http2/hpack: build static table with go generate

As the static version of headerFieldTable in hpack is generated in runtime, we may use the go:generate to prepare the struct before the initialization phase. This is supposed to save init time and allocations for many binaries, as net/http imports hpack. Before: init golang.org/x/net/http2/hpack @1.1 ms, 0.097 ms clock, 21240 bytes, 29 allocs After: init golang.org/x/net/http2/hpack @0.67 ms, 0.015 ms clock, 8120 bytes, 9 allocs Fixes golang/go#55881 Change-Id: Ia6575f67ffcba7cc4d75899b24a9c56deb58ccac Reviewed-on: https://go-review.googlesource.com/c/net/ /434875 Run-TryBot: Damien Neil <[email protected]> TryBot-Result: Gopher Robot <[email protected]> Reviewed-by: Damien Neil <[email protected]> Reviewed-by: Bryan Mills <[email protected]>
golang · Oct 27, 2022 · 84c13af · 84c13af
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diff --git a/http2/hpack/gen.go b/http2/hpack/gen.go
@@ -0,0 1,184 @@
 // Copyright 2022 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 //go:build ignore
 // build ignore
 
 package main
 
 import (
  "bytes"
  "fmt"
  "go/format"
  "io/ioutil"
  "os"
  "sort"
 
  "golang.org/x/net/http2/hpack"
 )
 
 // http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-07#appendix-B
 var staticTableEntries = [...]hpack.HeaderField{
  {Name: ":authority"},
  {Name: ":method", Value: "GET"},
  {Name: ":method", Value: "POST"},
  {Name: ":path", Value: "/"},
  {Name: ":path", Value: "/index.html"},
  {Name: ":scheme", Value: "http"},
  {Name: ":scheme", Value: "https"},
  {Name: ":status", Value: "200"},
  {Name: ":status", Value: "204"},
  {Name: ":status", Value: "206"},
  {Name: ":status", Value: "304"},
  {Name: ":status", Value: "400"},
  {Name: ":status", Value: "404"},
  {Name: ":status", Value: "500"},
  {Name: "accept-charset"},
  {Name: "accept-encoding", Value: "gzip, deflate"},
  {Name: "accept-language"},
  {Name: "accept-ranges"},
  {Name: "accept"},
  {Name: "access-control-allow-origin"},
  {Name: "age"},
  {Name: "allow"},
  {Name: "authorization"},
  {Name: "cache-control"},
  {Name: "content-disposition"},
  {Name: "content-encoding"},
  {Name: "content-language"},
  {Name: "content-length"},
  {Name: "content-location"},
  {Name: "content-range"},
  {Name: "content-type"},
  {Name: "cookie"},
  {Name: "date"},
  {Name: "etag"},
  {Name: "expect"},
  {Name: "expires"},
  {Name: "from"},
  {Name: "host"},
  {Name: "if-match"},
  {Name: "if-modified-since"},
  {Name: "if-none-match"},
  {Name: "if-range"},
  {Name: "if-unmodified-since"},
  {Name: "last-modified"},
  {Name: "link"},
  {Name: "location"},
  {Name: "max-forwards"},
  {Name: "proxy-authenticate"},
  {Name: "proxy-authorization"},
  {Name: "range"},
  {Name: "referer"},
  {Name: "refresh"},
  {Name: "retry-after"},
  {Name: "server"},
  {Name: "set-cookie"},
  {Name: "strict-transport-security"},
  {Name: "transfer-encoding"},
  {Name: "user-agent"},
  {Name: "vary"},
  {Name: "via"},
  {Name: "www-authenticate"},
 }
 
 type pairNameValue struct {
  name, value string
 }
 
 type byNameItem struct {
  name string
  id uint64
 }
 
 type byNameValueItem struct {
  pairNameValue
  id uint64
 }
 
 func headerFieldToString(f hpack.HeaderField) string {
  return fmt.Sprintf("{Name: \"%s\", Value:\"%s\", Sensitive: %t}", f.Name, f.Value, f.Sensitive)
 }
 
 func pairNameValueToString(v pairNameValue) string {
  return fmt.Sprintf("{name: \"%s\", value:\"%s\"}", v.name, v.value)
 }
 
 const header = `
 // go generate gen.go
 // Code generated by the command above; DO NOT EDIT.
 
 package hpack
 
 var staticTable = &headerFieldTable{
  evictCount: 0,
  byName: map[string]uint64{
 `
 
 //go:generate go run gen.go
 func main() {
  var bb bytes.Buffer
  fmt.Fprintf(&bb, header)
  byName := make(map[string]uint64)
  byNameValue := make(map[pairNameValue]uint64)
  for index, entry := range staticTableEntries {
  id := uint64(index)   1
  byName[entry.Name] = id
  byNameValue[pairNameValue{entry.Name, entry.Value}] = id
  }
  // Sort maps for deterministic generation.
  byNameItems := sortByName(byName)
  byNameValueItems := sortByNameValue(byNameValue)
 
  for _, item := range byNameItems {
  fmt.Fprintf(&bb, "\"%s\":%d,\n", item.name, item.id)
  }
  fmt.Fprintf(&bb, "},\n")
  fmt.Fprintf(&bb, "byNameValue: map[pairNameValue]uint64{\n")
  for _, item := range byNameValueItems {
  fmt.Fprintf(&bb, "%s:%d,\n", pairNameValueToString(item.pairNameValue), item.id)
  }
  fmt.Fprintf(&bb, "},\n")
  fmt.Fprintf(&bb, "ents: []HeaderField{\n")
  for _, value := range staticTableEntries {
  fmt.Fprintf(&bb, "%s,\n", headerFieldToString(value))
  }
  fmt.Fprintf(&bb, "},\n")
  fmt.Fprintf(&bb, "}\n")
  genFile("static_table.go", &bb)
 }
 
 func sortByNameValue(byNameValue map[pairNameValue]uint64) []byNameValueItem {
  var byNameValueItems []byNameValueItem
  for k, v := range byNameValue {
  byNameValueItems = append(byNameValueItems, byNameValueItem{k, v})
  }
  sort.Slice(byNameValueItems, func(i, j int) bool {
  return byNameValueItems[i].id < byNameValueItems[j].id
  })
  return byNameValueItems
 }
 
 func sortByName(byName map[string]uint64) []byNameItem {
  var byNameItems []byNameItem
  for k, v := range byName {
  byNameItems = append(byNameItems, byNameItem{k, v})
  }
  sort.Slice(byNameItems, func(i, j int) bool {
  return byNameItems[i].id < byNameItems[j].id
  })
  return byNameItems
 }
 
 func genFile(name string, buf *bytes.Buffer) {
  b, err := format.Source(buf.Bytes())
  if err != nil {
  fmt.Fprintln(os.Stderr, err)
  os.Exit(1)
  }
  if err := ioutil.WriteFile(name, b, 0644); err != nil {
  fmt.Fprintln(os.Stderr, err)
  os.Exit(1)
  }
 }
diff --git a/http2/hpack/static_table.go b/http2/hpack/static_table.go