Initial commit

.gitignore

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+# Files and directories created by pub.
+.dart_tool/
+.packages
+
+# Conventional directory for build outputs.
+build/
+
+# Omit committing pubspec.lock for library packages; see
+# https://dart.dev/guides/libraries/private-files#pubspeclock.
+pubspec.lock

CHANGELOG.md

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+## 1.0.0
+
+- Initial version.

README.md

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+<!-- 
+This README describes the package. If you publish this package to pub.dev,
+this README's contents appear on the landing page for your package.
+
+For information about how to write a good package README, see the guide for
+[writing package pages](https://dart.dev/guides/libraries/writing-package-pages). 
+
+For general information about developing packages, see the Dart guide for
+[creating packages](https://dart.dev/guides/libraries/create-library-packages)
+and the Flutter guide for
+[developing packages and plugins](https://flutter.dev/developing-packages). 
+-->
+
+TODO: Put a short description of the package here that helps potential users
+know whether this package might be useful for them.
+
+## Features
+
+TODO: List what your package can do. Maybe include images, gifs, or videos.
+
+## Getting started
+
+TODO: List prerequisites and provide or point to information on how to
+start using the package.
+
+## Usage
+
+TODO: Include short and useful examples for package users. Add longer examples
+to `/example` folder. 
+
+```dart
+const like = 'sample';
+```
+
+## Additional information
+
+TODO: Tell users more about the package: where to find more information, how to 
+contribute to the package, how to file issues, what response they can expect 
+from the package authors, and more.

analysis_options.yaml

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+# This file configures the static analysis results for your project (errors,
+# warnings, and lints).
+#
+# This enables the 'recommended' set of lints from `package:lints`.
+# This set helps identify many issues that may lead to problems when running
+# or consuming Dart code, and enforces writing Dart using a single, idiomatic
+# style and format.
+#
+# If you want a smaller set of lints you can change this to specify
+# 'package:lints/core.yaml'. These are just the most critical lints
+# (the recommended set includes the core lints).
+# The core lints are also what is used by pub.dev for scoring packages.
+
+include: package:lints/recommended.yaml
+
+# Uncomment the following section to specify additional rules.
+
+# linter:
+#   rules:
+#     - camel_case_types
+
+# analyzer:
+#   exclude:
+#     - path/to/excluded/files/**
+
+# For more information about the core and recommended set of lints, see
+# https://dart.dev/go/core-lints
+
+# For additional information about configuring this file, see
+# https://dart.dev/guides/language/analysis-options

lib/character_conversion.dart

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+import 'dart:math';
+
+const Map<String, String> numbers = {
+  'yen': '円',
+  '0': '冷',
+  '1': '一',
+  '2': '二',
+  '3': '三',
+  '4': '四',
+  '5': '五',
+  '6': '六',
+  '7': '七',
+  '8': '八',
+  '9': '九',
+  '10': '十',
+  '100': '百',
+  '1000': '千',
+  '10000': '万',
+  '10^8': '億',
+  '10^12': '兆',
+  '10^16': '京',
+  '10^20': '垓',
+  '10^24': '𥝱',
+  '10^28': '穣',
+  '10^32': '溝',
+  '10^36': '澗',
+  '10^40': '正',
+  '10^44': '載',
+  '10^48': '極',
+};
+
+const Map<String, String> formalNumbers = {
+  'yen': '圓',
+  '0': '冷',
+  '1': '壱',
+  '2': '弐',
+  '3': '参',
+  '4': '肆',
+  '5': '伍',
+  '6': '陸',
+  '7': '漆',
+  '8': '捌',
+  '9': '玖',
+  '10': '拾',
+  '100': '陌',
+  '1000': '阡',
+  '10000': '萬',
+};
+
+String numberToKanji(
+  int number, {
+  bool placeValue = false,
+  bool formal = false,
+  bool yen = false,
+}) {
+  if (placeValue) {
+    return number
+            .toString()
+            .split('')
+            .map((e) => e == '0' ? '〇' : numbers[e]!)
+            .join() +
+        (yen ? numbers['yen']! : '');
+  } else {
+    final Map<String, String> numberSet = formal ? numbers : formalNumbers;
+    // int i = number;
+    // while(i )
+  }
+  throw UnimplementedError();
+}
+
+enum RomanizationSystem { hepburn, nippon, passport }
+
+// FullwidthChar
+// FullwidthNum
+// Hiragana
+// Katakana
+// Halfwidth katakana
+
+
+void main(List<String> args) {
+  print(numberToKanji(2012, placeValue: true));
+}

