internal/gcimporter: synchronize with internal/exportdata

Use the copies of the functions from internal/exportdata.

The implementations are now quite uniform between
exportdata.go in GOROOT/src/internal/exportdata and internal/gcimporter
as well as gcimporter.go in GOROOT/src/go/internal/gcimporter and
internal/gcimporter.

Fixes golang/go#70651

Change-Id: I8c2a55ca8c09d504315b9ccd7c676a5c2023ca68
Reviewed-on: https://go-review.googlesource.com/c/tools/+/633660
Commit-Queue: Tim King <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Robert Griesemer <[email protected]>
Reviewed-by: Robert Findley <[email protected]>

internal/gcimporter/exportdata.go

@@ -31,58 +31,33 @@ import (
 // accept inputs produced by the last two releases of cmd/compile,
 // plus tip.
 func FindExportData(r *bufio.Reader) (size int64, err error) {
-	// Read first line to make sure this is an object file.
-	line, err := r.ReadSlice('\n')
+	arsize, err := FindPackageDefinition(r)
 	if err != nil {
-		err = fmt.Errorf("can't find export data (%v)", err)
-		return
-	}
-
-	// Is the first line an archive file signature?
-	if string(line) != "!<arch>\n" {
-		err = fmt.Errorf("not the start of an archive file (%q)", line)
-		return
-	}
-
-	// Archive file with the first file being __.PKGDEF.
-	arsize := readArchiveHeader(r, "__.PKGDEF")
-	if arsize <= 0 {
-		err = fmt.Errorf("not a package file")
 		return
 	}
 	size = int64(arsize)
 
-	// Read first line of __.PKGDEF data, so that line
-	// is once again the first line of the input.
-	if line, err = r.ReadSlice('\n'); err != nil {
-		err = fmt.Errorf("can't find export data (%v)", err)
-		return
-	}
-	size -= int64(len(line))
-
-	// Now at __.PKGDEF in archive or still at beginning of file.
-	// Either way, line should begin with "go object ".
-	if !strings.HasPrefix(string(line), "go object ") {
-		err = fmt.Errorf("not a Go object file")
+	objapi, headers, err := ReadObjectHeaders(r)
+	if err != nil {
 		return
 	}
-
-	// Skip over object headers to get to the export data section header "$$B\n".
-	// Object headers are lines that do not start with '$'.
-	for line[0] != '$' {
-		if line, err = r.ReadSlice('\n'); err != nil {
-			err = fmt.Errorf("can't find export data (%v)", err)
-			return
-		}
-		size -= int64(len(line))
+	size -= int64(len(objapi))
+	for _, h := range headers {
+		size -= int64(len(h))
 	}
 
 	// Check for the binary export data section header "$$B\n".
+	// TODO(taking): Unify with ReadExportDataHeader so that it stops at the 'u' instead of reading
+	line, err := r.ReadSlice('\n')
+	if err != nil {
+		return
+	}
 	hdr := string(line)
 	if hdr != "$$B\n" {
 		err = fmt.Errorf("unknown export data header: %q", hdr)
 		return
 	}
+	size -= int64(len(hdr))
 
 	// For files with a binary export data header "$$B\n",
 	// these are always terminated by an end-of-section marker "\n$$\n".

internal/gcimporter/gcimporter.go

@@ -46,7 +46,7 @@ const (
 // 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 filename, id string
+	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.
@@ -65,6 +65,7 @@ func Import(fset *token.FileSet, packages map[string]*types.Package, path, srcDi
 		}
 		rc = f
 	} else {
+		var filename string
 		filename, id, err = FindPkg(path, srcDir)
 		if filename == "" {
 			if path == "unsafe" {
@@ -93,43 +94,15 @@ func Import(fset *token.FileSet, packages map[string]*types.Package, path, srcDi
 	}
 	defer rc.Close()
 
-	var size int64
 	buf := bufio.NewReader(rc)
-	if size, err = FindExportData(buf); err != nil {
-		return
-	}
-
-	var data []byte
-	data, err = io.ReadAll(buf)
+	data, err := ReadUnified(buf)
 	if err != nil {
+		err = fmt.Errorf("import %q: %v", path, err)
 		return
 	}
-	if len(data) == 0 {
-		return nil, fmt.Errorf("no data to load a package from for path %s", id)
-	}
 
-	// Select appropriate importer.
-	switch data[0] {
-	case 'v', 'c', 'd':
-		// binary: emitted by cmd/compile till go1.10; obsolete.
-		return nil, fmt.Errorf("binary (%c) import format is no longer supported", data[0])
+	// unified: emitted by cmd/compile since go1.20.
+	_, pkg, err = UImportData(fset, packages, data, id)
 
-	case 'i':
-		// indexed: emitted by cmd/compile till go1.19;
-		// now used only for serializing go/types.
-		// See https://github.com/golang/go/issues/69491.
-		return nil, fmt.Errorf("indexed (i) import format is no longer supported")
-
-	case 'u':
-		// unified: emitted by cmd/compile since go1.20.
-		_, pkg, err := UImportData(fset, packages, data[1:size], id)
-		return pkg, err
-
-	default:
-		l := len(data)
-		if l > 10 {
-			l = 10
-		}
-		return nil, fmt.Errorf("unexpected export data with prefix %q for path %s", string(data[:l]), id)
-	}
+	return
 }