/*
 * Copyright 2016 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 "flatbuffers/util.h"

namespace flatbuffers {

bool FileExistsRaw(const char *name) {
  std::ifstream ifs(name);
  return ifs.good();
}

bool LoadFileRaw(const char *name, bool binary, std::string *buf) {
  std::ifstream ifs(name, binary ? std::ifstream::binary : std::ifstream::in);
  if (!ifs.is_open()) return false;
  if (binary) {
    // The fastest way to read a file into a string.
    ifs.seekg(0, std::ios::end);
    (*buf).resize(static_cast<size_t>(ifs.tellg()));
    ifs.seekg(0, std::ios::beg);
    ifs.read(&(*buf)[0], (*buf).size());
  } else {
    // This is slower, but works correctly on all platforms for text files.
    std::ostringstream oss;
    oss << ifs.rdbuf();
    *buf = oss.str();
  }
  return !ifs.bad();
}

static LoadFileFunction g_load_file_function = LoadFileRaw;
static FileExistsFunction g_file_exists_function = FileExistsRaw;

bool LoadFile(const char *name, bool binary, std::string *buf) {
  assert(g_load_file_function);
  return g_load_file_function(name, binary, buf);
}

bool FileExists(const char *name) {
  assert(g_file_exists_function);
  return g_file_exists_function(name);
}

LoadFileFunction SetLoadFileFunction(LoadFileFunction load_file_function) {
  LoadFileFunction previous_function = g_load_file_function;
  g_load_file_function = load_file_function ? load_file_function : LoadFileRaw;
  return previous_function;
}

FileExistsFunction SetFileExistsFunction(
    FileExistsFunction file_exists_function) {
  FileExistsFunction previous_function = g_file_exists_function;
  g_file_exists_function = file_exists_function ?
      file_exists_function : FileExistsRaw;
  return previous_function;
}

}  // namespace flatbuffers