lib/iconv/character_set_conversion.dart

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+// KangXi to Unified CJK
+// Unified CJK to KangXi
+
+import 'dart:convert';
+
+import 'character_sets/jisx0208.dart';
+import 'datatypes.dart';
+
+class ConverterException implements Exception {
+  String cause;
+  ConverterException(this.cause);
+}
+
+/// raw 7 or 8 bit encoding?
+class JSIX0201 {}
+
+/// Character sets that supports this:
+/// Shift JIS ("SJIS")
+/// ISO-2022-JP ("JIS")
+/// EUC-JP ("UJIS")
+///
+/// Takes a unicode character code and converts it to its JSIX0208 equivalent
+/// If no such symbol is found, it will return a null value.
+class JSIX0208Decoder extends Converter<int, int?> {
+  /// See jisx0208_mbtowc(...) at
+  /// https://github.com/xbmc/libiconv/blob/master/lib/jisx0208.h
+  static int? decode16BitCharacter(int character) {
+    int c1 = character >> 8;
+    int c2 = character & 0x00FF;
+    if (!((c1.between(0x21, 0x28) || c1.between(0x30, 0x74)) &&
+        c2.between(0x21, 0x7e))) {
+      throw ConverterException("Illegal sequence");
+    }
+
+    int i = 94 * (c1 - 0x21) + (c2 - 0x21);
+    int? wc;
+    if (i < 690) {
+      wc = jisx0208_2uni_page21[i];
+    } else if (i < 7808) {
+      wc = jisx0208_2uni_page30[i - 1410];
+    }
+    return wc;
+  }
+
+  @override
+  convert(int input) => decode16BitCharacter(input);
+}
+
+class JSIX0208Encoder extends Converter<int, int?> {
+  /// See jisx0208_wctomb(...) at
+  /// https://github.com/xbmc/libiconv/blob/master/lib/jisx0208.h
+  int? encode16BitCharacter(int character) {
+    S16? summary;
+    if (character.betweenTo(0x0000, 0x0100)) {
+      summary = jisx0208_uni2indx_page00[(character >> 4)];
+    } else if (character.betweenTo(0x0300, 0x0460)) {
+      summary = jisx0208_uni2indx_page03[(character >> 4) - 0x030];
+    } else if (character.betweenTo(0x2000, 0x2320)) {
+      summary = jisx0208_uni2indx_page20[(character >> 4) - 0x200];
+    } else if (character.betweenTo(0x2500, 0x2670)) {
+      summary = jisx0208_uni2indx_page25[(character >> 4) - 0x250];
+    } else if (character.betweenTo(0x3000, 0x3100)) {
+      summary = jisx0208_uni2indx_page30[(character >> 4) - 0x300];
+    } else if (character.betweenTo(0x4e00, 0x9fb0)) {
+      summary = jisx0208_uni2indx_page4e[(character >> 4) - 0x4e0];
+    } else if (character.betweenTo(0xff00, 0xfff0)) {
+      summary = jisx0208_uni2indx_pageff[(character >> 4) - 0xff0];
+    }
+
+    final int i = (1 << (character & 0x0f)).asShort;
+    if (summary == null || ((summary.used & i) == 0)) {
+      return null;
+    }
+
+    int used = summary.used;
+    /* Keep in 'used' only the bits 0..i-1. */
+    used &= i - 1;
+    /* Add 'summary.index' and the number of bits set in 'used'. */
+    used = (used & 0x5555) + ((used & 0xaaaa) >> 1);
+    used = (used & 0x3333) + ((used & 0xcccc) >> 2);
+    used = (used & 0x0f0f) + ((used & 0xf0f0) >> 4);
+    used = (used & 0x00ff) + (used >> 8);
+    return jisx0208_2charset[summary.index + used];
+  }
+
+  @override
+  int? convert(int input) => encode16BitCharacter(input);
+}
+
+/// EUC-JP
+/// ISO-2022-JP-1
+class JSIX0212 {}
+
+/// Shift_JIS-2004
+/// ISO-2022-JP-2004
+/// EUC-JIS-2004
+class JSIX0213 {}
+
+
+// to_utf8
+// from_utf8
+// from_code
+// to_code
+
+// X
+
+// JSX0208
+// JSX0211
+// JSX0212
+// JSX0213
+// EUC_JP
+// JIS
+// SJIS
+

