Trim map based on trailer data

internal/maps/maps.go

@@ -72,18 +72,6 @@ type Thingy struct {}
 
 type Thingies []Thingy
 
-func (h Header) Width() int {
-	return MaxWidth
-}
-
-func (h Header) Length() int {
-	return MaxLength
-}
-
-func (h Header) Height() int {
-	return MaxHeight
-}
-
 func (h Header) MapSetName() string {
 	idx := bytes.IndexByte(h.SetName[:], 0)
 	if idx < 0 {
@@ -233,10 +221,10 @@ type GameMap struct {
 
 func (m *GameMap) Rect() image.Rectangle {
 	return image.Rect(
-		int(0),
-		int(0),
-		int(m.Width()-1),
-		int(m.Length()-1),
+		int(m.TrailerHeader.MinWidth),
+		int(m.TrailerHeader.MinLength),
+		int(m.TrailerHeader.MaxWidth-1),
+		int(m.TrailerHeader.MaxLength-1),
 	)
 }
 
@@ -343,6 +331,11 @@ func loadMapFile(filename string) (*GameMap, error) {
 		return nil, fmt.Errorf("Error parsing cells for %s: %v", filename, err)
 	}
 
+	// no gzip.SeekReader, so discard unread trailer bytes for now
+	if _, err := io.CopyN(ioutil.Discard, zr, int64(3320-2)); err != nil { // observed
+		return nil, err
+	}
+
 	if err := binary.Read(zr, binary.LittleEndian, &out.TrailerHeader); err != nil {
 		return nil, fmt.Errorf("Error parsing trailer header for %s: %v", filename, err)
 	}