Update (#807)

- fix formatting
 - fix type conversion
 - fix no-op arithmetic with null-pointer
 - improve performance of hash_longest_match64
 - go: detect read after close
 - java decoder: support compound dictionary
 - remove executable flag on non-scripts

c/dec/decode.c

@@ -275,7 +275,8 @@ static BrotliDecoderErrorCode BROTLI_NOINLINE DecodeMetaBlockLength(
             s->loop_counter = i;
             return BROTLI_DECODER_NEEDS_MORE_INPUT;
           }
-          if (i + 1 == (int)s->size_nibbles && s->size_nibbles > 4 && bits == 0) {
+          if (i + 1 == (int)s->size_nibbles && s->size_nibbles > 4 &&
+              bits == 0) {
             return BROTLI_FAILURE(BROTLI_DECODER_ERROR_FORMAT_EXUBERANT_NIBBLE);
           }
           s->meta_block_remaining_len |= (int)(bits << (i * 4));
@@ -324,7 +325,8 @@ static BrotliDecoderErrorCode BROTLI_NOINLINE DecodeMetaBlockLength(
             s->loop_counter = i;
             return BROTLI_DECODER_NEEDS_MORE_INPUT;
           }
-          if (i + 1 == (int)s->size_nibbles && s->size_nibbles > 1 && bits == 0) {
+          if (i + 1 == (int)s->size_nibbles && s->size_nibbles > 1 &&
+              bits == 0) {
             return BROTLI_FAILURE(
                 BROTLI_DECODER_ERROR_FORMAT_EXUBERANT_META_NIBBLE);
           }

c/dec/huffman.h

@@ -83,7 +83,7 @@ typedef BROTLI_ALIGNED(4) uint32_t HuffmanCode;
 
 static BROTLI_INLINE HuffmanCode ConstructHuffmanCode(const uint8_t bits,
     const uint16_t value) {
-  return ((value & 0xFFFF) << 16) | (bits & 0xFF);
+  return (HuffmanCode) ((value & 0xFFFF) << 16) | (bits & 0xFF);
 }
 
 #define BROTLI_HC_MARK_TABLE_FOR_FAST_LOAD(H) uint32_t __fastload_##H = (*H)

c/enc/compress_fragment_two_pass.c

@@ -524,7 +524,7 @@ static void StoreCommands(MemoryManager* m,
 static BROTLI_BOOL ShouldCompress(
     const uint8_t* input, size_t input_size, size_t num_literals) {
   double corpus_size = (double)input_size;
-  if (num_literals < MIN_RATIO * corpus_size) {
+  if ((double)num_literals < MIN_RATIO * corpus_size) {
     return BROTLI_TRUE;
   } else {
     uint32_t literal_histo[256] = { 0 };

c/enc/encode.c

@@ -516,7 +516,7 @@ static BROTLI_BOOL ShouldCompress(
   /* TODO: find more precise minimal block overhead. */
   if (bytes <= 2) return BROTLI_FALSE;
   if (num_commands < (bytes >> 8) + 2) {
-    if (num_literals > 0.99 * (double)bytes) {
+    if ((double)num_literals > 0.99 * (double)bytes) {
       uint32_t literal_histo[256] = { 0 };
       static const uint32_t kSampleRate = 13;
       static const double kMinEntropy = 7.92;
@@ -1686,8 +1686,10 @@ static BROTLI_BOOL BrotliEncoderCompressStreamFast(
             &storage_ix, storage);
         if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
       }
-      *next_in += block_size;
-      *available_in -= block_size;
+      if (block_size != 0) {
+        *next_in += block_size;
+        *available_in -= block_size;
+      }
       if (inplace) {
         size_t out_bytes = storage_ix >> 3;
         BROTLI_DCHECK(out_bytes <= *available_out);

c/enc/fast_log.h

@@ -32,7 +32,7 @@ static BROTLI_INLINE uint32_t Log2FloorNonZero(size_t n) {
    computation.
 
