亡灵术。
- 首先，检查字节顺序标记：
- 如果这不起作用，您可以尝试使用 Mozilla Universal Charset Detector C# port 从文本内容推断编码。
- 如果这不起作用，您只需返回 CurrentCulture/InstalledUiCulture/System-Encoding - 或其他任何内容。
- 如果系统编码不起作用，我们可以返回 ASCII 或 UTF8。由于 UTF8 的 0-127 项与 ASCII 相同，因此我们只需返回 UTF8。
示例（DetectOrGuessEncoding）：
namespace SQLMerge
{
class EncodingDetector
{
public static System.Text.Encoding BomInfo(string srcFile)
{
return BomInfo(srcFile, false);
} // End Function BomInfo
public static System.Text.Encoding BomInfo(string srcFile, bool thorough)
{
byte[] b = new byte[5];
using (System.IO.FileStream file = new System.IO.FileStream(srcFile, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.Read))
{
int numRead = file.Read(b, 0, 5);
if (numRead < 5)
System.Array.Resize(ref b, numRead);
file.Close();
} // End Using file
if (b.Length >= 4 && b[0] == 0x00 && b[1] == 0x00 && b[2] == 0xFE && b[3] == 0xFF) // UTF32-BE
return System.Text.Encoding.GetEncoding("utf-32BE"); // UTF-32, big-endian
else if (b.Length >= 4 && b[0] == 0xFF && b[1] == 0xFE && b[2] == 0x00 && b[3] == 0x00) // UTF32-LE
return System.Text.Encoding.UTF32; // UTF-32, little-endian
// https://en.wikipedia.org/wiki/Byte_order_mark#cite_note-14
else if (b.Length >= 4 && b[0] == 0x2b && b[1] == 0x2f && b[2] == 0x76 && (b[3] == 0x38 || b[3] == 0x39 || b[3] == 0x2B || b[3] == 0x2F)) // UTF7
return System.Text.Encoding.UTF7; // UTF-7
else if (b.Length >= 3 && b[0] == 0xEF && b[1] == 0xBB && b[2] == 0xBF) // UTF-8
return System.Text.Encoding.UTF8; // UTF-8
else if (b.Length >= 2 && b[0] == 0xFE && b[1] == 0xFF) // UTF16-BE
return System.Text.Encoding.BigEndianUnicode; // UTF-16, big-endian
else if (b.Length >= 2 && b[0] == 0xFF && b[1] == 0xFE) // UTF16-LE
return System.Text.Encoding.Unicode; // UTF-16, little-endian
// Maybe there is a future encoding ...
// PS: The above yields more than this - this doesn't find UTF7 ...
if (thorough)
{
System.Collections.Generic.List<System.Collections.Generic.KeyValuePair<System.Text.Encoding, byte[]>> lsPreambles =
new System.Collections.Generic.List<System.Collections.Generic.KeyValuePair<System.Text.Encoding, byte[]>>();
foreach (System.Text.EncodingInfo ei in System.Text.Encoding.GetEncodings())
{
System.Text.Encoding enc = ei.GetEncoding();
byte[] preamble = enc.GetPreamble();
if (preamble == null)
continue;
if (preamble.Length == 0)
continue;
if (preamble.Length > b.Length)
continue;
System.Collections.Generic.KeyValuePair<System.Text.Encoding, byte[]> kvp =
new System.Collections.Generic.KeyValuePair<System.Text.Encoding, byte[]>(enc, preamble);
lsPreambles.Add(kvp);
} // Next ei
// li.Sort((a, b) => a.CompareTo(b)); // ascending sort
// li.Sort((a, b) => b.CompareTo(a)); // descending sort
lsPreambles.Sort(
delegate (
System.Collections.Generic.KeyValuePair<System.Text.Encoding, byte[]> kvp1,
System.Collections.Generic.KeyValuePair<System.Text.Encoding, byte[]> kvp2)
{
return kvp2.Value.Length.CompareTo(kvp1.Value.Length);
}
);
for (int j = 0; j < lsPreambles.Count; ++j)
{
for (int i = 0; i < lsPreambles[j].Value.Length; ++i)
{
if (b[i] != lsPreambles[j].Value[i])
{
goto NEXT_J_AND_NOT_NEXT_I;
}
} // Next i
return lsPreambles[j].Key;
NEXT_J_AND_NOT_NEXT_I: continue;
} // Next j
} // End if (thorough)
return null;
} // End Function BomInfo
public static System.Text.Encoding DetectOrGuessEncoding(string fileName)
{
return DetectOrGuessEncoding(fileName, false);
}
public static System.Text.Encoding DetectOrGuessEncoding(string fileName, bool withOutput)
{
if (!System.IO.File.Exists(fileName))
return null;
System.ConsoleColor origBack = System.ConsoleColor.Black;
System.ConsoleColor origFore = System.ConsoleColor.White;
if (withOutput)
{
origBack = System.Console.BackgroundColor;
origFore = System.Console.ForegroundColor;
}
// System.Text.Encoding systemEncoding = System.Text.Encoding.Default; // Returns hard-coded UTF8 on .NET Core ...
