feat: payload from sysex packets

Allow payload bytes to be read from individual sysex
packets. This should allow the use case where people don't
handle the full message but manually buffer the payload on
a per-packet basis.

Author: BenLeadbetter

midi2/src/sysex7/packet.rs

@@ -75,10 +75,72 @@ pub enum Status {
     End,
 }
 
+pub struct PayloadIterator<'a> {
+    data: &'a [u32; 2],
+    index: usize,
+}
+
+impl core::iter::Iterator for PayloadIterator<'_> {
+    type Item = crate::ux::u7;
+    fn next(&mut self) -> Option<Self::Item> {
+        use crate::detail::BitOps;
+        if self.index >= self.packet_size() {
+            return None;
+        }
+        let v = self.data[(self.index + 2) / 4].septet((self.index + 2) % 4);
+        self.index += 1;
+        Some(v)
+    }
+
+    fn nth(&mut self, n: usize) -> Option<Self::Item> {
+        use crate::detail::BitOps;
+        if self.index + n >= self.packet_size() {
+            self.index = (self.index + n).min(6);
+            return None;
+        }
+        let v = self.data[(self.index + n + 2) / 4].septet((self.index + n + 2) % 4);
+        self.index += n + 1;
+        Some(v)
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let len = self.len();
+        (len, Some(len))
+    }
+
+    fn count(self) -> usize {
+        self.len()
+    }
+}
+
+impl core::iter::FusedIterator for PayloadIterator<'_> {}
+
+impl core::iter::ExactSizeIterator for PayloadIterator<'_> {
+    fn len(&self) -> usize {
+        self.packet_size() - self.index
+    }
+}
+
+impl PayloadIterator<'_> {
+    fn packet_size(&self) -> usize {
+        use crate::detail::BitOps;
+        let len = u8::from(self.data[0].nibble(3)) as usize;
+        debug_assert!(len <= 6);
+        len
+    }
+}
+
 impl Packet {
     pub fn status(&self) -> Status {
         status_from_data(&self.0[..]).unwrap()
     }
+
+    pub fn payload(&self) -> PayloadIterator {
+        PayloadIterator {
+            data: &self.0,
+            index: 0,
+        }
+    }
 }
 
 fn status_from_data(data: &[u32]) -> Result<Status, error::InvalidData> {
@@ -180,4 +242,149 @@ mod tests {
             Status::End,
         );
     }
+
+    #[test]
+    fn payload_empty() {
+        assert_eq!(
+            Packet::try_from(&[0x3000_0000, 0x0000_0000][..])
+                .unwrap()
+                .payload()
+                .collect::<std::vec::Vec<ux::u7>>(),
+            std::vec::Vec::<ux::u7>::new(),
+        );
+    }
+
+    #[test]
+    fn payload_one_item() {
+        assert_eq!(
+            Packet::try_from(&[0x3001_7F00, 0x0000_0000][..])
+                .unwrap()
+                .payload()
+                .collect::<std::vec::Vec<ux::u7>>(),
+            std::vec![ux::u7::new(0x7F),]
+        );
+    }
+
+    #[test]
+    fn payload_two_items() {
+        assert_eq!(
+            Packet::try_from(&[0x3002_0102, 0x0000_0000][..])
+                .unwrap()
+                .payload()
+                .collect::<std::vec::Vec<ux::u7>>(),
+            std::vec![ux::u7::new(0x01), ux::u7::new(0x02)],
+        );
+    }
+
+    #[test]
+    fn payload_full_payload() {
+        assert_eq!(
+            Packet::try_from(&[0x3006_0102, 0x0304_0506][..])
+                .unwrap()
+                .payload()
+                .collect::<std::vec::Vec<ux::u7>>(),
+            std::vec![
+                ux::u7::new(0x01),
+                ux::u7::new(0x02),
+                ux::u7::new(0x03),
+                ux::u7::new(0x04),
+                ux::u7::new(0x05),
+                ux::u7::new(0x06),
+            ],
+        );
+    }
+
+    #[test]
+    #[allow(clippy::iter_nth_zero)]
+    fn payload_nth_0() {
+        assert_eq!(
+            Packet::try_from(&[0x3006_0102, 0x0304_0506][..])
+                .unwrap()
+                .payload()
+                .nth(0),
+            Some(ux::u7::new(0x01)),
+        );
+    }
+
+    #[test]
+    fn payload_nth_1() {
+        assert_eq!(
+            Packet::try_from(&[0x3006_0102, 0x0304_0506][..])
+                .unwrap()
+                .payload()
+                .nth(1),
+            Some(ux::u7::new(0x02)),
+        );
+    }
+
+    #[test]
+    fn payload_nth_5() {
+        assert_eq!(
+            Packet::try_from(&[0x3006_0102, 0x0304_0506][..])
+                .unwrap()
+                .payload()
+                .nth(5),
+            Some(ux::u7::new(0x06)),
+        );
+    }
+
+    #[test]
+    fn payload_nth_6() {
+        assert_eq!(
+            Packet::try_from(&[0x3006_0102, 0x0304_0506][..])
+                .unwrap()
+                .payload()
+                .nth(6),
+            None,
+        );
+    }
+
+    #[test]
+    fn payload_nth_6_followed_by_next_should_return_none() {
+        let buffer = [0x3006_0102, 0x0304_0506];
+        let message = Packet::try_from(&buffer[..]).unwrap();
+        let mut iter = message.payload();
+        assert_eq!(iter.nth(6), None);
+        assert_eq!(iter.next(), None);
+    }
+
+    #[test]
+    fn payload_call_next_and_the_iterator_length_should_be_one_fewer() {
+        let buffer = [0x3006_0102, 0x0304_0506];
+        let message = Packet::try_from(&buffer[..]).unwrap();
+        let mut iter = message.payload();
+        assert_eq!(iter.len(), 6);
+        iter.next();
+        assert_eq!(iter.len(), 5);
+    }
+
+    #[test]
+    fn payload_exhaustive_nth_should_leave_iter_length_0() {
+        let buffer = [0x3006_0102, 0x0304_0506];
+        let message = Packet::try_from(&buffer[..]).unwrap();
+        let mut iter = message.payload();
+        assert_eq!(iter.len(), 6);
+        iter.nth(6);
+        assert_eq!(iter.len(), 0);
+    }
+
+    #[test]
+    fn payload_over_exhaustive_nth_should_leave_iter_length_0() {
+        let buffer = [0x3006_0102, 0x0304_0506];
+        let message = Packet::try_from(&buffer[..]).unwrap();
+        let mut iter = message.payload();
+        assert_eq!(iter.len(), 6);
+        iter.nth(7);
+        assert_eq!(iter.len(), 0);
+    }
+
+    #[test]
+    fn payload_nth_should_leave_iter_with_n_fewer_length() {
+        let buffer = [0x3006_0102, 0x0304_0506];
+        let message = Packet::try_from(&buffer[..]).unwrap();
+        let mut iter = message.payload();
+        assert_eq!(iter.len(), 6);
+        iter.nth(2);
+        assert_eq!(iter.len(), 3);
+    }
 }