feat(proto): add special messages

proto/src/message/mod.rs

@@ -2,3 +2,4 @@ pub mod backend;
 pub mod frontend;
 pub mod primitive;
 pub mod proto_message;
+pub mod special;

proto/src/message/special.rs

@@ -0,0 +1,60 @@
+use crate::message::primitive::pgstring::PgString;
+use bincode::de::Decoder;
+use bincode::enc::Encoder;
+use bincode::error::{DecodeError, EncodeError};
+use bincode::{Decode, Encode};
+
+#[derive(Debug)]
+pub enum SpecialMessage {
+    CancelRequest(CancelRequestData),
+    SSLRequest,
+    StartupMessage(StartupMessageData),
+}
+
+#[derive(Debug, Clone, Encode, Decode)]
+pub struct CancelRequestData {
+    pub pid: i32,
+    pub secret: i32,
+}
+
+#[derive(Debug, Clone)]
+pub struct StartupMessageData {
+    pub version: i32,
+    pub params: Vec<(PgString, PgString)>,
+}
+
+impl Encode for StartupMessageData {
+    fn encode<E: Encoder>(&self, encoder: &mut E) -> Result<(), EncodeError> {
+        self.version.encode(encoder)?;
+        for (key, value) in &self.params {
+            key.encode(encoder)?;
+            value.encode(encoder)?;
+        }
+        Ok(())
+    }
+}
+
+impl Decode for StartupMessageData {
+    fn decode<D: Decoder>(decoder: &mut D) -> Result<Self, DecodeError> {
+        let version = i32::decode(decoder)?;
+        let mut params = Vec::new();
+        loop {
+            let maybe_key = PgString::decode(decoder);
+            match maybe_key {
+                Ok(_) => {}
+                Err(DecodeError::UnexpectedEnd { .. }) => break,
+                Err(e) => return Err(e),
+            }
+
+            let maybe_value = PgString::decode(decoder);
+            match maybe_value {
+                Ok(_) => {}
+                Err(DecodeError::UnexpectedEnd { .. }) => break,
+                Err(e) => return Err(e),
+            }
+
+            params.push((maybe_key.unwrap(), maybe_value.unwrap()));
+        }
+        Ok(StartupMessageData { version, params })
+    }
+}