init

rustitch/src/pes/header.rs

@@ -0,0 +1,65 @@
+use super::Error;
+
+#[derive(Debug)]
+pub struct PesHeader {
+    pub version: [u8; 4],
+    pub pec_offset: u32,
+}
+
+pub fn parse_header(data: &[u8]) -> Result<PesHeader, Error> {
+    if data.len() < 12 {
+        return Err(Error::TooShort {
+            expected: 12,
+            actual: data.len(),
+        });
+    }
+
+    let magic = &data[0..4];
+    if magic != b"#PES" {
+        let mut m = [0u8; 4];
+        m.copy_from_slice(magic);
+        return Err(Error::InvalidMagic(m));
+    }
+
+    let mut version = [0u8; 4];
+    version.copy_from_slice(&data[4..8]);
+
+    let pec_offset = u32::from_le_bytes([data[8], data[9], data[10], data[11]]);
+
+    Ok(PesHeader {
+        version,
+        pec_offset,
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_valid_header() {
+        let mut data = vec![0u8; 20];
+        data[0..4].copy_from_slice(b"#PES");
+        data[4..8].copy_from_slice(b"0001");
+        // PEC offset = 16 (little-endian)
+        data[8..12].copy_from_slice(&16u32.to_le_bytes());
+
+        let header = parse_header(&data).unwrap();
+        assert_eq!(&header.version, b"0001");
+        assert_eq!(header.pec_offset, 16);
+    }
+
+    #[test]
+    fn reject_invalid_magic() {
+        let data = b"NOTPES0001\x10\x00\x00\x00";
+        let err = parse_header(data).unwrap_err();
+        assert!(matches!(err, Error::InvalidMagic(_)));
+    }
+
+    #[test]
+    fn reject_too_short() {
+        let data = b"#PES00";
+        let err = parse_header(data).unwrap_err();
+        assert!(matches!(err, Error::TooShort { .. }));
+    }
+}