ios - Decoding word-encoded Content-Disposition header file name in Objective-C -

i trying retrieve file name can't represented in ascii content-disposition header.

this file name word-encoded. below encoded file name:

=?utf-8?q?=c3=abst=c3=a9_=c3=a9_=c3=bam_n=c3=b4m=c3=a9?= =?utf-8?q?_a=c3=a7ent=c3=baad=c3=b5.xlsx?=

how decoded file name (that "ësté é úm nômé açentúadõ.xlsx")?

ps: looking objective-c implementation.

you want search mime handling framework, searched online , came nothing, so....

i couldn't find example online, i'm showing algorithm here. it's not best example since i'm making big assumption. being string utf-8 q-encoded.

q-encoding url-encoding (percent-encoding), foundation's nsstring has support decoding. (practical) difference when decoding (there bigger differences when encoding) % encodings = encodings instead.

then there's lead-in , lead-out stuff. each encoded block has format =?charset-name?encoding-type? ... encoded string here ... ?=. should read charset name use encoding, , should read encoding-type, since may "q" or "b" (base64).

this example works q-encoding (a subset of quoted-printable). should able modify handle different charsets , handle base64 encoding however.

#import <foundation/foundation.h>  int main(void) {     nsautoreleasepool *pool = [[nsautoreleasepool alloc] init];      nsstring *encodedstring = @"=?utf-8?q?=c3=abst=c3=a9_=c3=a9_=c3=bam_n=c3=b4m=c3=a9?= =?utf-8?q?_a=c3=a7ent=c3=baad=c3=b5.xlsx?=";        nsscanner *scanner = [nsscanner scannerwithstring:encodedstring];     nsstring *buf = nil;     nsmutablestring *decodedstring = [[nsmutablestring alloc] init];      while ([scanner scanstring:@"=?utf-8?q?" intostring:null]         || ([scanner scanuptostring:@"=?utf-8?q?" intostring:&buf] && [scanner scanstring:@"=?utf-8?q?" intostring:null])) {         if (buf != nil) {             [decodedstring appendstring:buf];         }          buf = nil;          nsstring *encodedrange;          if (![scanner scanuptostring:@"?=" intostring:&encodedrange]) {             break; // invalid encoding         }          [scanner scanstring:@"?=" intostring:null]; // skip terminating "?="          // decode encoded portion (naively using utf-8 , assuming q encoded)         // i'm doing naively, should work          // firstly i'm encoding % signs can cheat , turn url-encoded string, nsstring can decode         encodedrange = [encodedrange stringbyreplacingoccurrencesofstring:@"%" withstring:@"=25"];          // turn url-encoded string         encodedrange = [encodedrange stringbyreplacingoccurrencesofstring:@"=" withstring:@"%"];          // remove underscores         encodedrange = [encodedrange stringbyreplacingoccurrencesofstring:@"_" withstring:@" "];          [decodedstring appendstring:[encodedrange stringbyreplacingpercentescapesusingencoding:nsutf8stringencoding]];     }      nslog(@"decoded string = %@", decodedstring);      [decodedstring release];      [pool drain];      return 0; } 

this outputs:

chrisbook-pro:~ chris$ ./qp-decode 2010-12-01 18:54:42.903 qp-decode[9643:903] decoded string = ësté é úm nômé açentúadõ.xlsx