一个 30 M 的int号码值一次性保存。和读取一次，避免保存为char 种类，进行格转变，格转换时间是非常耗时。

#include <iostream>

#include <fstream>

#include <time.h>

using namespace  std;

#define  MAXNUM  2560*1920

void 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");

}