Added brotli enc/ and tools/ directories.

third_party/brotli/enc/ringbuffer.h

+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+// Sliding window over the input data.
+
+#ifndef BROTLI_ENC_RINGBUFFER_H_
+#define BROTLI_ENC_RINGBUFFER_H_
+
+#include <cstdlib>  /* free, realloc */
+
+#include "./port.h"
+#include "./types.h"
+
+namespace brotli {
+
+// A RingBuffer(window_bits, tail_bits) contains `1 << window_bits' bytes of
+// data in a circular manner: writing a byte writes it to:
+//   `position() % (1 << window_bits)'.
+// For convenience, the RingBuffer array contains another copy of the
+// first `1 << tail_bits' bytes:
+//   buffer_[i] == buffer_[i + (1 << window_bits)], if i < (1 << tail_bits),
+// and another copy of the last two bytes:
+//   buffer_[-1] == buffer_[(1 << window_bits) - 1] and
+//   buffer_[-2] == buffer_[(1 << window_bits) - 2].
+class RingBuffer {
+ public:
+  RingBuffer(int window_bits, int tail_bits)
+      : size_(1u << window_bits),
+        mask_((1u << window_bits) - 1),
+        tail_size_(1u << tail_bits),
+        total_size_(size_ + tail_size_),
+        cur_size_(0),
+        pos_(0),
+        data_(0),
+        buffer_(0) {}
+
+  ~RingBuffer(void) {
+    free(data_);
+  }
+
+  // Allocates or re-allocates data_ to the given length + plus some slack
+  // region before and after. Fills the slack regions with zeros.
+  inline void InitBuffer(const uint32_t buflen) {
+    static const size_t kSlackForEightByteHashingEverywhere = 7;
+    cur_size_ = buflen;
+    data_ = static_cast<uint8_t*>(realloc(
+        data_, 2 + buflen + kSlackForEightByteHashingEverywhere));
+    buffer_ = data_ + 2;
+    buffer_[-2] = buffer_[-1] = 0;
+    for (size_t i = 0; i < kSlackForEightByteHashingEverywhere; ++i) {
+      buffer_[cur_size_ + i] = 0;
+    }
+  }
+
+  // Push bytes into the ring buffer.
+  void Write(const uint8_t *bytes, size_t n) {
+    if (pos_ == 0 && n < tail_size_) {
+      // Special case for the first write: to process the first block, we don't
+      // need to allocate the whole ringbuffer and we don't need the tail
+      // either. However, we do this memory usage optimization only if the
+      // first write is less than the tail size, which is also the input block
+      // size, otherwise it is likely that other blocks will follow and we
+      // will need to reallocate to the full size anyway.
+      pos_ = static_cast<uint32_t>(n);
+      InitBuffer(pos_);
+      memcpy(buffer_, bytes, n);
+      return;
+    }
+    if (cur_size_ < total_size_) {
+      // Lazily allocate the full buffer.
+      InitBuffer(total_size_);
+      // Initialize the last two bytes to zero, so that we don't have to worry
+      // later when we copy the last two bytes to the first two positions.
+      buffer_[size_ - 2] = 0;
+      buffer_[size_ - 1] = 0;
+    }
+    const size_t masked_pos = pos_ & mask_;
+    // The length of the writes is limited so that we do not need to worry
+    // about a write
+    WriteTail(bytes, n);
+    if (PREDICT_TRUE(masked_pos + n <= size_)) {
+      // A single write fits.
+      memcpy(&buffer_[masked_pos], bytes, n);
+    } else {
+      // Split into two writes.
+      // Copy into the end of the buffer, including the tail buffer.
+      memcpy(&buffer_[masked_pos], bytes,
+             std::min(n, total_size_ - masked_pos));
+      // Copy into the beginning of the buffer
+      memcpy(&buffer_[0], bytes + (size_ - masked_pos),
+             n - (size_ - masked_pos));
+    }
+    buffer_[-2] = buffer_[size_ - 2];
+    buffer_[-1] = buffer_[size_ - 1];
+    pos_ += static_cast<uint32_t>(n);
+    if (pos_ > (1u << 30)) {  /* Wrap, but preserve not-a-first-lap feature. */
+      pos_ = (pos_ & ((1u << 30) - 1)) | (1u << 30);
+    }
+  }
+
+  void Reset(void) {
+    pos_ = 0;
+  }
+
+  // Logical cursor position in the ring buffer.
+  uint32_t position(void) const { return pos_; }
+
+  // Bit mask for getting the physical position for a logical position.
+  uint32_t mask(void) const { return mask_; }
+
+  uint8_t *start(void) { return &buffer_[0]; }
+  const uint8_t *start(void) const { return &buffer_[0]; }
+
+ private:
+  void WriteTail(const uint8_t *bytes, size_t n) {
+    const size_t masked_pos = pos_ & mask_;
+    if (PREDICT_FALSE(masked_pos < tail_size_)) {
+      // Just fill the tail buffer with the beginning data.
+      const size_t p = size_ + masked_pos;
+      memcpy(&buffer_[p], bytes, std::min(n, tail_size_ - masked_pos));
+    }
+  }
+
+  // Size of the ringbuffer is (1 << window_bits) + tail_size_.
+  const uint32_t size_;
+  const uint32_t mask_;
+  const uint32_t tail_size_;
+  const uint32_t total_size_;
+
+  uint32_t cur_size_;
+  // Position to write in the ring buffer.
+  uint32_t pos_;
+  // The actual ring buffer containing the copy of the last two bytes, the data,
+  // and the copy of the beginning as a tail.
+  uint8_t *data_;
+  // The start of the ringbuffer.
+  uint8_t *buffer_;
+};
+
+}  // namespace brotli
+
+#endif  // BROTLI_ENC_RINGBUFFER_H_