From: baycore <dxasu@qq.com>
Date: Mon, 27 Oct 2025 04:43:32 +0000 (+0000)
Subject: time: rewrite IsZero method to use wall and ext fields
X-Git-Tag: go1.26rc1~472
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=189f2c08cc769fdc98d28ec536010b6f119e645f;p=gostls13.git

time: rewrite IsZero method to use wall and ext fields

Using wall and ext fields will be more efficient.

Fixes #76001

Change-Id: If2b9f597562e0d0d3f8ab300556fa559926480a0
GitHub-Last-Rev: 4a91948413079047cb6c382ed29844f456f3064d
GitHub-Pull-Request: golang/go#76006
Reviewed-on: https://go-review.googlesource.com/c/go/+/713720
Reviewed-by: Ian Lance Taylor <iant@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: David Chase <drchase@google.com>
---

diff --git a/src/time/time.go b/src/time/time.go
index cf9abc7196..32a1ce4307 100644
--- a/src/time/time.go
+++ b/src/time/time.go
@@ -260,7 +260,11 @@ func (t *Time) mono() int64 {
 // IsZero reports whether t represents the zero time instant,
 // January 1, year 1, 00:00:00 UTC.
 func (t Time) IsZero() bool {
-	return t.sec() == 0 && t.nsec() == 0
+	// If hasMonotonic is set in t.wall, then the time can't be before 1885, so it can't be the year 1.
+	// If hasMonotonic is zero, then all the bits in wall other than the nanoseconds field should be 0.
+	// So if there are no nanoseconds then t.wall == 0, and if there are no seconds then t.ext == 0.
+	// This is equivalent to t.sec() == 0 && t.nsec() == 0, but is more efficient.
+	return t.wall == 0 && t.ext == 0
 }
 
 // After reports whether the time instant t is after u.