Add serialization/deserialization of structs for mojo java bindings.

mojo/bindings/java/src/org/chromium/mojo/bindings/Decoder.java

Index: mojo/bindings/java/src/org/chromium/mojo/bindings/Decoder.java
diff --git a/mojo/bindings/java/src/org/chromium/mojo/bindings/Decoder.java b/mojo/bindings/java/src/org/chromium/mojo/bindings/Decoder.java
new file mode 100644
index 0000000000000000000000000000000000000000..86a038fc503fab3261a4f038c043686ef3fbeebb
--- /dev/null
+++ b/mojo/bindings/java/src/org/chromium/mojo/bindings/Decoder.java
@@ -0,0 +1,486 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.mojo.bindings;
+
+import org.chromium.mojo.bindings.Struct.DataHeader;
+import org.chromium.mojo.system.DataPipe;
+import org.chromium.mojo.system.Handle;
+import org.chromium.mojo.system.InvalidHandle;
+import org.chromium.mojo.system.MessagePipeHandle;
+import org.chromium.mojo.system.SharedBufferHandle;
+
+import java.nio.ByteOrder;
+import java.nio.charset.Charset;
+
+/**
+ * A Decoder is a helper class for deserializing a mojo struct. It enables deserialization of basic
+ * types from a {@link Message} object at a given offset into it's byte buffer.
+ */
+public class Decoder {
+
+    /**
+     * Helper class to validate the decoded message.
+     */
+    static final class Validator {
+
+        /**
+         * Minimal value for the next handle to deserialize.
+         */
+        private int mMinNextClaimedHandle = 0;
+        /**
+         * Minimal value of the start of the next memory to claim.
+         */
+        private long mMinNextMemory = 0;
+
+        /**
+         * The maximal memory accessible.
+         */
+        private final long mMaxMemory;
+
+        /**
+         * Constructor.
+         */
+        Validator(long maxMemory) {
+            mMaxMemory = maxMemory;
+        }
+
+        public void claimHandle(int handle) {
+            if (handle < mMinNextClaimedHandle) {
+                throw new DeserializationException(
+                        "Trying to access handle out of order.");
+            }
+            mMinNextClaimedHandle = handle + 1;
+        }
+
+        public void claimMemory(long start, long end) {
+            if (start < mMinNextMemory) {
+                throw new DeserializationException("Trying to access memory out of order.");
+            }
+            if (end < start) {
+                throw new DeserializationException("Incorrect memory range.");
+            }
+            if (end > mMaxMemory) {
+                throw new DeserializationException("Trying to access out of range memory.");
+            }
+            if (start % BindingsHelper.ALIGNMENT != 0 || end % BindingsHelper.ALIGNMENT != 0) {
+                throw new DeserializationException("Incorrect alignment.");
+            }
+            mMinNextMemory = end;
+        }
+    }
+
+    /**
+     * The message to deserialize from.
+     */
+    private final Message mMessage;
+
+    /**
+     * The base offset in the byte buffer.
+     */
+    private final int mBaseOffset;
+
+    /**
+     * Validator for the decoded message.
+     */
+    private final Validator mValidator;
+
+    /**
+     * Constructor.
+     *
+     * @param message The message to decode.
+     */
+    public Decoder(Message message) {
+        this(message, new Validator(message.buffer.limit()), 0);
+    }
+
+    private Decoder(Message message, Validator validator, int baseOffset) {
+        mMessage = message;
+        mMessage.buffer.order(ByteOrder.nativeOrder());
+        mBaseOffset = baseOffset;
+        mValidator = validator;
+        // Claim the memory for the header.
+        mValidator.claimMemory(mBaseOffset, mBaseOffset + DataHeader.HEADER_SIZE);
+    }
+
+    /**
+     * Deserializes a {@link DataHeader} at the given offset.
+     */
+    public DataHeader readDataHeader() {
+        int size = readInt(DataHeader.SIZE_OFFSET);
+        int numFields = readInt(DataHeader.NUM_FIELDS_OFFSET);
+        // The memory for the header has already been claimed.
+        mValidator.claimMemory(mBaseOffset + DataHeader.HEADER_SIZE, mBaseOffset + size);
+        DataHeader res = new DataHeader(size, numFields);
+        return res;
+    }
+
+    /**
+     * Deserializes a byte at the given offset.
