fstream 示例代码

2024-08-22 11:32

文章标签 代码示例 fstream

本文主要是介绍fstream 示例代码，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

fstream 示例代码

参考：C++中文件流(fstream)的使用方法及示例

获取流长度，并读取。

int _tmain(int argc, _TCHAR* argv[])
{using namespace std;ifstream stream("F:\\WorkSpace\\StreamDemo\\Debug\\abc.txt", ios::in);if(!stream)cerr << "Open failed" << endl;stream.seekg(0, ios::end);int len = stream.tellg();stream.seekg(0, ios::beg);char* buffer = new char[len];memset(buffer, '\0', len);if(!stream.read(buffer, len)){cout << "Read error:" << stream.rdstate() << endl;}cout.write(buffer, len);stream.close();system("pause");return 0;
}

mysql 读取blob。

std::stringstream s;s << "SELECT * FROM Dao WHERE gender = "<< data <<"";prepStmt = con->prepareStatement (s.str());res = prepStmt->executeQuery();unsigned char* ptr;size_t blobSize=100;std::istream *is;while(res->next()){tempFR.uuId = res->getInt64("uuId");tempFR.cameraNo = res->getInt("cameraNo");tempFR.age = res->getInt("age");tempFR.gender = res->getInt("gender");is = res->getBlob("image");is->seekg (0, std::ios::end);blobSize = is->tellg();is->seekg (0, std::ios::beg);unsigned char * image = new unsigned char[blobSize];is->read((char*)image, blobSize);size_t imageSize = blobSize;}

另外一种没用过：

std::istream *blobData = set->getBlob("image");
std::istreambuf_iterator<char> isb = std::istreambuf_iterator<char>(*blobData);
std::string blobString = std::string(isb, std::istreambuf_iterator<char>());
unsigned char * image = blobString.c_str();
blobData->seekg(0, ios::end);
size_t imageSize = blobData->tellg();