/* Copyright 2016 The TensorFlow Authors. 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.
==============================================================================*/

#include "tensorflow/core/lib/io/random_inputstream.h"
#include <memory>

namespace tensorflow {
namespace io {

RandomAccessInputStream::RandomAccessInputStream(RandomAccessFile* file)
    : file_(file) {}

Status RandomAccessInputStream::ReadNBytes(int64 bytes_to_read,
                                           string* result) {
  if (bytes_to_read < 0) {
    return errors::InvalidArgument("Cannot read negative number of bytes");
  }
  result->clear();
  result->resize(bytes_to_read);
  char* result_buffer = &(*result)[0];
  StringPiece data;
  Status s = file_->Read(pos_, bytes_to_read, &data, result_buffer);
  if (data.data() != result_buffer) {
    memmove(result_buffer, data.data(), data.size());
  }
  result->resize(data.size());
  if (s.ok() || errors::IsOutOfRange(s)) {
    pos_ += data.size();
  } else {
    return s;
  }
  // If the amount of data we read is less than what we wanted, we return an
  // out of range error. We need to catch this explicitly since file_->Read()
  // would not do so if at least 1 byte is read (b/30839063).
  if (data.size() < bytes_to_read) {
    return errors::OutOfRange("reached end of file");
  }
  return Status::OK();
}

int64 RandomAccessInputStream::Tell() const { return pos_; }

}  // namespace io
}  // namespace tensorflow