+     */
+    public byte readByte(int offset) {
+        return mMessage.buffer.get(mBaseOffset + offset);
+    }
+
+    /**
+     * Deserializes a boolean at the given offset, re-using any partially read byte.
+     */
+    public boolean readBoolean(int offset, int bit) {
+        return (readByte(offset) & (1 << bit)) != 0;
+    }
+
+    /**
+     * Deserializes a short at the given offset.
+     */
+    public short readShort(int offset) {
+        return mMessage.buffer.getShort(mBaseOffset + offset);
+    }
+
+    /**
+     * Deserializes an int at the given offset.
+     */
+    public int readInt(int offset) {
+        return mMessage.buffer.getInt(mBaseOffset + offset);
+    }
+
+    /**
+     * Deserializes a float at the given offset.
+     */
+    public float readFloat(int offset) {
+        return mMessage.buffer.getFloat(mBaseOffset + offset);
+    }
+
+    /**
+     * Deserializes a long at the given offset.
+     */
+    public long readLong(int offset) {
+        return mMessage.buffer.getLong(mBaseOffset + offset);
+    }
+
+    /**
+     * Deserializes a double at the given offset.
+     */
+    public double readDouble(int offset) {
+        return mMessage.buffer.getDouble(mBaseOffset + offset);
+    }
+
+    /**
+     * Deserializes a pointer at the given offset. Returns a Decoder suitable to decode the content
+     * of the pointer.
+     */
+    public Decoder readPointer(int offset) {
+        int basePosition = mBaseOffset + offset;
+        long pointerOffset = readLong(offset);
+        if (pointerOffset == 0) {
+            return null;
+        }
+        int newPosition = (int) (basePosition + pointerOffset);
+        // The method |getDecoderAtPosition| will validate that the pointer address is valid.
+        return getDecoderAtPosition(newPosition);
+
+    }
+
+    /**
+     * Deserializes an array of boolean at the given offset.
+     */
+    public boolean[] readBooleans(int offset) {
+        Decoder d = readPointer(offset);
+        if (d == null) {
+            return null;
+        }
+        DataHeader si = d.readDataHeader();
+        byte[] bytes = new byte[si.numFields + 7 / BindingsHelper.ALIGNMENT];
+        d.mMessage.buffer.position(d.mBaseOffset + DataHeader.HEADER_SIZE);
+        d.mMessage.buffer.get(bytes);
+        boolean[] result = new boolean[si.numFields];
+        for (int i = 0; i < bytes.length; ++i) {
+            for (int j = 0; j < BindingsHelper.ALIGNMENT; ++j) {
+                int booleanIndex = i * BindingsHelper.ALIGNMENT + j;
+                if (booleanIndex < result.length) {
+                    result[booleanIndex] = (bytes[i] & (1 << j)) != 0;
+                }
+            }
+        }
+        return result;
+    }
+
+    /**
+     * Deserializes an array of bytes at the given offset.
+     */
+    public byte[] readBytes(int offset) {
+        Decoder d = readPointer(offset);
+        if (d == null) {
+            return null;
+        }
+        DataHeader si = d.readDataHeader();
+        byte[] result = new byte[si.numFields];
+        d.mMessage.buffer.position(d.mBaseOffset + DataHeader.HEADER_SIZE);
+        d.mMessage.buffer.get(result);
+        return result;
+    }
+
+    /**
+     * Deserializes an array of shorts at the given offset.
+     */
+    public short[] readShorts(int offset) {
+        Decoder d = readPointer(offset);
+        if (d == null) {
+            return null;
+        }
+        DataHeader si = d.readDataHeader();
+        short[] result = new short[si.numFields];
+        d.mMessage.buffer.position(d.mBaseOffset + DataHeader.HEADER_SIZE);
+        d.mMessage.buffer.asShortBuffer().get(result);
+        return result;
+    }
+
+    /**
+     * Deserializes an array of ints at the given offset.
+     */
+    public int[] readInts(int offset) {
+        Decoder d = readPointer(offset);
+        if (d == null) {
+            return null;
+        }
+        DataHeader si = d.readDataHeader();
+        int[] result = new int[si.numFields];
+        d.mMessage.buffer.position(d.mBaseOffset + DataHeader.HEADER_SIZE);
+        d.mMessage.buffer.asIntBuffer().get(result);
+        return result;
+    }
+
+    /**
+     * Deserializes an array of floats at the given offset.
