Echo Writes Code

transcoding.cpp

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
#include "crucible/windows/transcoding.hpp"

#include <Windows.h>

namespace crucible::windows::transcoding {
  auto MultiByteToWideCharFailed::format() const -> std::string {
    return "MultiByteToWideChar() failed";
  }

  auto WideCharToMultiByteFailed::format() const -> std::string {
    return "WideCharToMultiByte() failed";
  }

  auto OutputTruncated::format() const -> std::string {
    return "Output was truncated";
  }

  auto TranscodingErrorDescription::format() const -> std::string {
    return "Transcoding error";
  }

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

    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;

    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));
    }
  }
}