diff options
author | 2018-01-02 18:29:58 -0800 | |
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committer | 2018-01-02 18:32:07 -0800 | |
commit | 6ad05df111478e412ea760b60039224d0497228b (patch) | |
tree | f9f126675811f987743538056cf0519221d805a1 /src/main/java/com/google/devtools/build/lib/skyframe/serialization/autocodec/UnsafeProvider.java | |
parent | 5a0857e54f96ab6cf763902e27ba79bc203d38d3 (diff) |
@AutoCodec: Uses sun.misc.Unsafe to retrieve fields for serialization.
This is fast (profiles indicate a 9% penalty vs getters) and does not require getters.
* Also adds a Marshaller for java.util.regex.Pattern.
* Minor fixes for codecs that were broken by this change.
PiperOrigin-RevId: 180619680
Diffstat (limited to 'src/main/java/com/google/devtools/build/lib/skyframe/serialization/autocodec/UnsafeProvider.java')
-rw-r--r-- | src/main/java/com/google/devtools/build/lib/skyframe/serialization/autocodec/UnsafeProvider.java | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/serialization/autocodec/UnsafeProvider.java b/src/main/java/com/google/devtools/build/lib/skyframe/serialization/autocodec/UnsafeProvider.java new file mode 100644 index 0000000000..4a1fe6c389 --- /dev/null +++ b/src/main/java/com/google/devtools/build/lib/skyframe/serialization/autocodec/UnsafeProvider.java @@ -0,0 +1,67 @@ +// Copyright 2017 The Bazel Authors. 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. + +package com.google.devtools.build.lib.skyframe.serialization.autocodec; + +import java.lang.reflect.Field; +import java.security.AccessController; +import java.security.PrivilegedActionException; +import java.security.PrivilegedExceptionAction; +import sun.misc.Unsafe; + +/** + * An accessor for Unsafe. + * + * <p>Not for general consumption. Public only so that generated codecs in different packages can + * access this. + */ +public class UnsafeProvider { + private static final Unsafe UNSAFE = getUnsafe(); + + public static Unsafe getInstance() { + return UNSAFE; + } + + /** + * Gets a reference to {@link sun.misc.Unsafe} throwing an {@link AssertionError} on failure. + * + * <p>Failure is highly unlikely, but possible if the underlying VM stores unsafe in an unexpected + * location. + */ + private static Unsafe getUnsafe() { + try { + // sun.misc.Unsafe is intentionally difficult to get a hold of - it gives us the power to + // do things like access raw memory and segfault the JVM. + return AccessController.doPrivileged( + new PrivilegedExceptionAction<Unsafe>() { + @Override + public Unsafe run() throws Exception { + Class<Unsafe> unsafeClass = Unsafe.class; + // Unsafe usually exists in the field 'theUnsafe', however check all fields + // in case it's somewhere else in this VM's version of Unsafe. + for (Field f : unsafeClass.getDeclaredFields()) { + f.setAccessible(true); + Object fieldValue = f.get(null); + if (unsafeClass.isInstance(fieldValue)) { + return unsafeClass.cast(fieldValue); + } + } + throw new AssertionError("Failed to find sun.misc.Unsafe instance"); + } + }); + } catch (PrivilegedActionException pae) { + throw new AssertionError("Unable to get sun.misc.Unsafe", pae); + } + } +} |