Class SnappyArrayWriter

snappy.cc:2292–2372

// Note that this is not a "ByteSink", but a type that matches the
// Writer template argument to SnappyDecompressor::DecompressAllTags().
class SnappyArrayWriter {
 private:
  char* base_;
  char* op_;
  char* op_limit_;
  // If op < op_limit_min_slop_ then it's safe to unconditionally write
  // kSlopBytes starting at op.
  char* op_limit_min_slop_;

 public:
  inline explicit SnappyArrayWriter(char* dst)
      : base_(dst),
        op_(dst),
        op_limit_(dst),
        op_limit_min_slop_(dst) {}  // Safe default see invariant.

  inline void SetExpectedLength(size_t len) {
    op_limit_ = op_ + len;
    // Prevent pointer from being past the buffer.
    op_limit_min_slop_ = op_limit_ - std::min<size_t>(kSlopBytes - 1, len);
  }

  inline bool CheckLength() const { return op_ == op_limit_; }

  char* GetOutputPtr() { return op_; }
  char* GetBase(ptrdiff_t* op_limit_min_slop) {
    *op_limit_min_slop = op_limit_min_slop_ - base_;
    return base_;
  }
  void SetOutputPtr(char* op) { op_ = op; }

  inline bool Append(const char* ip, size_t len, char** op_p) {
    char* op = *op_p;
    const size_t space_left = op_limit_ - op;
    if (space_left < len) return false;
    std::memcpy(op, ip, len);
    *op_p = op + len;
    return true;
  }

  inline bool TryFastAppend(const char* ip, size_t available, size_t len,
                            char** op_p) {
    char* op = *op_p;
    const size_t space_left = op_limit_ - op;
    if (len <= 16 && available >= 16 + kMaximumTagLength && space_left >= 16) {
      // Fast path, used for the majority (about 95%) of invocations.
      UnalignedCopy128(ip, op);
      *op_p = op + len;
      return true;
    } else {
      return false;
    }
  }

  SNAPPY_ATTRIBUTE_ALWAYS_INLINE
  inline bool AppendFromSelf(size_t offset, size_t len, char** op_p) {
    assert(len > 0);
    char* const op = *op_p;