int 類型的數值一次性寫入一次性讀取

標籤：c++

將一個20M 的int數值一次性保持，並一次性讀取，避免儲存為char 類型，進行格式轉換的時候很耗時。

#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);}// 擷取檔案大小。ifs.seekg(0, ios::end);streampos pos = (ifs.tellg());ifs.seekg(0, ios::beg);  // 注意要將檔案指標移動到檔案頭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;system("pause");}