convert an hex string to a NSData

How can I convert a string in hex format to retrieve from it an NSData and after that an UIImage inside of my iPhone app?

I've got a string (str) that contains a value like X'FFD8FFE000104A46....01010000010001000'.

That string is created from a xml file by the method:

- (void)parser:(NSXMLParser *)parse开发者_运维百科r foundCharacters:(NSString *)string {
     str = [str stringByAppendingString:string];
}

How can I get the image back from that string?

Thanks in advance,

Andrea

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For converting NSData to a NSString, try "initWithData:encoding:"

For converting NSData to an UIImage, try "imageWithData:"

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You may find GTMStringEncoding helpful, from Google Toolbox For Mac.

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my sample code , updated!

   -(NSData*)toString:(NSString*)uniStr
{
    int len=[uniStr length]/4;
    unichar *oux=alloca(len*sizeof(unichar));
    unichar *p = oux;

    for (int i=0; i<[uniStr length]/4; i++) {


        NSInteger first= i*4;
        NSUInteger a =toInde([uniStr characterAtIndex:first])<<4;//3 3c
        NSUInteger b =toInde([uniStr characterAtIndex:(first+1)]);//2
        NSUInteger c =toInde([uniStr characterAtIndex:(first+2)])<<12 ;//0 68
        NSUInteger d =toInde([uniStr characterAtIndex:(first+3)])<<8;//0

        unichar x = a+b+c+d;//十进制 3c68->683c
        memcpy(p, &x, 2);
        p++;

    }

    return [NSData dataWithBytes:oux length:len*2];
}

int toInde(int x)
{

    char b=0;
    sprintf(&b, "%c",a);
    return b;
}