PgLsn type.

postgres-protocol/src/lib.rs

@@ -24,6 +24,9 @@ pub mod types;
 /// A Postgres OID.
 pub type Oid = u32;
 
+/// A Postgres Log Sequence Number (LSN).
+pub type Lsn = u64;
+
 /// An enum indicating if a value is `NULL` or not.
 pub enum IsNull {
     /// The value is `NULL`.

postgres-protocol/src/types/mod.rs

@@ -8,7 +8,7 @@ use std::io::Read;
 use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
 use std::str;
 
-use crate::{write_nullable, FromUsize, IsNull, Oid};
+use crate::{write_nullable, FromUsize, IsNull, Lsn, Oid};
 
 #[cfg(test)]
 mod test;
@@ -142,6 +142,22 @@ pub fn int8_from_sql(mut buf: &[u8]) -> Result<i64, StdBox<dyn Error + Sync + Se
     Ok(v)
 }
 
+/// Serializes a `PG_LSN` value.
+#[inline]
+pub fn lsn_to_sql(v: Lsn, buf: &mut BytesMut) {
+    buf.put_u64(v);
+}
+
+/// Deserializes a `PG_LSN` value.
+#[inline]
+pub fn lsn_from_sql(mut buf: &[u8]) -> Result<Lsn, StdBox<dyn Error + Sync + Send>> {
+    let v = buf.read_u64::<BigEndian>()?;
+    if !buf.is_empty() {
+        return Err("invalid buffer size".into());
+    }
+    Ok(v)
+}
+
 /// Serializes a `FLOAT4` value.
 #[inline]
 pub fn float4_to_sql(v: f32, buf: &mut BytesMut) {