    ", ".join(["%.16ff" % x for x in [0.0]+[log2(x) for x in range(1, 256)]]) */
-static const float kLog2Table[] = {
+static const double kLog2Table[] = {
   0.0000000000000000f, 0.0000000000000000f, 1.0000000000000000f,
   1.5849625007211563f, 2.0000000000000000f, 2.3219280948873622f,
   2.5849625007211561f, 2.8073549220576042f, 3.0000000000000000f,
@@ -123,8 +123,9 @@ static const float kLog2Table[] = {
 
 /* Visual Studio 2012 and Android API levels < 18 do not have the log2()
  * function defined, so we use log() and a multiplication instead. */
-#ifndef BROTLI_HAVE_LOG2
-#if ((defined(_MSC_VER) && _MSC_VER <= 1700) || (defined(__ANDROID_API__) && __ANDROID_API__ < 18))
+#if !defined(BROTLI_HAVE_LOG2)
+#if ((defined(_MSC_VER) && _MSC_VER <= 1700) || \
+     (defined(__ANDROID_API__) && __ANDROID_API__ < 18))
 #define BROTLI_HAVE_LOG2 0
 #else
 #define BROTLI_HAVE_LOG2 1

c/enc/hash_longest_match64_inc.h

@@ -115,8 +115,8 @@ static BROTLI_INLINE void FN(Store)(
                                      self->hash_shift_);
   const size_t minor_ix = num[key] & self->block_mask_;
   const size_t offset = minor_ix + (key << self->block_bits_);
-  buckets[offset] = (uint32_t)ix;
   ++num[key];
+  buckets[offset] = (uint32_t)ix;
 }
 
 static BROTLI_INLINE void FN(StoreRange)(HashLongestMatch* BROTLI_RESTRICT self,

c/enc/utf8_util.c

@@ -77,7 +77,7 @@ BROTLI_BOOL BrotliIsMostlyUTF8(
     i += bytes_read;
     if (symbol < 0x110000) size_utf8 += bytes_read;
   }
-  return TO_BROTLI_BOOL(size_utf8 > min_fraction * (double)length);
+  return TO_BROTLI_BOOL((double)size_utf8 > min_fraction * (double)length);
 }
 
 #if defined(__cplusplus) || defined(c_plusplus)

docs/constants.h.3

@@ -0,0 +1,47 @@
+.TH "constants.h" 3 "Wed May 13 2020" "Brotli" \" -*- nroff -*-
+.ad l
+.nh
+.SH NAME
+constants.h \- Common constants used in decoder and encoder API\&.  
+
+.SH SYNOPSIS
+.br
+.PP
+.SS "Macros"
+
+.in +1c
+.ti -1c
+.RI "#define \fBBROTLI_LARGE_MAX_DISTANCE_BITS\fP   62U"
+.br
+.RI "\fIThe theoretical maximum number of distance bits specified for large window brotli, for 64-bit encoders and decoders\&. \fP"
+.ti -1c
+.RI "#define \fBBROTLI_LARGE_MAX_WBITS\fP   30"
+.br
+.RI "\fIThe maximum supported large brotli window bits by the encoder and decoder\&. \fP"
+.ti -1c
+.RI "#define \fBBROTLI_MAX_NPOSTFIX\fP   3"
+.br
+.RI "\fIMaximal number of 'postfix' bits\&. \fP"
+.in -1c
+.SH "Detailed Description"
+.PP 
+Common constants used in decoder and encoder API\&. 
+
+
+.SH "Macro Definition Documentation"
+.PP 
+.SS "#define BROTLI_LARGE_MAX_DISTANCE_BITS   62U"
+
+.PP
+The theoretical maximum number of distance bits specified for large window brotli, for 64-bit encoders and decoders\&. Even when in practice 32-bit encoders and decoders only support up to 30 max distance bits, the value is set to 62 because it affects the large window brotli file format\&. Specifically, it affects the encoding of simple huffman tree for distances, see Specification RFC 7932 chapter 3\&.4\&. 
+.SS "#define BROTLI_LARGE_MAX_WBITS   30"
+
+.PP
+The maximum supported large brotli window bits by the encoder and decoder\&. Large window brotli allows up to 62 bits, however the current encoder and decoder, designed for 32-bit integers, only support up to 30 bits maximum\&. 
+.SS "#define BROTLI_MAX_NPOSTFIX   3"
+
+.PP
+Maximal number of 'postfix' bits\&. Number of 'postfix' bits is stored as 2 bits in meta-block header\&. 
+.SH "Author"
+.PP 
+Generated automatically by Doxygen for Brotli from the source code\&.

