JAVA BINDINGS WIP.

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

Index: mojo/bindings/java/src/org/chromium/mojo/bindings/MessageHeader.java
diff --git a/mojo/bindings/java/src/org/chromium/mojo/bindings/MessageHeader.java b/mojo/bindings/java/src/org/chromium/mojo/bindings/MessageHeader.java
new file mode 100644
index 0000000000000000000000000000000000000000..5d637ad846a82c8a74bea4119564db53d35a282b
--- /dev/null
+++ b/mojo/bindings/java/src/org/chromium/mojo/bindings/MessageHeader.java
@@ -0,0 +1,177 @@
+// 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;
+
+/**
+ * Header information for a message.
+ */
+public class MessageHeader {
+
+    /**
+     * The struct header of a message header that doesn't represent a method with return values.
+     */
+    private static final DataHeader SIMPLE_MESSAGE_STRUCT_INFO = new DataHeader(16, 2);
+
+    /**
+     * The struct header of a message header that represents a method with return values.
+     */
+    private static final DataHeader MESSAGE_WITH_REQUEST_ID_STRUCT_INFO = new DataHeader(24, 3);
+
+    /**
+     * Flag for a header of a message that expected a response.
+     */
+    public static final int MESSAGE_EXPECTS_RESPONSE_FLAG = 1 << 0;
+
+    /**
+     * Flag for a header of a message that is a response.
+     */
+    public static final int MESSAGE_IS_RESPONSE_FLAG = 1 << 1;
+
+    /**
+     * return whether a message with the given flags must have a request Id.
+     */
+    public static boolean mustHaveRequestId(int flags) {
+        return (flags & (MESSAGE_EXPECTS_RESPONSE_FLAG | MESSAGE_IS_RESPONSE_FLAG)) != 0;
+    }
+
+    private final DataHeader mDataHeader;
+    private final int mType;
+    private final int mFlags;
+    private long mRequestId;
+
+    /**
+     * Constructor, parsing the header from a message.
+     */
+    public MessageHeader(Message message) {
+        Decoder decoder = new Decoder(message);
+        mDataHeader = decoder.readDataHeader();
+        if (mDataHeader.numFields < 2) {
+            throw new DeserializationException(
+                    "Incorrect number of fields, expecting at least 2, but got: "
+                    + mDataHeader.numFields);
+        }
+        if (mDataHeader.size < SIMPLE_MESSAGE_STRUCT_INFO.size) {
+            throw new DeserializationException(
+                    "Incorrect message size, expecting at least " + SIMPLE_MESSAGE_STRUCT_INFO.size
+                    + ", but got: " + mDataHeader.size);
+        }
+        mType = decoder.readInt(8);
+        mFlags = decoder.readInt(12);
+        if (mustHaveRequestId(mFlags)) {
+            if (mDataHeader.size < MESSAGE_WITH_REQUEST_ID_STRUCT_INFO.size) {
+                throw new DeserializationException("Incorrect message size, expecting at least "
+                        + MESSAGE_WITH_REQUEST_ID_STRUCT_INFO.size + ", but got: "
+                        + mDataHeader.size);
+
+            }
+            mRequestId = decoder.readLong(16);
+        } else {
+            mRequestId = 0;
+        }
+    }
+
+    /**
+     * Constructor for the header of a message not having a response.
+     */
+    public MessageHeader(int type, int flags) {
+        assert !mustHaveRequestId(flags);
+        mDataHeader = SIMPLE_MESSAGE_STRUCT_INFO;
+        mType = type;
+        mFlags = flags;
+        mRequestId = 0;
+    }
+
+    /**
+     * Constructor for the header of a message not having response or the response of a message.
+     */
+    public MessageHeader(int type, int flags, long requestId) {
+        assert mustHaveRequestId(flags);
+        mDataHeader = MESSAGE_WITH_REQUEST_ID_STRUCT_INFO;
+        mType = type;
+        mFlags = flags;
+        mRequestId = requestId;
+    }
+
+    public int getSize() {
+        return mDataHeader.size;
+    }
+
+    /**
+     * Returns the type of the message.
+     */
+    public int getType() {
+        return mType;
+    }
+
+    /**
+     * Returns the flags associated to the message.
+     */
+    public int getFlags() {
+        return mFlags;
+    }
+
+    /**
+     * Returns if the message has the given flag.
+     */
+    public boolean hasFlag(int flag) {
+        return (mFlags & flag) == flag;
+    }
+
+    /**
+     * Returns if the message has a request id.
+     */
+    public boolean hasRequestId() {
+        return mustHaveRequestId(mFlags);
+    }
+
+    /**
+     * Return the request id for the message. Must only be called if the message has a request id.
+     */
+    public long getRequestId() {
+        assert hasRequestId();
+        return mRequestId;
+    }
+
+    /**
+     * Encode the header.
+     */
+    public void encode(Encoder encoder) {
+        encoder.encode(mDataHeader);
+        encoder.encode(getType(), 8);
+        encoder.encode(getFlags(), 12);
+        if (mustHaveRequestId(getFlags())) {
+            encoder.encode(getRequestId(), 16);
+        }
+    }
+
+    /**
+     * Returns if the header has the expected flags. Only consider flags this class knows about to
+     * allow working with future version of the header format.
+     */
+    public boolean validateHeader(int expectedFlags) {
+        int knownFlags = getFlags() & (MESSAGE_EXPECTS_RESPONSE_FLAG | MESSAGE_IS_RESPONSE_FLAG);
+        return knownFlags == expectedFlags;
+    }
+
+    /**
+     * Returns if the header has the expected type and flags. Only consider flags this class knows
+     * about to allow working with future version of the header format.
+     */
+    public boolean validateHeader(int expectedType, int expectedFlags) {
+        return getType() == expectedType && validateHeader(expectedFlags);
+    }
+
+    /**
+     * Set the given request id on the given message. Should only be called if the message requires
+     * a request id.
+     */
+    public static void setRequestId(Message message, long requestId) {
+        assert new MessageHeader(message).hasRequestId();
+        message.buffer.putLong(16, requestId);
+    }
+
+}