下面是常用编码的识别符, 在 Delphi(2009) 中如何获取呢?
Unicode: FF FE; BigEndianUnicode: FE FF; UTF8: EF BB BF
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var
bs: TBytes;
b: Byte;
str: string;
begin
{只有 Unicode、BigEndianUnicode、UTF8 编码有识别符}
bs := TEncoding.Unicode.GetPreamble;
str := '';
for b in bs do str := Format('%s %x', [str, b]);
ShowMessage(str); {FF FE}

bs := TEncoding.BigEndianUnicode.GetPreamble;
str := '';
for b in bs do str := Format('%s %x', [str, b]);
ShowMessage(str); {FE FF}

bs := TEncoding.UTF8.GetPreamble;
str := '';
for b in bs do str := Format('%s %x', [str, b]);
ShowMessage(str); {EF BB BF}

{ASCII、UTF7 和 Default(默认编码) 没有识别符}
bs := TEncoding.ASCII.GetPreamble;
str := '';
for b in bs do str := Format('%s %x', [str, b]);
ShowMessage(str); {无}

bs := TEncoding.UTF7.GetPreamble;
str := '';
for b in bs do str := Format('%s %x', [str, b]);
ShowMessage(str); {无}

bs := TEncoding.Default.GetPreamble;
str := '';
for b in bs do str := Format('%s %x', [str, b]);
ShowMessage(str); {无}
end;