go/cbrotli/cbrotli_test.go

@@ -274,6 +274,10 @@ func TestReader(t *testing.T) {
 			"<%d bytes>",
 			got, len(content))
 	}
+	buf := make([]byte, 4)
+	if _, err := r.Read(buf); err != errReaderClosed {
+		t.Errorf("Read-after-Close returned %v, expected %v", err, errReaderClosed)
+	}
 }
 
 func TestDecode(t *testing.T) {

go/cbrotli/reader.go

@@ -82,6 +82,9 @@ func (r *Reader) Close() error {
 }
 
 func (r *Reader) Read(p []byte) (n int, err error) {
+	if r.state == nil {
+		return 0, errReaderClosed
+	}
 	if int(C.BrotliDecoderHasMoreOutput(r.state)) == 0 && len(r.in) == 0 {
 		m, readErr := r.src.Read(r.buf)
 		if m == 0 {

java/org/brotli/common/BUILD

@@ -0,0 +1,11 @@
+# Description:
+#   Java port of Brotli.
+
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])  # MIT
+
+java_library(
+    name = "shared_dictionary",
+    srcs = ["SharedDictionaryType.java"],
+)

java/org/brotli/common/SharedDictionaryType.java

@@ -0,0 +1,15 @@
+/* Copyright 2018 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.common;
+
+/** POJO enum that mirrors C BrotliSharedDictionaryType. */
+public class SharedDictionaryType {
+  // Disallow instantiation.
+  private SharedDictionaryType() {}
+
+  public static final int RAW = 0;
+  public static final int SERIALIZED = 1;
+}

java/org/brotli/dec/BrotliInputStream.java

@@ -84,6 +84,10 @@ public class BrotliInputStream extends InputStream {
     }
   }
 
+  public void attachDictionaryChunk(byte[] data) {
+    Decode.attachDictionaryChunk(state, data);
+  }
+
   public void enableEagerOutput() {
     Decode.enableEagerOutput(state);
   }

java/org/brotli/dec/CompoundDictionaryTest.java

@@ -0,0 +1,63 @@
+/* Copyright 2020 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 static org.junit.Assert.assertEquals;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/**
+ * Tests for {@link Dictionary}.
+ */
+@RunWith(JUnit4.class)
+public class CompoundDictionaryTest {
+
+  /** See {@link SynthTest} */
+  private static final byte[] ONE_COPY = {
+      (byte) 0xa1, (byte) 0xa8, (byte) 0x00, (byte) 0xc0, (byte) 0x2f, (byte) 0x01, (byte) 0x10,
+      (byte) 0xc4, (byte) 0x44, (byte) 0x09, (byte) 0x00
+    };
+
+  private static final String TEXT = "Kot lomom kolol slona!";
+
+  @Test
+  public void testNoDictionary() throws IOException {
+    BrotliInputStream decoder = new BrotliInputStream(new ByteArrayInputStream(ONE_COPY));
+    byte[] buffer = new byte[32];
+    int length = decoder.read(buffer, 0, buffer.length);
+    assertEquals(TEXT.length(), length);
+    assertEquals("alternate\" type=\"appli", new String(buffer, 0, length, "US-ASCII"));
+    decoder.close();
+  }
+
+  @Test
+  public void testOnePieceDictionary() throws IOException {
+    BrotliInputStream decoder = new BrotliInputStream(new ByteArrayInputStream(ONE_COPY));
+    decoder.attachDictionaryChunk(TEXT.getBytes("US-ASCII"));
+    byte[] buffer = new byte[32];
+    int length = decoder.read(buffer, 0, buffer.length);
+    assertEquals(TEXT.length(), length);
+    assertEquals(TEXT, new String(buffer, 0, length, "US-ASCII"));
+    decoder.close();
+  }
+
+  @Test
+  public void testTwoPieceDictionary() throws IOException {
+    BrotliInputStream decoder = new BrotliInputStream(new ByteArrayInputStream(ONE_COPY));
+    decoder.attachDictionaryChunk(TEXT.substring(0, 13).getBytes("US-ASCII"));
+    decoder.attachDictionaryChunk(TEXT.substring(13).getBytes("US-ASCII"));
+    byte[] buffer = new byte[32];
+    int length = decoder.read(buffer, 0, buffer.length);
+    assertEquals(TEXT.length(), length);
+    assertEquals(TEXT, new String(buffer, 0, length, "US-ASCII"));
+    decoder.close();
+  }
+}

java/org/brotli/dec/Decode.java

@@ -8,6 +8,7 @@ package org.brotli.dec;
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.ByteBuffer;
 
