| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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 org.apache.coyote.http2; |
| |
| import java.nio.ByteBuffer; |
| |
| import org.apache.tomcat.util.res.StringManager; |
| |
| /** |
| * A decoder for HPACK. |
| */ |
| public class HpackDecoder { |
| |
| protected static final StringManager sm = StringManager.getManager(HpackDecoder.class); |
| |
| private static final int DEFAULT_RING_BUFFER_SIZE = 10; |
| |
| /** |
| * The object that receives the headers that are emitted from this decoder |
| */ |
| private HeaderEmitter headerEmitter; |
| |
| /** |
| * The header table |
| */ |
| private Hpack.HeaderField[] headerTable; |
| |
| /** |
| * The current HEAD position of the header table. We use a ring buffer type |
| * construct as it would be silly to actually shuffle the items around in the |
| * array. |
| */ |
| private int firstSlotPosition = 0; |
| |
| /** |
| * The current table size by index (aka the number of index positions that are filled up) |
| */ |
| private int filledTableSlots = 0; |
| |
| /** |
| * the current calculates memory size, as per the HPACK algorithm |
| */ |
| private int currentMemorySize = 0; |
| |
| /** |
| * The maximum allowed memory size |
| */ |
| private int maxMemorySize; |
| |
| private final StringBuilder stringBuilder = new StringBuilder(); |
| |
| public HpackDecoder(int maxMemorySize) { |
| this.maxMemorySize = maxMemorySize; |
| headerTable = new Hpack.HeaderField[DEFAULT_RING_BUFFER_SIZE]; |
| } |
| |
| public HpackDecoder() { |
| this(Hpack.DEFAULT_TABLE_SIZE); |
| } |
| |
| /** |
| * Decodes the provided frame data. If this method leaves data in the buffer |
| * then this buffer should be compacted so this data is preserved, unless |
| * there is no more data in which case this should be considered a protocol error. |
| * |
| * @param buffer The buffer |
| * |
| * @throws HpackException If the packed data is not valid |
| */ |
| public void decode(ByteBuffer buffer) throws HpackException { |
| while (buffer.hasRemaining()) { |
| int originalPos = buffer.position(); |
| byte b = buffer.get(); |
| if ((b & 0b10000000) != 0) { |
| //if the first bit is set it is an indexed header field |
| buffer.position(buffer.position() - 1); //unget the byte |
| int index = Hpack.decodeInteger(buffer, 7); //prefix is 7 |
| if (index == -1) { |
| buffer.position(originalPos); |
| return; |
| } else if(index == 0) { |
| throw new HpackException( |
| sm.getString("hpackdecoder.zeroNotValidHeaderTableIndex")); |
| } |
| handleIndex(index); |
| } else if ((b & 0b01000000) != 0) { |
| //Literal Header Field with Incremental Indexing |
| String headerName = readHeaderName(buffer, 6); |
| if (headerName == null) { |
| buffer.position(originalPos); |
| return; |
| } |
| String headerValue = readHpackString(buffer); |
| if (headerValue == null) { |
| buffer.position(originalPos); |
| return; |
| } |
| headerEmitter.emitHeader(headerName, headerValue, false); |
| addEntryToHeaderTable(new Hpack.HeaderField(headerName, headerValue)); |
| } else if ((b & 0b11110000) == 0) { |
| //Literal Header Field without Indexing |
| String headerName = readHeaderName(buffer, 4); |
| if (headerName == null) { |
| buffer.position(originalPos); |
| return; |
| } |
| String headerValue = readHpackString(buffer); |
| if (headerValue == null) { |
| buffer.position(originalPos); |
| return; |
| } |
| headerEmitter.emitHeader(headerName, headerValue, false); |
| } else if ((b & 0b11110000) == 0b00010000) { |
| //Literal Header Field never indexed |
