com.squareup.okhttp.internal.framed.Huffman Maven / Gradle / Ivy
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/*
* Copyright 2013 Twitter, Inc.
*
* 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.squareup.okhttp.internal.framed;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
/**
* This class was originally composed from the following classes in
* Twitter Hpack.
*
* - {@code com.twitter.hpack.HuffmanEncoder}
* - {@code com.twitter.hpack.HuffmanDecoder}
* - {@code com.twitter.hpack.HpackUtil}
*
*/
class Huffman {
// Appendix C: Huffman Codes
// http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-12#appendix-B
private static final int[] CODES = {
0x1ff8, 0x7fffd8, 0xfffffe2, 0xfffffe3, 0xfffffe4, 0xfffffe5, 0xfffffe6, 0xfffffe7, 0xfffffe8,
0xffffea, 0x3ffffffc, 0xfffffe9, 0xfffffea, 0x3ffffffd, 0xfffffeb, 0xfffffec, 0xfffffed,
0xfffffee, 0xfffffef, 0xffffff0, 0xffffff1, 0xffffff2, 0x3ffffffe, 0xffffff3, 0xffffff4,
0xffffff5, 0xffffff6, 0xffffff7, 0xffffff8, 0xffffff9, 0xffffffa, 0xffffffb, 0x14, 0x3f8,
0x3f9, 0xffa, 0x1ff9, 0x15, 0xf8, 0x7fa, 0x3fa, 0x3fb, 0xf9, 0x7fb, 0xfa, 0x16, 0x17, 0x18,
0x0, 0x1, 0x2, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x5c, 0xfb, 0x7ffc, 0x20, 0xffb,
0x3fc, 0x1ffa, 0x21, 0x5d, 0x5e, 0x5f, 0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,
0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, 0x70, 0x71, 0x72, 0xfc, 0x73, 0xfd, 0x1ffb, 0x7fff0,
0x1ffc, 0x3ffc, 0x22, 0x7ffd, 0x3, 0x23, 0x4, 0x24, 0x5, 0x25, 0x26, 0x27, 0x6, 0x74, 0x75,
0x28, 0x29, 0x2a, 0x7, 0x2b, 0x76, 0x2c, 0x8, 0x9, 0x2d, 0x77, 0x78, 0x79, 0x7a, 0x7b, 0x7ffe,
0x7fc, 0x3ffd, 0x1ffd, 0xffffffc, 0xfffe6, 0x3fffd2, 0xfffe7, 0xfffe8, 0x3fffd3, 0x3fffd4,
0x3fffd5, 0x7fffd9, 0x3fffd6, 0x7fffda, 0x7fffdb, 0x7fffdc, 0x7fffdd, 0x7fffde, 0xffffeb,
0x7fffdf, 0xffffec, 0xffffed, 0x3fffd7, 0x7fffe0, 0xffffee, 0x7fffe1, 0x7fffe2, 0x7fffe3,
0x7fffe4, 0x1fffdc, 0x3fffd8, 0x7fffe5, 0x3fffd9, 0x7fffe6, 0x7fffe7, 0xffffef, 0x3fffda,
0x1fffdd, 0xfffe9, 0x3fffdb, 0x3fffdc, 0x7fffe8, 0x7fffe9, 0x1fffde, 0x7fffea, 0x3fffdd,
0x3fffde, 0xfffff0, 0x1fffdf, 0x3fffdf, 0x7fffeb, 0x7fffec, 0x1fffe0, 0x1fffe1, 0x3fffe0,
0x1fffe2, 0x7fffed, 0x3fffe1, 0x7fffee, 0x7fffef, 0xfffea, 0x3fffe2, 0x3fffe3, 0x3fffe4,
0x7ffff0, 0x3fffe5, 0x3fffe6, 0x7ffff1, 0x3ffffe0, 0x3ffffe1, 0xfffeb, 0x7fff1, 0x3fffe7,
0x7ffff2, 0x3fffe8, 0x1ffffec, 0x3ffffe2, 0x3ffffe3, 0x3ffffe4, 0x7ffffde, 0x7ffffdf,
0x3ffffe5, 0xfffff1, 0x1ffffed, 0x7fff2, 0x1fffe3, 0x3ffffe6, 0x7ffffe0, 0x7ffffe1, 0x3ffffe7,
0x7ffffe2, 0xfffff2, 0x1fffe4, 0x1fffe5, 0x3ffffe8, 0x3ffffe9, 0xffffffd, 0x7ffffe3,
0x7ffffe4, 0x7ffffe5, 0xfffec, 0xfffff3, 0xfffed, 0x1fffe6, 0x3fffe9, 0x1fffe7, 0x1fffe8,
0x7ffff3, 0x3fffea, 0x3fffeb, 0x1ffffee, 0x1ffffef, 0xfffff4, 0xfffff5, 0x3ffffea, 0x7ffff4,
0x3ffffeb, 0x7ffffe6, 0x3ffffec, 0x3ffffed, 0x7ffffe7, 0x7ffffe8, 0x7ffffe9, 0x7ffffea,
0x7ffffeb, 0xffffffe, 0x7ffffec, 0x7ffffed, 0x7ffffee, 0x7ffffef, 0x7fffff0, 0x3ffffee
};
private static final byte[] CODE_LENGTHS = {
13, 23, 28, 28, 28, 28, 28, 28, 28, 24, 30, 28, 28, 30, 28, 28, 28, 28, 28, 28, 28, 28, 30,
28, 28, 28, 28, 28, 28, 28, 28, 28, 6, 10, 10, 12, 13, 6, 8, 11, 10, 10, 8, 11, 8, 6, 6, 6, 5,
5, 5, 6, 6, 6, 6, 6, 6, 6, 7, 8, 15, 6, 12, 10, 13, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 7, 8, 13, 19, 13, 14, 6, 15, 5, 6, 5, 6, 5, 6, 6, 6, 5, 7, 7, 6,
