userdir_windows.go

// +build windows

// Package userdir provides functions to get user directories
package userdir

import (
	"strings"
	"syscall"
	"unsafe"
)

// GetDataHome returns the user data directory.
func GetDataHome() string {
	return getRoamingAppDataDir()
}

// GetConfigHome returns the user config directory.
func GetConfigHome() string {
	return getRoamingAppDataDir()
}

var (
	modshell32               = syscall.NewLazyDLL("shell32.dll")
	modole32                 = syscall.NewLazyDLL("ole32.dll")
	procSHGetKnownFolderPath = modshell32.NewProc("SHGetKnownFolderPath")
	procCoTaskMemFree        = modole32.NewProc("CoTaskMemFree")

	roamingAppData = syscall.GUID{
		0x3EB685DB,
		0x65F9,
		0x4CF6,
		[8]byte{0xA0, 0x3A, 0xE3, 0xEF, 0x65, 0x72, 0x9F, 0x3D},
	}
)

func coTaskMemFree(ptr uintptr) {
	procCoTaskMemFree.Call(ptr)
}

func getRoamingAppDataDir() string {
	var pwstr uintptr

	// NOTE(vincent): ignore the returned HRESULT, because, according to https://msdn.microsoft.com/en-us/library/windows/desktop/bb762188(v=vs.85).aspx
	//  - the E_FAIL error can't be returned since the rfid we pass is static and well-defined.
	//  - the E_INVALIDARG error, as far as I know, can't be returned either since Roaming/AppData is always there.
	_, _, _ = procSHGetKnownFolderPath.Call(
		uintptr(unsafe.Pointer(&roamingAppData)),
		uintptr(uint32(0)),
		uintptr(unsafe.Pointer(nil)),
		uintptr(unsafe.Pointer(&pwstr)),
	)
	defer coTaskMemFree(pwstr)

	return strings.Replace(utf16PtrToString(pwstr), "\\", "/", -1)
}

func utf16PtrToString(str uintptr) string {
	// TODO(vincent): see if we can do anything about go vet complaining
	ptr := unsafe.Pointer(str)
	return syscall.UTF16ToString((*[1 << 16]uint16)(ptr)[:])
}