 /**
  * API for Brotli decompression.
@@ -31,11 +32,12 @@ final class Decode {
   private static final int COPY_UNCOMPRESSED = 6;
   private static final int INSERT_LOOP = 7;
   private static final int COPY_LOOP = 8;
-  private static final int TRANSFORM = 9;
+  private static final int USE_DICTIONARY = 9;
   private static final int FINISHED = 10;
   private static final int CLOSED = 11;
   private static final int INIT_WRITE = 12;
   private static final int WRITE = 13;
+  private static final int COPY_FROM_COMPOUND_DICTIONARY = 14;
 
   private static final int DEFAULT_CODE_LENGTH = 8;
   private static final int CODE_LENGTH_REPEAT_CODE = 16;
@@ -45,6 +47,7 @@ final class Decode {
   private static final int LITERAL_CONTEXT_BITS = 6;
   private static final int DISTANCE_CONTEXT_BITS = 2;
 
+  private static final int CD_BLOCK_MAP_BITS = 8;
   private static final int HUFFMAN_TABLE_BITS = 8;
   private static final int HUFFMAN_TABLE_MASK = 0xFF;
 
@@ -85,20 +88,8 @@ final class Decode {
       0x020000, 0x020004, 0x020003, 0x030002, 0x020000, 0x020004, 0x020003, 0x040005
   };
 
-  static final int[] DICTIONARY_OFFSETS_BY_LENGTH = {
-    0, 0, 0, 0, 0, 4096, 9216, 21504, 35840, 44032, 53248, 63488, 74752, 87040, 93696, 100864,
-    104704, 106752, 108928, 113536, 115968, 118528, 119872, 121280, 122016
-  };
-
-  static final int[] DICTIONARY_SIZE_BITS_BY_LENGTH = {
-    0, 0, 0, 0, 10, 10, 11, 11, 10, 10, 10, 10, 10, 9, 9, 8, 7, 7, 8, 7, 7, 6, 6, 5, 5
-  };
-
-  static final int MIN_WORD_LENGTH = 4;
-
-  static final int MAX_WORD_LENGTH = 24;
-
-  static final int MAX_TRANSFORMED_WORD_LENGTH = 5 + MAX_WORD_LENGTH + 8;
+  // TODO: generalize.
+  static final int MAX_TRANSFORMED_WORD_LENGTH = 5 + 24 + 8;
 
   private static final int MAX_DISTANCE_BITS = 24;
   private static final int MAX_LARGE_WINDOW_DISTANCE_BITS = 62;
@@ -274,6 +265,25 @@ final class Decode {
     s.isLargeWindow = 1;
   }
 
+  // TODO: do we need byte views?
+  static void attachDictionaryChunk(State s, byte[] data) {
+    if (s.runningState != INITIALIZED) {
+      throw new IllegalStateException("State MUST be freshly initialized");
+    }
+    if (s.cdNumChunks == 0) {
+      s.cdChunks = new byte[16][];
+      s.cdChunkOffsets = new int[16];
+      s.cdBlockBits = -1;
+    }
+    if (s.cdNumChunks == 15) {
+      throw new IllegalStateException("Too many dictionary chunks");
+    }
+    s.cdChunks[s.cdNumChunks] = data;
+    s.cdNumChunks++;
+    s.cdTotalSize += data.length;
+    s.cdChunkOffsets[s.cdNumChunks] = s.cdTotalSize;
+  }
+
   /**
    * Associate input with decoder state.
    *
@@ -821,7 +831,6 @@ final class Decode {
     BitReader.fillBitWindow(s);
     s.distancePostfixBits = BitReader.readFewBits(s, 2);
     s.numDirectDistanceCodes = BitReader.readFewBits(s, 4) << s.distancePostfixBits;
-    s.distancePostfixMask = (1 << s.distancePostfixBits) - 1;
     // TODO: Reuse?
     s.contextModes = new byte[s.numLiteralBlockTypes];
     for (int i = 0; i < s.numLiteralBlockTypes;) {
@@ -945,6 +954,118 @@ final class Decode {
     return result;
   }
 
