1 files changed, 261 insertions, 0 deletions
diff --git a/src/go/internal/gccgoimporter/importer.go b/src/go/internal/gccgoimporter/importer.go
new file mode 100644
index 0000000..94f2def
--- /dev/null
+++ b/src/go/internal/gccgoimporter/importer.go
@@ -0,0 +1,261 @@
+// Copyright 2013 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.
+
+// Package gccgoimporter implements Import for gccgo-generated object files.
+package gccgoimporter // import "go/internal/gccgoimporter"
+
+import (
+	"bytes"
+	"debug/elf"
+	"fmt"
+	"go/types"
+	"internal/xcoff"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// A PackageInit describes an imported package that needs initialization.
+type PackageInit struct {
+	Name     string // short package name
+	InitFunc string // name of init function
+	Priority int    // priority of init function, see InitData.Priority
+}
+
+// The gccgo-specific init data for a package.
+type InitData struct {
+	// Initialization priority of this package relative to other packages.
+	// This is based on the maximum depth of the package's dependency graph;
+	// it is guaranteed to be greater than that of its dependencies.
+	Priority int
+
+	// The list of packages which this package depends on to be initialized,
+	// including itself if needed. This is the subset of the transitive closure of
+	// the package's dependencies that need initialization.
+	Inits []PackageInit
+}
+
+// Locate the file from which to read export data.
+// This is intended to replicate the logic in gofrontend.
+func findExportFile(searchpaths []string, pkgpath string) (string, error) {
+	for _, spath := range searchpaths {
+		pkgfullpath := filepath.Join(spath, pkgpath)
+		pkgdir, name := filepath.Split(pkgfullpath)
+
+		for _, filepath := range [...]string{
+			pkgfullpath,
+			pkgfullpath + ".gox",
+			pkgdir + "lib" + name + ".so",
+			pkgdir + "lib" + name + ".a",
+			pkgfullpath + ".o",
+		} {
+			fi, err := os.Stat(filepath)
+			if err == nil && !fi.IsDir() {
+				return filepath, nil
+			}
+		}
+	}
+
+	return "", fmt.Errorf("%s: could not find export data (tried %s)", pkgpath, strings.Join(searchpaths, ":"))
+}
+
+const (
+	gccgov1Magic    = "v1;\n"
+	gccgov2Magic    = "v2;\n"
+	gccgov3Magic    = "v3;\n"
+	goimporterMagic = "\n$$ "
+	archiveMagic    = "!<ar"
+	aixbigafMagic   = "<big"
+)
+
+// Opens the export data file at the given path. If this is an ELF file,
+// searches for and opens the .go_export section. If this is an archive,
+// reads the export data from the first member, which is assumed to be an ELF file.
+// This is intended to replicate the logic in gofrontend.
+func openExportFile(fpath string) (reader io.ReadSeeker, closer io.Closer, err error) {
+	f, err := os.Open(fpath)
+	if err != nil {
+		return
+	}
+	closer = f
+	defer func() {
+		if err != nil && closer != nil {
+			f.Close()
+		}
+	}()
+
+	var magic [4]byte
+	_, err = f.ReadAt(magic[:], 0)
+	if err != nil {
+		return
+	}
+
+	var objreader io.ReaderAt
+	switch string(magic[:]) {
+	case gccgov1Magic, gccgov2Magic, gccgov3Magic, goimporterMagic:
+		// Raw export data.
+		reader = f
+		return
+
+	case archiveMagic, aixbigafMagic:
+		reader, err = arExportData(f)
+		return
+
+	default:
+		objreader = f
+	}
+
+	ef, err := elf.NewFile(objreader)
+	if err == nil {
+		sec := ef.Section(".go_export")
+		if sec == nil {
+			err = fmt.Errorf("%s: .go_export section not found", fpath)
+			return
+		}
+		reader = sec.Open()
+		return
+	}
+
+	xf, err := xcoff.NewFile(objreader)
+	if err == nil {
+		sdat := xf.CSect(".go_export")
+		if sdat == nil {
+			err = fmt.Errorf("%s: .go_export section not found", fpath)
+			return
+		}
+		reader = bytes.NewReader(sdat)
+		return
+	}
+
+	err = fmt.Errorf("%s: unrecognized file format", fpath)
+	return
+}
+
+// An Importer resolves import paths to Packages. The imports map records
+// packages already known, indexed by package path.
