From f3cbc8ce0431efb1196727a7e6016a5928dcbd55 Mon Sep 17 00:00:00 2001
From: Jeff Davis <jeff@j-davis.com>
Date: Mon, 14 Dec 2020 11:56:21 -0800
Subject: [PATCH] PgLsn type.

---
 postgres-protocol/src/lib.rs           |  3 +
 postgres-protocol/src/types/mod.rs     | 18 +++++-
 postgres-types/src/lib.rs              |  4 ++
 postgres-types/src/pg_lsn.rs           | 79 ++++++++++++++++++++++++++
 tokio-postgres/tests/test/types/mod.rs | 15 ++++-
 5 files changed, 117 insertions(+), 2 deletions(-)
 create mode 100644 postgres-types/src/pg_lsn.rs

diff --git a/postgres-protocol/src/lib.rs b/postgres-protocol/src/lib.rs
index b4374afa..13de51e7 100644
--- a/postgres-protocol/src/lib.rs
+++ b/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`.
diff --git a/postgres-protocol/src/types/mod.rs b/postgres-protocol/src/types/mod.rs
index 621c01cc..436132c2 100644
--- a/postgres-protocol/src/types/mod.rs
+++ b/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) {
diff --git a/postgres-types/src/lib.rs b/postgres-types/src/lib.rs
index 2909b81e..e7cc781c 100644
--- a/postgres-types/src/lib.rs
+++ b/postgres-types/src/lib.rs
@@ -130,6 +130,9 @@ use crate::type_gen::{Inner, Other};
 #[doc(inline)]
 pub use postgres_protocol::Oid;
 
+#[doc(inline)]
+pub use pg_lsn::PgLsn;
+
 pub use crate::special::{Date, Timestamp};
 use bytes::BytesMut;
 
@@ -204,6 +207,7 @@ mod uuid_08;
 #[cfg(feature = "with-time-0_2")]
 extern crate time_02 as time;
 
+mod pg_lsn;
 #[doc(hidden)]
 pub mod private;
 mod special;
diff --git a/postgres-types/src/pg_lsn.rs b/postgres-types/src/pg_lsn.rs
new file mode 100644
index 00000000..f0bbf402
--- /dev/null
+++ b/postgres-types/src/pg_lsn.rs
@@ -0,0 +1,79 @@
+//! Log Sequence Number (LSN) type for PostgreSQL Write-Ahead Log
+//! (WAL), also known as the transaction log.
+
+use bytes::BytesMut;
+use postgres_protocol::types;
+use std::error::Error;
+use std::fmt;
+use std::str::FromStr;
+
+use crate::{FromSql, IsNull, ToSql, Type};
+
+/// Postgres `PG_LSN` type.
+#[derive(Clone, Copy, Eq, Ord, PartialEq, PartialOrd)]
+pub struct PgLsn(u64);
+
+/// Error parsing LSN.
+#[derive(Debug)]
+pub struct ParseLsnError(());
+
+impl From<u64> for PgLsn {
+    fn from(lsn_u64: u64) -> Self {
+        PgLsn(lsn_u64)
+    }
+}
+
+impl From<PgLsn> for u64 {
+    fn from(lsn: PgLsn) -> u64 {
+        lsn.0
+    }
+}
+
+impl FromStr for PgLsn {
+    type Err = ParseLsnError;
+
+    fn from_str(lsn_str: &str) -> Result<Self, Self::Err> {
+        let split: Vec<&str> = lsn_str.split('/').collect();
+        if split.len() == 2 {
+            let (hi, lo) = (
+                u64::from_str_radix(split[0], 16).map_err(|_| ParseLsnError(()))?,
+                u64::from_str_radix(split[1], 16).map_err(|_| ParseLsnError(()))?,
+            );
+            Ok(PgLsn((hi << 32) | lo))
+        } else {
+            Err(ParseLsnError(()))
+        }
+    }
+}
+
+impl fmt::Display for PgLsn {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:X}/{:X}", self.0 >> 32, self.0 & 0x00000000ffffffff)
+    }
+}
+
+impl fmt::Debug for PgLsn {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_fmt(format_args!("{}", self))
+    }
+}
+
+impl<'a> FromSql<'a> for PgLsn {
+    fn from_sql(_: &Type, raw: &'a [u8]) -> Result<Self, Box<dyn Error + Sync + Send>> {
+        let v = types::lsn_from_sql(raw)?;
+        Ok(v.into())
+    }
+
+    accepts!(PG_LSN);
+}
+
+impl ToSql for PgLsn {
+    fn to_sql(&self, _: &Type, out: &mut BytesMut) -> Result<IsNull, Box<dyn Error + Sync + Send>> {
+        types::lsn_to_sql((*self).into(), out);
+        Ok(IsNull::No)
+    }
+
+    accepts!(PG_LSN);
+
+    to_sql_checked!();
+}
diff --git a/tokio-postgres/tests/test/types/mod.rs b/tokio-postgres/tests/test/types/mod.rs
index 168ca3a4..c1480bf8 100644
--- a/tokio-postgres/tests/test/types/mod.rs
+++ b/tokio-postgres/tests/test/types/mod.rs
@@ -6,8 +6,9 @@ use std::f64;
 use std::fmt;
 use std::net::IpAddr;
 use std::result;
+use std::str::FromStr;
 use std::time::{Duration, UNIX_EPOCH};
-use tokio_postgres::types::{FromSql, FromSqlOwned, IsNull, Kind, ToSql, Type, WrongType};
+use tokio_postgres::types::{FromSql, FromSqlOwned, IsNull, Kind, PgLsn, ToSql, Type, WrongType};
 
 use crate::connect;
 use bytes::BytesMut;
@@ -135,6 +136,18 @@ async fn test_i64_params() {
     .await;
 }
 
+#[tokio::test]
+async fn test_lsn_params() {
+    test_type(
+        "PG_LSN",
+        &[
+            (Some(PgLsn::from_str("2B/1757980").unwrap()), "'2B/1757980'"),
+            (None, "NULL"),
+        ],
+    )
+    .await
+}
+
 #[tokio::test]
 async fn test_f32_params() {
     test_type(