Simple example of calling classic Windows APIs from Swift

hello-win32.swift

import WinSDK

// Call a simple Win32 function and pass in strings
MessageBoxA(nil, "Hello from Swift running on Windows", "Swift Message Box", UINT(MB_OK))

// Call a Win32 function that passes a variable by pointer
var memorySizeInBytes: LONGLONG = 0
GetPhysicallyInstalledSystemMemory(&memorySizeInBytes)
print("System has \(memorySizeInBytes / 1024 / 1024)GB of RAM installed.");

// Create a String and pass its pointer to a Win32 function
let desktopPath = String(unsafeUninitializedCapacity: Int(MAX_PATH)) { buffer in
    SHGetFolderPathA(nil, CSIDL_DESKTOP, nil, 0, buffer.baseAddress)
    return buffer.firstIndex(of: 0) ?? 0 // tell Swift where the string ends
}
print("Desktop folder is at \(desktopPath)")

// Create a struct and use it to interrogate system battery life
var powerStatus = SYSTEM_POWER_STATUS()
let hr = GetSystemPowerStatus(&powerStatus)
let systemHasBattery = powerStatus.BatteryFlag < 128
let batteryLifePercent = powerStatus.BatteryLifePercent
if systemHasBattery { 
    print("System has a battery. Battery life remaining: \(batteryLifePercent)%") 
} else {
    print("System has no battery.")
}