| String headerName = readHeaderName(buffer, 4); |
| if (headerName == null) { |
| buffer.position(originalPos); |
| return; |
| } |
| String headerValue = readHpackString(buffer); |
| if (headerValue == null) { |
| buffer.position(originalPos); |
| return; |
| } |
| headerEmitter.emitHeader(headerName, headerValue, true); |
| } else if ((b & 0b11100000) == 0b00100000) { |
| //context update max table size change |
| if (!handleMaxMemorySizeChange(buffer, originalPos)) { |
| return; |
| } |
| } else { |
| throw new RuntimeException("Not yet implemented"); |
| } |
| } |
| } |
| |
| private boolean handleMaxMemorySizeChange(ByteBuffer buffer, int originalPos) throws HpackException { |
| buffer.position(buffer.position() - 1); //unget the byte |
| int size = Hpack.decodeInteger(buffer, 5); |
| if (size == -1) { |
| buffer.position(originalPos); |
| return false; |
| } |
| maxMemorySize = size; |
| if (currentMemorySize > maxMemorySize) { |
| int newTableSlots = filledTableSlots; |
| int tableLength = headerTable.length; |
| int newSize = currentMemorySize; |
| while (newSize > maxMemorySize) { |
| int clearIndex = firstSlotPosition; |
| firstSlotPosition++; |
| if (firstSlotPosition == tableLength) { |
| firstSlotPosition = 0; |
| } |
| Hpack.HeaderField oldData = headerTable[clearIndex]; |
| headerTable[clearIndex] = null; |
| newSize -= oldData.size; |
| newTableSlots--; |
| } |
| this.filledTableSlots = newTableSlots; |
| currentMemorySize = newSize; |
| } |
| return true; |
| } |
| |
| private String readHeaderName(ByteBuffer buffer, int prefixLength) throws HpackException { |
| buffer.position(buffer.position() - 1); //unget the byte |
| int index = Hpack.decodeInteger(buffer, prefixLength); |
| if (index == -1) { |
| return null; |
| } else if (index != 0) { |
| return handleIndexedHeaderName(index); |
| } else { |
| return readHpackString(buffer); |
| } |
| } |
| |
| private String readHpackString(ByteBuffer buffer) throws HpackException { |
| if (!buffer.hasRemaining()) { |
| return null; |
| } |
| byte data = buffer.get(buffer.position()); |
| |
| int length = Hpack.decodeInteger(buffer, 7); |
| if (buffer.remaining() < length) { |
| return null; |
| } |
| boolean huffman = (data & 0b10000000) != 0; |
| if (huffman) { |
| return readHuffmanString(length, buffer); |
| } |
| for (int i = 0; i < length; ++i) { |
| stringBuilder.append((char) buffer.get()); |
| } |
| String ret = stringBuilder.toString(); |
| stringBuilder.setLength(0); |
| return ret; |
| } |
| |
| private String readHuffmanString(int length, ByteBuffer buffer) throws HpackException { |
| HPackHuffman.decode(buffer, length, stringBuilder); |
| String ret = stringBuilder.toString(); |
| stringBuilder.setLength(0); |
| return ret; |
| } |
| |
| private String handleIndexedHeaderName(int index) throws HpackException { |
| if (index <= Hpack.STATIC_TABLE_LENGTH) { |
| return Hpack.STATIC_TABLE[index].name; |
| } else { |
| if (index >= Hpack.STATIC_TABLE_LENGTH + filledTableSlots) { |
| throw new HpackException(); |
| } |
| int adjustedIndex = getRealIndex(index - Hpack.STATIC_TABLE_LENGTH); |
| Hpack.HeaderField res = headerTable[adjustedIndex]; |
| if (res == null) { |
| throw new HpackException(); |
| } |
| return res.name; |
| } |
| } |
| |
| /** |
| * Handle an indexed header representation |
| * |
| * @param index The index |
| * @throws HpackException |
| */ |
| private void handleIndex(int index) throws HpackException { |
| if (index <= Hpack.STATIC_TABLE_LENGTH) { |
| addStaticTableEntry(index); |
| } else { |