lib/iconv/codecs.dart

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+// https://en.wikipedia.org/wiki/JIS_encoding
+// https://en.wikipedia.org/wiki/Japanese_Industrial_Standards
+
+import 'dart:convert';
+import 'dart:io';
+import 'dart:typed_data';
+
+import 'datatypes.dart';
+import 'character_set_conversion.dart';
+
+/// ISO-2002-JP (Usually abbreviated "JIS")
+/// Encodes, decodes: JIS X 0202
+///
+///
+// class ISO2002JP extends Encoding {}
+
+enum ShiftJISCharacterSet {
+  jisx0201,
+  jisx0208,
+  lundeRange,
+}
+
+/// Shift JIS (Usually abbreviated "SJIS")
+/// Encodes, decodes: JIS X 0208
+///
+/// https://en.wikipedia.org/wiki/Shift_JIS
+class ShiftJIS extends Encoding {
+  int? decodeWithJsix0201(int char) {
+    throw UnimplementedError();
+  }
+
+  /// Decode 16 bit character
+  int? decodeWithJsix0208(int char) {
+    int s1 = char >> 8;
+    int s2 = char & 0x00FF;
+
+    if (!((s1.between(0x81, 0x9f) || s1.between(0xe0, 0xea)) &&
+        (s1.between(0x40, 0x7e) || s1.between(0x80, 0xfc)))) {
+      return null;
+    }
+
+    int t1 = (s1 < 0xe0 ? s1 - 0x81 : s1 - 0xc1);
+    int t2 = (s2 < 0x80 ? s2 - 0x40 : s2 - 0x41);
+
+    int ffoo = 2 * t1 + (t2 < 0x5e ? 0 : 1) + 0x21;
+    int ooff = (t2 < 0x5e ? t2 : t2 - 0x5e) + 0x21;
+    int ffff = (ffoo << 8) + ooff;
+
+    return JSIX0208Decoder().convert(ffff);
+  }
+
+  int? decodeWithLundeRange(int char) {
+    throw UnimplementedError();
+  }
+
+  int? encodeWithJisx0201(int char) {
+    throw UnimplementedError();
+  }
+
+  int? encodeWithJisx0208(int char) {
+    final jsixEncoded = JSIX0208Encoder().convert(char);
+
+    if (jsixEncoded == null) {
+      return null;
+    }
+
+    int c1 = jsixEncoded >> 8;
+    int c2 = jsixEncoded & 0x00FF;
+
+    if (!(c1.between(0x21, 0x74) && c2.between(0x21, 0x7e))) {
+      return null;
+    }
+
+    int t1 = (c1 - 0x21) >> 1;
+    int t2 = ((((c1 - 0x21) & 1) != 0) ? 0x5e : 0) + (c2 - 0x21);
+
+    int ffoo = (t1 < 0x1f ? t1 + 0x81 : t1 + 0xc1);
+    int ooff = (t2 < 0x3f ? t2 + 0x40 : t2 + 0x41);
+
+    return (ffoo << 8) + ooff;
+  }
+
+  int? encodeWithLundeRange(int char) {
+    throw UnimplementedError();
+  }
+
+  @override
+  List<int> encode(
+    String input, {
+    ShiftJISCharacterSet? forceCharacterSet,
+    bool ignoreUnknownCharacters = false,
+  }) {
+    List<int> result = [];
+    List<int> toEncode = input.codeUnits;
+    for (int i = 0; i < toEncode.length; i++) {
+      final int charcode = toEncode[i];
+      final int? encodedChar = encodeWithJisx0208(charcode);
+      if (encodedChar == null) {
+        if (ignoreUnknownCharacters) {
+          continue;
+        } else {
+          throw ConverterException(
+            "Unable to convert character '${String.fromCharCode(charcode)}' at index [$i]",
+          );
+        }
+      }
+      result.add(encodedChar);
+    }
+    return result;
+  }
+
+  @override
+  String decode(
+    List<int> encoded, {
+    ShiftJISCharacterSet? forceCharacterSet,
+    bool ignoreUnknownCharacters = false,
+  }) {
+    List<int> result = [];
+    for (int i = 0; i < encoded.length; i++) {
+      final int encodedChar = encoded[i];
+      final int? translatedChar = decodeWithJsix0208(encodedChar);
+      if (translatedChar == null) {
+        if (ignoreUnknownCharacters) {
+          continue;
+        } else {
+          throw ConverterException(
+            "Unknown character: ${encodedChar.hex} at index [$i]",
+          );
+        }
+      }
+      result.add(translatedChar);
+    }
+    return String.fromCharCodes(result);
+  }
+
+  @override
+  Converter<String, List<int>> get encoder => throw UnimplementedError();
+
+  @override
+  Converter<List<int>, String> get decoder => throw UnimplementedError();
+
+  @override
+  String get name => "Shift JIS";
+}
+
+/// EUC-JP (Usually abbreviated "UJIS")
+/// Unixized JIS
+/// Encodes, decodes: JIS X 0201, JIS X 0208, JIS X 0212
+///
+/// https://en.wikipedia.org/wiki/Extended_Unix_Code#EUC-JP=
+class EUCJP {}
+
+void main() {
+  final file = File("test.sjis.txt");
+  final ByteData data = ByteData.sublistView(file.readAsBytesSync());
+  final List<int> characterCodes = [
+    for (int i = 0; i < ((data.lengthInBytes) / 2).floor(); i++)
+      data.getUint16(i * 2)
+  ];
+  print(characterCodes);
+
+  // print(ShiftJIS().decode(characterCodes));
+
+  // print(JSIX0208Encoder().encode16BitCharacter('あ'.codeUnitAt(0)));
+  // print(JSIX0208Encoder().encode16BitCharacter('幹'.codeUnitAt(0)));
+  final x = ShiftJIS().encode("この文章は読めるかな？");
+  print(data.buffer.asUint8List());
+  File("test.sjis2.txt").writeAsBytesSync(Uint16List.fromList(x));
+}

