Initial commit

pkg/vars/boot.go

@@ -0,0 +1,32 @@
+package vars
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+)
+
+var (
+	bootVarPrefix = []byte("direktil.var.")
+)
+
+func BootArgs() [][]byte {
+	ba, err := ioutil.ReadFile("/proc/cmdline")
+	if err != nil {
+		// should not happen
+		panic(fmt.Errorf("failed to read /proc/cmdline: ", err))
+	}
+
+	return bytes.Split(ba, []byte{' '})
+}
+
+func BootArgValue(prefix, defaultValue string) string {
+	prefixB := []byte("direktil." + prefix + "=")
+	for _, ba := range BootArgs() {
+		if bytes.HasPrefix(ba, prefixB) {
+			return string(ba[len(prefixB):])
+		}
+	}
+
+	return defaultValue
+}

pkg/vars/vars.go

@@ -0,0 +1,60 @@
+package vars
+
+import (
+	"bytes"
+
+	"novit.nc/direktil/pkg/config"
+)
+
+type Var struct {
+	Template []byte
+	Value    []byte
+}
+
+func Vars(cfg *config.Config) []Var {
+	res := make([]Var, 0)
+
+	for _, arg := range BootArgs() {
+		if !bytes.HasPrefix(arg, bootVarPrefix) {
+			continue
+		}
+
+		parts := bytes.SplitN(arg[len(bootVarPrefix):], []byte{'='}, 2)
+
+		res = append(res, Var{
+			Template: append(append([]byte("$(var:"), parts[0]...), ')'),
+			Value:    parts[1],
+		})
+	}
+
+configVarsLoop:
+	for _, v := range cfg.Vars {
+		t := []byte("$(var:" + v.Name + ")")
+		for _, prev := range res {
+			if bytes.Equal(prev.Template, t) {
+				continue configVarsLoop
+			}
+		}
+
+		res = append(res, Var{t, []byte(v.Default)})
+	}
+
+	return res
+}
+
+// Substitute variables in src
+func Substitute(src []byte, cfg *config.Config) (dst []byte) {
+	dst = src
+
+	for _, bv := range Vars(cfg) {
+		if !bytes.Contains(dst, bv.Template) {
+			continue
+		}
+
+		v := bytes.TrimSpace(bv.Value)
+
+		dst = bytes.Replace(dst, bv.Template, v, -1)
+	}
+
+	return
+}