Echo Writes Code

transcoding.cpp

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#include "crucible/windows/transcoding.hpp"

#include <Windows.h>

#include <limits>

namespace crucible::windows::transcoding {
  auto transcode_utf8_to_utf16(std::string const &utf8) -> TranscodingResult<std::wstring> {
    constexpr ::UINT CODEPAGE = CP_UTF8;
    constexpr ::DWORD FLAGS = MB_ERR_INVALID_CHARS;

    if (utf8.size() > std::numeric_limits<int>::max()) {
      return core::result::make_failure<TranscodingError>(InputTooLarge());
    }

    auto const utf8_size = static_cast<int>(utf8.size());

    int const required_size = ::MultiByteToWideChar(CODEPAGE, FLAGS, utf8.data(), utf8_size, nullptr, 0);
    if (required_size <= 0) {
      return core::result::make_failure<TranscodingError>(MultiByteToWideCharFailed());
    }

    std::wstring utf16(required_size, L'\0');
    int const characters_written = ::MultiByteToWideChar(CODEPAGE, FLAGS, utf8.data(), utf8_size, utf16.data(), required_size);

    if (characters_written <= 0) {
      return core::result::make_failure<TranscodingError>(MultiByteToWideCharFailed());
    } else if (characters_written != required_size) {
      return core::result::make_failure<TranscodingError>(OutputTruncated());
    } else {
      return core::result::make_success(std::move(utf16));
    }
  }

  auto transcode_utf16_to_utf8(std::wstring const &utf16) -> TranscodingResult<std::string> {
    constexpr ::UINT CODEPAGE = CP_UTF8;
    constexpr ::DWORD FLAGS = WC_ERR_INVALID_CHARS;

    ::LPCCH default_character = nullptr;
    ::LPBOOL used_default_character = nullptr;

    if (utf16.size() > std::numeric_limits<int>::max()) {
      return core::result::make_failure<TranscodingError>(InputTooLarge());
    }

    auto const utf16_size = static_cast<int>(utf16.size());

    int const required_size = ::WideCharToMultiByte(CODEPAGE, FLAGS, utf16.data(), utf16_size, nullptr, 0, default_character, used_default_character);
    if (required_size <= 0) {
      return core::result::make_failure<TranscodingError>(WideCharToMultiByteFailed());
    }

    std::string utf8(required_size, '\0');
    int const bytes_written = ::WideCharToMultiByte(CODEPAGE, FLAGS, utf16.data(), utf16_size, utf8.data(), required_size, default_character, used_default_character);

    if (bytes_written <= 0) {
      return core::result::make_failure<TranscodingError>(WideCharToMultiByteFailed());
    } else if (bytes_written != required_size) {
      return core::result::make_failure<TranscodingError>(OutputTruncated());
    } else {
      return core::result::make_success(std::move(utf8));
    }
  }
}