+  private static void doUseDictionary(State s, int fence) {
+    if (s.distance > MAX_ALLOWED_DISTANCE) {
+      throw new BrotliRuntimeException("Invalid backward reference");
+    }
+    int address = s.distance - s.maxDistance - 1 - s.cdTotalSize;
+    if (address < 0) {
+      initializeCompoundDictionaryCopy(s, -address - 1, s.copyLength);
+      s.runningState = COPY_FROM_COMPOUND_DICTIONARY;
+    } else {
+      // Force lazy dictionary initialization.
+      ByteBuffer dictionaryData = Dictionary.getData();
+      int wordLength = s.copyLength;
+      if (wordLength > Dictionary.MAX_DICTIONARY_WORD_LENGTH) {
+        throw new BrotliRuntimeException("Invalid backward reference"); // COV_NF_LINE
+      }
+      int shift = Dictionary.sizeBits[wordLength];
+      if (shift == 0) {
+        throw new BrotliRuntimeException("Invalid backward reference"); // COV_NF_LINE
+      }
+      int offset = Dictionary.offsets[wordLength];
+      int mask = (1 << shift) - 1;
+      int wordIdx = address & mask;
+      int transformIdx = address >>> shift;
+      offset += wordIdx * wordLength;
+      Transform.Transforms transforms = Transform.RFC_TRANSFORMS;
+      if (transformIdx >= transforms.numTransforms) {
+        throw new BrotliRuntimeException("Invalid backward reference"); // COV_NF_LINE
+      }
+      int len = Transform.transformDictionaryWord(s.ringBuffer, s.pos, dictionaryData,
+          offset, wordLength, transforms, transformIdx);
+      s.pos += len;
+      s.metaBlockLength -= len;
+      if (s.pos >= fence) {
+        s.nextRunningState = MAIN_LOOP;
+        s.runningState = INIT_WRITE;
+        return;
+      }
+      s.runningState = MAIN_LOOP;
+    }
+  }
+
+  private static void initializeCompoundDictionary(State s) {
+    s.cdBlockMap = new byte[1 << CD_BLOCK_MAP_BITS];
+    int blockBits = CD_BLOCK_MAP_BITS;
+    // If this function is executed, then s.cdTotalSize > 0.
+    while (((s.cdTotalSize - 1) >>> blockBits) != 0) {
+      blockBits++;
+    }
+    blockBits -= CD_BLOCK_MAP_BITS;
+    s.cdBlockBits = blockBits;
+    int cursor = 0;
+    int index = 0;
+    while (cursor < s.cdTotalSize) {
+      while (s.cdChunkOffsets[index + 1] < cursor) {
+        index++;
+      }
+      s.cdBlockMap[cursor >>> blockBits] = (byte) index;
+      cursor += 1 << blockBits;
+    }
+  }
+
+  private static void initializeCompoundDictionaryCopy(State s, int address, int length) {
+    if (s.cdBlockBits == -1) {
+      initializeCompoundDictionary(s);
+    }
+    int index = s.cdBlockMap[address >>> s.cdBlockBits];
+    while (address >= s.cdChunkOffsets[index + 1]) {
+      index++;
+    }
+    if (s.cdTotalSize > address + length) {
+      throw new BrotliRuntimeException("Invalid backward reference");
+    }
+    /* Update the recent distances cache */
+    s.distRbIdx = (s.distRbIdx + 1) & 0x3;
+    s.rings[s.distRbIdx] = s.distance;
+    s.metaBlockLength -= length;
+    s.cdBrIndex = index;
+    s.cdBrOffset = address - s.cdChunkOffsets[index];
+    s.cdBrLength = length;
+    s.cdBrCopied = 0;
+  }
+
+  private static int copyFromCompoundDictionary(State s, int fence) {
+    int pos = s.pos;
+    int origPos = pos;
+    while (s.cdBrLength != s.cdBrCopied) {
+      int space = fence - pos;
+      int chunkLength = s.cdChunkOffsets[s.cdBrIndex + 1] - s.cdChunkOffsets[s.cdBrIndex];
+      int remChunkLength = chunkLength - s.cdBrOffset;
+      int length = s.cdBrLength - s.cdBrCopied;
+      if (length > remChunkLength) {
+        length = remChunkLength;
+      }
+      if (length > space) {
+        length = space;
+      }
+      Utils.copyBytes(
+          s.ringBuffer, pos, s.cdChunks[s.cdBrIndex], s.cdBrOffset, s.cdBrOffset + length);
+      pos += length;
+      s.cdBrOffset += length;
+      s.cdBrCopied += length;
+      if (length == remChunkLength) {
+        s.cdBrIndex++;
+        s.cdBrOffset = 0;
+      }
+      if (pos >= fence) {
+        break;
+      }
+    }
+    return pos - origPos;
+  }
+
   /**
    * Actual decompress implementation.
    */
@@ -1110,7 +1231,7 @@ final class Decode {
           }
 
           if (s.distance > s.maxDistance) {
-            s.runningState = TRANSFORM;
+            s.runningState = USE_DICTIONARY;
             continue;
           }
 
@@ -1164,35 +1285,16 @@ final class Decode {
           }
           continue;
 
