Reuse bytes when cleaning the URL paths (#2179)

* path: use stack buffer in CleanPath to avoid allocs in common case

Sync from 8222db13db

* path: sync test code from httprouter

* path: update path_test.go to the latest code

Co-authored-by: Bo-Yi Wu <appleboy.tw@gmail.com>
This commit is contained in:
Andy Pan 2020-01-07 17:37:18 +08:00 committed by thinkerou
parent fd8a65b252
commit 025950afe9
2 changed files with 83 additions and 15 deletions

33
path.go
View File

@ -5,6 +5,8 @@
package gin package gin
const stackBufSize = 128
// cleanPath is the URL version of path.Clean, it returns a canonical URL path // cleanPath is the URL version of path.Clean, it returns a canonical URL path
// for p, eliminating . and .. elements. // for p, eliminating . and .. elements.
// //
@ -24,8 +26,11 @@ func cleanPath(p string) string {
return "/" return "/"
} }
// Reasonably sized buffer on stack to avoid allocations in the common case.
// If a larger buffer is required, it gets allocated dynamically.
buf := make([]byte, 0, stackBufSize)
n := len(p) n := len(p)
var buf []byte
// Invariants: // Invariants:
// reading from path; r is index of next byte to process. // reading from path; r is index of next byte to process.
@ -37,7 +42,12 @@ func cleanPath(p string) string {
if p[0] != '/' { if p[0] != '/' {
r = 0 r = 0
buf = make([]byte, n+1)
if n+1 > stackBufSize {
buf = make([]byte, n+1)
} else {
buf = buf[:n+1]
}
buf[0] = '/' buf[0] = '/'
} }
@ -69,7 +79,7 @@ func cleanPath(p string) string {
// can backtrack // can backtrack
w-- w--
if buf == nil { if len(buf) == 0 {
for w > 1 && p[w] != '/' { for w > 1 && p[w] != '/' {
w-- w--
} }
@ -103,7 +113,7 @@ func cleanPath(p string) string {
w++ w++
} }
if buf == nil { if len(buf) == 0 {
return p[:w] return p[:w]
} }
return string(buf[:w]) return string(buf[:w])
@ -111,13 +121,20 @@ func cleanPath(p string) string {
// internal helper to lazily create a buffer if necessary. // internal helper to lazily create a buffer if necessary.
func bufApp(buf *[]byte, s string, w int, c byte) { func bufApp(buf *[]byte, s string, w int, c byte) {
if *buf == nil { b := *buf
if len(b) == 0 {
if s[w] == c { if s[w] == c {
return return
} }
*buf = make([]byte, len(s)) if l := len(s); l > cap(b) {
copy(*buf, s[:w]) *buf = make([]byte, len(s))
} else {
*buf = (*buf)[:l]
}
b = *buf
copy(b, s[:w])
} }
(*buf)[w] = c b[w] = c
} }

View File

@ -6,15 +6,17 @@
package gin package gin
import ( import (
"runtime" "strings"
"testing" "testing"
"github.com/stretchr/testify/assert" "github.com/stretchr/testify/assert"
) )
var cleanTests = []struct { type cleanPathTest struct {
path, result string path, result string
}{ }
var cleanTests = []cleanPathTest{
// Already clean // Already clean
{"/", "/"}, {"/", "/"},
{"/abc", "/abc"}, {"/abc", "/abc"},
@ -77,13 +79,62 @@ func TestPathCleanMallocs(t *testing.T) {
if testing.Short() { if testing.Short() {
t.Skip("skipping malloc count in short mode") t.Skip("skipping malloc count in short mode")
} }
if runtime.GOMAXPROCS(0) > 1 {
t.Log("skipping AllocsPerRun checks; GOMAXPROCS>1")
return
}
for _, test := range cleanTests { for _, test := range cleanTests {
allocs := testing.AllocsPerRun(100, func() { cleanPath(test.result) }) allocs := testing.AllocsPerRun(100, func() { cleanPath(test.result) })
assert.EqualValues(t, allocs, 0) assert.EqualValues(t, allocs, 0)
} }
} }
func BenchmarkPathClean(b *testing.B) {
b.ReportAllocs()
for i := 0; i < b.N; i++ {
for _, test := range cleanTests {
cleanPath(test.path)
}
}
}
func genLongPaths() (testPaths []cleanPathTest) {
for i := 1; i <= 1234; i++ {
ss := strings.Repeat("a", i)
correctPath := "/" + ss
testPaths = append(testPaths, cleanPathTest{
path: correctPath,
result: correctPath,
}, cleanPathTest{
path: ss,
result: correctPath,
}, cleanPathTest{
path: "//" + ss,
result: correctPath,
}, cleanPathTest{
path: "/" + ss + "/b/..",
result: correctPath,
})
}
return
}
func TestPathCleanLong(t *testing.T) {
cleanTests := genLongPaths()
for _, test := range cleanTests {
assert.Equal(t, test.result, cleanPath(test.path))
assert.Equal(t, test.result, cleanPath(test.result))
}
}
func BenchmarkPathCleanLong(b *testing.B) {
cleanTests := genLongPaths()
b.ResetTimer()
b.ReportAllocs()
for i := 0; i < b.N; i++ {
for _, test := range cleanTests {
cleanPath(test.path)
}
}
}