src

gcimporter.go (3136B)

---

 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 // This file is a reduced copy of $GOROOT/src/go/internal/gcimporter/gcimporter.go.
 
 // Package gcimporter provides various functions for reading
 // gc-generated object files that can be used to implement the
 // Importer interface defined by the Go 1.5 standard library package.
 //
 // The encoding is deterministic: if the encoder is applied twice to
 // the same types.Package data structure, both encodings are equal.
 // This property may be important to avoid spurious changes in
 // applications such as build systems.
 //
 // However, the encoder is not necessarily idempotent. Importing an
 // exported package may yield a types.Package that, while it
 // represents the same set of Go types as the original, may differ in
 // the details of its internal representation. Because of these
 // differences, re-encoding the imported package may yield a
 // different, but equally valid, encoding of the package.
 package gcimporter // import "golang.org/x/tools/internal/gcimporter"
 
 import (
 	"bufio"
 	"fmt"
 	"go/token"
 	"go/types"
 	"io"
 	"os"
 )
 
 const (
 	// Enable debug during development: it adds some additional checks, and
 	// prevents errors from being recovered.
 	debug = false
 
 	// If trace is set, debugging output is printed to std out.
 	trace = false
 )
 
 // Import imports a gc-generated package given its import path and srcDir, adds
 // the corresponding package object to the packages map, and returns the object.
 // The packages map must contain all packages already imported.
 //
 // Import is only used in tests.
 func Import(fset *token.FileSet, packages map[string]*types.Package, path, srcDir string, lookup func(path string) (io.ReadCloser, error)) (pkg *types.Package, err error) {
 	var rc io.ReadCloser
 	var id string
 	if lookup != nil {
 		// With custom lookup specified, assume that caller has
 		// converted path to a canonical import path for use in the map.
 		if path == "unsafe" {
 			return types.Unsafe, nil
 		}
 		id = path
 
 		// No need to re-import if the package was imported completely before.
 		if pkg = packages[id]; pkg != nil && pkg.Complete() {
 			return
 		}
 		f, err := lookup(path)
 		if err != nil {
 			return nil, err
 		}
 		rc = f
 	} else {
 		var filename string
 		filename, id, err = FindPkg(path, srcDir)
 		if filename == "" {
 			if path == "unsafe" {
 				return types.Unsafe, nil
 			}
 			return nil, err
 		}
 
 		// no need to re-import if the package was imported completely before
 		if pkg = packages[id]; pkg != nil && pkg.Complete() {
 			return
 		}
 
 		// open file
 		f, err := os.Open(filename)
 		if err != nil {
 			return nil, err
 		}
 		defer func() {
 			if err != nil {
 				// add file name to error
 				err = fmt.Errorf("%s: %v", filename, err)
 			}
 		}()
 		rc = f
 	}
 	defer rc.Close()
 
 	buf := bufio.NewReader(rc)
 	data, err := ReadUnified(buf)
 	if err != nil {
 		err = fmt.Errorf("import %q: %v", path, err)
 		return
 	}
 
 	// unified: emitted by cmd/compile since go1.20.
 	_, pkg, err = UImportData(fset, packages, data, id)
 
 	return
 }