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/*
* 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 java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import org.apache.tomcat.util.res.StringManager;
public class HPackHuffman {
protected static final StringManager sm = StringManager.getManager(HPackHuffman.class);
private static final HuffmanCode[] HUFFMAN_CODES;
/**
* array based tree representation of a huffman code.
*
* the high two bytes corresponds to the tree node if the bit is set, and the low two bytes for if it is clear if
* the high bit is set it is a terminal node, otherwise it contains the next node position.
*/
private static final int[] DECODING_TABLE;
private static final int LOW_TERMINAL_BIT = (0b10000000) << 8;
private static final int HIGH_TERMINAL_BIT = (0b10000000) << 24;
private static final int LOW_MASK = 0b0111111111111111;
static {
HuffmanCode[] codes = new HuffmanCode[257];
codes[0] = new HuffmanCode(0x1ff8, 13);
codes[1] = new HuffmanCode(0x7fffd8, 23);
codes[2] = new HuffmanCode(0xfffffe2, 28);
codes[3] = new HuffmanCode(0xfffffe3, 28);
codes[4] = new HuffmanCode(0xfffffe4, 28);
codes[5] = new HuffmanCode(0xfffffe5, 28);
codes[6] = new HuffmanCode(0xfffffe6, 28);
codes[7] = new HuffmanCode(0xfffffe7, 28);
codes[8] = new HuffmanCode(0xfffffe8, 28);
codes[9] = new HuffmanCode(0xffffea, 24);
codes[10] = new HuffmanCode(0x3ffffffc, 30);
codes[11] = new HuffmanCode(0xfffffe9, 28);
codes[12] = new HuffmanCode(0xfffffea, 28);
codes[13] = new HuffmanCode(0x3ffffffd, 30);
codes[14] = new HuffmanCode(0xfffffeb, 28);
codes[15] = new HuffmanCode(0xfffffec, 28);
codes[16] = new HuffmanCode(0xfffffed, 28);
codes[17] = new HuffmanCode(0xfffffee, 28);
codes[18] = new HuffmanCode(0xfffffef, 28);
codes[19] = new HuffmanCode(0xffffff0, 28);
codes[20] = new HuffmanCode(0xffffff1, 28);
codes[21] = new HuffmanCode(0xffffff2, 28);
codes[22] = new HuffmanCode(0x3ffffffe, 30);
codes[23] = new HuffmanCode(0xffffff3, 28);
codes[24] = new HuffmanCode(0xffffff4, 28);
codes[25] = new HuffmanCode(0xffffff5, 28);
codes[26] = new HuffmanCode(0xffffff6, 28);
codes[27] = new HuffmanCode(0xffffff7, 28);
codes[28] = new HuffmanCode(0xffffff8, 28);
codes[29] = new HuffmanCode(0xffffff9, 28);
codes[30] = new HuffmanCode(0xffffffa, 28);
codes[31] = new HuffmanCode(0xffffffb, 28);
codes[32] = new HuffmanCode(0x14, 6);
codes[33] = new HuffmanCode(0x3f8, 10);
codes[34] = new HuffmanCode(0x3f9, 10);
codes[35] = new HuffmanCode(0xffa, 12);
codes[36] = new HuffmanCode(0x1ff9, 13);
codes[37] = new HuffmanCode(0x15, 6);
codes[38] = new HuffmanCode(0xf8, 8);
codes[39] = new HuffmanCode(0x7fa, 11);
codes[40] = new HuffmanCode(0x3fa, 10);
codes[41] = new HuffmanCode(0x3fb, 10);
codes[42] = new HuffmanCode(0xf9, 8);
codes[43] = new HuffmanCode(0x7fb, 11);
codes[44] = new HuffmanCode(0xfa, 8);
codes[45] = new HuffmanCode(0x16, 6);
codes[46] = new HuffmanCode(0x17, 6);
codes[47] = new HuffmanCode(0x18, 6);
codes[48] = new HuffmanCode(0x0, 5);
codes[49] = new HuffmanCode(0x1, 5);
