Make initializer optional

Author: Devoter

plugin.go

@@ -14,24 +14,31 @@ package dlplugin
 
 // PluginInitializer provides an interface which is used to initialize a plugin interface.
 type PluginInitializer interface {
-	// Init denotes a function type which initializes a plugin API.
+	// Init initializes a plugin API.
 	Init(lookup func(symName string) (uintptr, error)) error
 }
 
 // Plugin is a loaded plugin.
 type Plugin struct {
 	handler  uintptr
 	filepath string
+	name     string
 }
 
 // Close closes a plugin.
 func (p *Plugin) Close() error {
 	return libClose(p)
 }
 
+// Init provides a lookup function and calls an initializer's Init method.
+func (p *Plugin) Init(initializer PluginInitializer) error {
+	return libInit(p, initializer)
+}
+
 // Open opens a plugin.
 // If a path has already been opened, then the existing *Plugin is returned.
 // It is safe for concurrent use by multiple goroutines.
+// If the initializer is nil the initialization process will be skipped.
 func Open(path string, initializer PluginInitializer) (*Plugin, error) {
 	return libOpen(path, initializer)
 }

plugin_dl.go

@@ -87,25 +87,17 @@ func libOpen(name string, initializer PluginInitializer) (*Plugin, error) {
 		plugins = make(map[string]*Plugin)
 	}
 
-	p = &Plugin{handler: uintptr(h), filepath: filepath}
+	p = &Plugin{handler: uintptr(h), filepath: filepath, name: name}
 
-	lookupFunc := func(symName string) (uintptr, error) {
-		cname := make([]byte, len(symName)+1)
-		copy(cname, symName)
+	if initializer != nil {
+		lookupFunc := produceLookup(h, name)
 
-		p := C.dlplugin_lookup(h, (*C.char)(unsafe.Pointer(&cname[0])), &cErr)
-		if p == 0 {
-			return 0, errors.New(`dlplugin.Open("` + name + `"): could not find symbol ` + symName + `: ` + C.GoString(cErr))
-		}
+		if err := initializer.Init(lookupFunc); err != nil {
+			C.dlplugin_close(C.uintptr_t(p.handler))
+			pluginsMu.Unlock()
 
-		return uintptr(p), nil
-	}
-
-	if err := initializer.Init(lookupFunc); err != nil {
-		C.dlplugin_close(C.uintptr_t(p.handler))
-		pluginsMu.Unlock()
-
-		return nil, err
+			return nil, err
+		}
 	}
 
 	plugins[filepath] = p
@@ -125,7 +117,33 @@ func libClose(p *Plugin) error {
 	return nil
 }
 
+func produceLookup(h C.uintptr_t, name string) func(symName string) (uintptr, error) {
+	return func(symName string) (uintptr, error) {
+		var cErr *C.char
+		cname := make([]byte, len(symName)+1)
+		copy(cname, symName)
+
+		p := C.dlplugin_lookup(h, (*C.char)(unsafe.Pointer(&cname[0])), &cErr)
+		if p == 0 {
+			return 0, errors.New(`dlplugin.Open("` + name + `"): could not find symbol ` + symName + `: ` + C.GoString(cErr))
+		}
+
+		return uintptr(p), nil
+	}
+}
+
+func libInit(p *Plugin, initializer PluginInitializer) error {
+	pluginsMu.RLock()
+
+	lookup := produceLookup(C.uintptr_t(p.handler), p.name)
+	err := initializer.Init(lookup)
+
+	pluginsMu.RUnlock()
+
+	return err
+}
+
 var (
-	pluginsMu sync.Mutex
+	pluginsMu sync.RWMutex
 	plugins   map[string]*Plugin
 )

plugin_stubs.go

@@ -17,3 +17,7 @@ func libOpen(name string, initializer PluginInitializer) (*Plugin, error) {
 func libClose(p *Plugin) error {
 	return errors.New("dlplugin: not implemented")
 }
+
+func libInit(p *Plugin, initializer PluginInitializer) error {
+	return errors.New("dlplugin: not implemented")
+}

plugin_win.go

@@ -94,23 +94,15 @@ func libOpen(name string, initializer PluginInitializer) (*Plugin, error) {
 
 	p = &Plugin{handler: uintptr(h), filepath: filepath}
 
-	lookupFunc := func(symName string) (uintptr, error) {
-		cname := make([]byte, len(symName)+1)
-		copy(cname, symName)
+	if initializer != nil {
+		lookupFunc := produceLookup(h, name)
 
-		p := C.dlplugin_lookup(h, (*C.char)(unsafe.Pointer(&cname[0])), &cErr)
-		if p == 0 {
-			return 0, errors.New(`dlplugin.Open("` + name + `"): could not find symbol ` + symName + `: ` + formatWinErr(cErr).Error())
-		}
+		if err := initializer.Init(lookupFunc); err != nil {
+			C.dlplugin_close(C.uintptr_t(p.handler))
+			pluginsMu.Unlock()
 
-		return uintptr(p), nil
-	}
-
-	if err := initializer.Init(lookupFunc); err != nil {
-		C.dlplugin_close(C.uintptr_t(p.handler))
-		pluginsMu.Unlock()
-
-		return nil, err
+			return nil, err
+		}
 	}
 
 	plugins[filepath] = p
@@ -134,7 +126,33 @@ func libClose(p *Plugin) error {
 	return nil
 }
 
+func produceLookup(h C.uintptr_t, name string) func(symName string) (uintptr, error) {
+	return func(symName string) (uintptr, error) {
+		var cErr *C.char
+		cname := make([]byte, len(symName)+1)
+		copy(cname, symName)
+
+		p := C.dlplugin_lookup(h, (*C.char)(unsafe.Pointer(&cname[0])), &cErr)
+		if p == 0 {
+			return 0, errors.New(`dlplugin.Open("` + name + `"): could not find symbol ` + symName + `: ` + formatWinErr(cErr).Error())
+		}
+
+		return uintptr(p), nil
+	}
+}
+
+func libInit(p *Plugin, initializer PluginInitializer) error {
+	pluginsMu.RLock()
+
+	lookup := produceLookup(C.uintptr_t(p.handler), p.name)
+	err := initializer.Init(lookup)
+
+	pluginsMu.RUnlock()
+
+	return err
+}
+
 var (
-	pluginsMu sync.Mutex
+	pluginsMu sync.RWMutex
 	plugins   map[string]*Plugin
 )