| /* Copyright 2015 Google Inc. All Rights Reserved. |
| |
| Distributed under MIT license. |
| See file LICENSE for detail or copy at https://opensource.org/licenses/MIT |
| */ |
| |
| package org.brotli.dec; |
| |
| import java.nio.ByteBuffer; |
| |
| /** |
| * Collection of static dictionary words. |
| * |
| * <p>Dictionary content is loaded from binary resource when {@link #getData()} is executed for the |
| * first time. Consequently, it saves memory and CPU in case dictionary is not required. |
| * |
| * <p>One possible drawback is that multiple threads that need dictionary data may be blocked (only |
| * once in each classworld). To avoid this, it is enough to call {@link #getData()} proactively. |
| */ |
| public final class Dictionary { |
| static final int MIN_DICTIONARY_WORD_LENGTH = 4; |
| static final int MAX_DICTIONARY_WORD_LENGTH = 31; |
| |
| private static ByteBuffer data = null; |
| static final int[] offsets = new int[32]; |
| static final int[] sizeBits = new int[32]; |
| |
| private static class DataLoader { |
| static final boolean OK; |
| |
| static { |
| boolean ok = true; |
| try { |
| Class.forName(Dictionary.class.getPackage().getName() + ".DictionaryData"); |
| } catch (Throwable ex) { |
| ok = false; |
| } |
| OK = ok; |
| } |
| } |
| |
| public static void setData(ByteBuffer newData, int[] newSizeBits) { |
| if ((Utils.isDirect(newData) == 0) || (Utils.isReadOnly(newData) == 0)) { |
| throw new BrotliRuntimeException("newData must be a direct read-only byte buffer"); |
| } |
| // TODO: is that so? |
| if (newSizeBits.length > MAX_DICTIONARY_WORD_LENGTH) { |
| throw new BrotliRuntimeException( |
| "sizeBits length must be at most " + MAX_DICTIONARY_WORD_LENGTH); |
| } |
| for (int i = 0; i < MIN_DICTIONARY_WORD_LENGTH; ++i) { |
| if (newSizeBits[i] != 0) { |
| throw new BrotliRuntimeException("first " + MIN_DICTIONARY_WORD_LENGTH + " must be 0"); |
| } |
| } |
| int[] dictionaryOffsets = Dictionary.offsets; |
| int[] dictionarySizeBits = Dictionary.sizeBits; |
| System.arraycopy(newSizeBits, 0, dictionarySizeBits, 0, newSizeBits.length); |
| int pos = 0; |
| int limit = newData.capacity(); |
| for (int i = 0; i < newSizeBits.length; ++i) { |
| dictionaryOffsets[i] = pos; |
| int bits = dictionarySizeBits[i]; |
| if (bits != 0) { |
| if (bits >= 31) { |
| throw new BrotliRuntimeException("newSizeBits values must be less than 31"); |
| } |
| pos += i << bits; |
| if (pos <= 0 || pos > limit) { |
| throw new BrotliRuntimeException("newSizeBits is inconsistent: overflow"); |
| } |
| } |
| } |
| for (int i = newSizeBits.length; i < 32; ++i) { |
| dictionaryOffsets[i] = pos; |
| } |
| if (pos != limit) { |
| throw new BrotliRuntimeException("newSizeBits is inconsistent: underflow"); |
| } |
| Dictionary.data = newData; |
| } |
| |
| public static ByteBuffer getData() { |
| if (data != null) { |
| return data; |
| } |
| if (!DataLoader.OK) { |
| throw new BrotliRuntimeException("brotli dictionary is not set"); |
| } |
| /* Might have been set when {@link DictionaryData} was loaded.*/ |
| return data; |
| } |
| } |