From 3d906d47dd2b42d6d34feab70006c99791e27306 Mon Sep 17 00:00:00 2001
From: Nuno Cruces <ncruces@users.noreply.github.com>
Date: Tue, 23 Jan 2024 17:50:11 +0000
Subject: [PATCH] Avoid allocations.

---
 driver/driver.go    |  9 +++++++--
 driver/time.go      | 13 ++++++-------
 driver/time_test.go | 24 ++++++------------------
 3 files changed, 19 insertions(+), 27 deletions(-)

diff --git a/driver/driver.go b/driver/driver.go
index 1d22bc8..ae55b00 100644
--- a/driver/driver.go
+++ b/driver/driver.go
@@ -538,8 +538,13 @@ func (r *rows) Next(dest []driver.Value) error {
 	for i := range dest {
 		if t, ok := r.decodeTime(i, dest[i]); ok {
 			dest[i] = t
-		} else if s, ok := dest[i].(string); ok {
-			dest[i] = stringOrTime(s)
+			continue
+		}
+		if s, ok := dest[i].(string); ok {
+			t, ok := maybeTime(s)
+			if ok {
+				dest[i] = t
+			}
 		}
 	}
 	return err
diff --git a/driver/time.go b/driver/time.go
index 9196f1c..630a5b1 100644
--- a/driver/time.go
+++ b/driver/time.go
@@ -1,7 +1,6 @@
 package driver
 
 import (
-	"database/sql/driver"
 	"time"
 )
 
@@ -9,24 +8,24 @@ import (
 // if it roundtrips back to the same string.
 // This way times can be persisted to, and recovered from, the database,
 // but if a string is needed, [database/sql] will recover the same string.
-func stringOrTime(text string) driver.Value {
+func maybeTime(text string) (_ time.Time, _ bool) {
 	// Weed out (some) values that can't possibly be
 	// [time.RFC3339Nano] timestamps.
 	if len(text) < len("2006-01-02T15:04:05Z") {
-		return text
+		return
 	}
 	if len(text) > len(time.RFC3339Nano) {
-		return text
+		return
 	}
 	if text[4] != '-' || text[10] != 'T' || text[16] != ':' {
-		return text
+		return
 	}
 
 	// Slow path.
 	var buf [len(time.RFC3339Nano)]byte
 	date, err := time.Parse(time.RFC3339Nano, text)
 	if err == nil && text == string(date.AppendFormat(buf[:0], time.RFC3339Nano)) {
-		return date
+		return date, true
 	}
-	return text
+	return
 }
diff --git a/driver/time_test.go b/driver/time_test.go
index ea0854c..a19380d 100644
--- a/driver/time_test.go
+++ b/driver/time_test.go
@@ -22,26 +22,18 @@ func Fuzz_stringOrTime_1(f *testing.F) {
 	f.Add("Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.")
 
 	f.Fuzz(func(t *testing.T, str string) {
-		value := stringOrTime(str)
-
-		switch v := value.(type) {
-		case time.Time:
+		v, ok := maybeTime(str)
+		if ok {
 			// Make sure times round-trip to the same string:
 			// https://pkg.go.dev/database/sql#Rows.Scan
 			if v.Format(time.RFC3339Nano) != str {
 				t.Fatalf("did not round-trip: %q", str)
 			}
-		case string:
-			if v != str {
-				t.Fatalf("did not round-trip: %q", str)
-			}
-
+		} else {
 			date, err := time.Parse(time.RFC3339Nano, str)
 			if err == nil && date.Format(time.RFC3339Nano) == str {
 				t.Fatalf("would round-trip: %q", str)
 			}
-		default:
-			t.Fatalf("invalid type %T: %q", v, str)
 		}
 	})
 }
@@ -59,10 +51,8 @@ func Fuzz_stringOrTime_2(f *testing.F) {
 	f.Add(int64(-763421161058), int64(222_222_222)) // twosday, year 22222BC
 
 	checkTime := func(t testing.TB, date time.Time) {
-		value := stringOrTime(date.Format(time.RFC3339Nano))
-
-		switch v := value.(type) {
-		case time.Time:
+		v, ok := maybeTime(date.Format(time.RFC3339Nano))
+		if ok {
 			// Make sure times round-trip to the same time:
 			if !v.Equal(date) {
 				t.Fatalf("did not round-trip: %v", date)
@@ -73,10 +63,8 @@ func Fuzz_stringOrTime_2(f *testing.F) {
 			if off1 != off2 {
 				t.Fatalf("did not round-trip: %v", date)
 			}
-		case string:
+		} else {
 			t.Fatalf("was not recovered: %v", date)
-		default:
-			t.Fatalf("invalid type %T: %v", v, date)
 		}
 	}