ReleaseBuffer只有一个作用，就是更新字符串的长度

最新推荐文章于 2025-04-11 16:55:25 发布

Hustudent20080101

最新推荐文章于 2025-04-11 16:55:25 发布

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分类专栏： c++MFC学习笔记

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本文详细解析了CString类在复制和更新字符串长度方面的应用，包括如何使用GetBuffer和ReleaseBuffer方法进行安全有效的字符串操作，并通过实例展示了不同操作的影响。

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void CStringBufferDlg::OnButton1() 
{
	// TODO: Add your control notification handler code here


CString WeatherZone = "";
int strLen = this->m_WeatherZone.GetLength();
memcpy(WeatherZone.GetBuffer(strLen),this->m_WeatherZone.GetBuffer(strLen),strLen);
WeatherZone.ReleaseBuffer();

CString  WeatherInfo = "";
strLen = this->m_szWeatherInfo.GetLength();
memcpy(WeatherInfo.GetBuffer(strLen),this->m_szWeatherInfo.GetBuffer(strLen),strLen);
WeatherInfo.ReleaseBuffer();

CString  Weatherglass= "";
strLen = this->m_szWeatherglass.GetLength();
memcpy(Weatherglass.GetBuffer(strLen),this->m_szWeatherglass.GetBuffer(strLen),strLen);
Weatherglass.ReleaseBuffer();

 CString weather = WeatherZone +" " +WeatherInfo +" "+Weatherglass;	

 SetDlgItemText(IDC_STATIC1,weather);
 // 为啥得带的这个weather 是"  "呢？而不是 "北京多云转晴 23~35度"呢？
 /*
 很明显ReleaseBuffer只有一个作用，就是更新字符串的长度。
 CString内，GetLength获取字符串长度并不是动态计算的，
 而是在赋值操作后计算并保存在一个int变量内的，
 当通过GetBuffer直接修改CString时，那个int变量并不可能自动更新，
 于是便有了ReleaseBuffer。	 
    其实，计算长度还能用strlen()，这个就算不ReleaseBuffer也不会出错，
	但如果不ReleaseBuffer，在+=这种赋值时字符串很可能会跟想要得到的不同。 
 */
}

void CStringBufferDlg::OnButton2() 
{
	// TODO: Add your control notification handler code here
	CString s="hello";	
    LPTSTR ps=s.GetBuffer(10);
	MessageBox(ps);
    strcpy(ps,"hi");
	MessageBox(ps);	
	MessageBox(s);	
	int len=s.GetLength();
	char buff[256];
	MessageBox(itoa(len,buff,10));
    s.ReleaseBuffer();	
	len=s.GetLength();
	MessageBox(itoa(len,buff,10));
}

void CStringBufferDlg::OnButton3() 
{
	// TODO: Add your control notification handler code here
	CString WeatherZone = "";
	int strLen = this->m_WeatherZone.GetLength();
	memcpy(WeatherZone.GetBuffer(strLen),this->m_WeatherZone.GetBuffer(strLen),strLen);
	//WeatherZone.ReleaseBuffer();
	
	CString  WeatherInfo = "";
	strLen = this->m_szWeatherInfo.GetLength();
	memcpy(WeatherInfo.GetBuffer(strLen),this->m_szWeatherInfo.GetBuffer(strLen),strLen);
	//WeatherInfo.ReleaseBuffer();
	
	CString  Weatherglass= "";
	strLen = this->m_szWeatherglass.GetLength();
	memcpy(Weatherglass.GetBuffer(strLen),this->m_szWeatherglass.GetBuffer(strLen),strLen);
	//Weatherglass.ReleaseBuffer();
	
	char buff[256];
	wsprintf(buff,"%s %s %s",WeatherZone.GetBuffer(0),WeatherInfo.GetBuffer(0),Weatherglass.GetBuffer(0));
	//CString weather = WeatherZone +" " +WeatherInfo +" "+Weatherglass;	
	
 SetDlgItemText(IDC_STATIC1,buff);	
}