lib/iconv/datatypes.dart

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+class S16 {
+  final int index;
+  final int used;
+
+  const S16(this.index, this.used);
+}
+
+
+/// Some tools that come in handy when working with bits and bytes.
+extension CharacterSetTools on int {
+  /// Casting to unsigned short would be the same as removing
+  /// all bytes except the 4 last.
+  int get asShort => this & 0xffff;
+
+  /// Ease of printing for debugging purposes.
+  String get hex => "0x${toRadixString(16)}";
+
+  /// Mask and bitshift
+  // int bitrange(int a, int b) => this >> a;
+
+  /// a <= this <= b
+  bool between(int a, int b) => a <= this && this <= b;
+
+  /// a <= this < b
+  bool betweenTo(int a, int b) => a <= this && this < b;
+}

lib/japanese_tools.dart

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+/// Support for doing something awesome.
+///
+/// More dartdocs go here.
+library japanese_tools;
+
+export 'iconv/character_set_conversion.dart';
+export 'iconv/codecs.dart';
+export 'character_conversion.dart';
+export 'radkfile.dart';
+export 'regex.dart';
+export 'unit_conversion.dart';

lib/regex.dart

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+
+/// The string version of a regex that will match any Unified CJK Character.
+/// This includes the ranges (), ()
+/// 
+/// See https://www.regular-expressions.info/unicode.html
+/// 
+/// Remember to turn on the unicode flag when making a new RegExp.
+const String rawKanjiRegex = r'\p{Script=Hani}';
+
+/// The string version of a regex that will match any katakana.
+/// This includes the ranges (), ()
+/// 
+/// See https://www.regular-expressions.info/unicode.html
+/// 
+/// Remember to turn on the unicode flag when making a new RegExp.
+const String rawKatakanaRegex = r'\p{Script=Katakana}';
+
+/// The string version of a regex that will match any hiragana.
+/// This includes the ranges (), ()
+/// 
+/// See https://www.regular-expressions.info/unicode.html
+/// 
+/// Remember to turn on the unicode flag when making a new RegExp.
+const String rawHiraganaRegex = r'\p{Script=Hiragana}';
+
+
+final RegExp kanjiRegex = RegExp(rawKanjiRegex, unicode: true);
+final RegExp katakanaRegex = RegExp(rawKatakanaRegex, unicode: true);
+final RegExp hiraganaRegex = RegExp(rawHiraganaRegex, unicode: true);
+
+// symbols
+
+
+
+
+//is
+//has
+
+// X
+
+// kana
+// katakana
+// hiragana
+// japanese
+// kanji

