src/kudu/util/faststring.cc

// Copyright 2013 Cloudera, Inc.
//
// 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.

#include "kudu/util/faststring.h"

#include <glog/logging.h>

#include "kudu/gutil/gscoped_ptr.h"

namespace kudu {

void faststring::GrowByAtLeast(size_t count) {
  // Not enough space, need to reserve more.
  // Don't reserve exactly enough space for the new string -- that makes it
  // too easy to write perf bugs where you get O(n^2) append.
  // Instead, alwayhs expand by at least 50%.

  size_t to_reserve = len_ + count;
  if (len_ + count < len_ * 3 / 2) {
    to_reserve = len_ *  3 / 2;
  }
  GrowArray(to_reserve);
}

void faststring::GrowArray(size_t newcapacity) {
  DCHECK_GE(newcapacity, capacity_);
  gscoped_array<uint8_t> newdata(new uint8_t[newcapacity]);
  if (len_ > 0) {
    memcpy(&newdata[0], &data_[0], len_);
  }
  capacity_ = newcapacity;
  if (data_ != initial_data_) {
    delete[] data_;
  } else {
    ASAN_POISON_MEMORY_REGION(initial_data_, arraysize(initial_data_));
  }

  data_ = newdata.release();
  ASAN_POISON_MEMORY_REGION(data_ + len_, capacity_ - len_);
}


} // namespace kudu