metainfo: Add helper methods to FileInfo

metainfo/fileinfo.go

@@ -0,0 +1,27 @@
+package metainfo
+
+import "strings"
+
+// Information specific to a single file inside the MetaInfo structure.
+type FileInfo struct {
+	Length int64    `bencode:"length"`
+	Path   []string `bencode:"path"`
+}
+
+func (fi *FileInfo) DisplayPath(info *Info) string {
+	if info.IsDir() {
+		return strings.Join(fi.Path, "/")
+	} else {
+		return info.Name
+	}
+}
+
+func (me FileInfo) Offset(info *Info) (ret int64) {
+	for _, fi := range info.Files {
+		if me.DisplayPath(info) == fi.DisplayPath(info) {
+			return
+		}
+		ret += fi.Length
+	}
+	panic("not found")
+}

metainfo/metainfo.go

@@ -20,12 +20,6 @@ type MetaInfo struct {
 	URLList      interface{}   `bencode:"url-list,omitempty"`
 }
 
-// Information specific to a single file inside the MetaInfo structure.
-type FileInfo struct {
-	Length int64    `bencode:"length"`
-	Path   []string `bencode:"path"`
-}
-
 // Load a MetaInfo from an io.Reader. Returns a non-nil error in case of
 // failure.
 func Load(r io.Reader) (*MetaInfo, error) {