lib/unit_conversion.dart

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+import 'dart:core';
+// extension on Date
+// Year　平成 昭和
+// Full date
+
+
+// Run in console on http://www.kumamotokokufu-h.ed.jp/kumamoto/bungaku/nengoui.html
+// Array.from(document.querySelectorAll('table')[1].querySelectorAll('tr')).slice(1).map(row => `DateTime(${row.children[3 + (row.children.length == 7)].innerHTML.replace(/～.*/, '')}, ${row.children[4 + (row.children.length == 7)].innerHTML.replace('/', ', ')}): '${row.children[2 + (row.children.length == 7)].innerHTML}'`).join('\n')
+
+Map<DateTime, String> periodsBeforeNanbokuchou = {
+  DateTime(645, 6, 19): '大化',
+  DateTime(650, 2, 15): '白雉',
+  DateTime(686, 7, 20): '朱鳥',
+  DateTime(701, 3, 21): '大宝',
+  DateTime(704, 5, 10): '慶雲',
+  DateTime(708, 1, 11): '和銅',
+  DateTime(715, 9, 2): '霊亀',
+  DateTime(717, 11, 17): '養老',
+  DateTime(724, 2, 4): '神亀',
+  DateTime(729, 8, 5): '天平',
+  DateTime(749, 4, 14): '天平感宝',
+  DateTime(749, 7, 2): '天平勝宝',
+  DateTime(757, 8, 18): '天平宝字',
+  DateTime(765, 1, 7): '天平神護',
+  DateTime(767, 8, 16): '神護景雲',
+  DateTime(770, 10, 1): '宝亀',
+  DateTime(781, 1, 1): '天応',
+  DateTime(782, 8, 19): '延暦',
+  DateTime(806, 5, 18): '大同',
+  DateTime(810, 9, 19): '弘仁',
+  DateTime(824, 1, 5): '天長',
+  DateTime(834, 1, 3): '承和',
+  DateTime(848, 6, 13): '嘉祥',
+  DateTime(851, 4, 28): '仁寿',
+  DateTime(854, 11, 30): '斎衡',
+  DateTime(857, 2, 21): '天安',
+  DateTime(859, 4, 15): '貞観',
+  DateTime(877, 4, 16): '元慶',
+  DateTime(885, 2, 21): '仁和',
+  DateTime(889, 4, 27): '寛平',
+  DateTime(898, 4, 26): '昌泰',
+  DateTime(901, 7, 15): '延喜',
+  DateTime(923, 4, 11): '延長',
+  DateTime(931, 4, 26): '承平',
+  DateTime(938, 5, 22): '天慶',
+  DateTime(947, 4, 22): '天暦',
+  DateTime(957, 10, 27): '天徳',
+  DateTime(961, 2, 16): '応和',
+  DateTime(964, 7, 10): '康保',
+  DateTime(968, 8, 13): '安和',
+  DateTime(970, 3, 25): '天禄',
+  DateTime(973, 12, 20): '天延',
+  DateTime(976, 7, 13): '貞元',
+  DateTime(978, 11, 29): '天元',
+  DateTime(983, 4, 15): '永観',
+  DateTime(985, 4, 27): '寛和',
+  DateTime(987, 4, 5): '永延',
+  DateTime(989, 8, 8): '永祚',
+  DateTime(990, 11, 7): '正暦',
+  DateTime(995, 2, 22): '長徳',
+  DateTime(999, 1, 13): '長保',
+  DateTime(1004, 7, 20): '寛弘',
+  DateTime(1012, 12, 25): '長和',
+  DateTime(1017, 4, 23): '寛仁',
+  DateTime(1021, 2, 2): '治安',
+  DateTime(1024, 7, 13): '万寿',
+  DateTime(1028, 7, 25): '長元',
+  DateTime(1037, 4, 21): '長暦',
+  DateTime(1040, 11, 10): '長久',
+  DateTime(1044, 11, 24): '寛徳',
+  DateTime(1046, 4, 14): '永承',
+  DateTime(1053, 1, 11): '天喜',