System.Text.Encoding systemEncoding = GetSystemEncoding();
System.Text.Encoding enc = BomInfo(fileName);
if (enc != null)
{
if (withOutput)
{
System.Console.BackgroundColor = System.ConsoleColor.Green;
System.Console.ForegroundColor = System.ConsoleColor.White;
System.Console.WriteLine(fileName);
System.Console.WriteLine(enc);
System.Console.BackgroundColor = origBack;
System.Console.ForegroundColor = origFore;
}
return enc;
}
using (System.IO.Stream strm = System.IO.File.OpenRead(fileName))
{
UtfUnknown.DetectionResult detect = UtfUnknown.CharsetDetector.DetectFromStream(strm);
if (detect != null && detect.Details != null && detect.Details.Count > 0 && detect.Details[0].Confidence < 1)
{
if (withOutput)
{
System.Console.BackgroundColor = System.ConsoleColor.Red;
System.Console.ForegroundColor = System.ConsoleColor.White;
System.Console.WriteLine(fileName);
System.Console.WriteLine(detect);
System.Console.BackgroundColor = origBack;
System.Console.ForegroundColor = origFore;
}
foreach (UtfUnknown.DetectionDetail detail in detect.Details)
{
if (detail.Encoding == systemEncoding
|| detail.Encoding == System.Text.Encoding.UTF8
)
return detail.Encoding;
}
return detect.Details[0].Encoding;
}
else if (detect != null && detect.Details != null && detect.Details.Count > 0)
{
if (withOutput)
{
System.Console.BackgroundColor = System.ConsoleColor.Green;
System.Console.ForegroundColor = System.ConsoleColor.White;
System.Console.WriteLine(fileName);
System.Console.WriteLine(detect);
System.Console.BackgroundColor = origBack;
System.Console.ForegroundColor = origFore;
}
return detect.Details[0].Encoding;
}
enc = GetSystemEncoding();
if (withOutput)
{
System.Console.BackgroundColor = System.ConsoleColor.DarkRed;
System.Console.ForegroundColor = System.ConsoleColor.Yellow;
System.Console.WriteLine(fileName);
System.Console.Write("Assuming ");
System.Console.Write(enc.WebName);
System.Console.WriteLine("...");
System.Console.BackgroundColor = origBack;
System.Console.ForegroundColor = origFore;
}
return systemEncoding;
} // End Using strm
} // End Function DetectOrGuessEncoding
public static System.Text.Encoding GetSystemEncoding()
{
// The OEM code page for use by legacy console applications
// int oem = System.Globalization.CultureInfo.CurrentCulture.TextInfo.OEMCodePage;
// The ANSI code page for use by legacy GUI applications
// int ansi = System.Globalization.CultureInfo.InstalledUICulture.TextInfo.ANSICodePage; // Machine
int ansi = System.Globalization.CultureInfo.CurrentCulture.TextInfo.ANSICodePage; // User
try
{
// https://stackoverflow.com/questions/38476796/how-to-set-net-core-in-if-statement-for-compilation
#if ( NETSTANDARD && !NETSTANDARD1_0 ) || NETCORE || NETCOREAPP3_0 || NETCOREAPP3_1
System.Text.Encoding.RegisterProvider(System.Text.CodePagesEncodingProvider.Instance);
#endif
System.Text.Encoding enc = System.Text.Encoding.GetEncoding(ansi);
return enc;
}
catch (System.Exception)
{ }
try
{
foreach (System.Text.EncodingInfo ei in System.Text.Encoding.GetEncodings())
{
System.Text.Encoding e = ei.GetEncoding();
// 20'127: US-ASCII
if (e.WindowsCodePage == ansi && e.CodePage != 20127)
{
return e;
}
}
}
catch (System.Exception)
{ }
// return System.Text.Encoding.GetEncoding("iso-8859-1");
return System.Text.Encoding.UTF8;
} // End Function GetSystemEncoding
} // End Class
}