加速控制台时Setvbuf（）问题 [英] Setvbuf() problem when speeding console

问题描述

为了在Windows中调高控制台输出，建议使用setvbuf（）。

我的问题是，在创建缓冲区之后，cout在被调用的函数中不起作用。



我必须在以下程序中插入main（）行：

In order to spped the console output in windows it is recommended to use setvbuf().
My problem is that after making the buffer, cout does not work in called functions.

I had to insert at the following program at main() the line:

cout<<"=== FIN ==="<<endl;

所以：

1.如何强制在函数内写入cout？

2.如果写入大小大于缓冲区大小会发生什么？



我尝试过：

So:
1. How force to write at cout within the function?
2. What happens if writting size is bigger than the buffer size?

What I have tried:

<pre>#include <iostream>
using namespace std;
void test1(){cout<<" function ini"<<endl;} //" function ini" is not written here

int main()
{
#ifndef __linux__   //Introduce this code at the beginning of main() to increase a lot the speed of cout in windows: 
	char buffer_setvbuf[1024];setvbuf(stdout, buffer_setvbuf, _IOFBF, sizeof buffer_setvbuf); 
#endif

	cout<<"=== INI ==="<<endl;
	test1();
	cout<<"=== FIN ==="<<endl;
}

注意：我也尝试将buffer_setvbuf []设置为具有相同结果的全局变量。

Note: I tried also set buffer_setvbuf[] as a global variable with same results.

推荐答案

在达到缓冲区的长度（或刷新输出）之前不会显示输出，请参阅此处的答案： C：为什么fprintf（stdout，....）这么慢？ - 堆栈溢出 [ ^ ]。

output is not displayed until the length of the buffer is reached (or output is flushed), see the answer here: C: Why is a fprintf(stdout,....) so slow? - Stack Overflow[^].

Quote：

1。如何在函数内强制写入cout？

1. How force to write at cout within the function?

我会维护行缓冲策略。另一方面，如果你坚持使用完整的缓冲区，那么你必须明确地刷新 cout 。

I would maintain the line buffer policy. On the other hand, if you insist on using the full buffer one, then you have to explicitely flush cout.

Quote：

2。如果写入大小大于缓冲区大小会发生什么？

2. What happens if writting size is bigger than the buffer size?

精彩：在达到缓冲区大小时，缓冲区内容被发送到屏幕，然后整个缓冲区可用于进一步输出。

The wonderful: on reaching buffer size, the buffer content is sent to the screen and the whole buffer is then available for further output.

请参阅缓冲效果 [ ^ ]

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