| int adjustedIndex = getRealIndex(index - Hpack.STATIC_TABLE_LENGTH); |
| Hpack.HeaderField headerField = headerTable[adjustedIndex]; |
| headerEmitter.emitHeader(headerField.name, headerField.value, false); |
| } |
| } |
| |
| /** |
| * because we use a ring buffer type construct, and don't actually shuffle |
| * items in the array, we need to figure out the real index to use. |
| * <p/> |
| * package private for unit tests |
| * |
| * @param index The index from the hpack |
| * @return the real index into the array |
| */ |
| int getRealIndex(int index) { |
| //the index is one based, but our table is zero based, hence -1 |
| //also because of our ring buffer setup the indexes are reversed |
| //index = 1 is at position firstSlotPosition + filledSlots |
| return (firstSlotPosition + (filledTableSlots - index)) % headerTable.length; |
| } |
| |
| private void addStaticTableEntry(int index) throws HpackException { |
| //adds an entry from the static table. |
| //this must be an entry with a value as far as I can determine |
| Hpack.HeaderField entry = Hpack.STATIC_TABLE[index]; |
| if (entry.value == null) { |
| throw new HpackException(); |
| } |
| headerEmitter.emitHeader(entry.name, entry.value, false); |
| } |
| |
| private void addEntryToHeaderTable(Hpack.HeaderField entry) { |
| if (entry.size > maxMemorySize) { |
| //it is to big to fit, so we just completely clear the table. |
| while (filledTableSlots > 0) { |
| headerTable[firstSlotPosition] = null; |
| firstSlotPosition++; |
| if (firstSlotPosition == headerTable.length) { |
| firstSlotPosition = 0; |
| } |
| filledTableSlots--; |
| } |
| currentMemorySize = 0; |
| return; |
| } |
| resizeIfRequired(); |
| int newTableSlots = filledTableSlots + 1; |
| int tableLength = headerTable.length; |
| int index = (firstSlotPosition + filledTableSlots) % tableLength; |
| headerTable[index] = entry; |
| int newSize = currentMemorySize + entry.size; |
| while (newSize > maxMemorySize) { |
| int clearIndex = firstSlotPosition; |
| firstSlotPosition++; |
| if (firstSlotPosition == tableLength) { |
| firstSlotPosition = 0; |
| } |
| Hpack.HeaderField oldData = headerTable[clearIndex]; |
| headerTable[clearIndex] = null; |
| newSize -= oldData.size; |
| newTableSlots--; |
| } |
| this.filledTableSlots = newTableSlots; |
| currentMemorySize = newSize; |
| } |
| |
| private void resizeIfRequired() { |
| if(filledTableSlots == headerTable.length) { |
| Hpack.HeaderField[] newArray = new Hpack.HeaderField[headerTable.length + 10]; //we only grow slowly |
| for(int i = 0; i < headerTable.length; ++i) { |
| newArray[i] = headerTable[(firstSlotPosition + i) % headerTable.length]; |
| } |
| firstSlotPosition = 0; |
| headerTable = newArray; |
| } |
| } |
| |
| |
| /** |
| * Interface that can be used to immediately validate headers (ex: uppercase detection). |
| */ |
| public interface HeaderEmitter { |
| void emitHeader(String name, String value, boolean neverIndex); |
| } |
| |
| |
| public HeaderEmitter getHeaderEmitter() { |
| return headerEmitter; |
| } |
| |
| public void setHeaderEmitter(HeaderEmitter headerEmitter) { |
| this.headerEmitter = headerEmitter; |
| } |
| |
| //package private fields for unit tests |
| |
| int getFirstSlotPosition() { |
| return firstSlotPosition; |
| } |
| |
| Hpack.HeaderField[] getHeaderTable() { |
| return headerTable; |
| } |
| |
| int getFilledTableSlots() { |
| return filledTableSlots; |
| } |
| |
| int getCurrentMemorySize() { |
| return currentMemorySize; |
| } |
| |
| int getMaxMemorySize() { |
| return maxMemorySize; |
| } |
| } |