From 0700e27127e4644dbd323b9a22d994209143fa2a Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Wed, 1 Jun 2022 00:06:26 +0200
Subject: [PATCH] Implement ToString and FromStr for bayou timestamp

---
 src/bayou.rs     | 38 +++++++++++++++++++++++---------------
 src/mail_uuid.rs |  2 +-
 2 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/src/bayou.rs b/src/bayou.rs
index c9ae67f..7a76222 100644
--- a/src/bayou.rs
+++ b/src/bayou.rs
@@ -1,3 +1,4 @@
+use std::str::FromStr;
 use std::time::{Duration, Instant};
 
 use anyhow::{anyhow, bail, Result};
@@ -123,7 +124,7 @@ impl<S: BayouState> Bayou<S> {
             .collect();
 
         // 3. List all operations starting from checkpoint
-        let ts_ser = self.checkpoint.0.serialize();
+        let ts_ser = self.checkpoint.0.to_string();
         debug!("(sync) looking up operations starting at {}", ts_ser);
         let ops_map = self
             .k2v
@@ -148,8 +149,9 @@ impl<S: BayouState> Bayou<S> {
 
         let mut ops = vec![];
         for (tsstr, val) in ops_map {
-            let ts = Timestamp::parse(&tsstr)
-                .ok_or(anyhow!("Invalid operation timestamp: {}", tsstr))?;
+            let ts = tsstr
+                .parse::<Timestamp>()
+                .map_err(|_| anyhow!("Invalid operation timestamp: {}", tsstr))?;
             if val.value.len() != 1 {
                 bail!("Invalid operation, has {} values", val.value.len());
             }
@@ -251,7 +253,7 @@ impl<S: BayouState> Bayou<S> {
         self.k2v
             .insert_item(
                 &self.path,
-                &ts.serialize(),
+                &ts.to_string(),
                 seal_serialize(&op, &self.key)?,
                 None,
             )
@@ -316,7 +318,7 @@ impl<S: BayouState> Bayou<S> {
         let ts_cp = self.history[i_cp].0;
         debug!(
             "(cp) we could checkpoint at time {} (index {} in history)",
-            ts_cp.serialize(),
+            ts_cp.to_string(),
             i_cp
         );
 
@@ -330,13 +332,13 @@ impl<S: BayouState> Bayou<S> {
             {
                 debug!(
                     "(cp) last checkpoint is too recent: {}, not checkpointing",
-                    last_cp.0.serialize()
+                    last_cp.0.to_string()
                 );
                 return Ok(());
             }
         }
 
-        debug!("(cp) saving checkpoint at {}", ts_cp.serialize());
+        debug!("(cp) saving checkpoint at {}", ts_cp.to_string());
 
         // Calculate state at time of checkpoint
         let mut last_known_state = (0, &self.checkpoint.1);
@@ -356,7 +358,7 @@ impl<S: BayouState> Bayou<S> {
 
         let mut por = PutObjectRequest::default();
         por.bucket = self.bucket.clone();
-        por.key = format!("{}/checkpoint/{}", self.path, ts_cp.serialize());
+        por.key = format!("{}/checkpoint/{}", self.path, ts_cp.to_string());
         por.body = Some(cryptoblob.into());
         self.s3.put_object(por).await?;
 
@@ -375,7 +377,7 @@ impl<S: BayouState> Bayou<S> {
             }
 
             // Delete corresponding range of operations
-            let ts_ser = existing_checkpoints[last_to_keep].0.serialize();
+            let ts_ser = existing_checkpoints[last_to_keep].0.to_string();
             self.k2v
                 .delete_batch(&[BatchDeleteOp {
                     partition_key: &self.path,
@@ -414,7 +416,7 @@ impl<S: BayouState> Bayou<S> {
         for object in checkpoints_res.contents.unwrap_or_default() {
             if let Some(key) = object.key {
                 if let Some(ckid) = key.strip_prefix(&prefix) {
-                    if let Some(ts) = Timestamp::parse(ckid) {
+                    if let Ok(ts) = ckid.parse::<Timestamp>() {
                         checkpoints.push((ts, key));
                     }
                 }
@@ -451,20 +453,26 @@ impl Timestamp {
     pub fn zero() -> Self {
         Self { msec: 0, rand: 0 }
     }
+}
 
-    pub fn serialize(&self) -> String {
+impl ToString for Timestamp {
+    fn to_string(&self) -> String {
         let mut bytes = [0u8; 16];
         bytes[0..8].copy_from_slice(&u64::to_be_bytes(self.msec));
         bytes[8..16].copy_from_slice(&u64::to_be_bytes(self.rand));
         hex::encode(&bytes)
     }
+}
 
-    pub fn parse(v: &str) -> Option<Self> {
-        let bytes = hex::decode(v).ok()?;
+impl FromStr for Timestamp {
+    type Err = &'static str;
+
+    fn from_str(s: &str) -> Result<Timestamp, &'static str> {
+        let bytes = hex::decode(s).map_err(|_| "invalid hex")?;
         if bytes.len() != 16 {
-            return None;
+            return Err("bad length");
         }
-        Some(Self {
+        Ok(Self {
             msec: u64::from_be_bytes(bytes[0..8].try_into().unwrap()),
             rand: u64::from_be_bytes(bytes[8..16].try_into().unwrap()),
         })
diff --git a/src/mail_uuid.rs b/src/mail_uuid.rs
index 647238f..ab76bce 100644
--- a/src/mail_uuid.rs
+++ b/src/mail_uuid.rs
@@ -1,5 +1,5 @@
-use std::sync::atomic::{AtomicU64, Ordering};
 use std::str::FromStr;
+use std::sync::atomic::{AtomicU64, Ordering};
 
 use lazy_static::lazy_static;
 use rand::prelude::*;