+  DateTime(1058, 8, 29): '康平',
+  DateTime(1065, 8, 2): '治暦',
+  DateTime(1069, 4, 13): '延久',
+  DateTime(1074, 8, 23): '承保',
+  DateTime(1077, 11, 17): '承暦',
+  DateTime(1081, 2, 10): '永保',
+  DateTime(1084, 2, 7): '応徳',
+  DateTime(1087, 4, 7): '寛治',
+  DateTime(1094, 12, 15): '嘉保',
+  DateTime(1096, 12, 17): '永長',
+  DateTime(1097, 11, 21): '承徳',
+  DateTime(1099, 8, 28): '康和',
+  DateTime(1104, 2, 10): '長治',
+  DateTime(1106, 4, 9): '嘉承',
+  DateTime(1108, 8, 3): '天仁',
+  DateTime(1110, 7, 13): '天永',
+  DateTime(1113, 7, 13): '永久',
+  DateTime(1118, 4, 3): '元永',
+  DateTime(1120, 4, 10): '保安',
+  DateTime(1124, 4, 3): '天治',
+  DateTime(1126, 1, 22): '大治',
+  DateTime(1131, 1, 29): '天承',
+  DateTime(1132, 8, 11): '長承',
+  DateTime(1135, 4, 27): '保延',
+  DateTime(1141, 7, 10): '永治',
+  DateTime(1142, 4, 28): '康治',
+  DateTime(1144, 2, 23): '天養',
+  DateTime(1145, 7, 22): '久安',
+  DateTime(1151, 1, 26): '仁平',
+  DateTime(1154, 10, 28): '久寿',
+  DateTime(1156, 4, 27): '保元',
+  DateTime(1159, 4, 20): '平治',
+  DateTime(1160, 1, 10): '永暦',
+  DateTime(1161, 9, 4): '応保',
+  DateTime(1163, 3, 29): '長寛',
+  DateTime(1165, 6, 5): '永万',
+  DateTime(1166, 8, 27): '仁安',
+  DateTime(1169, 4, 8): '嘉応',
+  DateTime(1171, 4, 21): '承安',
+  DateTime(1175, 7, 28): '安元',
+  DateTime(1177, 8, 4): '治承',
+  DateTime(1181, 7, 14): '養和',
+  DateTime(1182, 5, 27): '寿永',
+  DateTime(1184, 4, 16): '元暦',
+  DateTime(1185, 8, 14): '文治',
+  DateTime(1190, 4, 11): '建久',
+  DateTime(1199, 4, 27): '正治',
+  DateTime(1201, 2, 13): '建仁',
+  DateTime(1204, 2, 20): '元久',
+  DateTime(1206, 4, 27): '建永',
+  DateTime(1207, 10, 25): '承元',
+  DateTime(1211, 3, 9): '建暦',
+  DateTime(1213, 12, 6): '建保',
+  DateTime(1219, 4, 12): '承久',
+  DateTime(1222, 4, 13): '貞応',
+  DateTime(1224, 11, 20): '元仁',
+  DateTime(1225, 4, 20): '嘉禄',
+  DateTime(1227, 12, 10): '安貞',
+  DateTime(1229, 3, 5): '寛喜',
+  DateTime(1232, 4, 2): '貞永',
+  DateTime(1233, 4, 15): '天福',
+  DateTime(1234, 11, 5): '文暦',
+  DateTime(1235, 9, 19): '嘉禎',
+  DateTime(1238, 11, 23): '暦仁',
+  DateTime(1239, 2, 7): '延応',
+  DateTime(1240, 7, 16): '仁治',
+  DateTime(1243, 2, 26): '寛元',
+  DateTime(1247, 2, 28): '宝治',
+  DateTime(1249, 3, 18): '建長',
+  DateTime(1256, 10, 5): '康元',
+  DateTime(1257, 3, 14): '正嘉',
+  DateTime(1259, 3, 26): '正元',
+  DateTime(1260, 4, 13): '文応',
+  DateTime(1261, 2, 20): '弘長',
+  DateTime(1264, 2, 28): '文永',
+  DateTime(1275, 4, 25): '建治',
+  DateTime(1278, 2, 29): '弘安',
+  DateTime(1288, 4, 28): '正応',
+  DateTime(1293, 8, 5): '永仁',
+  DateTime(1299, 4, 25): '正安',
+  DateTime(1302, 11, 21): '乾元',
