compress/flate: use go generate to create fixedhuff.go

LGTM=r
R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/137750043

src/pkg/compress/flate/fixedhuff.go

@@ -4,7 +4,7 @@
 
 package flate
 
-// autogenerated by gen.go, DO NOT EDIT
+// autogenerated by go run gen.go -output fixedhuff.go, DO NOT EDIT
 
 var fixedHuffmanDecoder = huffmanDecoder{
 	7,

src/pkg/compress/flate/gen.go

@@ -7,14 +7,21 @@
 // This program generates fixedhuff.go
 // Invoke as
 //
-//      go run gen.go |gofmt >fixedhuff.go
+//	go run gen.go -output fixedhuff.go
 
 package main
 
 import (
+	"bytes"
+	"flag"
 	"fmt"
+	"go/format"
+	"io/ioutil"
+	"log"
 )
 
+var filename = flag.String("output", "fixedhuff.go", "output file name")
+
 const maxCodeLen = 16
 
 // Note: the definition of the huffmanDecoder struct is copied from
@@ -113,6 +120,8 @@ func (h *huffmanDecoder) init(bits []int) bool {
 }
 
 func main() {
+	flag.Parse()
+
 	var h huffmanDecoder
 	var bits [288]int
 	initReverseByte()
@@ -129,27 +138,43 @@ func main() {
 		bits[i] = 8
 	}
 	h.init(bits[:])
-	fmt.Println("package flate")
-	fmt.Println()
-	fmt.Println("// autogenerated by gen.go, DO NOT EDIT")
-	fmt.Println()
-	fmt.Println("var fixedHuffmanDecoder = huffmanDecoder{")
-	fmt.Printf("\t%d,\n", h.min)
-	fmt.Println("\t[huffmanNumChunks]uint32{")
+
+	var buf bytes.Buffer
+
+	fmt.Fprintf(&buf, `// Copyright 2013 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.`+"\n\n")
+
+	fmt.Fprintln(&buf, "package flate")
+	fmt.Fprintln(&buf)
+	fmt.Fprintln(&buf, "// autogenerated by go run gen.go -output fixedhuff.go, DO NOT EDIT")
+	fmt.Fprintln(&buf)
+	fmt.Fprintln(&buf, "var fixedHuffmanDecoder = huffmanDecoder{")
+	fmt.Fprintf(&buf, "\t%d,\n", h.min)
+	fmt.Fprintln(&buf, "\t[huffmanNumChunks]uint32{")
 	for i := 0; i < huffmanNumChunks; i++ {
 		if i&7 == 0 {
-			fmt.Printf("\t\t")
+			fmt.Fprintf(&buf, "\t\t")
 		} else {
-			fmt.Printf(" ")
+			fmt.Fprintf(&buf, " ")
 		}
-		fmt.Printf("0x%04x,", h.chunks[i])
+		fmt.Fprintf(&buf, "0x%04x,", h.chunks[i])
 		if i&7 == 7 {
-			fmt.Println()
+			fmt.Fprintln(&buf)
+		}
+	}
+	fmt.Fprintln(&buf, "\t},")
+	fmt.Fprintln(&buf, "\tnil, 0,")
+	fmt.Fprintln(&buf, "}")
+
+	data, err := format.Source(buf.Bytes())
+	if err != nil {
+		log.Fatal(err)
 	}
+	err = ioutil.WriteFile(*filename, data, 0644)
+	if err != nil {
+		log.Fatal(err)
 	}
-	fmt.Println("\t},")
-	fmt.Println("\tnil, 0,")
-	fmt.Println("}")
 }
 
 var reverseByte [256]byte

src/pkg/compress/flate/inflate.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:generate go run gen.go -output fixedhuff.go
+
 // Package flate implements the DEFLATE compressed data format, described in
 // RFC 1951.  The gzip and zlib packages implement access to DEFLATE-based file
 // formats.