Add filesystem glob support

glob.go

@@ -1,6 +1,10 @@
 package pcre
 
 import (
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
 	"unsafe"
 
 	"go.arsenm.dev/pcre/lib"
@@ -66,3 +70,93 @@ func CompileGlob(glob string) (*Regexp, error) {
 	// Compile converted glob and return results
 	return Compile(pattern)
 }
+
+// Glob returns a list of matches for the given glob pattern.
+// It returns nil if there was no match. If the glob contains
+// "**", it will recurse through the directory, which may be
+// extremely slow depending on which directory is being searched.
+func Glob(glob string) ([]string, error) {
+	// If glob is empty, return nil
+	if glob == "" {
+		return nil, nil
+	}
+
+	// If the glob is a file path, return the file
+	_, err := os.Lstat(glob)
+	if err == nil {
+		return []string{glob}, nil
+	}
+
+	// If the glob has no glob characters, return nil
+	if !hasGlobChars(glob) {
+		return nil, nil
+	}
+
+	// Split glob by filepath separator
+	paths := strings.Split(glob, string(filepath.Separator))
+
+	var splitDir []string
+	// For every path in split list
+	for _, path := range paths {
+		// If glob characters forund, stop
+		if hasGlobChars(path) {
+			break
+		}
+		// Add path to splitDir
+		splitDir = append(splitDir, path)
+	}
+
+	// Join splitDir and add filepath separator. This is the directory that will be searched.
+	dir := filepath.Join(splitDir...)
+	
+	if filepath.IsAbs(glob) {
+		dir = string(filepath.Separator) + dir
+	}
+
+	// If the directory is not accessible, return error
+	_, err = os.Lstat(dir)
+	if err != nil {
+		return nil, err
+	}
+
+	// Compile glob pattern
+	r, err := CompileGlob(glob)
+	if err != nil {
+		return nil, err
+	}
+	defer r.Close()
+
+	var matches []string
+	// If glob contains "**" (starstar), walk recursively. Otherwise, only search dir.
+	if strings.Contains(glob, "**") {
+		err = filepath.WalkDir(dir, func(path string, d fs.DirEntry, err error) error {
+			if r.MatchString(path) {
+				matches = append(matches, path)
+			}
+			return nil
+		})
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		files, err := os.ReadDir(dir)
+		if err != nil {
+			return nil, err
+		}
+		for _, file := range files {
+			// Get full path of file
+			path := filepath.Join(dir, file.Name())
+			if r.MatchString(path) {
+				matches = append(matches, path)
+			}
+		}
+	}
+
+	return matches, nil
+}
+
+// hasGlobChars checks if the string has any
+// characters that are part of a glob.
+func hasGlobChars(s string) bool {
+	return strings.ContainsAny(s, "*[]?")
+}