int 类型的数值一次性写入一次性读取

来源：互联网发布：sql数据清洗编辑：程序博客网时间：2024/06/10 02:49

将一个 30 M 的int数值一次性保存，并一次性读取，避免保存为char 类型，进行格式转换，格式转换的时候很耗时。

#include <iostream>#include <fstream>#include <time.h>using namespace  std;#define  MAXNUM  2560*1920void savedata(char *filename,int *pdata){ofstream out;out.open(filename,ios::binary);if(!out.is_open())return ;for (int i=0;i<MAXNUM;i++){pdata[i] = i;}out.write((char *)pdata,MAXNUM*sizeof(int));out.close();cout<<endl;}void readdata(char *filename,int *pdata,int length){ifstream ifs(filename,ios::binary);if (!ifs){cout << "File open error!" << endl; exit(1);}// 获取文件大小。ifs.seekg(0, ios::end);streampos pos = (ifs.tellg());ifs.seekg(0, ios::beg);  // 注意要将文件指针移动到文件头if (pos > 0){ifs.read((char*)pdata, pos);for (int i = 0; i < pos/4; i++){cout << pdata[i];cout << endl;}}ifs.close();}void main(){int  *pd = new int[MAXNUM];memset(pd,'0',MAXNUM);for (int i=0;i<MAXNUM;i++){pd[i] = i;}savedata("datat.img",pd);int* buff = new int[MAXNUM];memset(buff,'0',MAXNUM);double start=clock();readdata("datat.img",buff,MAXNUM);double end=clock();cout<<(end - start)<<endl;delete[] pd;delete[] buff;system("pause");}

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