Added CodeIndexNumber::event_size function

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - `TryFrom<&UsbMidiEventPacket>` implementation for `Message` type.
 - `Message::into_packet` function.
 - `Message::code_index_number` function.
+- `CodeIndexNumber::event_size()` function.
 - Re-exports of common items in crate root.
 
 ### Changed

src/packet/code_index_number.rs

@@ -90,3 +90,28 @@ impl From<CodeIndexNumber> for U4 {
         U4::from_overflowing_u8(value as u8)
     }
 }
+
+impl CodeIndexNumber {
+    /// Returns the size of the MIDI_x event in bytes.
+    pub fn event_size(&self) -> usize {
+        match self {
+            Self::SystemCommon1Byte | Self::SingleByte => 1,
+            Self::SystemCommon2Bytes
+            | Self::SysexEnds2Bytes
+            | Self::ProgramChange
+            | Self::ChannelPressure => 2,
+            Self::SystemCommon3Bytes
+            | Self::SysexEnds3Bytes
+            | Self::SysexStartsOrContinues
+            | Self::NoteOff
+            | Self::NoteOn
+            | Self::PolyKeyPress
+            | Self::ControlChange
+            | Self::PitchBendChange => 3,
+
+            // These variants are reserved for future use.
+            // We assume the maximum length of 3 bytes so that no data can get lost.
+            Self::MiscFunction | Self::CableEvents => 3,
+        }
+    }
+}

src/packet/event_packet.rs

@@ -4,6 +4,7 @@ use crate::data::u4::U4;
 use crate::message::raw::{Payload, Raw};
 use crate::message::Message;
 use crate::packet::cable_number::CableNumber;
+use crate::packet::code_index_number::CodeIndexNumber;
 
 /// A packet that communicates with the host.
 ///
@@ -65,21 +66,17 @@ impl TryFrom<&[u8]> for UsbMidiEventPacket {
 impl UsbMidiEventPacket {
     /// Returns the cable number.
     pub fn cable_number(&self) -> CableNumber {
-        let raw_cable_number = self.raw.first().unwrap() >> 4;
+        let raw_cable_number = self.raw[0] >> 4;
 
         CableNumber::try_from(raw_cable_number).unwrap()
     }
 
     /// Returns a slice to the message bytes. The length is dependent on the message type.
     pub fn as_message_bytes(&self) -> &[u8] {
-        let r = Raw::from(Message::try_from(self).unwrap());
-        let length = match r.payload {
-            Payload::Empty => 1,
-            Payload::SingleByte(_) => 2,
-            Payload::DoubleByte(_, _) => 3,
-        };
+        let cin = CodeIndexNumber::try_from(self.raw[0] & 0x0F).unwrap();
+        let size = cin.event_size();
 
-        &self.raw[1..1 + length]
+        &self.raw[1..1 + size]
     }
 
     /// Returns a reference to the raw bytes.