I switched the advertising on at Store Presence->Pricing & Distribution page:
Parsing GUID in C++ with a regular expression
The code below demonstrates how to parse GUID in C++ using a regular expression:
#include <iostream>
#include <string>
#include <regex>
int main()
{
static const std::wregex regex(L"[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}");
std::wstring sample = L"850fe1da-0ea6-c1a8-9810-0c1cece30698";
std::match_results<std::wstring::const_iterator> match;
if (std::regex_match(sample, match, regex))
{
std::wcout << L"matches" << std::endl;
}
else
{
std::wcout << L"does not match" << std::endl;
}
return 0;
}
A simple example demonstrating how std::forward works in C++
For example, std::forward comes to play if I implement a template container with two ‘insert‘ function overloads that take the parameters of type const T & and T && respectively. I implement all the private insertion logic with T&&, but when I need to know the original value type passed to ‘insert‘ method I use std::forward as shown in the example below:
#include <iostream>
#include <string>
class Value
{
public:
Value(const char * sz) : m_s(sz)
{
}
Value(const Value & other) : m_s(other.m_s)
{
std::cout << "copy constructor: " << m_s << std::endl;
}
Value(Value && other) : m_s(std::move(other.m_s))
{
std::cout << "move constructor: " << m_s << std::endl;
}
const std::string & ToString() const
{
return m_s;
}
private:
std::string m_s;
};
Compiling OpenSSL 1.1 with MSVC2017 for using with QT 5.13
QT does not work with OpenSSL 1.0 anymore. Versions QT 5.12.4 and above require OpenSSL 1.1, but fortunately OpenSSL 1.1 can be easily compiled with MS2017 as follows:
set PATH=%PATH%;C:\Perl64\bin
set PATH=%PATH%;C:\PFiles\nasm-2.14.02-win64
perl Configure VC-WIN64A
nmake
The key to the success is using ‘VS2017 x64 Native Tools Command Prompt‘, but not ‘VS2017 Developer Command Prompt’.
To make QT use OpenSSL, two dlls
libcrypto-1_1-x64.dll
libssl-1_1-x64.dll
should be copied to QT binary directory, for example, C:\Qt\Qt5.13.0\5.13.0\msvc2017_64\bin
Oracle Database user and role IDs
Below I provided the results of two following queries:
SELECT USERNAME, USER_ID FROM DBA_USERS ORDER BY USER_ID DESC;
SELECT ROLE, ROLE_ID FROM DBA_ROLES ORDER BY ROLE_ID DESC;
that display Oracle Database 18 users, roles and their IDs:
(more…)How to change MySQL 5.7 root password
First, check MySQL version:
SHOW VARIABLES LIKE "%version%";
+-------------------------+-------------------------+
| Variable_name | Value |
+-------------------------+-------------------------+
| innodb_version | 5.7.25 |
| protocol_version | 10 |
| slave_type_conversions | |
| tls_version | TLSv1,TLSv1.1 |
| version | 5.7.25-0ubuntu0.16.04.2 |
| version_comment | (Ubuntu) |
| version_compile_machine | x86_64 |
| version_compile_os | Linux |
+-------------------------+-------------------------+
The string representation of a type is implementation defined in C++
The string representation of a type is implementation defined in C++, for example the following code produce the different output with MSVC, GCC and CLang:
#include <string>
#include <iostream>
struct A {};
class B {};
namespace ns
{
struct X {};
}
int main()
{
std::cout << typeid(A).name() << ", " << typeid(B).name() << ", " << typeid(ns::X).name() << ", " << typeid(std::string).name() << std::endl;
return 0;
}
Determining .NET Framework version from the native C++ code.
.NET Framework version 4.5 and higher can be determined with the following C++ code:
#include <windows.h>
bool IsDotNet45Installed()
{
DWORD value{};
DWORD dataSize = sizeof(value);
const LONG retCode = ::RegGetValue(
HKEY_LOCAL_MACHINE,
L"SOFTWARE\\Microsoft\\NET Framework Setup\\NDP\\v4\\Full\\",
L"Release",
RRF_RT_REG_DWORD,
nullptr,
&value,
&dataSize
);
if (retCode != ERROR_SUCCESS)
{
return false;
}
return value >= 378389;
}
Handling errors at compile time in C++
We had a discussion with colleagues on why in the following code we cannot simply use
static_assert(false)
but need to do a trick with ‘always_false’:
#include <type_traits>
template<typename>
struct always_false : std::false_type {};
template<typename Type>
constexpr int Get()
{
if constexpr (std::is_same_v<Type, int>)
{
return 1;
}
else if constexpr (std::is_same_v<Type, bool>)
{
return 2;
}
else {
static_assert(always_false<Type>::value);
}
}
Accessing Oracle Database in C++ with MS VS2017.
Download binaries (redistributables) and C++ SDK from Oracle website. For 64bit platform they are respectively:
instantclient-basic-windows.x64-18.5.0.0.0dbru.zip
instantclient-sdk-windows.x64-18.5.0.0.0dbru.zip
Extract them, create a C++ project in VS2017 and link oraocci18.lib in Release configuration and oraocci18d.lib in Debug configuration.
(more…)