NSString Encoding issue

StringEncoding

// 1.usedEncoding. try to determine the encoding, and return the encoding which was used.

NSURL *url = xxx;
NSStringEncoding encoding = NSUTF8StringEncoding;
NSError *error = nil;

NSString *foo = [NSString stringWithContentsOfURL:url usedEncoding:&encoding error:&error];
if (foo == nil) {
    NSLog(@"%@", error);
    
    NSLog(@"%@", [NSNumber numberWithUnsignedLong:encoding]);
    NSLog(@"%@", [NSString localizedNameOfStringEncoding:encoding]);
}

// 2.availableStringEncodings

const NSStringEncoding *availableStringEncodings = [NSString availableStringEncodings];
NSStringEncoding endcoding;

NSData *data = xxx;
NSString *foo = nil;
while ((endcoding = *availableStringEncodings++) != 0) {
    foo = [[NSString alloc] initWithData:data encoding:endcoding];
    
    if (foo != nil) {
        NSLog(@"%@", [NSNumber numberWithUnsignedLong:endcoding]);
        break;
    }
}

// 3. CFStringConvertEncodingToNSStringEncoding

NSData *data = xxx;
NSString *foo = [[NSString alloc] initWithData:data encoding:CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingHZ_GB_2312)];