Added gas generator defaults

generators/defaults.go

@@ -0,0 +1,62 @@
+//go:generate go run defaults.go default.json defs.go
+
+package main //build !none
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path"
+	"strings"
+)
+
+func fatal(str string, v ...interface{}) {
+	fmt.Fprintf(os.Stderr, str, v...)
+	os.Exit(1)
+}
+
+type setting struct {
+	Value   int64  `json:"v"`
+	Comment string `json:"d"`
+}
+
+func main() {
+	if len(os.Args) < 3 {
+		fatal("usage %s <input> <output>\n", os.Args[0])
+	}
+
+	content, err := ioutil.ReadFile(os.Args[1])
+	if err != nil {
+		fatal("error reading file %v\n", err)
+	}
+
+	m := make(map[string]setting)
+	json.Unmarshal(content, &m)
+
+	filepath := path.Join(os.Getenv("GOPATH"), "src", "github.com", "ethereum", "go-ethereum", "core", os.Args[2])
+	output, err := os.OpenFile(filepath, os.O_RDWR|os.O_CREATE, os.ModePerm /*0777*/)
+	if err != nil {
+		fatal("error opening file for writing %v\n", err)
+	}
+
+	output.WriteString(`package core
+
+import "math/big"
+
+var (
+`)
+
+	for name, setting := range m {
+		output.WriteString(fmt.Sprintf("%s=big.NewInt(%d) // %s\n", strings.Title(name), setting.Value, setting.Comment))
+	}
+
+	output.WriteString(")\n")
+	output.Close()
+
+	cmd := exec.Command("gofmt", "-w", filepath)
+	if err := cmd.Run(); err != nil {
+		fatal("gofmt failed: %v\n", err)
+	}
+}