+// An importer must determine the canonical package path and check imports
+// to see if it is already present in the map. If so, the Importer can return
+// the map entry. Otherwise, the importer must load the package data for the
+// given path into a new *Package, record it in imports map, and return the
+// package.
+type Importer func(imports map[string]*types.Package, path, srcDir string, lookup func(string) (io.ReadCloser, error)) (*types.Package, error)
+
+func GetImporter(searchpaths []string, initmap map[*types.Package]InitData) Importer {
+	return func(imports map[string]*types.Package, pkgpath, srcDir string, lookup func(string) (io.ReadCloser, error)) (pkg *types.Package, err error) {
+		// TODO(gri): Use srcDir.
+		// Or not. It's possible that srcDir will fade in importance as
+		// the go command and other tools provide a translation table
+		// for relative imports (like ./foo or vendored imports).
+		if pkgpath == "unsafe" {
+			return types.Unsafe, nil
+		}
+
+		var reader io.ReadSeeker
+		var fpath string
+		var rc io.ReadCloser
+		if lookup != nil {
+			if p := imports[pkgpath]; p != nil && p.Complete() {
+				return p, nil
+			}
+			rc, err = lookup(pkgpath)
+			if err != nil {
+				return nil, err
+			}
+		}
+		if rc != nil {
+			defer rc.Close()
+			rs, ok := rc.(io.ReadSeeker)
+			if !ok {
+				return nil, fmt.Errorf("gccgo importer requires lookup to return an io.ReadSeeker, have %T", rc)
+			}
+			reader = rs
+			fpath = "<lookup " + pkgpath + ">"
+			// Take name from Name method (like on os.File) if present.
+			if n, ok := rc.(interface{ Name() string }); ok {
+				fpath = n.Name()
+			}
+		} else {
+			fpath, err = findExportFile(searchpaths, pkgpath)
+			if err != nil {
+				return nil, err
+			}
+
+			r, closer, err := openExportFile(fpath)
+			if err != nil {
+				return nil, err
+			}
+			if closer != nil {
+				defer closer.Close()
+			}
+			reader = r
+		}
+
+		var magics string
+		magics, err = readMagic(reader)
+		if err != nil {
+			return
+		}
+
+		if magics == archiveMagic || magics == aixbigafMagic {
+			reader, err = arExportData(reader)
+			if err != nil {
+				return
+			}
+			magics, err = readMagic(reader)
+			if err != nil {
+				return
+			}
+		}
+
+		switch magics {
+		case gccgov1Magic, gccgov2Magic, gccgov3Magic:
+			var p parser
+			p.init(fpath, reader, imports)
+			pkg = p.parsePackage()
+			if initmap != nil {
+				initmap[pkg] = p.initdata
+			}
+
+		// Excluded for now: Standard gccgo doesn't support this import format currently.
+		// case goimporterMagic:
+		// 	var data []byte
+		// 	data, err = io.ReadAll(reader)
+		// 	if err != nil {
+		// 		return
+		// 	}
+		// 	var n int
+		// 	n, pkg, err = importer.ImportData(imports, data)
+		// 	if err != nil {
+		// 		return
+		// 	}
+
+		// 	if initmap != nil {
+		// 		suffixreader := bytes.NewReader(data[n:])
+		// 		var p parser
+		// 		p.init(fpath, suffixreader, nil)
+		// 		p.parseInitData()
+		// 		initmap[pkg] = p.initdata
+		// 	}
+
+		default:
+			err = fmt.Errorf("unrecognized magic string: %q", magics)
+		}
+
+		return
+	}
+}
+
+// readMagic reads the four bytes at the start of a ReadSeeker and
+// returns them as a string.
+func readMagic(reader io.ReadSeeker) (string, error) {
+	var magic [4]byte
+	if _, err := reader.Read(magic[:]); err != nil {
+		return "", err
+	}
+	if _, err := reader.Seek(0, io.SeekStart); err != nil {
+		return "", err
+	}
+	return string(magic[:]), nil
+}