Add brotli decompressor

This commit is for the decoder for brotli compression format. Brotli is a generic byte-level compression algorithm.
2013-10-11 10:26:07 +02:00
parent 5ce8fad3ab
commit 04163a87d0
13 changed files with 1935 additions and 0 deletions
@@ -0,0 +1,122 @@
+// Copyright 2013 Google Inc. All Rights Reserved.
+//
+// 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.
+//
+// Bit reading helpers
+
+#include <assert.h>
+
+#include "./bit_reader.h"
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+#define MAX_NUM_BIT_READ 25
+
+#define LBITS 64      // Number of bits prefetched.
+#define WBITS 32      // Minimum number of bytes needed after
+                      // BrotliFillBitWindow.
+#define LOG8_WBITS 4  // Number of bytes needed to store WBITS bits.
+
+static const uint32_t kBitMask[MAX_NUM_BIT_READ] = {
+  0, 1, 3, 7, 15, 31, 63, 127, 255, 511, 1023, 2047, 4095, 8191, 16383, 32767,
+  65535, 131071, 262143, 524287, 1048575, 2097151, 4194303, 8388607, 16777215
+};
+
+void BrotliInitBitReader(BrotliBitReader* const br,
+                         const uint8_t* const start,
+                         size_t length) {
+  size_t i;
+  assert(br != NULL);
+  assert(start != NULL);
+  assert(length < 0xfffffff8u);   // can't happen with a RIFF chunk.
+
+  br->buf_ = start;
+  br->len_ = length;
+  br->val_ = 0;
+  br->pos_ = 0;
+  br->bit_pos_ = 0;
+  br->eos_ = 0;
+  br->error_ = 0;
+  for (i = 0; i < sizeof(br->val_) && i < br->len_; ++i) {
+    br->val_ |= ((uint64_t)br->buf_[br->pos_]) << (8 * i);
+    ++br->pos_;
+  }
+}
+
+void BrotliBitReaderSetBuffer(BrotliBitReader* const br,
+                              const uint8_t* const buf, size_t len) {
+  assert(br != NULL);
+  assert(buf != NULL);
+  assert(len < 0xfffffff8u);   // can't happen with a RIFF chunk.
+  br->eos_ = (br->pos_ >= len);
+  br->buf_ = buf;
+  br->len_ = len;
+}
+
+// If not at EOS, reload up to LBITS byte-by-byte
+static void ShiftBytes(BrotliBitReader* const br) {
+  while (br->bit_pos_ >= 8 && br->pos_ < br->len_) {
+    br->val_ >>= 8;
+    br->val_ |= ((uint64_t)br->buf_[br->pos_]) << (LBITS - 8);
+    ++br->pos_;
+    br->bit_pos_ -= 8;
+  }
+}
+
+void BrotliFillBitWindow(BrotliBitReader* const br) {
+  if (br->bit_pos_ >= WBITS) {
+#if (defined(__x86_64__) || defined(_M_X64))
+    if (br->pos_ + sizeof(br->val_) < br->len_) {
+      br->val_ >>= WBITS;
+      br->bit_pos_ -= WBITS;
+      // The expression below needs a little-endian arch to work correctly.
+      // This gives a large speedup for decoding speed.
+      br->val_ |= *(const uint64_t*)(br->buf_ + br->pos_) << (LBITS - WBITS);
+      br->pos_ += LOG8_WBITS;
+      return;
+    }
+#endif
+    ShiftBytes(br);       // Slow path.
+    if (br->pos_ == br->len_ && br->bit_pos_ == LBITS) {
+      br->eos_ = 1;
+    }
+  }
+}
+
+uint32_t BrotliReadBits(BrotliBitReader* const br, int n_bits) {
+  assert(n_bits >= 0);
+  // Flag an error if end_of_stream or n_bits is more than allowed limit.
+  if (n_bits == 0 || (!br->eos_ && n_bits < MAX_NUM_BIT_READ)) {
+    const uint32_t val =
+        (uint32_t)(br->val_ >> br->bit_pos_) & kBitMask[n_bits];
+    const int new_bits = br->bit_pos_ + n_bits;
+    br->bit_pos_ = new_bits;
+    // If this read is going to cross the read buffer, set the eos flag.
+    if (br->pos_ == br->len_) {
+      if (new_bits >= LBITS) {
+        br->eos_ = 1;
+      }
+    }
+    ShiftBytes(br);
+    return val;
+  } else {
+    br->error_ = 1;
+    return 0;
+  }
+}
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}    // extern "C"
+#endif