// 文件大小格式化显示
- (NSString *)convert_FileSize:(long long)file_size {
    long kb = 1024;
    long mb = kb * 1024;
    long gb = mb * 1024;
    
    if (file_size >= gb) {
        return [NSString stringWithFormat:@"%.1f GB", (float) file_size / gb];
    }
    else if (file_size >= mb) {
        float gc_float = (float) file_size / mb;
        if (gc_float > 100) {
            return [NSString stringWithFormat:@"%.0f MB", gc_float];
        }
        else {
            return [NSString stringWithFormat:@"%.1f MB", gc_float];
        }
    }
    else if (file_size >= kb) {
        float gc_float = (float) file_size / kb;
        if (gc_float > 100) {
            return [NSString stringWithFormat:@"%.0f KB", gc_float];
        }
        else {
            return [NSString stringWithFormat:@"%.1f KB", gc_float];
        }
    } else
        return [NSString stringWithFormat:@"%lld B", file_size];
}