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Library providing APIs to talk to Android devices
/* //device/tools/ddms/libs/ddmlib/src/com/android/ddmlib/JdwpPacket.java
**
** Copyright 2007, The Android Open Source Project
**
** 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.android.ddmlib;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.channels.SocketChannel;
/**
* A JDWP packet, sitting at the start of a ByteBuffer somewhere.
*
* This allows us to wrap a "pointer" to the data with the results of
* decoding the packet.
*
* None of the operations here are synchronized. If multiple threads will
* be accessing the same ByteBuffers, external sync will be required.
*
* Use the constructor to create an empty packet, or "findPacket()" to
* wrap a JdwpPacket around existing data.
*/
public final class JdwpPacket {
public static final int JDWP_HEADER_LEN = 11;
private static final int REPLY_PACKET = 0x80;
private ByteBuffer mBuffer;
private int mLength;
private int mId;
private int mFlags;
private int mCmdSet;
private int mCmd;
private int mErrCode;
private static int sSerialId = 0x40000000;
/**
* Create a new, empty packet, in "buf".
*/
JdwpPacket(ByteBuffer buf) {
mBuffer = buf;
}
/**
* Finish a packet created with newPacket().
*
* This always creates a command packet, with the next serial number
* in sequence.
*
* We have to take "payloadLength" as an argument because we can't
* see the position in the "slice" returned by getPayload(). We could
* fish it out of the chunk header, but it's legal for there to be
* more than one chunk in a JDWP packet.
*
* On exit, "position" points to the end of the data.
*/
void finishPacket(int cmdSet, int cmd, int payloadLength) {
ByteOrder oldOrder = mBuffer.order();
mBuffer.order(ChunkHandler.CHUNK_ORDER);
mLength = JDWP_HEADER_LEN + payloadLength;
mId = getNextSerial();
mFlags = 0;
mCmdSet = cmdSet;
mCmd = cmd;
mBuffer.putInt(0x00, mLength);
mBuffer.putInt(0x04, mId);
mBuffer.put(0x08, (byte) mFlags);
mBuffer.put(0x09, (byte) mCmdSet);
mBuffer.put(0x0a, (byte) mCmd);
mBuffer.order(oldOrder);
mBuffer.position(mLength);
}
/**
* Get the next serial number. This creates a unique serial number
* across all connections, not just for the current connection. This
* is a useful property when debugging, but isn't necessary.
*
* We can't synchronize on an int, so we use a sync method.
*/
private static synchronized int getNextSerial() {
return sSerialId++;
}
/**
* Return a slice of the byte buffer, positioned past the JDWP header
* to the start of the chunk header. The buffer's limit will be set
* to the size of the payload if the size is known; if this is a
* packet under construction the limit will be set to the end of the
* buffer.
*
* Doesn't examine the packet at all -- works on empty buffers.
*/
public ByteBuffer getPayload() {
ByteBuffer buf;
int oldPosn = mBuffer.position();
mBuffer.position(JDWP_HEADER_LEN);
buf = mBuffer.slice(); // goes from position to limit
mBuffer.position(oldPosn);
if (mLength > 0)
buf.limit(mLength - JDWP_HEADER_LEN);
buf.order(ChunkHandler.CHUNK_ORDER);
return buf;
}
/**
* Returns "true" if this JDWP packet is tagged as a reply.
*/
public boolean isReply() {
return (mFlags & REPLY_PACKET) != 0;
}
/**
* Returns "true" if this JDWP packet is a reply with a nonzero
* error code.
*/
boolean isError() {
return isReply() && mErrCode != 0;
}
/**
* Returns "true" if this JDWP packet has no data.
*/
boolean isEmpty() {
return (mLength == JDWP_HEADER_LEN);
}
/**
* Return the packet's ID. For a reply packet, this allows us to
* match the reply with the original request.
*/
public int getId() {
return mId;
}
/**
* Return the length of a packet. This includes the header, so an
* empty packet is 11 bytes long.
*/
int getLength() {
return mLength;
}
/**
* Write our packet to "chan".
*
* The JDWP packet starts at offset 0 and ends at mBuffer.position().
*/
void write(SocketChannel chan) throws IOException {
assert mLength > 0;
int oldPosn = mBuffer.position();
mBuffer.position(0);
mBuffer.limit(mLength);
while (mBuffer.position() != mBuffer.limit()) {
chan.write(mBuffer);
}
// position should now be at end of packet
assert mBuffer.position() == mLength;
mBuffer.limit(mBuffer.capacity());
mBuffer.position(oldPosn);
}
/**
* "Move" the packet data out of the buffer we're sitting on and into
* buf at the current position.
*/
void move(ByteBuffer buf) {
int oldPosn = mBuffer.position();
mBuffer.position(0);
mBuffer.limit(mLength);
buf.put(mBuffer);
mBuffer.limit(mBuffer.capacity());
mBuffer.position(oldPosn);
}
/**
* Consume the JDWP packet.
*
* On entry and exit, "position" is at the end of data in buffer.
*/
void consume()
{
/*
* The "flip" call sets "limit" equal to the position (usually the
* end of data) and "position" equal to zero.
*
* compact() copies everything from "position" and "limit" to the
* start of the buffer, sets "position" to the end of data, and
* sets "limit" to the capacity.
*
* On entry, "position" is set to the amount of data in the buffer
* and "limit" is set to the capacity. We want to call flip()
* so that position..limit spans our data, advance "position" past
* the current packet, then compact.
*/
mBuffer.flip();
mBuffer.position(mLength);
mBuffer.compact();
mLength = 0;
}
/**
* Find the JDWP packet at the start of "buf". The start is known,
* but the length has to be parsed out.
*
* On entry, the packet data in "buf" must start at offset 0 and end
* at "position". "limit" should be set to the buffer capacity. This
* method does not alter "buf"s attributes.
*
* Returns a new JdwpPacket if a full one is found in the buffer. If
* not, returns null. Throws an exception if the data doesn't look like
* a valid JDWP packet.
*/
static JdwpPacket findPacket(ByteBuffer buf) {
int count = buf.position();
int length, id, flags, cmdSet, cmd;
if (count < JDWP_HEADER_LEN)
return null;
ByteOrder oldOrder = buf.order();
buf.order(ChunkHandler.CHUNK_ORDER);
length = buf.getInt(0x00);
id = buf.getInt(0x04);
flags = buf.get(0x08) & 0xff;
cmdSet = buf.get(0x09) & 0xff;
cmd = buf.get(0x0a) & 0xff;
buf.order(oldOrder);
if (length < JDWP_HEADER_LEN)
throw new BadPacketException();
if (count < length)
return null;
JdwpPacket pkt = new JdwpPacket(buf);
//pkt.mBuffer = buf;
pkt.mLength = length;
pkt.mId = id;
pkt.mFlags = flags;
if ((flags & REPLY_PACKET) == 0) {
pkt.mCmdSet = cmdSet;
pkt.mCmd = cmd;
pkt.mErrCode = -1;
} else {
pkt.mCmdSet = -1;
pkt.mCmd = -1;
pkt.mErrCode = cmdSet | (cmd << 8);
}
return pkt;
}
@Override
public String toString() {
return isReply() ? " < # " + mId : " > " + mCmdSet + "." + mCmd + " # " + mId;
}
public boolean is(int cmdSet, int cmd) {
return cmdSet == mCmdSet && cmd == mCmd;
}
}
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