/* Copyright 2015 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.
==============================================================================*/

#include "tensorflow/core/lib/io/inputbuffer.h"
#include "tensorflow/core/lib/core/errors.h"

namespace tensorflow {
namespace io {

InputBuffer::InputBuffer(RandomAccessFile* file, size_t buffer_bytes)
    : file_(file),
      file_pos_(0),
      size_(buffer_bytes),
      buf_(new char[size_]),
      pos_(buf_),
      limit_(buf_) {}

InputBuffer::~InputBuffer() {
  delete file_;
  delete[] buf_;
}

Status InputBuffer::FillBuffer() {
  StringPiece data;
  Status s = file_->Read(file_pos_, size_, &data, buf_);
  if (data.data() != buf_) {
    memmove(buf_, data.data(), data.size());
  }
  pos_ = buf_;
  limit_ = pos_ + data.size();
  file_pos_ += data.size();
  return s;
}

Status InputBuffer::ReadLine(string* result) {
  result->clear();
  int i;
  Status s;
  for (i = 0;; i++) {
    if (pos_ == limit_) {
      // Get more data into buffer
      s = FillBuffer();
      if (limit_ == buf_) {
        break;
      }
    }
    char c = *pos_++;
    if (c == '\n') {
      // We don't append the '\n' to *result
      return Status::OK();
    }
    // We don't append '\r' to *result
    if (c != '\r') {
      *result += c;
    }
  }
  if (errors::IsOutOfRange(s) && !result->empty()) {
    return Status::OK();
  }
  return s;
}

Status InputBuffer::ReadNBytes(int64 bytes_to_read, string* result) {
  result->clear();
  if (bytes_to_read < 0) {
    return errors::InvalidArgument("Can't read a negative number of bytes: ",
                                   bytes_to_read);
  }
  result->reserve(bytes_to_read);
  Status s;
  while (result->size() < static_cast<size_t>(bytes_to_read)) {
    if (pos_ == limit_) {
      // Get more data into buffer
      s = FillBuffer();
      if (limit_ == buf_) {
        break;
      }
    }
    const int64 bytes_to_copy =
        std::min<int64>(limit_ - pos_, bytes_to_read - result->size());
    result->insert(result->size(), pos_, bytes_to_copy);
    pos_ += bytes_to_copy;
  }
  if (errors::IsOutOfRange(s) &&
      (result->size() == static_cast<size_t>(bytes_to_read))) {
    return Status::OK();
  }
  return s;
}

Status InputBuffer::SkipNBytes(int64 bytes_to_skip) {
  if (bytes_to_skip < 0) {
    return errors::InvalidArgument("Can only skip forward, not ",
                                   bytes_to_skip);
  }
  int64 bytes_skipped = 0;
  Status s;
  while (bytes_skipped < bytes_to_skip) {
    if (pos_ == limit_) {
      // Get more data into buffer
      s = FillBuffer();
      if (limit_ == buf_) {
        break;
      }
    }
    const int64 bytes_to_advance =
        std::min<int64>(limit_ - pos_, bytes_to_skip - bytes_skipped);
    bytes_skipped += bytes_to_advance;
    pos_ += bytes_to_advance;
  }
  if (errors::IsOutOfRange(s) && bytes_skipped == bytes_to_skip) {
    return Status::OK();
  }
  return s;
}

}  // namespace io
}  // namespace tensorflow
