1 files changed, 91 insertions, 0 deletions
diff --git a/go/runfiles/manifest.go b/go/runfiles/manifest.go
new file mode 100644
index 00000000..4d8e8798
--- /dev/null
+++ b/go/runfiles/manifest.go
@@ -0,0 +1,91 @@
+// Copyright 2020, 2021 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package runfiles
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+// ManifestFile specifies the location of the runfile manifest file.  You can
+// pass this as an option to New.  If unset or empty, use the value of the
+// environmental variable RUNFILES_MANIFEST_FILE.
+type ManifestFile string
+
+func (f ManifestFile) new(sourceRepo SourceRepo) (*Runfiles, error) {
+	m, err := f.parse()
+	if err != nil {
+		return nil, err
+	}
+	r := &Runfiles{
+		impl:       m,
+		env:        manifestFileVar + "=" + string(f),
+		sourceRepo: string(sourceRepo),
+	}
+	err = r.loadRepoMapping()
+	return r, err
+}
+
+type manifest map[string]string
+
+func (f ManifestFile) parse() (manifest, error) {
+	r, err := os.Open(string(f))
+	if err != nil {
+		return nil, fmt.Errorf("runfiles: can’t open manifest file: %w", err)
+	}
+	defer r.Close()
+
+	s := bufio.NewScanner(r)
+	m := make(manifest)
+	for s.Scan() {
+		fields := strings.SplitN(s.Text(), " ", 2)
+		if len(fields) != 2 || fields[0] == "" {
+			return nil, fmt.Errorf("runfiles: bad manifest line %q in file %s", s.Text(), f)
+		}
+		m[fields[0]] = filepath.FromSlash(fields[1])
+	}
+
+	if err := s.Err(); err != nil {
+		return nil, fmt.Errorf("runfiles: error parsing manifest file %s: %w", f, err)
+	}
+
+	return m, nil
+}
+
+func (m manifest) path(s string) (string, error) {
+	r, ok := m[s]
+	if ok && r == "" {
+		return "", ErrEmpty
+	}
+	if ok {
+		return r, nil
+	}
+
+	// If path references a runfile that lies under a directory that itself is a
+	// runfile, then only the directory is listed in the manifest. Look up all
+	// prefixes of path in the manifest.
+	for prefix := s; prefix != ""; prefix, _ = path.Split(prefix) {
+		prefix = strings.TrimSuffix(prefix, "/")
+		if prefixMatch, ok := m[prefix]; ok {
+			return prefixMatch + filepath.FromSlash(strings.TrimPrefix(s, prefix)), nil
+		}
+	}
+
+	return "", os.ErrNotExist
+}