diff options
Diffstat (limited to 'container-search/src/main/java/com/yahoo/fs4/PacketDecoder.java')
| -rw-r--r-- | container-search/src/main/java/com/yahoo/fs4/PacketDecoder.java | 200 |
1 files changed, 200 insertions, 0 deletions
diff --git a/container-search/src/main/java/com/yahoo/fs4/PacketDecoder.java b/container-search/src/main/java/com/yahoo/fs4/PacketDecoder.java new file mode 100644 index 00000000000..3e673717d02 --- /dev/null +++ b/container-search/src/main/java/com/yahoo/fs4/PacketDecoder.java @@ -0,0 +1,200 @@ +// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root. +package com.yahoo.fs4; + +import java.nio.ByteBuffer; + +/** + * Returns the correct package for a package byte stream + * + * @author bratseth + * @author <a href="mailto:borud@yahoo-inc.com">Bj\u00f8rn Borud</a> + */ +public class PacketDecoder { + + /** Represents a packet and the data used to construct it */ + public static class DecodedPacket { + public BasicPacket packet; + public ByteBuffer consumedBytes; + + DecodedPacket(BasicPacket packet, ByteBuffer consumedBytes) { + this.packet = packet; + this.consumedBytes = consumedBytes; + } + } + + private PacketDecoder() {} + + /** + * Returns the package starting at the current position in the buffer + * + * @throws IllegalArgumentException if an unknown package code is + * encountered + * @throws java.nio.BufferUnderflowException if the buffer contains too little + * data to decode the pcode. + */ + public static BasicPacket decode(ByteBuffer buffer) { + int packetCode = buffer.getInt(buffer.position()+4); + packetCode &= BasicPacket.CODE_MASK; + + switch (packetCode) { + case 200: + return EolPacket.create().decode(buffer); + + case 203: + return ErrorPacket.create().decode(buffer); + + case 205: + return DocsumPacket.create().decode(buffer); + + case 217: + return QueryResultPacket.create().decode(buffer); + + case 221: + return PongPacket.create().decode(buffer); + + default: + throw new IllegalArgumentException("No support for packet " + packetCode); + } + } + + /** Gives the packet along with the bytes consumed to construct it. */ + public static DecodedPacket decodePacket(ByteBuffer buffer) { + ByteBuffer dataUsed = buffer.slice(); + int start = buffer.position(); + + BasicPacket packet = decode(buffer); + dataUsed.limit(buffer.position() - start); + return new DecodedPacket(packet, dataUsed); + } + + /** Sniff channel ID for query result packets */ + public static int sniffChannel(ByteBuffer buffer) { + int remaining = buffer.remaining(); + if (remaining < 12) { + return 0; + } + int packetCode = buffer.getInt(buffer.position()+4); + packetCode &= BasicPacket.CODE_MASK; + switch (packetCode) { + case 202: + case 208: + case 214: + case 217: + return buffer.getInt(buffer.position()+8); + default: + return 0; + } + } + + /** + * Test whether the buffer contains (the start of) a pong packet. + * + * Returns false if there is not enough data to determine the + * answer. + */ + public static boolean isPongPacket(ByteBuffer buffer) { + + int remaining = buffer.remaining(); + if (remaining < 8) + return false; + int packetCode = buffer.getInt(buffer.position()+4); + packetCode &= BasicPacket.CODE_MASK; + if (packetCode == 221) + return true; + else + return false; + } + + /** + * Note that it assumes that the position of the ByteBuffer is at the + * start of a packet and that we have enough data to actually read + * an integer out of the buffer. + * + * @return Return the length of the fs4 packet. Returns -1 if length + * could not be determined because we had too little + * data in the buffer. + * + */ + public static int packetLength(ByteBuffer buffer) + { + if (buffer.remaining() < 4) { + return -1; + } + return (buffer.getInt(buffer.position()) + 4); + } + + /** + * Takes a buffer possibly containing a packet. + * + * <P> + * If we return a packet when we return: + * <UL> + * <LI> the buffer is positioned at the beginning of the next + * packet when we return. + * <LI> limit is unchanged + * </UL> + * + * <P> + * If we return <code>null</code> there were no more packets + * there to decode and the following is true of the buffer + * <UL> + * <LI> the buffer is compacted, ie. partial packet is + * moved to the start, or if no more data is available + * the buffer is cleared. + * <LI> the position is set to the next byte after the valid + * data so the buffer is ready for reading. + * </UL> + * + * If there are no packets to be returned the buffer is compacted + * (ie. content is moved to the start and read-pointer is positioned + * + * @return Returns the next available packet from the buffer or + * <code>null</code> if there are no more <b>complete</b> + * packets in the buffer at this time. + */ + public static DecodedPacket extractPacket(ByteBuffer buffer) + throws BufferTooSmallException + { + int remaining = buffer.remaining(); + + // if we are empty we can reset the buffer + if (remaining == 0) { + buffer.clear(); + return null; + } + + // if we can't figure out the size because we have less than + // 4 bytes we prepare the buffer for more data reading. + if (remaining < 4) { + buffer.compact(); + return null; + } + + int plen = packetLength(buffer); + + // -1 means that we do not have enough data to read the packet + // size yet + if (plen == -1) { + buffer.compact(); + return null; + } + + // if we haven't read an entire packet yet, we compact and return + // (same as above but separate code for clarity). note that this + // also occurs when there is no physical room for the packet, so + // clients of this API need to be aware of this and check for it + if (remaining < plen) { + + // if the read buffer is too small we must take drastic action + if (buffer.capacity() < plen) { + throw new BufferTooSmallException("Buffer too small to hold packet"); + } + + buffer.compact(); + return null; + } + + return PacketDecoder.decodePacket(buffer); + } + +} |