// Copyright 2014 The Chromium Authors
// 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 java.nio.ByteBuffer;
/** Header information for a message. */
public class MessageHeader {
private static final int SIMPLE_MESSAGE_SIZE = 24;
private static final int SIMPLE_MESSAGE_VERSION = 0;
private static final DataHeader SIMPLE_MESSAGE_STRUCT_INFO =
new DataHeader(SIMPLE_MESSAGE_SIZE, SIMPLE_MESSAGE_VERSION);
private static final int MESSAGE_WITH_REQUEST_ID_SIZE = 32;
private static final int MESSAGE_WITH_REQUEST_ID_VERSION = 1;
private static final DataHeader MESSAGE_WITH_REQUEST_ID_STRUCT_INFO =
new DataHeader(MESSAGE_WITH_REQUEST_ID_SIZE, MESSAGE_WITH_REQUEST_ID_VERSION);
private static final int INTERFACE_ID_OFFSET = 8;
private static final int TYPE_OFFSET = 12;
private static final int FLAGS_OFFSET = 16;
private static final int REQUEST_ID_OFFSET = 24;
/** Flag for a header of a simple message. */
public static final int NO_FLAG = 0;
/** 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;
/** Flag for a header of a message that is a response to a sync method. */
public static final int MESSAGE_IS_SYNC_FLAG = 1 << 2;
private final DataHeader mDataHeader;
private final int mType;
private final int mFlags;
private long mRequestId;
/** Constructor for the header of a message which does not have a response. */
public MessageHeader(int type) {
mDataHeader = SIMPLE_MESSAGE_STRUCT_INFO;
mType = type;
mFlags = 0;
mRequestId = 0;
}
/** Constructor for the header of a message which have a response or being itself a response. */
public MessageHeader(int type, int flags, long requestId) {
assert mustHaveRequestId(flags);
mDataHeader = MESSAGE_WITH_REQUEST_ID_STRUCT_INFO;
mType = type;
mFlags = flags;
mRequestId = requestId;
}
/**
* Constructor, parsing the header from a message. Should only be used by {@link Message}
* itself.
*/
MessageHeader(Message message) {
Decoder decoder = new Decoder(message);
mDataHeader = decoder.readDataHeader();
validateDataHeader(mDataHeader);
// Currently associated interfaces are not supported.
int interfaceId = decoder.readInt(INTERFACE_ID_OFFSET);
if (interfaceId != 0) {
throw new DeserializationException(
"Non-zero interface ID, expecting zero since "
+ "associated interfaces are not yet supported.");
}
mType = decoder.readInt(TYPE_OFFSET);
mFlags = decoder.readInt(FLAGS_OFFSET);
if (mustHaveRequestId(mFlags)) {
if (mDataHeader.size < MESSAGE_WITH_REQUEST_ID_SIZE) {
throw new DeserializationException(
"Incorrect message size, expecting at least "
+ MESSAGE_WITH_REQUEST_ID_SIZE
+ " for a message with a request identifier, but got: "
+ mDataHeader.size);
}
mRequestId = decoder.readLong(REQUEST_ID_OFFSET);
} else {
mRequestId = 0;
}
}
/** Returns the size in bytes of the serialization of the header. */
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);
// Set the interface ID field to 0.
encoder.encode(0, INTERFACE_ID_OFFSET);
encoder.encode(getType(), TYPE_OFFSET);
encoder.encode(getFlags(), FLAGS_OFFSET);
if (hasRequestId()) {
encoder.encode(getRequestId(), REQUEST_ID_OFFSET);
}
}
/**
* Returns true if the header has the expected flags. Only considers flags this class knows
* about in order to allow this class to work with future version of the header format.
*/
public boolean validateHeader(int expectedFlags) {
int knownFlags =
getFlags()
& (MESSAGE_EXPECTS_RESPONSE_FLAG
| MESSAGE_IS_RESPONSE_FLAG
| MESSAGE_IS_SYNC_FLAG);
return knownFlags == expectedFlags;
}
/**
* Returns true if the header has the expected type and flags. Only consider flags this class
* knows about in order to allow this class to work with future version of the header format.
*/
public boolean validateHeader(int expectedType, int expectedFlags) {
return getType() == expectedType && validateHeader(expectedFlags);
}
/**
* @see Object#hashCode()
*/
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((mDataHeader == null) ? 0 : mDataHeader.hashCode());
result = prime * result + mFlags;
result = prime * result + (int) (mRequestId ^ (mRequestId >>> 32));
result = prime * result + mType;
return result;
}
/**
* @see Object#equals(Object)
*/
@Override
public boolean equals(Object object) {
if (object == this) return true;
if (object == null) return false;
if (getClass() != object.getClass()) return false;
MessageHeader other = (MessageHeader) object;
return (BindingsHelper.equals(mDataHeader, other.mDataHeader)
&& mFlags == other.mFlags
&& mRequestId == other.mRequestId
&& mType == other.mType);
}
/** Set the request id on the message contained in the given buffer. */
void setRequestId(ByteBuffer buffer, long requestId) {
assert mustHaveRequestId(buffer.getInt(FLAGS_OFFSET));
buffer.putLong(REQUEST_ID_OFFSET, requestId);
mRequestId = requestId;
}
/** Returns whether a message with the given flags must have a request Id. */
private static boolean mustHaveRequestId(int flags) {
return (flags & (MESSAGE_EXPECTS_RESPONSE_FLAG | MESSAGE_IS_RESPONSE_FLAG)) != 0;
}
/** Validate that the given {@link DataHeader} can be the data header of a message header. */
private static void validateDataHeader(DataHeader dataHeader) {
if (dataHeader.elementsOrVersion < SIMPLE_MESSAGE_VERSION) {
throw new DeserializationException(
"Incorrect number of fields, expecting at least "
+ SIMPLE_MESSAGE_VERSION
+ ", but got: "
+ dataHeader.elementsOrVersion);
}
if (dataHeader.size < SIMPLE_MESSAGE_SIZE) {
throw new DeserializationException(
"Incorrect message size, expecting at least "
+ SIMPLE_MESSAGE_SIZE
+ ", but got: "
+ dataHeader.size);
}
if (dataHeader.elementsOrVersion == SIMPLE_MESSAGE_VERSION
&& dataHeader.size != SIMPLE_MESSAGE_SIZE) {
throw new DeserializationException(
"Incorrect message size for a message with "
+ SIMPLE_MESSAGE_VERSION
+ " fields, expecting "
+ SIMPLE_MESSAGE_SIZE
+ ", but got: "
+ dataHeader.size);
}
if (dataHeader.elementsOrVersion == MESSAGE_WITH_REQUEST_ID_VERSION
&& dataHeader.size != MESSAGE_WITH_REQUEST_ID_SIZE) {
throw new DeserializationException(
"Incorrect message size for a message with "
+ MESSAGE_WITH_REQUEST_ID_VERSION
+ " fields, expecting "
+ MESSAGE_WITH_REQUEST_ID_SIZE
+ ", but got: "
+ dataHeader.size);
}
}
}
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