-        case TRANSFORM:
-          // This check is done here to unburden the hot loop.
-          if (s.distance > MAX_ALLOWED_DISTANCE) {
-            throw new BrotliRuntimeException("Invalid backward reference"); // COV_NF_LINE
-          }
-          if (s.copyLength >= MIN_WORD_LENGTH
-              && s.copyLength <= MAX_WORD_LENGTH) {
-            int offset = DICTIONARY_OFFSETS_BY_LENGTH[s.copyLength];
-            int wordId = s.distance - s.maxDistance - 1;
-            int shift = DICTIONARY_SIZE_BITS_BY_LENGTH[s.copyLength];
-            int mask = (1 << shift) - 1;
-            int wordIdx = wordId & mask;
-            int transformIdx = wordId >>> shift;
-            offset += wordIdx * s.copyLength;
-            if (transformIdx < Transform.NUM_RFC_TRANSFORMS) {
-              int len = Transform.transformDictionaryWord(ringBuffer, s.pos, Dictionary.getData(),
-                  offset, s.copyLength, Transform.RFC_TRANSFORMS, transformIdx);
-              s.pos += len;
-              s.metaBlockLength -= len;
-              if (s.pos >= fence) {
-                s.nextRunningState = MAIN_LOOP;
-                s.runningState = INIT_WRITE;
-                continue;
-              }
-            } else {
-              throw new BrotliRuntimeException("Invalid backward reference"); // COV_NF_LINE
-            }
-          } else {
-            throw new BrotliRuntimeException("Invalid backward reference"); // COV_NF_LINE
+        case USE_DICTIONARY:
+          doUseDictionary(s, fence);
+          continue;
+
+        case COPY_FROM_COMPOUND_DICTIONARY:
+          s.pos += copyFromCompoundDictionary(s, fence);
+          if (s.pos >= fence) {
+            s.nextRunningState = COPY_FROM_COMPOUND_DICTIONARY;
+            s.runningState = INIT_WRITE;
+            return;
           }
           s.runningState = MAIN_LOOP;
           continue;
@@ -1208,7 +1310,6 @@ final class Decode {
           s.runningState = BLOCK_START;
           continue;
 
-
         case COPY_UNCOMPRESSED:
           copyUncompressedData(s);
           continue;

java/org/brotli/dec/Dictionary.java

@@ -18,7 +18,12 @@ import java.nio.ByteBuffer;
  * once in each classworld). To avoid this, it is enough to call {@link #getData()} proactively.
  */
 public final class Dictionary {
-  private static volatile ByteBuffer data;
+  static final int MIN_DICTIONARY_WORD_LENGTH = 4;
+  static final int MAX_DICTIONARY_WORD_LENGTH = 31;
+
+  private static ByteBuffer data;
+  static final int[] offsets = new int[32];
+  static final int[] sizeBits = new int[32];
 
   private static class DataLoader {
     static final boolean OK;
@@ -34,10 +39,44 @@ public final class Dictionary {
     }
   }
 
-  public static void setData(ByteBuffer data) {
+  public static void setData(ByteBuffer data, int[] sizeBits) {
     if (!data.isDirect() || !data.isReadOnly()) {
       throw new BrotliRuntimeException("data must be a direct read-only byte buffer");
     }
+    // TODO: is that so?
+    if (sizeBits.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 (sizeBits[i] != 0) {
+        throw new BrotliRuntimeException("first " + MIN_DICTIONARY_WORD_LENGTH + " must be 0");
+      }
+    }
+    int[] dictionaryOffsets = Dictionary.offsets;
+    int[] dictionarySizeBits = Dictionary.sizeBits;
+    System.arraycopy(sizeBits, 0, dictionarySizeBits, 0, sizeBits.length);
+    int pos = 0;
+    int limit = data.capacity();
+    for (int i = 0; i < sizeBits.length; ++i) {
+      dictionaryOffsets[i] = pos;
+      int bits = dictionarySizeBits[i];
+      if (bits != 0) {
+        if (bits >= 31) {
+          throw new BrotliRuntimeException("sizeBits values must be less than 31");
+        }
+        pos += i << bits;
+        if (pos <= 0 || pos > limit) {
+          throw new BrotliRuntimeException("sizeBits is inconsistent: overflow");
+        }
+      }
+    }
+    for (int i = sizeBits.length; i < 32; ++i) {
+      dictionaryOffsets[i] = pos;
+    }
+    if (pos != limit) {
+      throw new BrotliRuntimeException("sizeBits is inconsistent: underflow");
+    }
     Dictionary.data = data;
   }
 

java/org/brotli/dec/SetDictionaryTest.java

@@ -65,7 +65,10 @@ public class SetDictionaryTest {
     FileChannel dictionaryChannel =
         new FileInputStream(System.getProperty("RFC_DICTIONARY")).getChannel();
     ByteBuffer dictionary = dictionaryChannel.map(FileChannel.MapMode.READ_ONLY, 0, 122784).load();
-    Dictionary.setData(dictionary);
+    int[] sizeBits = {
+      0, 0, 0, 0, 10, 10, 11, 11, 10, 10, 10, 10, 10, 9, 9, 8, 7, 7, 8, 7, 7, 6, 6, 5, 5
+    };
+    Dictionary.setData(dictionary, sizeBits);
 
