attr: generate code from textflag.h (#176)

attr/make_textflag.go

@@ -0,0 +1,200 @@
+// +build ignore
+
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"flag"
+	"fmt"
+	"go/format"
+	"io"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"strings"
+)
+
+var (
+	TextFlagPath = "src/runtime/textflag.h"
+	TextFlagName = filepath.Base(TextFlagPath)
+)
+
+var (
+	download = flag.Bool("download", false, "download new version of "+TextFlagName)
+	version  = flag.String("version", runtime.Version(), "go version to download file from")
+	textflag = flag.String("textflag", TextFlagName, "path to "+TextFlagName)
+	output   = flag.String("output", "", "path to output file")
+)
+
+func main() {
+	if err := mainerr(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func mainerr() error {
+	flag.Parse()
+
+	// Download new version, if requested.
+	if *download {
+		if err := DownloadGoSourceFile(*textflag, *version, TextFlagPath); err != nil {
+			return err
+		}
+		log.Printf("downloaded %q from version %s to %q", TextFlagPath, *version, *textflag)
+	}
+
+	// Parse text flags header.
+	fs, err := ParseFile(*textflag)
+	if err != nil {
+		return err
+	}
+
+	// Determine output.
+	w := os.Stdout
+	if *output != "" {
+		f, err := os.Create(*output)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		w = f
+	}
+
+	// Generate code and format it.
+	buf := bytes.NewBuffer(nil)
+	PrintFlagAttributes(buf, fs)
+
+	src, err := format.Source(buf.Bytes())
+	if err != nil {
+		return err
+	}
+
+	// Write output.
+	_, err = w.Write(src)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// DownloadGoSourceFile downloads a Go source file from a specific version.
+func DownloadGoSourceFile(outpath, v, srcpath string) (err error) {
+	// Download from github.
+	url := "https://github.com/golang/go/raw/" + v + "/" + srcpath
+	res, err := http.Get(url)
+	if err != nil {
+		return err
+	}
+	defer func() {
+		if errc := res.Body.Close(); errc != nil && err == nil {
+			err = errc
+		}
+	}()
+
+	// Write to file.
+	buf := bytes.NewBuffer(nil)
+	fmt.Fprintf(buf, "// Code generated by downloading from %s. DO NOT EDIT.\n\n", url)
+
+	if _, err := io.Copy(buf, res.Body); err != nil {
+		return err
+	}
+
+	if err := ioutil.WriteFile(outpath, buf.Bytes(), 0644); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+type Flag struct {
+	Doc   []string
+	Name  string
+	Value int
+}
+
+// Parse text flags header format.
+func Parse(r io.Reader) ([]Flag, error) {
+	var fs []Flag
+	var doc []string
+
+	s := bufio.NewScanner(r)
+	for s.Scan() {
+		line := s.Text()
+		switch {
+		case strings.Contains(line, "TODO"):
+			// skip
+
+		case strings.HasPrefix(line, "// "):
+			doc = append(doc, strings.TrimPrefix(line, "// "))
+
+		case strings.HasPrefix(line, "#define"):
+			fields := strings.Fields(line)
+			if len(fields) != 3 || fields[0] != "#define" {
+				return nil, fmt.Errorf("unexpected line format %q", line)
+			}
+			v, err := strconv.Atoi(fields[2])
+			if err != nil {
+				return nil, err
+			}
+
+			fs = append(fs, Flag{
+				Doc:   doc,
+				Name:  fields[1],
+				Value: v,
+			})
+			doc = nil
+
+		case line == "" || line == "//":
+			doc = nil
+
+		default:
+			return nil, errors.New("unexpected format")
+		}
+	}
+
+	if err := s.Err(); err != nil {
+		return nil, err
+	}
+
+	return fs, nil
+}
+
+// ParseFile parses text flags header file.
+func ParseFile(filename string) ([]Flag, error) {
+	b, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+	return Parse(bytes.NewReader(b))
+}
+
+func PrintFlagAttributes(w io.Writer, fs []Flag) {
+	_, self, _, _ := runtime.Caller(0)
+	fmt.Fprintf(w, "// Code generated by %s. DO NOT EDIT.\n\n", filepath.Base(self))
+	fmt.Fprintf(w, "package attr\n")
+
+	// Attribute constants.
+	fmt.Fprintf(w, "\n// Attribute values defined in %s.\n", TextFlagName)
+	fmt.Fprintf(w, "const (\n")
+	for _, f := range fs {
+		for _, line := range f.Doc {
+			fmt.Fprintf(w, "\t// %s\n", line)
+		}
+		fmt.Fprintf(w, "\t%s Attribute = %d\n\n", f.Name, f.Value)
+	}
+	fmt.Fprintf(w, ")\n")
+
+	// String map.
+	fmt.Fprintf(w, "\nvar attrname = map[Attribute]string{\n")
+	for _, f := range fs {
+		fmt.Fprintf(w, "\t%s: %q,\n", f.Name, f.Name)
+	}
+	fmt.Fprintf(w, "}\n")
+}