iostream 读二进制

//打开文件
string fileName = "test.dat"
fstream readFile;
readFile.open(fileName, ios::binary | ios::in);
if (!readFile.is_open())
{
    cout << "cannot open file : " << fileName << endl;
    //处理打开失败的情况。 这里没找到失败原因如何打印。
}

//读数据
struct stData stdata;
while (readFile.peek() != EOF)
{
    readFile.read((char*)&stdata,sizeof(stdata));
    if (readFile.gcount() < sizeof(stdata)) {
        cout << "the last data is not complete." << endl;
        break;
    }
    //处理数据
}

//关闭文件
readFile.close();

FILE* 读

//打开文件
FILE* readFile;
errno_t err;
string readFileName = "test.dat";
int err = fopen_s(&readFile, readFileName.c_str(), "rb");//r表示read，b表示二进制

//检查打开错误信息
char errmsg[64];
if (err != 0) {
    strerror_s(errmsg, 64, err);
    cout << "cannot open file '" << readFileName <<"' : "<< errmsg <<endl;
    continue;
}

//读数据
struct stData *st = new stData[10];
int readNum=0;
readNum = fread(&st, sizeof(st), 10, readFile);//从readFile中读取10个stData，返回读成功的个数。

//关闭文件
fclose(readFile);

FILE* 写

//打开文件
FILE* writeFile;
string writeFileName = "test.txt";
int err = fopen_s(&writeFile, writeFileName.c_str(), "w");

//检查打开写文件的错误信息
char errmsg[64];
if (err != 0) {
    strerror_s(errmsg, 64, err);
    cout << "cannot open write file '" << writeFileName <<"' : "<< errmsg <<endl;
    continue;
}

//写入
fprintf(writeFile, "write someting to file %d.\n", 123);

//关闭文件
fclose(writeFile);