+     */
+    public float[] readFloats(int offset) {
+        Decoder d = readPointer(offset);
+        if (d == null) {
+            return null;
+        }
+        DataHeader si = d.readDataHeader();
+        float[] result = new float[si.numFields];
+        d.mMessage.buffer.position(d.mBaseOffset + DataHeader.HEADER_SIZE);
+        d.mMessage.buffer.asFloatBuffer().get(result);
+        return result;
+    }
+
+    /**
+     * Deserializes an array of longs at the given offset.
+     */
+    public long[] readLongs(int offset) {
+        Decoder d = readPointer(offset);
+        if (d == null) {
+            return null;
+        }
+        DataHeader si = d.readDataHeader();
+        long[] result = new long[si.numFields];
+        d.mMessage.buffer.position(d.mBaseOffset + DataHeader.HEADER_SIZE);
+        d.mMessage.buffer.asLongBuffer().get(result);
+        return result;
+    }
+
+    /**
+     * Deserializes an array of doubles at the given offset.
+     */
+    public double[] readDoubles(int offset) {
+        Decoder d = readPointer(offset);
+        if (d == null) {
+            return null;
+        }
+        DataHeader si = d.readDataHeader();
+        double[] result = new double[si.numFields];
+        d.mMessage.buffer.position(d.mBaseOffset + DataHeader.HEADER_SIZE);
+        d.mMessage.buffer.asDoubleBuffer().get(result);
+        return result;
+    }
+
+    /**
+     * Deserializes an |Handle| at the given offset.
+     */
+    public Handle readHandle(int offset) {
+        int index = readInt(offset);
+        if (index == -1) {
+            return InvalidHandle.INSTANCE;
+        }
+        mValidator.claimHandle(index);
+        return mMessage.handles.get(index);
+    }
+
+    /**
+     * Deserializes a |ConsumerHandle| at the given offset.
+     */
+    public DataPipe.ConsumerHandle readConsumerHandle(int offset) {
+        return readHandle(offset).toUntypedHandle().toDataPipeConsumerHandle();
+    }
+
+    /**
+     * Deserializes a |ProducerHandle| at the given offset.
+     */
+    public DataPipe.ProducerHandle readProducerHandle(int offset) {
+        return readHandle(offset).toUntypedHandle().toDataPipeProducerHandle();
+    }
+
+    /**
+     * Deserializes a |MessagePipeHandle| at the given offset.
+     */
+    public MessagePipeHandle readMessagePipeHandle(int offset) {
+        return readHandle(offset).toUntypedHandle().toMessagePipeHandle();
+    }
+
+    /**
+     * Deserializes a |SharedBufferHandle| at the given offset.
+     */
+    public SharedBufferHandle readSharedBufferHandle(int offset) {
+        return readHandle(offset).toUntypedHandle().toSharedBufferHandle();
+    }
+
+    /**
+     * Deserializes a |ServiceHandle| at the given offset.
+     */
+    public <S extends Interface> S readServiceInterface(int offset, Object builder) {
+        // TODO(qsr): To be implemented when interfaces proxy and stubs are implemented.
+        throw new UnsupportedOperationException("Unimplemented operation");
+    }
+
+    /**
+     * Deserializes a |InterfaceRequest| at the given offset.
+     */
+    public <S extends Interface> InterfaceRequest<S> readInterfaceRequest(int offset) {
+        // TODO(qsr): To be implemented when interfaces proxy and stubs are implemented.
+        throw new UnsupportedOperationException("Unimplemented operation");
+    }
+
+    /**
+     * Deserializes a string at the given offset.
+     */
+    public String readString(int offset) {
+        byte[] bytes = readBytes(offset);
+        if (bytes == null) {
+            return null;
+        }
+        return new String(bytes, Charset.forName("utf8"));
+    }
+
+    /**
+     * Deserializes an array of |Handle| at the given offset.
