求文件大小

fileSizeCal.m

- (NSString *)formattedFileSize:(unsignedlonglong)size
{
    NSString *formattedStr = nil;
         if (size == 0)
              formattedStr = @"Empty";
          else
              if (size > 0 && size < 1024)
                    formattedStr = [NSStringstringWithFormat:@"%qu bytes", size];
        // Lilac-Annotation: %qu: Unsigned 64-bit integer (unsigned long long)
               else
                      if (size >= 1024 && size < pow(1024, 2))
                          formattedStr = [NSStringstringWithFormat:@"%.1f KB", (size / 1024.)];
                      else
                          if (size >= pow(1024, 2) && size < pow(1024, 3))
                               formattedStr = [NSStringstringWithFormat:@"%.2f MB", (size / pow(1024, 2))];
                // Lilac-Annotation: pow(x,y),计算x的y次幂
                     else
                         if (size >= pow(1024, 3))
                             formattedStr = [NSStringstringWithFormat:@"%.3f GB", (size / pow(1024, 3))];

    return formattedStr;
}