedEncodingException e) { 95 // This should never happen since all JVMs are required to implement 96 // ISO-8859-1. 97 throw new IllegalStateException( 98 "Java VM does not support a standard character set.", e); 99 } 100 } 101 102 /** 103 * Interface for an enum value or value descriptor, to be used in FieldSet. 104 * The lite library stores enum values directly in FieldSets but the full 105 * library stores EnumValueDescriptors in order to better support reflection. 106 */ 107 public interface EnumLite { getNumber()108 int getNumber(); 109 } 110 111 /** 112 * Interface for an object which maps integers to {@link EnumLite}s. 113 * {@link Descriptors.EnumDescriptor} implements this interface by mapping 114 * numbers to {@link Descriptors.EnumValueDescriptor}s. Additionally, 115 * every generated enum type has a static method internalGetValueMap() which 116 * returns an implementation of this type that maps numbers to enum values. 117 */ 118 public interface EnumLiteMap<T extends EnumLite> { findValueByNumber(int number)119 T findValueByNumber(int number); 120 } 121 } 122