6, 6, 5, 6, 7, 6, 5, 5, 6, 7, 7, 7, 7, 7, 15, 11, 14, 13, 28, 20, 22, 20, 20, 22, 22, 22, 23,
22, 23, 23, 23, 23, 23, 24, 23, 24, 24, 22, 23, 24, 23, 23, 23, 23, 21, 22, 23, 22, 23, 23,
24, 22, 21, 20, 22, 22, 23, 23, 21, 23, 22, 22, 24, 21, 22, 23, 23, 21, 21, 22, 21, 23, 22,
23, 23, 20, 22, 22, 22, 23, 22, 22, 23, 26, 26, 20, 19, 22, 23, 22, 25, 26, 26, 26, 27, 27,
26, 24, 25, 19, 21, 26, 27, 27, 26, 27, 24, 21, 21, 26, 26, 28, 27, 27, 27, 20, 24, 20, 21,
22, 21, 21, 23, 22, 22, 25, 25, 24, 24, 26, 23, 26, 27, 26, 26, 27, 27, 27, 27, 27, 28, 27,
27, 27, 27, 27, 26
};
private static final Huffman INSTANCE = new Huffman();
public static Huffman get() {
return INSTANCE;
}
private final Node root = new Node();
private Huffman() {
buildTree();
}
void encode(byte[] data, OutputStream out) throws IOException {
long current = 0;
int n = 0;
for (int i = 0; i < data.length; i++) {
int b = data[i] & 0xFF;
int code = CODES[b];
int nbits = CODE_LENGTHS[b];
current <<= nbits;
current |= code;
n += nbits;
while (n >= 8) {
n -= 8;
out.write(((int) (current >> n)));
}
}
if (n > 0) {
current <<= (8 - n);
current |= (0xFF >>> n);
out.write((int) current);
}
}
int encodedLength(byte[] bytes) {
long len = 0;
for (int i = 0; i < bytes.length; i++) {
int b = bytes[i] & 0xFF;
len += CODE_LENGTHS[b];
}
return (int) ((len + 7) >> 3);
}
byte[] decode(byte[] buf) throws IOException {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
Node node = root;
int current = 0;
int nbits = 0;
for (int i = 0; i < buf.length; i++) {
int b = buf[i] & 0xFF;
current = (current << 8) | b;
nbits += 8;
while (nbits >= 8) {
int c = (current >>> (nbits - 8)) & 0xFF;
node = node.children[c];
if (node.children == null) {
// terminal node
baos.write(node.symbol);
nbits -= node.terminalBits;
node = root;
} else {
// non-terminal node
nbits -= 8;
}
}
}
while (nbits > 0) {
int c = (current << (8 - nbits)) & 0xFF;
node = node.children[c];
if (node.children != null || node.terminalBits > nbits) {
break;
}
baos.write(node.symbol);
nbits -= node.terminalBits;
node = root;
}
return baos.toByteArray();
}
private void buildTree() {
for (int i = 0; i < CODE_LENGTHS.length; i++) {
addCode(i, CODES[i], CODE_LENGTHS[i]);
}
}
private void addCode(int sym, int code, byte len) {
Node terminal = new Node(sym, len);
Node current = root;
while (len > 8) {
len -= 8;
int i = ((code >>> len) & 0xFF);
if (current.children == null) {
throw new IllegalStateException("invalid dictionary: prefix not unique");
}
if (current.children[i] == null) {
current.children[i] = new Node();
}
current = current.children[i];
}
int shift = 8 - len;
int start = (code << shift) & 0xFF;
int end = 1 << shift;
for (int i = start; i < start + end; i++) {
current.children[i] = terminal;
}
}
private static final class Node {
// Null if terminal.
private final Node[] children;
// Terminal nodes have a symbol.
private final int symbol;
// Number of bits represented in the terminal node.
private final int terminalBits;
/** Construct an internal node. */
Node() {
this.children = new Node[256];
this.symbol = 0; // Not read.
this.terminalBits = 0; // Not read.
}
/**
* Construct a terminal node.
*
* @param symbol symbol the node represents
* @param bits length of Huffman code in bits
*/
Node(int symbol, int bits) {
this.children = null;
this.symbol = symbol;
int b = bits & 0x07;
this.terminalBits = b == 0 ? 8 : b;
}
}
}