Package com.google.protobuf

Class UnsafeByteOperations

java.lang.Object
com.google.protobuf.UnsafeByteOperations
public final class UnsafeByteOperations extends Object
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 ByteString to the application.

DISCLAIMER: The methods in this class should only be called if it is guaranteed that the buffer backing the ByteString will never change! Mutation of a 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!

  • Method Details

    • unsafeWrap

      public static ByteString unsafeWrap(byte[] buffer)
      An unsafe operation that returns a ByteString that is backed by the provided buffer.
      Parameters:
      buffer - the buffer to be wrapped
      Returns:
      a ByteString backed by the provided buffer

    • unsafeWrap

      public static ByteString unsafeWrap(byte[] buffer, int offset, int length)
      An unsafe operation that returns a ByteString that is backed by a subregion of the provided buffer.
      Parameters:
      buffer - the buffer to be wrapped
      offset - the offset of the wrapped region
      length - the number of bytes of the wrapped region
      Returns:
      a ByteString backed by the provided buffer

    • unsafeWrap

      public static ByteString unsafeWrap(ByteBuffer buffer)
      An unsafe operation that returns a ByteString that is backed by the provided buffer.
      Parameters:
      buffer - the Java NIO buffer to be wrapped
      Returns:
      a ByteString backed by the provided buffer

    • unsafeWriteTo

      public static void unsafeWriteTo(ByteString bytes, ByteOutput output) throws IOException
      Writes the given ByteString to the provided ByteOutput. Calling this method may result in multiple operations on the target ByteOutput (i.e. for roped ByteStrings).

      This method exposes the internal backing buffer(s) of the ByteString to the ByteOutput in order to avoid additional copying overhead. It would be possible for a malicious ByteOutput to corrupt the ByteString. Use with caution!

      NOTE: The ByteOutput MUST NOT modify the provided buffers. Doing so may result in corrupted data, which would be difficult to debug.

      Parameters:
      bytes - the ByteString to be written
      output - the output to receive the bytes
      Throws:
      IOException - if an I/O error occurs