/*
 * Copyright 2016 Facebook, 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 <folly/Unicode.h>

namespace folly {

//////////////////////////////////////////////////////////////////////

std::string codePointToUtf8(char32_t cp) {
  std::string result;

  // Based on description from http://en.wikipedia.org/wiki/UTF-8.

  if (cp <= 0x7f) {
    result.resize(1);
    result[0] = static_cast<char>(cp);
  } else if (cp <= 0x7FF) {
    result.resize(2);
    result[1] = static_cast<char>(0x80 | (0x3f & cp));
    result[0] = static_cast<char>(0xC0 | (cp >> 6));
  } else if (cp <= 0xFFFF) {
    result.resize(3);
    result[2] = static_cast<char>(0x80 | (0x3f & cp));
    result[1] = (0x80 | static_cast<char>((0x3f & (cp >> 6))));
    result[0] = (0xE0 | static_cast<char>(cp >> 12));
  } else if (cp <= 0x10FFFF) {
    result.resize(4);
    result[3] = static_cast<char>(0x80 | (0x3f & cp));
    result[2] = static_cast<char>(0x80 | (0x3f & (cp >> 6)));
    result[1] = static_cast<char>(0x80 | (0x3f & (cp >> 12)));
    result[0] = static_cast<char>(0xF0 | (cp >> 18));
  }

  return result;
}

//////////////////////////////////////////////////////////////////////

}