codes[50] = new HuffmanCode(0x2, 5);
codes[51] = new HuffmanCode(0x19, 6);
codes[52] = new HuffmanCode(0x1a, 6);
codes[53] = new HuffmanCode(0x1b, 6);
codes[54] = new HuffmanCode(0x1c, 6);
codes[55] = new HuffmanCode(0x1d, 6);
codes[56] = new HuffmanCode(0x1e, 6);
codes[57] = new HuffmanCode(0x1f, 6);
codes[58] = new HuffmanCode(0x5c, 7);
codes[59] = new HuffmanCode(0xfb, 8);
codes[60] = new HuffmanCode(0x7ffc, 15);
codes[61] = new HuffmanCode(0x20, 6);
codes[62] = new HuffmanCode(0xffb, 12);
codes[63] = new HuffmanCode(0x3fc, 10);
codes[64] = new HuffmanCode(0x1ffa, 13);
codes[65] = new HuffmanCode(0x21, 6);
codes[66] = new HuffmanCode(0x5d, 7);
codes[67] = new HuffmanCode(0x5e, 7);
codes[68] = new HuffmanCode(0x5f, 7);
codes[69] = new HuffmanCode(0x60, 7);
codes[70] = new HuffmanCode(0x61, 7);
codes[71] = new HuffmanCode(0x62, 7);
codes[72] = new HuffmanCode(0x63, 7);
codes[73] = new HuffmanCode(0x64, 7);
codes[74] = new HuffmanCode(0x65, 7);
codes[75] = new HuffmanCode(0x66, 7);
codes[76] = new HuffmanCode(0x67, 7);
codes[77] = new HuffmanCode(0x68, 7);
codes[78] = new HuffmanCode(0x69, 7);
codes[79] = new HuffmanCode(0x6a, 7);
codes[80] = new HuffmanCode(0x6b, 7);
codes[81] = new HuffmanCode(0x6c, 7);
codes[82] = new HuffmanCode(0x6d, 7);
codes[83] = new HuffmanCode(0x6e, 7);
codes[84] = new HuffmanCode(0x6f, 7);
codes[85] = new HuffmanCode(0x70, 7);
codes[86] = new HuffmanCode(0x71, 7);
codes[87] = new HuffmanCode(0x72, 7);
codes[88] = new HuffmanCode(0xfc, 8);
codes[89] = new HuffmanCode(0x73, 7);
codes[90] = new HuffmanCode(0xfd, 8);
codes[91] = new HuffmanCode(0x1ffb, 13);
codes[92] = new HuffmanCode(0x7fff0, 19);
codes[93] = new HuffmanCode(0x1ffc, 13);
codes[94] = new HuffmanCode(0x3ffc, 14);
codes[95] = new HuffmanCode(0x22, 6);
codes[96] = new HuffmanCode(0x7ffd, 15);
codes[97] = new HuffmanCode(0x3, 5);
codes[98] = new HuffmanCode(0x23, 6);
codes[99] = new HuffmanCode(0x4, 5);
codes[100] = new HuffmanCode(0x24, 6);
codes[101] = new HuffmanCode(0x5, 5);
codes[102] = new HuffmanCode(0x25, 6);
codes[103] = new HuffmanCode(0x26, 6);
codes[104] = new HuffmanCode(0x27, 6);
codes[105] = new HuffmanCode(0x6, 5);
codes[106] = new HuffmanCode(0x74, 7);
codes[107] = new HuffmanCode(0x75, 7);
codes[108] = new HuffmanCode(0x28, 6);
codes[109] = new HuffmanCode(0x29, 6);
codes[110] = new HuffmanCode(0x2a, 6);
codes[111] = new HuffmanCode(0x7, 5);
codes[112] = new HuffmanCode(0x2b, 6);
codes[113] = new HuffmanCode(0x76, 7);
codes[114] = new HuffmanCode(0x2c, 6);
codes[115] = new HuffmanCode(0x8, 5);
codes[116] = new HuffmanCode(0x9, 5);
codes[117] = new HuffmanCode(0x2d, 6);
codes[118] = new HuffmanCode(0x77, 7);
codes[119] = new HuffmanCode(0x78, 7);
codes[120] = new HuffmanCode(0x79, 7);
codes[121] = new HuffmanCode(0x7a, 7);
codes[122] = new HuffmanCode(0x7b, 7);
codes[123] = new HuffmanCode(0x7ffe, 15);
codes[124] = new HuffmanCode(0x7fc, 11);
codes[125] = new HuffmanCode(0x3ffd, 14);
codes[126] = new HuffmanCode(0x1ffd, 13);
