view/SchoolIdolFestivalSimulator.Components/FileEncoding.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace SchoolIdolFestivalSimulator.Components {
    public class FileEncoding {
        public static Encoding GetFileEncoding(string fileName) {
            using(FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read)) {
                byte[] bs = new byte[fs.Length - 1];
                fs.Read(bs, 0, bs.Length);
                fs.Close();
                return GetEncoding(bs);
            }
        }
        /// <summary>
        /// 文字コードを判別する
        /// </summary>
        /// <remarks>
        /// Jcode.pmのgetcodeメソッドを移植したものです。
        /// Jcode.pm(http://openlab.ring.gr.jp/Jcode/index-j.html)
        /// Jcode.pmのCopyright: Copyright 1999-2005 Dan Kogai
        /// </remarks>
        /// <param name="bytes">文字コードを調べるデータ</param>
        /// <returns>適当と思われるEncodingオブジェクト。
        /// 判断できなかった時はnull。</returns>
        public static System.Text.Encoding GetEncoding(byte[] bytes) {
            const byte bEscape = 0x1B;
            const byte bAt = 0x40;
            const byte bDollar = 0x24;
            const byte bAnd = 0x26;
            const byte bOpen = 0x28;    //'('
            const byte bB = 0x42;
            const byte bD = 0x44;
            const byte bJ = 0x4A;
            const byte bI = 0x49;

            int len = bytes.Length;
            byte b1, b2, b3, b4;

            //Encode::is_utf8 は無視
            bool isBinary = false;
            for(int i = 0;i < len;i++) {
                b1 = bytes[i];
                if(b1 <= 0x06 || b1 == 0x7F || b1 == 0xFF) {
                    //'binary'
                    isBinary = true;
                    if(b1 == 0x00 && i < len - 1 && bytes[i + 1] <= 0x7F) {
                        //smells like raw unicode
                        return System.Text.Encoding.Unicode;
                    }
                }
            }
            if(isBinary) {
                return null;
            }

            //not Japanese
            bool notJapanese = true;
            for(int i = 0;i < len;i++) {
                b1 = bytes[i];
                if(b1 == bEscape || 0x80 <= b1) {
                    notJapanese = false;
                    break;
                }
            }
            if(notJapanese) {
                return System.Text.Encoding.ASCII;
            }

            for(int i = 0;i < len - 2;i++) {
                b1 = bytes[i];
                b2 = bytes[i + 1];
                b3 = bytes[i + 2];

                if(b1 == bEscape) {
                    if(b2 == bDollar && b3 == bAt) {
                        //JIS_0208 1978
                        //JIS
                        return System.Text.Encoding.GetEncoding(50220);
                    } else if(b2 == bDollar && b3 == bB) {
                        //JIS_0208 1983
                        //JIS
                        return System.Text.Encoding.GetEncoding(50220);
                    } else if(b2 == bOpen && (b3 == bB || b3 == bJ)) {
                        //JIS_ASC
                        //JIS
                        return System.Text.Encoding.GetEncoding(50220);
                    } else if(b2 == bOpen && b3 == bI) {
                        //JIS_KANA
                        //JIS
                        return System.Text.Encoding.GetEncoding(50220);
                    }
                    if(i < len - 3) {
                        b4 = bytes[i + 3];
                        if(b2 == bDollar && b3 == bOpen && b4 == bD) {
                            //JIS_0212
                            //JIS
                            return System.Text.Encoding.GetEncoding(50220);
                        }
                        if(i < len - 5 &&
                        b2 == bAnd && b3 == bAt && b4 == bEscape &&
                        bytes[i + 4] == bDollar && bytes[i + 5] == bB) {
                            //JIS_0208 1990
                            //JIS
                            return System.Text.Encoding.GetEncoding(50220);
                        }
                    }
                }
            }

            //should be euc|sjis|utf8
            //use of (?:) by Hiroki Ohzaki <ohzaki@iod.ricoh.co.jp>
            int sjis = 0;
            int euc = 0;
            int utf8 = 0;
            for(int i = 0;i < len - 1;i++) {
                b1 = bytes[i];
                b2 = bytes[i + 1];
                if(((0x81 <= b1 && b1 <= 0x9F) || (0xE0 <= b1 && b1 <= 0xFC)) &&
                ((0x40 <= b2 && b2 <= 0x7E) || (0x80 <= b2 && b2 <= 0xFC))) {
                    //SJIS_C
                    sjis += 2;
                    i++;
                }
            }
            for(int i = 0;i < len - 1;i++) {
                b1 = bytes[i];
                b2 = bytes[i + 1];
                if(((0xA1 <= b1 && b1 <= 0xFE) && (0xA1 <= b2 && b2 <= 0xFE)) ||
                (b1 == 0x8E && (0xA1 <= b2 && b2 <= 0xDF))) {
                    //EUC_C
                    //EUC_KANA
                    euc += 2;
                    i++;
                } else if(i < len - 2) {
                    b3 = bytes[i + 2];
                    if(b1 == 0x8F && (0xA1 <= b2 && b2 <= 0xFE) &&
                    (0xA1 <= b3 && b3 <= 0xFE)) {
                        //EUC_0212
                        euc += 3;
                        i += 2;
                    }
                }
            }
            for(int i = 0;i < len - 1;i++) {
                b1 = bytes[i];
                b2 = bytes[i + 1];
                if((0xC0 <= b1 && b1 <= 0xDF) && (0x80 <= b2 && b2 <= 0xBF)) {
                    //UTF8
                    utf8 += 2;
                    i++;
                } else if(i < len - 2) {
                    b3 = bytes[i + 2];
                    if((0xE0 <= b1 && b1 <= 0xEF) && (0x80 <= b2 && b2 <= 0xBF) &&
                    (0x80 <= b3 && b3 <= 0xBF)) {
                        //UTF8
                        utf8 += 3;
                        i += 2;
                    }
                }
            }
            //M. Takahashi's suggestion
            //utf8 += utf8 / 2;

            System.Diagnostics.Debug.WriteLine(
            string.Format("sjis = {0}, euc = {1}, utf8 = {2}", sjis, euc, utf8));
            if(euc > sjis && euc > utf8) {
                //EUC
                return System.Text.Encoding.GetEncoding(51932);
            } else if(sjis > euc && sjis > utf8) {
                //SJIS
                return System.Text.Encoding.GetEncoding(932);
            } else if(utf8 > euc && utf8 > sjis) {
                //UTF8
                return System.Text.Encoding.UTF8;
            }
            return null;
        }
    }
}