added DST, EXP, JEF, VP3

rustitch/src/format.rs

@@ -0,0 +1,34 @@
+use std::path::Path;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Format {
+    Pes,
+    Dst,
+    Exp,
+    Jef,
+    Vp3,
+}
+
+/// Detect format from file content (magic bytes).
+pub fn detect_from_bytes(data: &[u8]) -> Option<Format> {
+    if data.len() >= 4 && &data[0..4] == b"#PES" {
+        return Some(Format::Pes);
+    }
+    if data.len() >= 5 && &data[0..5] == b"%vsm%" {
+        return Some(Format::Vp3);
+    }
+    None
+}
+
+/// Detect format from file extension.
+pub fn detect_from_extension(path: &Path) -> Option<Format> {
+    let ext = path.extension()?.to_str()?;
+    match ext.to_ascii_lowercase().as_str() {
+        "pes" => Some(Format::Pes),
+        "dst" => Some(Format::Dst),
+        "exp" => Some(Format::Exp),
+        "jef" => Some(Format::Jef),
+        "vp3" => Some(Format::Vp3),
+        _ => None,
+    }
+}