codes[127] = new HuffmanCode(0xffffffc, 28);
codes[128] = new HuffmanCode(0xfffe6, 20);
codes[129] = new HuffmanCode(0x3fffd2, 22);
codes[130] = new HuffmanCode(0xfffe7, 20);
codes[131] = new HuffmanCode(0xfffe8, 20);
codes[132] = new HuffmanCode(0x3fffd3, 22);
codes[133] = new HuffmanCode(0x3fffd4, 22);
codes[134] = new HuffmanCode(0x3fffd5, 22);
codes[135] = new HuffmanCode(0x7fffd9, 23);
codes[136] = new HuffmanCode(0x3fffd6, 22);
codes[137] = new HuffmanCode(0x7fffda, 23);
codes[138] = new HuffmanCode(0x7fffdb, 23);
codes[139] = new HuffmanCode(0x7fffdc, 23);
codes[140] = new HuffmanCode(0x7fffdd, 23);
codes[141] = new HuffmanCode(0x7fffde, 23);
codes[142] = new HuffmanCode(0xffffeb, 24);
codes[143] = new HuffmanCode(0x7fffdf, 23);
codes[144] = new HuffmanCode(0xffffec, 24);
codes[145] = new HuffmanCode(0xffffed, 24);
codes[146] = new HuffmanCode(0x3fffd7, 22);
codes[147] = new HuffmanCode(0x7fffe0, 23);
codes[148] = new HuffmanCode(0xffffee, 24);
codes[149] = new HuffmanCode(0x7fffe1, 23);
codes[150] = new HuffmanCode(0x7fffe2, 23);
codes[151] = new HuffmanCode(0x7fffe3, 23);
codes[152] = new HuffmanCode(0x7fffe4, 23);
codes[153] = new HuffmanCode(0x1fffdc, 21);
codes[154] = new HuffmanCode(0x3fffd8, 22);
codes[155] = new HuffmanCode(0x7fffe5, 23);
codes[156] = new HuffmanCode(0x3fffd9, 22);
codes[157] = new HuffmanCode(0x7fffe6, 23);
codes[158] = new HuffmanCode(0x7fffe7, 23);
codes[159] = new HuffmanCode(0xffffef, 24);
codes[160] = new HuffmanCode(0x3fffda, 22);
codes[161] = new HuffmanCode(0x1fffdd, 21);
codes[162] = new HuffmanCode(0xfffe9, 20);
codes[163] = new HuffmanCode(0x3fffdb, 22);
codes[164] = new HuffmanCode(0x3fffdc, 22);
codes[165] = new HuffmanCode(0x7fffe8, 23);
codes[166] = new HuffmanCode(0x7fffe9, 23);
codes[167] = new HuffmanCode(0x1fffde, 21);
codes[168] = new HuffmanCode(0x7fffea, 23);
codes[169] = new HuffmanCode(0x3fffdd, 22);
codes[170] = new HuffmanCode(0x3fffde, 22);
codes[171] = new HuffmanCode(0xfffff0, 24);
codes[172] = new HuffmanCode(0x1fffdf, 21);
codes[173] = new HuffmanCode(0x3fffdf, 22);
codes[174] = new HuffmanCode(0x7fffeb, 23);
codes[175] = new HuffmanCode(0x7fffec, 23);
codes[176] = new HuffmanCode(0x1fffe0, 21);
codes[177] = new HuffmanCode(0x1fffe1, 21);
codes[178] = new HuffmanCode(0x3fffe0, 22);
codes[179] = new HuffmanCode(0x1fffe2, 21);
codes[180] = new HuffmanCode(0x7fffed, 23);
codes[181] = new HuffmanCode(0x3fffe1, 22);
codes[182] = new HuffmanCode(0x7fffee, 23);
codes[183] = new HuffmanCode(0x7fffef, 23);
codes[184] = new HuffmanCode(0xfffea, 20);
codes[185] = new HuffmanCode(0x3fffe2, 22);
codes[186] = new HuffmanCode(0x3fffe3, 22);
codes[187] = new HuffmanCode(0x3fffe4, 22);
codes[188] = new HuffmanCode(0x7ffff0, 23);
codes[189] = new HuffmanCode(0x3fffe5, 22);
codes[190] = new HuffmanCode(0x3fffe6, 22);
codes[191] = new HuffmanCode(0x7ffff1, 23);
codes[192] = new HuffmanCode(0x3ffffe0, 26);
codes[193] = new HuffmanCode(0x3ffffe1, 26);
codes[194] = new HuffmanCode(0xfffeb, 20);
codes[195] = new HuffmanCode(0x7fff1, 19);
