EX_25/2/19

1.

封装一个 File 类，用有私有成员

File* fp

实现以下功能

File f = "文件名" 要求打开该文件

f.write(string str) 要求将str数据写入文件中

string str = f.read(int size) 从文件中读取最多size个字节，并将读取到的数据返回

析构函数

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <unistd.h>
#include <sstream>
#include <vector>
#include <memory>using namespace std;                 class File
{
private:FILE* fp;
public:File();File(const string& str);~File();void write(const string&str);string read(const int& size);
};File::File()
{fp=NULL;
}File::File(const string& str)
{const char* buf=str.data();fp=fopen(buf,"a+");
}File::~File()
{if(fp!=NULL){fclose(fp);}
}void File::write(const string& str)
{const char* buf=str.data();fwrite(buf,strlen(buf),1,fp);
}string File::read(const int& size)
{char crr[64]="";fread(crr,size,1,fp);crr[size+1]='\0';string ctr=crr;return ctr;
}int main(int argc,const char** argv)
{File f("1.text");f.write("abc");string ret=f.read(3);cout<<ret<<endl;return 0;
}

2.封装一个 Mutex 互斥锁类

要求：

构造函数：初始化互斥锁，并选择互斥锁的种类

lock 上锁互斥锁

unlock 解锁互斥锁

析构函数，销毁互斥锁

并且开启一个线程测试该互斥锁

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <unistd.h>
#include <sstream>
#include <vector>
#include <memory>using namespace std;                 class Mutex
{
private:pthread_mutex_t m;
public:Mutex();Mutex(char* kind);~Mutex();void lock();void unlock();
};
Mutex::Mutex()
{pthread_mutex_init(&m,NULL);
}
Mutex::Mutex(char* kind)
{string st=kind;pthread_mutexattr_t attr;pthread_mutexattr_init(&attr);pthread_mutexattr_settype(&attr,st);
}
void Mutex::lock()
{pthread_mutex_lock(&m);
}
void Mutex::unlock()
{pthread_mutex_unlock(&m);
}
Mutex::~Mutex()
{pthread_mutex_destroy(&m);
}
int a=0;
Mutex mut("PTHREAD_MUTEX_FAST_NP");
void *thread_main(void* arg)
{while(1){mut.lock();a=100;mut.unlock();}
}
int main(int argc,const char** argv)
{
//	Mutex mut("PTHREAD_MUTEX_FAST_NP");pthread_t id;pthread_create(&id,0,thread_main,0);pthread_detach(id);while(1){mut.lock();a=999;mut.unlock();}return 0;
}