iOS 10进制字符串转16进制（任一大小）

-  (NSString *)getHexByDecimal:(NSDecimalNumber *)decimal {
    
    //10进制转换16进制（支持无穷大数）
    NSString *hex =@"";
    NSString *letter;
    NSDecimalNumber *lastNumber = decimal;
    for (int i = 0; i<999; i++) {
        NSDecimalNumber *tempShang = [lastNumber decimalNumberByDividingBy:[NSDecimalNumber decimalNumberWithString:@"16"]];
        NSString *tempShangString = [tempShang stringValue];
        if ([tempShangString containsString:@"."]) {
            // 有小数
            tempShangString = [tempShangString substringToIndex:[tempShangString rangeOfString:@"."].location];
            //            DLog(@"%@", tempShangString);
            NSDecimalNumber *number = [[NSDecimalNumber decimalNumberWithString:tempShangString] decimalNumberByMultiplyingBy:[NSDecimalNumber decimalNumberWithString:@"16"]];
            NSDecimalNumber *yushu = [lastNumber decimalNumberBySubtracting:number];
            int yushuInt = [[yushu stringValue] intValue];
            switch (yushuInt) {
                case 10:
                    letter =@"A"; break;
                case 11:
                    letter =@"B"; break;
                case 12:
                    letter =@"C"; break;
                case 13:
                    letter =@"D"; break;
                case 14:
                    letter =@"E"; break;
                case 15:
                    letter =@"F"; break;
                default:
                    letter = [NSString stringWithFormat:@"%d", yushuInt];
            }
            lastNumber = [NSDecimalNumber decimalNumberWithString:tempShangString];
        } else {
            // 没有小数
            if (tempShangString.length <= 2 && [tempShangString intValue] < 16) {
                int num = [tempShangString intValue];
                if (num == 0) {
                    break;
                }
                switch (num) {
                    case 10:
                        letter =@"A"; break;
                    case 11:
                        letter =@"B"; break;
                    case 12:
                        letter =@"C"; break;
                    case 13:
                        letter =@"D"; break;
                    case 14:
                        letter =@"E"; break;
                    case 15:
                        letter =@"F"; break;
                    default:
                        letter = [NSString stringWithFormat:@"%d", num];
                }
                hex = [letter stringByAppendingString:hex];
                break;
            } else {
                letter = @"0";
            }
            lastNumber = tempShang;
        }
        
        hex = [letter stringByAppendingString:hex];
    }
    //    return hex;
    return hex.length > 0 ? hex : @"0";
}