+  DateTime(1303, 8, 5): '嘉元',
+  DateTime(1306, 12, 14): '徳治',
+  DateTime(1308, 10, 9): '延慶',
+  DateTime(1311, 4, 28): '応長',
+  DateTime(1312, 3, 20): '正和',
+  DateTime(1317, 2, 3): '文保',
+  DateTime(1319, 4, 28): '元応',
+  DateTime(1321, 2, 23): '元亨',
+  DateTime(1324, 12, 9): '正中',
+  DateTime(1326, 4, 26): '嘉暦',
+};
+
+final Map<DateTime, String> periodsNanbokuchouNorth = {
+  DateTime(1329, 8, 29): '元徳',
+  DateTime(1332, 4, 28): '正慶',
+  DateTime(1334, 1, 29): '建武',
+  DateTime(1338, 8, 28): '暦応',
+  DateTime(1342, 4, 27): '康永',
+  DateTime(1345, 10, 21): '貞和',
+  DateTime(1350, 2, 27): '観応',
+  DateTime(1352, 9, 27): '文和',
+  DateTime(1356, 3, 28): '延文',
+  DateTime(1361, 3, 29): '康安',
+  DateTime(1362, 9, 23): '貞治',
+  DateTime(1368, 2, 18): '応安',
+  DateTime(1375, 2, 27): '永和',
+  DateTime(1379, 3, 22): '康暦',
+  DateTime(1381, 2, 24): '永徳',
+  DateTime(1384, 2, 27): '至徳',
+  DateTime(1387, 8, 23): '嘉慶',
+  DateTime(1389, 2, 9): '康応',
+  DateTime(1390, 3, 26): '明徳',
+};
+
+final Map<DateTime, String> periodsNanbokuchouSouth = {
+  DateTime(1329, 8, 29): '元徳',
+  DateTime(1331, 8, 9): '元弘',
+  DateTime(1334, 1, 29): '建武',
+  DateTime(1336, 2, 29): '延元',
+  DateTime(1340, 4, 28): '興国',
+  DateTime(1346, 12, 8): '正平',
+  DateTime(1370, 7, 24): '建徳',
+  DateTime(1372, 4, 4): '文中',
+  DateTime(1375, 5, 27): '天授',
+  DateTime(1381, 2, 10): '弘和',
+  DateTime(1384, 4, 28): '元中',
+};
+
+final Map<DateTime, String> periodsAfterNanbokuchou = {
+  // DateTime(1392, ): '室町時代',
+  DateTime(1394, 7, 5): '応永',
+  DateTime(1428, 4, 27): '正長',
+  DateTime(1429, 9, 5): '永享',
+  DateTime(1441, 2, 17): '嘉吉',
+  DateTime(1444, 2, 5): '文安',
+  DateTime(1449, 7, 28): '宝徳',
+  DateTime(1452, 7, 25): '享徳',
+  DateTime(1455, 7, 25): '康正',
+  DateTime(1457, 9, 28): '長禄',
+  DateTime(1460, 12, 21): '寛正',
+  DateTime(1466, 2, 28): '文正',
+  DateTime(1467, 3, 5): '応仁',
+  DateTime(1469, 4, 28): '文明',
+  DateTime(1487, 7, 20): '長享',
+  DateTime(1489, 8, 21): '延徳',
+  DateTime(1492, 7, 19): '明応',
+  DateTime(1501, 2, 29): '文亀',
+  DateTime(1504, 2, 30): '永正',
+  DateTime(1521, 8, 23): '大永',
+  DateTime(1528, 8, 20): '享禄',
+  DateTime(1532, 7, 29): '天文',
+  DateTime(1555, 10, 23): '弘治',
+  DateTime(1558, 2, 28): '永禄',
+  DateTime(1570, 4, 23): '元亀',
+  DateTime(1573, 7, 28): '天正',
+  DateTime(1592, 12, 8): '文禄',
+  DateTime(1596, 10, 27): '慶長',
+  DateTime(1615, 7, 13): '元和',
+  DateTime(1624, 2, 30): '寛永',
+  DateTime(1644, 12, 16): '正保',
+  DateTime(1648, 2, 15): '慶安',
+  DateTime(1652, 9, 18): '承応',
+  DateTime(1655, 4, 13): '明暦',