codes[196] = new HuffmanCode(0x3fffe7, 22);
codes[197] = new HuffmanCode(0x7ffff2, 23);
codes[198] = new HuffmanCode(0x3fffe8, 22);
codes[199] = new HuffmanCode(0x1ffffec, 25);
codes[200] = new HuffmanCode(0x3ffffe2, 26);
codes[201] = new HuffmanCode(0x3ffffe3, 26);
codes[202] = new HuffmanCode(0x3ffffe4, 26);
codes[203] = new HuffmanCode(0x7ffffde, 27);
codes[204] = new HuffmanCode(0x7ffffdf, 27);
codes[205] = new HuffmanCode(0x3ffffe5, 26);
codes[206] = new HuffmanCode(0xfffff1, 24);
codes[207] = new HuffmanCode(0x1ffffed, 25);
codes[208] = new HuffmanCode(0x7fff2, 19);
codes[209] = new HuffmanCode(0x1fffe3, 21);
codes[210] = new HuffmanCode(0x3ffffe6, 26);
codes[211] = new HuffmanCode(0x7ffffe0, 27);
codes[212] = new HuffmanCode(0x7ffffe1, 27);
codes[213] = new HuffmanCode(0x3ffffe7, 26);
codes[214] = new HuffmanCode(0x7ffffe2, 27);
codes[215] = new HuffmanCode(0xfffff2, 24);
codes[216] = new HuffmanCode(0x1fffe4, 21);
codes[217] = new HuffmanCode(0x1fffe5, 21);
codes[218] = new HuffmanCode(0x3ffffe8, 26);
codes[219] = new HuffmanCode(0x3ffffe9, 26);
codes[220] = new HuffmanCode(0xffffffd, 28);
codes[221] = new HuffmanCode(0x7ffffe3, 27);
codes[222] = new HuffmanCode(0x7ffffe4, 27);
codes[223] = new HuffmanCode(0x7ffffe5, 27);
codes[224] = new HuffmanCode(0xfffec, 20);
codes[225] = new HuffmanCode(0xfffff3, 24);
codes[226] = new HuffmanCode(0xfffed, 20);
codes[227] = new HuffmanCode(0x1fffe6, 21);
codes[228] = new HuffmanCode(0x3fffe9, 22);
codes[229] = new HuffmanCode(0x1fffe7, 21);
codes[230] = new HuffmanCode(0x1fffe8, 21);
codes[231] = new HuffmanCode(0x7ffff3, 23);
codes[232] = new HuffmanCode(0x3fffea, 22);
codes[233] = new HuffmanCode(0x3fffeb, 22);
codes[234] = new HuffmanCode(0x1ffffee, 25);
codes[235] = new HuffmanCode(0x1ffffef, 25);
codes[236] = new HuffmanCode(0xfffff4, 24);
codes[237] = new HuffmanCode(0xfffff5, 24);
codes[238] = new HuffmanCode(0x3ffffea, 26);
codes[239] = new HuffmanCode(0x7ffff4, 23);
codes[240] = new HuffmanCode(0x3ffffeb, 26);
codes[241] = new HuffmanCode(0x7ffffe6, 27);
codes[242] = new HuffmanCode(0x3ffffec, 26);
codes[243] = new HuffmanCode(0x3ffffed, 26);
codes[244] = new HuffmanCode(0x7ffffe7, 27);
codes[245] = new HuffmanCode(0x7ffffe8, 27);
codes[246] = new HuffmanCode(0x7ffffe9, 27);
codes[247] = new HuffmanCode(0x7ffffea, 27);
codes[248] = new HuffmanCode(0x7ffffeb, 27);
codes[249] = new HuffmanCode(0xffffffe, 28);
codes[250] = new HuffmanCode(0x7ffffec, 27);
codes[251] = new HuffmanCode(0x7ffffed, 27);
codes[252] = new HuffmanCode(0x7ffffee, 27);
codes[253] = new HuffmanCode(0x7ffffef, 27);
codes[254] = new HuffmanCode(0x7fffff0, 27);
codes[255] = new HuffmanCode(0x3ffffee, 26);
codes[256] = new HuffmanCode(0x3fffffff, 30);
HUFFMAN_CODES = codes;
// lengths determined by experimentation, just set it to something large then see how large it actually ends up
int[] codingTree = new int[256];
// the current position in the tree
int pos = 0;
int allocated = 1; // the next position to allocate to