+     */
+    public Handle[] readHandles(int offset) {
+        Decoder d = readPointer(offset);
+        if (d == null) {
+            return null;
+        }
+        DataHeader si = d.readDataHeader();
+        Handle[] result = new Handle[si.numFields];
+        for (int i = 0; i < result.length; ++i) {
+            result[i] = d.readHandle(
+                    DataHeader.HEADER_SIZE + BindingsHelper.SERIALIZED_HANDLE_SIZE * i);
+        }
+        return result;
+    }
+
+    /**
+     * Deserializes an array of |ConsumerHandle| at the given offset.
+     */
+    public DataPipe.ConsumerHandle[] readConsumerHandles(int offset) {
+        Decoder d = readPointer(offset);
+        if (d == null) {
+            return null;
+        }
+        DataHeader si = d.readDataHeader();
+        DataPipe.ConsumerHandle[] result = new DataPipe.ConsumerHandle[si.numFields];
+        for (int i = 0; i < result.length; ++i) {
+            result[i] = d.readConsumerHandle(
+                    DataHeader.HEADER_SIZE + BindingsHelper.SERIALIZED_HANDLE_SIZE * i);
+        }
+        return result;
+    }
+
+    /**
+     * Deserializes an array of |ProducerHandle| at the given offset.
+     */
+    public DataPipe.ProducerHandle[] readProducerHandles(int offset) {
+        Decoder d = readPointer(offset);
+        if (d == null) {
+            return null;
+        }
+        DataHeader si = d.readDataHeader();
+        DataPipe.ProducerHandle[] result = new DataPipe.ProducerHandle[si.numFields];
+        for (int i = 0; i < result.length; ++i) {
+            result[i] = d.readProducerHandle(
+                    DataHeader.HEADER_SIZE + BindingsHelper.SERIALIZED_HANDLE_SIZE * i);
+        }
+        return result;
+
+    }
+
+    /**
+     * Deserializes an array of |MessagePipeHandle| at the given offset.
+     */
+    public MessagePipeHandle[] readMessagePipeHandles(int offset) {
+        Decoder d = readPointer(offset);
+        if (d == null) {
+            return null;
+        }
+        DataHeader si = d.readDataHeader();
+        MessagePipeHandle[] result = new MessagePipeHandle[si.numFields];
+        for (int i = 0; i < result.length; ++i) {
+            result[i] = d.readMessagePipeHandle(
+                    DataHeader.HEADER_SIZE + BindingsHelper.SERIALIZED_HANDLE_SIZE * i);
+        }
+        return result;
+
+    }
+
+    /**
+     * Deserializes an array of |SharedBufferHandle| at the given offset.
+     */
+    public SharedBufferHandle[] readSharedBufferHandles(int offset) {
+        Decoder d = readPointer(offset);
+        if (d == null) {
+            return null;
+        }
+        DataHeader si = d.readDataHeader();
+        SharedBufferHandle[] result = new SharedBufferHandle[si.numFields];
+        for (int i = 0; i < result.length; ++i) {
+            result[i] = d.readSharedBufferHandle(
+                    DataHeader.HEADER_SIZE + BindingsHelper.SERIALIZED_HANDLE_SIZE * i);
+        }
+        return result;
+
+    }
+
+    /**
+     * Deserializes an array of |ServiceHandle| at the given offset.
+     */
+    public <S extends Interface> S[] readServiceInterfaces(int offset, Object builder) {
+        // TODO(qsr): To be implemented when interfaces proxy and stubs are implemented.
+        throw new UnsupportedOperationException("Unimplemented operation");
+    }
+
+    /**
+     * Deserializes an array of |InterfaceRequest| at the given offset.
+     */
+    public <S extends Interface> InterfaceRequest<S>[] readInterfaceRequests(int offset) {
+        Decoder d = readPointer(offset);
+        if (d == null) {
+            return null;
+        }
+        DataHeader si = d.readDataHeader();
+        @SuppressWarnings("unchecked")
+        InterfaceRequest<S>[] result = new InterfaceRequest[si.numFields];
+        for (int i = 0; i < result.length; ++i) {
+            result[i] = d.readInterfaceRequest(
+                    DataHeader.HEADER_SIZE + BindingsHelper.SERIALIZED_HANDLE_SIZE * i);
+        }
+        return result;
+    }
+
+    /**
+     * Returns a view of this decoder at the offset |offset|.
+     */
+    private Decoder getDecoderAtPosition(int offset) {
+        return new Decoder(mMessage, mValidator, offset);
+    }
+
+}