+  DateTime(1658, 7, 23): '万治',
+  DateTime(1661, 4, 25): '寛文',
+  DateTime(1673, 9, 21): '延宝',
+  DateTime(1681, 9, 29): '天和',
+  DateTime(1684, 2, 21): '貞享',
+  DateTime(1688, 9, 30): '元禄',
+  DateTime(1704, 3, 13): '宝永',
+  DateTime(1711, 4, 25): '正徳',
+  DateTime(1716, 6, 22): '享保',
+  DateTime(1736, 4, 28): '元文',
+  DateTime(1741, 2, 27): '寛保',
+  DateTime(1744, 2, 21): '延享',
+  DateTime(1748, 7, 12): '寛延',
+  DateTime(1751, 10, 27): '宝暦',
+  DateTime(1764, 6, 2): '明和',
+  DateTime(1772, 11, 16): '安永',
+  DateTime(1781, 4, 2): '天明',
+  DateTime(1789, 1, 25): '寛政',
+  DateTime(1801, 2, 5): '享和',
+  DateTime(1804, 2, 11): '文化',
+  DateTime(1818, 4, 22): '文政',
+  DateTime(1830, 12, 10): '天保',
+  DateTime(1844, 12, 2): '弘化',
+  DateTime(1848, 2, 28): '嘉永',
+  DateTime(1854, 11, 27): '安政',
+  DateTime(1860, 3, 18): '万延',
+  DateTime(1861, 2, 19): '文久',
+  DateTime(1864, 2, 20): '元治',
+  DateTime(1865, 4, 7): '慶応',
+  DateTime(1868, 9, 8): '明治',
+  DateTime(1912, 7, 30): '大正',
+  DateTime(1926, 12, 25): '昭和',
+  DateTime(1989, 1, 8): '平成'
+};
+
+
+
+extension on DateTime {
+  String get japaneseEra {
+    throw UnimplementedError();
+  }
+
+  /// Note: In the years between 1336 and 1392, Japan was split in two
+  /// because of an ongoing conflict. As a result, Japan has two timelines
+  /// during these years. Unless you turn off [nanbokuchouPeriodUsesNorth],
+  /// function will give you the timeline from the northern part of Japan
+  /// as a default.
+  /// 
+  /// See more info here:
+  /// - https://en.wikipedia.org/wiki/Nanboku-ch%C5%8D_period
+  /// - http://www.kumamotokokufu-h.ed.jp/kumamoto/bungaku/nengoui.html
+  String japaneseYear({bool nanbokuchouPeriodUsesNorth = true}) {
+    throw UnimplementedError();
+  }
+
+  String get japaneseWeekday => [
+    '月',
+    '火',
+    '水',
+    '木',
+    '金',
+    '土',
+    '日',
+  ][weekday - 1];
+
+  String japaneseDate({bool showWeekday = false}) => '$month月$day日' + (showWeekday ? '（$japaneseWeekday）' : '');
+}

pubspec.yaml

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+name: japanese_tools
+description: A starting point for Dart libraries or applications.
+version: 1.0.0
+# homepage: https://www.example.com
+
+environment:
+  sdk: '>=2.16.1 <3.0.0'
+
+
+# dependencies:
+#   path: ^1.8.0
+
+dev_dependencies:
+  lints: ^1.0.0
+  test: ^1.16.0

test.sjis.txt

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+この文章は読めるかな？

test.sjis2.txt

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+ｱﾌｶﾍﾍﾇﾟ鬩ﾈH

test.txt

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+この文章は読めるかな？