// map of the current state at a given position
// only used while building the tree
HuffmanCode[] currentCode = new HuffmanCode[256];
currentCode[0] = new HuffmanCode(0, 0);
final Set allCodes = new HashSet<>(Arrays.asList(HUFFMAN_CODES));
while (!allCodes.isEmpty()) {
int length = currentCode[pos].length;
int code = currentCode[pos].value;
int newLength = length + 1;
HuffmanCode high = new HuffmanCode(code << 1 | 1, newLength);
HuffmanCode low = new HuffmanCode(code << 1, newLength);
int newVal = 0;
boolean highTerminal = allCodes.remove(high);
if (highTerminal) {
// bah, linear search
int i = 0;
for (i = 0; i < codes.length; ++i) {
if (codes[i].equals(high)) {
break;
}
}
newVal = LOW_TERMINAL_BIT | i;
} else {
int highPos = allocated++;
currentCode[highPos] = high;
newVal = highPos;
}
newVal <<= 16;
boolean lowTerminal = allCodes.remove(low);
if (lowTerminal) {
// bah, linear search
int i = 0;
for (i = 0; i < codes.length; ++i) {
if (codes[i].equals(low)) {
break;
}
}
newVal |= LOW_TERMINAL_BIT | i;
} else {
int lowPos = allocated++;
currentCode[lowPos] = low;
newVal |= lowPos;
}
codingTree[pos] = newVal;
pos++;
}
DECODING_TABLE = codingTree;
}
/**
* Decodes a huffman encoded string into the target StringBuilder. There must be enough space left in the buffer for
* this method to succeed.
*
* @param data The byte buffer
* @param length The length of data from the buffer to decode
* @param target The target for the decompressed data
*
* @throws HpackException If the Huffman encoded value in HPACK headers did not end with EOS padding
*/
public static void decode(ByteBuffer data, int length, StringBuilder target) throws HpackException {
assert data.remaining() >= length;
int treePos = 0;
boolean eosBits = true;
int eosBitCount = 0;
for (int i = 0; i < length; ++i) {
byte b = data.get();
int bitPos = 7;
while (bitPos >= 0) {
int val = DECODING_TABLE[treePos];
if (((1 << bitPos) & b) == 0) {
// bit not set, we want the lower part of the tree
if ((val & LOW_TERMINAL_BIT) == 0) {
treePos = val & LOW_MASK;
eosBits = false;
eosBitCount = 0;
} else {
target.append((char) (val & LOW_MASK));
treePos = 0;
eosBits = true;
}
} else {
if (eosBits) {
eosBitCount++;
}
// bit not set, we want the lower part of the tree
if ((val & HIGH_TERMINAL_BIT) == 0) {
treePos = (val >> 16) & LOW_MASK;
} else {
if (eosBitCount != 0) {
// This must be the EOS symbol which MUST be treated
// as an error
throw new HpackException(sm.getString("hpackhuffman.stringLiteralEOS"));
}
target.append((char) ((val >> 16) & LOW_MASK));
treePos = 0;
eosBits = true;
}
}
bitPos--;
}
}
if (eosBitCount > 7) {
throw new HpackException(sm.getString("hpackhuffman.stringLiteralTooMuchPadding"));
}
if (!eosBits) {
throw new HpackException(sm.getString("hpackhuffman.huffmanEncodedHpackValueDidNotEndWithEOS"));
}
}
/**
* Encodes the given string into the buffer. If there is not enough space in the buffer, or the encoded version is
* bigger than the original it will return false and not modify the buffers position.
