github.com/tailscale/wireguard-go@v0.0.20201119-0.20210522003738-46b531feb08a/tun/wintun/dll_fromfile_windows.go (about)

     1  // +build !load_wintun_from_rsrc
     2  
     3  /* SPDX-License-Identifier: MIT
     4   *
     5   * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
     6   */
     7  
     8  package wintun
     9  
    10  import (
    11  	"fmt"
    12  	"sync"
    13  	"sync/atomic"
    14  	"unsafe"
    15  
    16  	"golang.org/x/sys/windows"
    17  )
    18  
    19  type lazyDLL struct {
    20  	Name   string
    21  	mu     sync.Mutex
    22  	module windows.Handle
    23  	onLoad func(d *lazyDLL)
    24  }
    25  
    26  func (d *lazyDLL) Load() error {
    27  	if atomic.LoadPointer((*unsafe.Pointer)(unsafe.Pointer(&d.module))) != nil {
    28  		return nil
    29  	}
    30  	d.mu.Lock()
    31  	defer d.mu.Unlock()
    32  	if d.module != 0 {
    33  		return nil
    34  	}
    35  
    36  	const (
    37  		LOAD_LIBRARY_SEARCH_APPLICATION_DIR = 0x00000200
    38  		LOAD_LIBRARY_SEARCH_SYSTEM32        = 0x00000800
    39  	)
    40  	module, err := windows.LoadLibraryEx(d.Name, 0, LOAD_LIBRARY_SEARCH_APPLICATION_DIR|LOAD_LIBRARY_SEARCH_SYSTEM32)
    41  	if err != nil {
    42  		return fmt.Errorf("Unable to load library: %w", err)
    43  	}
    44  
    45  	atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&d.module)), unsafe.Pointer(module))
    46  	if d.onLoad != nil {
    47  		d.onLoad(d)
    48  	}
    49  	return nil
    50  }
    51  
    52  func (p *lazyProc) nameToAddr() (uintptr, error) {
    53  	return windows.GetProcAddress(p.dll.module, p.Name)
    54  }