iOS字符串写入沙盒的效率对比

    NSData *data = [str dataUsingEncoding:(NSUTF8StringEncoding)];
    
    // 获取Document目录
    NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    //构造字符串文件的存储路径
    
    NSString *strPath1 = [docPath stringByAppendingPathComponent:@"text1.txt"];
    
    
    CFAbsoluteTime startTime =CFAbsoluteTimeGetCurrent();
    //在这写入要计算时间的代码
    [str writeToFile:strPath1 atomically:YES encoding:NSUTF8StringEncoding error:nil];
    CFAbsoluteTime linkTime = (CFAbsoluteTimeGetCurrent() - startTime);
    NSLog(@"C函数压缩时间 %f ms", linkTime *1000.0);

    NSString *strPath2 = [docPath stringByAppendingPathComponent:@"text2.txt"];
    CFAbsoluteTime startTime2 =CFAbsoluteTimeGetCurrent();
    //在这写入要计算时间的代码
    FILE * fp = fopen(strPath2.UTF8String, "a");
    if(fp){
        fwrite(str.UTF8String, strlen(str.UTF8String) + 1, 1, fp);
        fclose(fp);
    }
    CFAbsoluteTime linkTime2 = (CFAbsoluteTimeGetCurrent() - startTime2);
    NSLog(@"C函数压缩时间 %f ms", linkTime2 *1000.0);

测试结果：
不分写入的内容，前者的耗时都是后者的5-20倍之间，平均耗时为15倍