*
* @param buffer The buffer to encode into
* @param toEncode The string to encode
* @param forceLowercase If the string should be encoded in lower case
*
* @return true if encoding succeeded
*/
public static boolean encode(ByteBuffer buffer, String toEncode, boolean forceLowercase) {
if (buffer.remaining() <= toEncode.length()) {
return false;
}
int start = buffer.position();
// this sucks, but we need to put the length first
// and we don't really have any option but to calculate it in advance to make sure we have left enough room
// so we end up iterating twice
int length = 0;
for (int i = 0; i < toEncode.length(); ++i) {
char c = toEncode.charAt(i);
if (c > 255) {
throw new IllegalArgumentException(
sm.getString("hpack.invalidCharacter", Character.toString(c), Integer.valueOf(c)));
}
if (forceLowercase) {
c = Hpack.toLower(c);
}
HuffmanCode code = HUFFMAN_CODES[c];
length += code.length;
}
int byteLength = length / 8 + (length % 8 == 0 ? 0 : 1);
buffer.put((byte) (1 << 7));
Hpack.encodeInteger(buffer, byteLength, 7);
int bytePos = 0;
byte currentBufferByte = 0;
for (int i = 0; i < toEncode.length(); ++i) {
char c = toEncode.charAt(i);
if (forceLowercase) {
c = Hpack.toLower(c);
}
HuffmanCode code = HUFFMAN_CODES[c];
if (code.length + bytePos <= 8) {
// it fits in the current byte
currentBufferByte |= ((code.value & 0xFF) << 8 - (code.length + bytePos));
bytePos += code.length;
} else {
// it does not fit, it may need up to 4 bytes
int val = code.value;
int rem = code.length;
while (rem > 0) {
if (!buffer.hasRemaining()) {
buffer.position(start);
return false;
}
int remainingInByte = 8 - bytePos;
if (rem > remainingInByte) {
currentBufferByte |= (val >> (rem - remainingInByte));
} else {
currentBufferByte |= (val << (remainingInByte - rem));
}
if (rem > remainingInByte) {
buffer.put(currentBufferByte);
currentBufferByte = 0;
bytePos = 0;
} else {
bytePos = rem;
}
rem -= remainingInByte;
}
}
if (bytePos == 8) {
if (!buffer.hasRemaining()) {
buffer.position(start);
return false;
}
buffer.put(currentBufferByte);
currentBufferByte = 0;
bytePos = 0;
}
if (buffer.position() - start > toEncode.length()) {
// the encoded version is longer than the original
// just return false
buffer.position(start);
return false;
}
}
if (bytePos > 0) {
// add the EOS bytes if we have not finished on a single byte
if (!buffer.hasRemaining()) {
buffer.position(start);
return false;
}
buffer.put((byte) (currentBufferByte | ((0xFF) >> bytePos)));
}
return true;
}
protected static class HuffmanCode {
/**
* The value of the least significant bits of the code
*/
int value;
/**
* length of the code, in bits
*/
int length;
public HuffmanCode(int value, int length) {
this.value = value;
this.length = length;
}
public int getValue() {
return value;
}
public int getLength() {
return length;
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
HuffmanCode that = (HuffmanCode) o;
if (length != that.length) {
return false;
}
if (value != that.value) {
return false;
}
return true;
}
@Override
public int hashCode() {
int result = value;
result = 31 * result + length;
return result;
}
@Override
public String toString() {
return "HuffmanCode{" + "value=" + value + ", length=" + length + '}';
}
}
}
