// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// http://code.google.com/p/protobuf/
//
// 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
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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package com.google.protobuf;
import java.io.UnsupportedEncodingException;
/**
* The classes contained within are used internally by the Protocol Buffer
* library and generated message implementations. They are public only because
* those generated messages do not reside in the {@code protobuf} package.
* Others should not use this class directly.
*
* @author kenton@google.com (Kenton Varda)
*/
public class Internal {
/**
* Helper called by generated code to construct default values for string
* fields.
* <p>
* The protocol compiler does not actually contain a UTF-8 decoder -- it
* just pushes UTF-8-encoded text around without touching it. The one place
* where this presents a problem is when generating Java string literals.
* Unicode characters in the string literal would normally need to be encoded
* using a Unicode escape sequence, which would require decoding them.
* To get around this, protoc instead embeds the UTF-8 bytes into the
* generated code and leaves it to the runtime library to decode them.
* <p>
* It gets worse, though. If protoc just generated a byte array, like:
* new byte[] {0x12, 0x34, 0x56, 0x78}
* Java actually generates *code* which allocates an array and then fills
* in each value. This is much less efficient than just embedding the bytes
* directly into the bytecode. To get around this, we need another
* work-around. String literals are embedded directly, so protoc actually
* generates a string literal corresponding to the bytes. The easiest way
* to do this is to use the ISO-8859-1 character set, which corresponds to
* the first 256 characters of the Unicode range. Protoc can then use
* good old CEscape to generate the string.
* <p>
* So we have a string literal which represents a set of bytes which
* represents another string. This function -- stringDefaultValue --
* converts from the generated string to the string we actually want. The
* generated code calls this automatically.
*/
public static String stringDefaultValue(String bytes) {
try {
return new String(bytes.getBytes("ISO-8859-1"), "UTF-8");
} catch (UnsupportedEncodingException e) {
// This should never happen since all JVMs are required to implement
// both of the above character sets.
throw new IllegalStateException(
"Java VM does not support a standard character set.", e);
}
}
/**
* Helper called by generated code to construct default values for bytes
* fields.
* <p>
* This is a lot like {@link #stringDefaultValue}, but for bytes fields.
* In this case we only need the second of the two hacks -- allowing us to
* embed raw bytes as a string literal with ISO-8859-1 encoding.
*/
public static ByteString bytesDefaultValue(String bytes) {
try {
return ByteString.copyFrom(bytes.getBytes("ISO-8859-1"));
} catch (UnsupportedEncodingException e) {
// This should never happen since all JVMs are required to implement
// ISO-8859-1.
throw new IllegalStateException(
"Java VM does not support a standard character set.", e);
}
}
/**
* Helper called by generated code to determine if a byte array is a valid
* UTF-8 encoded string such that the original bytes can be converted to
* a String object and then back to a byte array round tripping the bytes
* without loss. More precisely, returns {@code true} whenever:
* <pre> {@code
* Arrays.equals(byteString.toByteArray(),
* new String(byteString.toByteArray(), "UTF-8").getBytes("UTF-8"))
* }</pre>
*
* <p>This method rejects "overlong" byte sequences, as well as
* 3-byte sequences that would map to a surrogate character, in
* accordance with the restricted definition of UTF-8 introduced in
* Unicode 3.1. Note that the UTF-8 decoder included in Oracle's
* JDK has been modified to also reject "overlong" byte sequences,
* but currently (2011) still accepts 3-byte surrogate character
* byte sequences.
*
* <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>As of 2011-02, this method simply returns the result of {@link
* ByteString#isValidUtf8()}. Calling that method directly is preferred.
*
* @param byteString the string to check
* @return whether the byte array is round trippable
*/
public static boolean isValidUtf8(ByteString byteString) {
return byteString.isValidUtf8();
}
/**
* Interface for an enum value or value descriptor, to be used in FieldSet.
* The lite library stores enum values directly in FieldSets but the full
* library stores EnumValueDescriptors in order to better support reflection.
*/
public interface EnumLite {
int getNumber();
}
/**
* Interface for an object which maps integers to {@link EnumLite}s.
* {@link Descriptors.EnumDescriptor} implements this interface by mapping
* numbers to {@link Descriptors.EnumValueDescriptor}s. Additionally,
* every generated enum type has a static method internalGetValueMap() which
* returns an implementation of this type that maps numbers to enum values.
*/
public interface EnumLiteMap<T extends EnumLite> {
T findValueByNumber(int number);
}
}
