CSharp examples for System:String Encode Decode
Guesses the encoding.
using System.Text; using System.Linq; using System.Collections.Generic; using System;//from www . j a v a2 s. com public class Main{ /// <summary> /// Guesses the encoding. /// </summary> /// <param name="bytes">bytes encoding a string, whose encoding should be guessed</param> /// <param name="hints">decode hints if applicable</param> /// <returns> /// name of guessed encoding; at the moment will only guess one of: /// <see cref="F:MessagingToolkit.Barcode.Common.StringHelper.ShiftJis"/> /// , /// <see cref="F:MessagingToolkit.Barcode.Common.StringHelper.Utf8"/> /// , /// <see cref="F:MessagingToolkit.Barcode.Common.StringHelper.ISO88591"/> /// , or the platform /// default encoding if none of these can possibly be correct /// </returns> public static String GuessEncoding(byte[] bytes) { // Does it start with the UTF-8 byte order mark? then guess it's UTF-8 if (bytes.Length > 3 && bytes[0] == (byte)0xEF && bytes[1] == (byte)0xBB && bytes[2] == (byte)0xBF) { return Utf8; } // For now, merely tries to distinguish ISO-8859-1, UTF-8 and Shift_JIS, // which should be by far the most common encodings. ISO-8859-1 // should not have bytes in the 0x80 - 0x9F range, while Shift_JIS // uses this as a first byte of a two-byte character. If we see this // followed by a valid second byte in Shift_JIS, assume it is Shift_JIS. // If we see something else in that second byte, we'll make the risky guess // that it's UTF-8. int length = bytes.Length; bool canBeISO88591 = true; bool canBeShiftJIS = true; bool canBeUTF8 = true; int utf8BytesLeft = 0; int maybeDoubleByteCount = 0; int maybeSingleByteKatakanaCount = 0; bool sawLatin1Supplement = false; bool sawUTF8Start = false; bool lastWasPossibleDoubleByteStart = false; for (int i = 0; i < length && (canBeISO88591 || canBeShiftJIS || canBeUTF8); i++) { int val = bytes[i] & 0xFF; // UTF-8 stuff if (val >= 0x80 && val <= 0xBF) { if (utf8BytesLeft > 0) { utf8BytesLeft--; } } else { if (utf8BytesLeft > 0) { canBeUTF8 = false; } if (val >= 0xC0 && val <= 0xFD) { sawUTF8Start = true; int valueCopy = val; while ((valueCopy & 0x40) != 0) { utf8BytesLeft++; valueCopy <<= 1; } } } // ISO-8859-1 stuff if ((val == 0xC2 || val == 0xC3) && i < length - 1) { // This is really a poor hack. The slightly more exotic characters people might want to put in // a QR Code, by which I mean the Latin-1 supplement characters (e.g. u-umlaut) have encodings // that start with 0xC2 followed by [0xA0,0xBF], or start with 0xC3 followed by [0x80,0xBF]. int nextValue = bytes[i + 1] & 0xFF; if (nextValue <= 0xBF && ((val == 0xC2 && nextValue >= 0xA0) || (val == 0xC3 && nextValue >= 0x80))) { sawLatin1Supplement = true; } } if (val >= 0x7F && val <= 0x9F) { canBeISO88591 = false; } // Shift_JIS stuff if (val >= 0xA1 && val <= 0xDF) { // count the number of characters that might be a Shift_JIS single-byte Katakana character if (!lastWasPossibleDoubleByteStart) { maybeSingleByteKatakanaCount++; } } if (!lastWasPossibleDoubleByteStart && ((val >= 0xF0 && val <= 0xFF) || val == 0x80 || val == 0xA0)) { canBeShiftJIS = false; } if ((val >= 0x81 && val <= 0x9F) || (val >= 0xE0 && val <= 0xEF)) { // These start double-byte characters in Shift_JIS. Let's see if it's followed by a valid // second byte. if (lastWasPossibleDoubleByteStart) { // If we just checked this and the last byte for being a valid double-byte // char, don't check starting on this byte. If this and the last byte // formed a valid pair, then this shouldn't be checked to see if it starts // a double byte pair of course. lastWasPossibleDoubleByteStart = false; } else { // ... otherwise do check to see if this plus the next byte form a valid // double byte pair encoding a character. lastWasPossibleDoubleByteStart = true; if (i >= bytes.Length - 1) { canBeShiftJIS = false; } else { int nextValue_0 = bytes[i + 1] & 0xFF; if (nextValue_0 < 0x40 || nextValue_0 > 0xFC) { canBeShiftJIS = false; } else { maybeDoubleByteCount++; } // There is some conflicting information out there about which bytes can follow which in // double-byte Shift_JIS characters. The rule above seems to be the one that matches practice. } } } else { lastWasPossibleDoubleByteStart = false; } } if (utf8BytesLeft > 0) { canBeUTF8 = false; } // Easy -- if assuming Shift_JIS and no evidence it can't be, done if (canBeShiftJIS && AssumeShiftJis) { return ShiftJis; } if (canBeUTF8 && sawUTF8Start) { return Utf8; } // Distinguishing Shift_JIS and ISO-8859-1 can be a little tough. The crude heuristic is: // - If we saw // - at least 3 bytes that starts a double-byte value (bytes that are rare in ISO-8859-1), or // - over 5% of bytes could be single-byte Katakana (also rare in ISO-8859-1), // - and, saw no sequences that are invalid in Shift_JIS, then we conclude Shift_JIS if (canBeShiftJIS && (maybeDoubleByteCount >= 3 || 20 * maybeSingleByteKatakanaCount > length)) { return ShiftJis; } // Otherwise, we default to ISO-8859-1 unless we know it can't be if (!sawLatin1Supplement && canBeISO88591) { return ISO88591; } // Otherwise, we take a wild guess with platform encoding return PlatformDefaultEncoding; } }