     // Retry decoding of dictionary item.
     decoder = new BrotliInputStream(new ByteArrayInputStream(BASE_DICT_WORD));

java/org/brotli/dec/State.java

@@ -60,7 +60,6 @@ final class State {
   int contextLookupOffset2;
   int distanceCode;
   int numDirectDistanceCodes;
-  int distancePostfixMask;
   int distancePostfixBits;
   int distance;
   int copyLength;
@@ -76,6 +75,18 @@ final class State {
   int isEager;
   int isLargeWindow;
 
+  // Compound dictionary
+  int cdNumChunks;
+  int cdTotalSize;
+  int cdBrIndex;
+  int cdBrOffset;
+  int cdBrLength;
+  int cdBrCopied;
+  byte[][] cdChunks;
+  int[] cdChunkOffsets;
+  int cdBlockBits;
+  byte[] cdBlockMap;
+
   InputStream input; // BitReader
 
   State() {

java/org/brotli/dec/Utils.java

@@ -58,6 +58,10 @@ final class Utils {
     }
   }
 
+  static void copyBytes(byte[] dst, int target, byte[] src, int start, int end) {
+    System.arraycopy(src, start, dst, target, end - start);
+  }
+
   static void copyBytesWithin(byte[] bytes, int target, int start, int end) {
     System.arraycopy(bytes, start, bytes, target, end - start);
   }

java/org/brotli/enc/BUILD

@@ -0,0 +1,14 @@
+# Description:
+#   Java port of Brotli decoder.
+
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])  # MIT
+
+java_library(
+    name = "prepared_dictionary",
+    srcs = [
+        "PreparedDictionary.java",
+        "PreparedDictionaryGenerator.java",
+    ],
+)

java/org/brotli/enc/PreparedDictionary.java

@@ -0,0 +1,16 @@
+/* Copyright 2018 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.enc;
+
+import java.nio.ByteBuffer;
+
+/**
+ * Prepared dictionary data provider.
+ */
+public interface PreparedDictionary {
+  ByteBuffer getData();
+}

