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ConfigParser.go
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ConfigParser.go
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package main
import (
"errors"
"fmt"
"reflect"
"strconv"
"strings"
)
func (r *Router) ApplyConfig(config string) error {
for i, line := range strings.Split(config, "\n") {
var err error
toks := strings.Fields(line)
switch {
case len(toks) == 0:
//blank line
continue
case strings.HasPrefix(toks[0], "#"):
//comment
continue
case strings.HasPrefix(toks[0], "node"):
// fmt.Printf("%d node decl\n", i)
err = r.NodeDecl(toks)
case strings.HasPrefix(toks[0], "conn"):
// fmt.Printf("%d conn decl\n", i)
err = r.ConnDecl(toks)
default:
errstr := fmt.Sprintf("Unknown syntax, line %d:\n\t%s", i, line)
err = errors.New(errstr)
}
if err != nil {
// TODO repackage with line num!
return err
}
}
return nil
}
// syntax is node <name> ::= <nodetype> [args ...]
// returns nil if configuration applied succesfully
func (r *Router) NodeDecl(toks []string) error {
if toks[2] != "::=" {
return errors.New("Invalid syntax: missing '::=' operator")
}
name := toks[1]
kind := toks[3]
args := toks[4:]
return r.CreateNode(name, kind, args...)
}
func (r *Router) CreateNode(name, kind string, args ...string) error {
n, ok := AvailableNodes[kind]
if !ok {
return errors.New("Unknown node type " + kind)
}
// extract the constructor function as a relfelct.Value
nodectr := reflect.ValueOf(n)
nodetype := reflect.TypeOf(n)
// make sure the arity of the constructor matches
// the number of args provided
if nodetype.NumIn() != len(args) {
return errors.New("Incorrect number of args provided!")
}
// now work out the types of the arguments
var err error
var val interface{}
var node Routeable
rargs := make([]reflect.Value, 0)
for i := 0; i < nodetype.NumIn(); i++ {
switch nodetype.In(i).Kind() {
case reflect.Bool:
val, err = strconv.ParseBool(args[i])
case reflect.Int:
val, err = strconv.ParseInt(args[i], 10, 32)
val = int(val.(int64))
case reflect.Int64:
val, err = strconv.ParseInt(args[i], 10, 64)
case reflect.Float64:
val, err = strconv.ParseFloat(args[i], 64)
case reflect.String:
val = args[i]
err = nil
default:
return errors.New("Invalid argument in node declaration: " + args[i])
}
if err != nil {
return err
} else {
rargs = append(rargs, reflect.ValueOf(val))
}
}
// finally call the constructor to get the new node value
res := nodectr.Call(rargs)
node = res[0].Interface().(Routeable)
if res[1].Interface() != nil {
return res[1].Interface().(error)
} else {
// if all was ok, register it with the router
return r.RegisterNode(name, node)
}
}
// syntax is conn <name> -> <name> [-> <name> ...]
func (r *Router) ConnDecl(toks []string) error {
//first pass, check the syntax
for i, tok := range toks {
if tok == "->" {
if (i-1 < 1) || (i+2 > len(toks)) {
return errors.New("Mismatched '->' operator")
}
}
}
// second pass, if we got here everything is ok
// so apply the configuration
for i, tok := range toks {
if tok == "->" {
src := toks[i-1]
dst := toks[i+1]
err := r.Connect(src, dst)
if err != nil {
return err
}
fmt.Printf("connected %s to %s\n", src, dst)
}
}
return nil
}