plugin.go

     1  // Copyright 2016 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package plugin implements loading and symbol resolution of Go plugins.
     6  //
     7  // A plugin is a Go main package with exported functions and variables that
     8  // has been built with:
     9  //
    10  //	go build -buildmode=plugin
    11  //
    12  // When a plugin is first opened, the init functions of all packages not
    13  // already part of the program are called. The main function is not run.
    14  // A plugin is only initialized once, and cannot be closed.
    15  //
    16  // Currently plugins are only supported on Linux, FreeBSD, and macOS.
    17  // Please report any issues.
    18  package plugin
    19  
    20  // Plugin is a loaded Go plugin.
    21  type Plugin struct {
    22  	pluginpath string
    23  	err        string        // set if plugin failed to load
    24  	loaded     chan struct{} // closed when loaded
    25  	syms       map[string]any
    26  }
    27  
    28  // Open opens a Go plugin.
    29  // If a path has already been opened, then the existing *Plugin is returned.
    30  // It is safe for concurrent use by multiple goroutines.
    31  func Open(path string) (*Plugin, error) {
    32  	return open(path)
    33  }
    34  
    35  // Lookup searches for a symbol named symName in plugin p.
    36  // A symbol is any exported variable or function.
    37  // It reports an error if the symbol is not found.
    38  // It is safe for concurrent use by multiple goroutines.
    39  func (p *Plugin) Lookup(symName string) (Symbol, error) {
    40  	return lookup(p, symName)
    41  }
    42  
    43  // A Symbol is a pointer to a variable or function.
    44  //
    45  // For example, a plugin defined as
    46  //
    47  //	package main
    48  //
    49  //	import "fmt"
    50  //
    51  //	var V int
    52  //
    53  //	func F() { fmt.Printf("Hello, number %d\n", V) }
    54  //
    55  // may be loaded with the Open function and then the exported package
    56  // symbols V and F can be accessed
    57  //
    58  //	p, err := plugin.Open("plugin_name.so")
    59  //	if err != nil {
    60  //		panic(err)
    61  //	}
    62  //	v, err := p.Lookup("V")
    63  //	if err != nil {
    64  //		panic(err)
    65  //	}
    66  //	f, err := p.Lookup("F")
    67  //	if err != nil {
    68  //		panic(err)
    69  //	}
    70  //	*v.(*int) = 7
    71  //	f.(func())() // prints "Hello, number 7"
    72  type Symbol any
    73
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