java/org/brotli/enc/PreparedDictionaryGenerator.java

@@ -0,0 +1,185 @@
+/* Copyright 2017 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.enc;
+
+import java.nio.Buffer;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.IntBuffer;
+import java.nio.ShortBuffer;
+
+/**
+ * Java prepared (raw) dictionary producer.
+ */
+public class PreparedDictionaryGenerator {
+
+  private static final int MAGIC = 0xDEBCEDE0;
+  private static final long HASH_MULTIPLIER = 0x1fe35a7bd3579bd3L;
+
+  private static class PreparedDictionaryImpl implements PreparedDictionary {
+    private final ByteBuffer data;
+
+    private PreparedDictionaryImpl(ByteBuffer data) {
+      this.data = data;
+    }
+
+    @Override
+    public ByteBuffer getData() {
+      return data;
+    }
+  }
+
+  // Disallow instantiation.
+  private PreparedDictionaryGenerator() { }
+
+  public static PreparedDictionary generate(ByteBuffer src) {
+    return generate(src, 17, 3, 40, 5);
+  }
+
+  public static PreparedDictionary generate(ByteBuffer src,
+      int bucketBits, int slotBits, int hashBits, int blockBits) {
+    ((Buffer) src).clear();  // Just in case...
+    if (blockBits > 12) {
+      throw new IllegalArgumentException("blockBits is too big");
+    }
+    if (bucketBits >= 24) {
+      throw new IllegalArgumentException("bucketBits is too big");
+    }
+    if (bucketBits - slotBits >= 16) {
+      throw new IllegalArgumentException("slotBits is too small");
+    }
+    int bucketLimit = 1 << blockBits;
+    int numBuckets = 1 << bucketBits;
+    int numSlots = 1 << slotBits;
+    int slotMask = numSlots - 1;
+    int hashShift = 64 - bucketBits;
+    long hashMask = (~0L) >>> (64 - hashBits);
+    int sourceSize = src.capacity();
+    if (sourceSize < 8) {
+      throw new IllegalArgumentException("src is too short");
+    }
+
+    /* Step 1: create "bloated" hasher. */
+    short[] num = new short[numBuckets];
+    int[] bucketHeads = new int[numBuckets];
+    int[] nextBucket = new int[sourceSize];
+
+    long accumulator = 0;
+    for (int i = 0; i < 7; ++i) {
+      accumulator |= (src.get(i) & 0xFFL) << (8 * i);
+    }
+    accumulator <<= 8;
+    /* TODO: apply custom "store" order. */
+    for (int i = 0; i + 7 < sourceSize; ++i) {
+      accumulator = (accumulator >>> 8) | ((src.get(i + 7) & 0xFFL) << 56);
+      long h = (accumulator & hashMask) * HASH_MULTIPLIER;
+      int key = (int) (h >>> hashShift);
+      int count = num[key];
+      nextBucket[i] = (count == 0) ? -1 : bucketHeads[key];
+      bucketHeads[key] = i;
+      count++;
+      if (count > bucketLimit) {
+        count = bucketLimit;
+      }
+      num[key] = (short) count;
+    }
+
+    /* Step 2: find slot limits. */
+    int[] slotLimit = new int[numSlots];
+    int[] slotSize = new int[numSlots];
+    int totalItems = 0;
+    for (int i = 0; i < numSlots; ++i) {
+      boolean overflow = false;
+      slotLimit[i] = bucketLimit;
+      while (true) {
+        overflow = false;
+        int limit = slotLimit[i];
+        int count = 0;
+        for (int j = i; j < numBuckets; j += numSlots) {
+          int size = num[j];
+          /* Last chain may span behind 64K limit; overflow happens only if
+             we are about to use 0xFFFF+ as item offset. */
+          if (count >= 0xFFFF) {
+            overflow = true;
+            break;
+          }
+          if (size > limit) {
+            size = limit;
+          }
+          count += size;
+        }
+        if (!overflow) {
+          slotSize[i] = count;
+          totalItems += count;
+          break;
+        }
+        slotLimit[i]--;
+      }
+    }
+
+    /* Step 3: transfer data to "slim" hasher. */
+    int part0 = 6 * 4;
+    int part1 = numSlots * 4;
+    int part2 = numBuckets * 2;
+    int part3 = totalItems * 4;
+    int allocSize = part0 + part1 + part2 + part3 + sourceSize;
+    ByteBuffer flat = ByteBuffer.allocateDirect(allocSize);
+    ByteBuffer pointer = flat.slice();
+    pointer.order(ByteOrder.nativeOrder());
+
+    IntBuffer struct = pointer.asIntBuffer();
+    pointer.position(pointer.position() + part0);
+    IntBuffer slotOffsets = pointer.asIntBuffer();
+    pointer.position(pointer.position() + part1);
+    ShortBuffer heads = pointer.asShortBuffer();
+    pointer.position(pointer.position() + part2);
+    IntBuffer items = pointer.asIntBuffer();
+    pointer.position(pointer.position() + part3);
+    ByteBuffer sourceCopy = pointer.slice();
+
+    /* magic         */ struct.put(0, MAGIC);
+    /* source_offset */ struct.put(1, totalItems);
+    /* source_size   */ struct.put(2, sourceSize);
+    /* hash_bits     */ struct.put(3, hashBits);
+    /* bucket_bits   */ struct.put(4, bucketBits);
+    /* slot_bits     */ struct.put(5, slotBits);
+
+    totalItems = 0;
+    for (int i = 0; i < numSlots; ++i) {
+      slotOffsets.put(i, totalItems);
+      totalItems += slotSize[i];
+      slotSize[i] = 0;
+    }
+
+    for (int i = 0; i < numBuckets; ++i) {
+      int slot = i & slotMask;
+      int count = num[i];
+      if (count > slotLimit[slot]) {
+        count = slotLimit[slot];
+      }
+      if (count == 0) {
+        heads.put(i, (short) 0xFFFF);
+        continue;
+      }
+      int cursor = slotSize[slot];
+      heads.put(i, (short) cursor);
+      cursor += slotOffsets.get(slot);
+      slotSize[slot] += count;
+      int pos = bucketHeads[i];
+      for (int j = 0; j < count; j++) {
+        items.put(cursor++, pos);
+        pos = nextBucket[pos];
+      }
+      cursor--;
+      items.put(cursor, items.get(cursor) | 0x80000000);
+    }
+
+    sourceCopy.put(src);
+
+    return new PreparedDictionaryImpl(flat);
+  }
+}