refactor: add standalone PgOid type

proto/src/message/backend.rs

@@ -1,6 +1,7 @@
 use crate::message::errors::{ProtoDeserializeError, ProtoSerializeError};
 use crate::message::primitive::data::MessageData;
 use crate::message::primitive::pglist::PgList;
+use crate::message::primitive::pgoid::PgOid;
 use crate::message::primitive::pgstring::PgString;
 use crate::message::proto_message::ProtoMessage;
 use bincode::{Decode, Encode};
@@ -186,9 +187,9 @@ impl From<RowDescriptionData> for BackendMessage {
 #[derive(Debug, Clone, Encode, Decode)]
 pub struct ColumnDescription {
     pub name: PgString,
-    pub table_oid: i32,
+    pub table_oid: PgOid,
     pub column_index: i16,
-    pub type_oid: i32,
+    pub type_oid: PgOid,
     pub type_size: i16,
     pub type_modifier: i32,
     pub format_code: i16,
@@ -330,9 +331,9 @@ mod tests {
         let backend = BackendMessage::RowDescription(RowDescriptionData {
             columns: PgList::from(vec![ColumnDescription {
                 name: PgString::from("Some name"),
-                table_oid: 123,
+                table_oid: PgOid::Simple(123),
                 column_index: 456,
-                type_oid: 789,
+                type_oid: PgOid::Simple(789),
                 type_size: 101,
                 type_modifier: 112,
                 format_code: 113,
@@ -347,9 +348,9 @@ mod tests {
                 let columns: Vec<ColumnDescription> = columns.into();
                 let column = &columns[0];
                 column.name.as_str() == "Some name"
-                    && column.table_oid == 123
+                    && column.table_oid.as_simple() == 123
                     && column.column_index == 456
-                    && column.type_oid == 789
+                    && column.type_oid.as_simple() == 789
                     && column.type_size == 101
                     && column.type_modifier == 112
                     && column.format_code == 113

proto/src/message/primitive/mod.rs

@@ -1,3 +1,4 @@
 pub(crate) mod data;
 pub mod pglist;
+pub mod pgoid;
 pub mod pgstring;

proto/src/message/primitive/pgoid.rs

@@ -0,0 +1,79 @@
+use bincode::de::Decoder;
+use bincode::enc::Encoder;
+use bincode::error::{DecodeError, EncodeError};
+use bincode::{BorrowDecode, Decode, Encode};
+use rand::Rng;
+use rand_pcg::Pcg64;
+use rand_seeder::Seeder;
+use std::fmt::Display;
+
+#[derive(Debug, Clone, Copy, BorrowDecode)]
+pub enum PgOid {
+    Simple(i32),
+    Nested(u16, u16),
+}
+
+impl PgOid {
+    /// Generates a pseudo-random OID from a name.
+    pub fn from_unique_name(name: &str) -> PgOid {
+        let mut rng: Pcg64 = Seeder::from(name).make_rng();
+        let oid = rng.gen::<i32>();
+        PgOid::Simple(oid)
+    }
+
+    pub fn as_nested(&self) -> (u16, u16) {
+        match self {
+            PgOid::Nested(a, b) => (*a, *b),
+            PgOid::Simple(oid) => {
+                let type_part = (oid & 0x0000FFFF) as u16;
+                let nest_part = (((*oid as u32) & 0xFFFF0000) >> 16) as u16;
+                (type_part, nest_part)
+            }
+        }
+    }
+
+    pub fn as_simple(&self) -> i32 {
+        match self {
+            PgOid::Simple(oid) => *oid,
+            PgOid::Nested(type_part, nest_part) => {
+                let oid = (*type_part as u32) | ((*nest_part as u32) << 16);
+                oid as i32
+            }
+        }
+    }
+}
+
+impl Display for PgOid {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let oid = self.as_simple();
+        write!(f, "{}", oid)
+    }
+}
+
+impl Encode for PgOid {
+    fn encode<E: Encoder>(&self, encoder: &mut E) -> Result<(), EncodeError> {
+        let oid = self.as_simple();
+        oid.encode(encoder)
+    }
+}
+
+impl Decode for PgOid {
+    fn decode<D: Decoder>(decoder: &mut D) -> Result<Self, DecodeError> {
+        let oid = i32::decode(decoder)?;
+        Ok(PgOid::Simple(oid))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_pgoid() {
+        let oid = PgOid::Simple(0x12345678);
+        let (type_part, nest_part) = oid.as_nested();
+        assert_eq!(type_part, 0x5678);
+        assert_eq!(nest_part, 0x1234);
+        assert_eq!(oid.as_simple(), 0x12345678);
+    }
+}