IOS basic encoding format conversion

Encoding and conversion in IOS

1. Conversion of UTF-8

Nsstring * Data = @ "Hello, Beijing! ";

// Convert to UTF-8

Nsstring * datautf8 = [Data
Stringbyaddingpercentescapesusingencoding: nsutf8stringencoding];

Nslog (@ "% @", datautf8 );

// UTF-8 to GBK, replace the utf8 code, the official explanation is as follows.

// Replaces all percent escapes with the matching characters as determined by the given encoding. returns nil if the transformation is not possible (I. e. the percent escapes give a byte sequence not legal in the given encoding ). see cfurlcreatestringbyreplacingpercentescapes
In cfurl. h for more complex transformations

Nsstring * datagbk = [datautf8
Stringbyreplacingpercentescapesusingencoding: nsutf8stringencoding];

Nslog (@ "% @", datagbk );

The execution result in xcode4.2 is as follows:

Encapsulate the preceding method as follows:

// Unicode-to-UTF-8

+ (Nsstring *) encodetopercentescapestring: (nsstring *) Input

{

// Encode all the reserved characters, per RFC 3986

// (<Http://www.ietf.org/rfc/rfc3986.txt>)

Nsstring * outputstr = (nsstring *)

Cfurlcreatestringbyaddingpercentescapes (kcfallocatordefault,

(Cfstringref) input,

Null,

(Cfstringref )@"! * '();: @ & = + $ ,/? % # [] ",

Kcfstringencodingutf8 );

Return outputstr;

}

+ (Nsstring *) decodefrompercentescapestring: (nsstring *) Input

{

Nsmutablestring * outputstr = [nsmutablestring
Stringwithstring: Input];

[Outputstr replaceoccurrencesofstring: @ "+"

Withstring :@""

Options: nsliteralsearch

Range: nsmakerange (0, [outputstr
Length])];

Return [outputstr
Stringbyreplacingpercentescapesusingencoding: nsutf8stringencoding];

}

2. UTF-8 and Unicode Conversion

// Unicode-to-UTF-8

+ (Nsstring *) replaceunicode :( nsstring *) aunicodestring

{

Nsstring * tempstr1 = [aunicodestring
Stringbyreplacingoccurrencesofstring: @ "\ U"
Withstring: @ "\ U"];

Nsstring * tempstr2 = [tempstr1
Stringbyreplacingoccurrencesofstring :@"\""
Withstring: @ "\" "];

Nsstring * tempstr3 = [[@"\""
Stringbyappendingstring: tempstr2] stringbyappendingstring: @ "\" "];

Nsdata * tempdata = [tempstr3
Datausingencoding: nsutf8stringencoding];

Nsstring * returnstr = [nspropertylistserialization
Propertylistfromdata: tempdata

Mutabilityoption: nspropertylistimmutable

Format: NULL

Errordescription: NULL];

Return [returnstr
Stringbyreplacingoccurrencesofstring: @ "\ r \ n"
Withstring: @ "\ n"];

}

+ (Nsstring *) utf8tounicode :( nsstring *) String

{

Nsuinteger length = [String
Length];

Nsmutablestring * s = [nsmutablestring
Stringwithcapacity: 0];

For (INT I =
0; I <length; I ++)

{

Unichar _ char = [String
Characteratindex: I];

// Determine whether it is an English or a number

If (_ char <= '9' & _ char> =
'0 ')

{

[S appendformat: @ "% @", [String
Substringwithrange: nsmakerange (I,
1)];

}

Else if (_ char> =
'A' & _ char <= 'Z ')

{

[S appendformat: @ "% @", [String
Substringwithrange: nsmakerange (I,
1)];

}

Else if (_ char> =
'A' & _ char <= 'Z ')

{

[S appendformat: @ "% @", [String
Substringwithrange: nsmakerange (I,
1)];

}

Else

{

[S appendformat: @ "\ U % x", [String
Characteratindex: I];

}

}

Return S;

}