From d45856ae09c003e848b22de3fba73db59152144f Mon Sep 17 00:00:00 2001
From: Iskander Sharipov <quasilyte@gmail.com>
Date: Fri, 20 Mar 2020 14:18:07 +0300
Subject: [PATCH] meta: make NameEquals alloc-free
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name                 old time/op    new time/op    delta
NameEquals/1part-8     76.2ns ± 2%    15.3ns ± 2%   -79.94%  (p=0.008 n=5+5)
NameEquals/3parts-8     174ns ± 1%      30ns ± 1%   -82.74%  (p=0.008 n=5+5)

name                 old alloc/op   new alloc/op   delta
NameEquals/1part-8      16.0B ± 0%      0.0B       -100.00%  (p=0.008 n=5+5)
NameEquals/3parts-8     48.0B ± 0%      0.0B       -100.00%  (p=0.008 n=5+5)

name                 old allocs/op  new allocs/op  delta
NameEquals/1part-8       1.00 ± 0%      0.00       -100.00%  (p=0.008 n=5+5)
NameEquals/3parts-8      1.00 ± 0%      0.00       -100.00%  (p=0.008 n=5+5)

Refs #364

Signed-off-by: Iskander Sharipov <quasilyte@gmail.com>
---
 src/meta/meta_test.go | 77 +++++++++++++++++++++++++++++++++++++++++++
 src/meta/metainfo.go  | 12 +++----
 2 files changed, 82 insertions(+), 7 deletions(-)
 create mode 100644 src/meta/meta_test.go

diff --git a/src/meta/meta_test.go b/src/meta/meta_test.go
new file mode 100644
index 000000000..f153aab59
--- /dev/null
+++ b/src/meta/meta_test.go
@@ -0,0 +1,77 @@
+package meta
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/VKCOM/noverify/src/php/parser/node"
+	"github.com/VKCOM/noverify/src/php/parser/node/name"
+)
+
+func TestNameEquals(t *testing.T) {
+	tests := []struct {
+		x    string
+		y    string
+		want bool
+	}{
+		{`foo`, `foo`, true},
+		{`foo\bar2`, `foo\bar2`, true},
+		{`foo\bar2\BazBaz`, `foo\bar2\BazBaz`, true},
+		{`foo \ bar`, `foo\bar`, true},
+		{`a\b\c\d`, `a\b\c\d`, true},
+
+		{`first`, ``, false},
+		{`first\second`, `first`, false},
+		{`first`, `first\second`, false},
+		{`first\first`, `first\second`, false},
+		{`first\second`, `firstsecond`, false},
+		{`firstsecond`, `first\second`, false},
+		{`a\b\c`, `a\b\x`, false},
+	}
+
+	makeNameNode := func(s string) *name.Name {
+		parts := strings.Split(s, `\`)
+		nm := &name.Name{Parts: make([]node.Node, len(parts))}
+		for i := range parts {
+			nm.Parts[i] = &name.NamePart{Value: strings.TrimSpace(parts[i])}
+		}
+		return nm
+	}
+
+	for _, test := range tests {
+		x := makeNameNode(test.x)
+		y := test.y
+		have := NameEquals(x, y)
+		if have != test.want {
+			t.Errorf("NameEquals(%q, %q): have %v, want %v",
+				test.x, test.y, have, test.want)
+		}
+	}
+}
+
+var theName1 = &name.Name{
+	Parts: []node.Node{
+		&name.NamePart{Value: `method_exists`},
+	},
+}
+
+var theName3 = &name.Name{
+	Parts: []node.Node{
+		&name.NamePart{Value: `a`},
+		&name.NamePart{Value: `b`},
+		&name.NamePart{Value: `c`},
+	},
+}
+
+func BenchmarkNameEquals(b *testing.B) {
+	b.Run("1part", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			_ = NameEquals(theName1, `method_exists`)
+		}
+	})
+	b.Run("3parts", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			_ = NameEquals(theName3, `a\b\c`)
+		}
+	})
+}
diff --git a/src/meta/metainfo.go b/src/meta/metainfo.go
index f83b85e01..fe79ac714 100644
--- a/src/meta/metainfo.go
+++ b/src/meta/metainfo.go
@@ -492,16 +492,14 @@ func NameEquals(n *name.Name, s string) bool {
 		return false
 	}
 
-	sParts := strings.Split(s, `\`)
-
+	rest := s
 	for i, part := range n.Parts {
-		p, ok := part.(*name.NamePart)
-		if !ok {
+		part := part.(*name.NamePart)
+		if !strings.HasPrefix(rest, part.Value) {
 			return false
 		}
-
-		if p.Value != sParts[i] {
-			return false
+		if i != len(n.Parts)-1 {
+			rest = rest[len(part.Value)+len(`\`):]
 		}
 	}