1 files changed, 119 insertions, 0 deletions
diff --git a/src/io/fs/glob.go b/src/io/fs/glob.go
new file mode 100644
index 0000000..45d9cb6
--- /dev/null
+++ b/src/io/fs/glob.go
@@ -0,0 +1,119 @@
+// Copyright 2020 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 fs
+
+import (
+	"path"
+)
+
+// A GlobFS is a file system with a Glob method.
+type GlobFS interface {
+	FS
+
+	// Glob returns the names of all files matching pattern,
+	// providing an implementation of the top-level
+	// Glob function.
+	Glob(pattern string) ([]string, error)
+}
+
+// Glob returns the names of all files matching pattern or nil
+// if there is no matching file. The syntax of patterns is the same
+// as in path.Match. The pattern may describe hierarchical names such as
+// usr/*/bin/ed.
+//
+// Glob ignores file system errors such as I/O errors reading directories.
+// The only possible returned error is path.ErrBadPattern, reporting that
+// the pattern is malformed.
+//
+// If fs implements GlobFS, Glob calls fs.Glob.
+// Otherwise, Glob uses ReadDir to traverse the directory tree
+// and look for matches for the pattern.
+func Glob(fsys FS, pattern string) (matches []string, err error) {
+	if fsys, ok := fsys.(GlobFS); ok {
+		return fsys.Glob(pattern)
+	}
+
+	// Check pattern is well-formed.
+	if _, err := path.Match(pattern, ""); err != nil {
+		return nil, err
+	}
+	if !hasMeta(pattern) {
+		if _, err = Stat(fsys, pattern); err != nil {
+			return nil, nil
+		}
+		return []string{pattern}, nil
+	}
+
+	dir, file := path.Split(pattern)
+	dir = cleanGlobPath(dir)
+
+	if !hasMeta(dir) {
+		return glob(fsys, dir, file, nil)
+	}
+
+	// Prevent infinite recursion. See issue 15879.
+	if dir == pattern {
+		return nil, path.ErrBadPattern
+	}
+
+	var m []string
+	m, err = Glob(fsys, dir)
+	if err != nil {
+		return
+	}
+	for _, d := range m {
+		matches, err = glob(fsys, d, file, matches)
+		if err != nil {
+			return
+		}
+	}
+	return
+}
+
+// cleanGlobPath prepares path for glob matching.
+func cleanGlobPath(path string) string {
+	switch path {
+	case "":
+		return "."
+	default:
+		return path[0 : len(path)-1] // chop off trailing separator
+	}
+}
+
+// glob searches for files matching pattern in the directory dir
+// and appends them to matches, returning the updated slice.
+// If the directory cannot be opened, glob returns the existing matches.
+// New matches are added in lexicographical order.
+func glob(fs FS, dir, pattern string, matches []string) (m []string, e error) {
+	m = matches
+	infos, err := ReadDir(fs, dir)
+	if err != nil {
+		return // ignore I/O error
+	}
+
+	for _, info := range infos {
+		n := info.Name()
+		matched, err := path.Match(pattern, n)
+		if err != nil {
+			return m, err
+		}
+		if matched {
+			m = append(m, path.Join(dir, n))
+		}
+	}
+	return
+}
+
+// hasMeta reports whether path contains any of the magic characters
+// recognized by path.Match.
+func hasMeta(path string) bool {
+	for i := 0; i < len(path); i++ {
+		switch path[i] {
+		case '*', '?', '[', '\\':
+			return true
+		}
+	}
+	return false
+}