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// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd
package com.google.protobuf;
import java.io.IOException;
import java.nio.ByteBuffer;
/**
* Provides a number of unsafe byte operations to be used by advanced applications with high
* performance requirements. These methods are referred to as "unsafe" because they potentially
* expose the backing buffer of a {@link ByteString} to the application.
*
* DISCLAIMER: The methods in this class should only be called if it is
* guaranteed that the buffer backing the {@link ByteString} will never change! Mutation of a {@link
* ByteString} can lead to unexpected and undesirable consequences in your application, and will
* likely be difficult to debug. Proceed with caution!
*
*
This can have a number of significant side effects that have spooky-action-at-a-distance-like
* behavior. In particular, if the bytes value changes out from under a Protocol Buffer:
*
*
* - serialization may throw
*
- serialization may succeed but the wrong bytes may be written out
*
- messages are no longer threadsafe
*
- hashCode may be incorrect
*
* - can result in a permanent memory leak when used as a key in a long-lived HashMap
*
- the semantics of many programs may be violated if this is the case
*
*
*
* Each of these issues will occur in parts of the code base that are entirely distinct from the
* parts of the code base modifying the buffer. In fact, both parts of the code base may be correct
* - it is the bridging with the unsafe operations that was in error!
*/
public final class UnsafeByteOperations {
private UnsafeByteOperations() {}
/**
* An unsafe operation that returns a {@link ByteString} that is backed by the provided buffer.
*
* @param buffer the buffer to be wrapped
* @return a {@link ByteString} backed by the provided buffer
*/
public static ByteString unsafeWrap(byte[] buffer) {
return ByteString.wrap(buffer);
}
/**
* An unsafe operation that returns a {@link ByteString} that is backed by a subregion of the
* provided buffer.
*
* @param buffer the buffer to be wrapped
* @param offset the offset of the wrapped region
* @param length the number of bytes of the wrapped region
* @return a {@link ByteString} backed by the provided buffer
*/
public static ByteString unsafeWrap(byte[] buffer, int offset, int length) {
return ByteString.wrap(buffer, offset, length);
}
/**
* An unsafe operation that returns a {@link ByteString} that is backed by the provided buffer.
*
* @param buffer the Java NIO buffer to be wrapped
* @return a {@link ByteString} backed by the provided buffer
*/
public static ByteString unsafeWrap(ByteBuffer buffer) {
return ByteString.wrap(buffer);
}
/**
* Writes the given {@link ByteString} to the provided {@link ByteOutput}. Calling this method may
* result in multiple operations on the target {@link ByteOutput} (i.e. for roped {@link
* ByteString}s).
*
* This method exposes the internal backing buffer(s) of the {@link ByteString} to the {@link
* ByteOutput} in order to avoid additional copying overhead. It would be possible for a malicious
* {@link ByteOutput} to corrupt the {@link ByteString}. Use with caution!
*
*
NOTE: The {@link ByteOutput} MUST NOT modify the provided buffers. Doing so
* may result in corrupted data, which would be difficult to debug.
*
* @param bytes the {@link ByteString} to be written
* @param output the output to receive the bytes
* @throws IOException if an I/O error occurs
*/
public static void unsafeWriteTo(ByteString bytes, ByteOutput output) throws IOException {
bytes.writeTo(output);
}
}