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// grammar of the config file
//
// Notes: We parse exactly three modules ("input", "filter", "output")
// in our configuration. Each module consists of two name-object pairs
// that are nested. We don't want to allow limitless recursion here.
//
// config = module module module
// module = name object name object
// name = 'input' | 'filter' | 'output' | etc.
// object = '{' keyvalue | keyvalue | ... '}'
// keyvalue = statement '=>' value
// statement = name | if
// value = literal | '[' literal ']'
// literal = '"' name '"'
package conf
import (
"fmt"
"io"
"os"
)
// Having a Config to Manager function could be nice? Or we could just
// return a Manager from here which may be even better...
type Config struct {
}
type parser struct {
s scanner
last token
cur token
}
func newParser(s *scanner) *parser {
p := &parser{
s: *s,
}
return p
}
func NewConfig(r io.Reader) *Config {
p := newParser(newScanner(r))
p.startparsing()
return &Config{}
}
func (p *parser) startparsing() {
p.module("input")
p.module("filter")
}
func (p *parser) advanceOneToken(place string) {
var err error
p.last = p.cur
p.cur, err = p.s.Scan()
if err != nil {
fmt.Fprintf(os.Stderr, "error when parsing %s. Scanner returned an error %v.\n", place, err)
os.Exit(1)
}
}
func (p *parser) module(firstname string) {
p.advanceOneToken("module")
fmt.Fprintf(os.Stderr, "tokentype: %d, token: %q\n", p.cur.Type, p.cur.Lit)
if p.cur.Lit != firstname {
fmt.Fprintf(os.Stderr, "error when parsing module. We were expecting name %q but got %q at line %d offset %d.\n", firstname, p.cur.Lit, p.cur.LineNr, p.cur.Offset)
}
p.advanceOneToken("module")
if p.cur.Type != ObjectDelimiter {
fmt.Fprintf(os.Stderr, "error when parsing module. We were expecting an opening bracket but got %q at line %d offset %d.\n", p.cur.Lit, p.cur.LineNr, p.cur.Offset)
}
p.advanceOneToken("module")
if p.cur.Type != Name {
fmt.Fprintf(os.Stderr, "error when parsing module. We were expecting another name but got %q at line %d offset %d.\n", p.cur.Lit, p.cur.LineNr, p.cur.Offset)
}
p.object()
p.advanceOneToken("module")
if p.cur.Lit[0] != '}' {
fmt.Fprintf(os.Stderr, "error when parsing module. Was expecting a closing bracket but got %s at line %d offset %d.\n", p.cur.Lit, p.cur.LineNr, p.cur.Offset)
}
}
func (p *parser) object() {
p.advanceOneToken("object")
if p.cur.Lit[0] != '{' {
fmt.Fprintf(os.Stderr, "error when parsing object. Was expecting an opening bracket but got %s at line %d offset %d.\n", p.cur.Lit, p.cur.LineNr, p.cur.Offset)
}
// hack to deal with case where there is no white space between
// the delimiters.
if p.cur.Lit == "{}" {
return
}
for {
more := p.keyvalue()
if !more {
break
}
}
}
func (p *parser) keyvalue() bool {
p.advanceOneToken("keyvalue")
fmt.Fprintf(os.Stderr, "keyvalue: tokentype: %d, token: %q\n", p.cur.Type, p.cur.Lit)
if p.cur.Type != Literal {
fmt.Fprintf(os.Stderr, "error when parsing keyvalue. Was expecting a name but got %q at line %d offset %d.\n", p.cur.Lit, p.cur.LineNr, p.cur.Offset)
}
p.advanceOneToken("keyvalue")
if p.cur.Lit != "=>" {
fmt.Fprintf(os.Stderr, "error when parsing keyvalue. Was expecting a '=>' but got %q at line %d offset %d.\n", p.cur.Lit, p.cur.LineNr, p.cur.Offset)
}
p.advanceOneToken("keyvalue")
if p.cur.Type != Literal && p.cur.Type != Name {
fmt.Fprintf(os.Stderr, "error when parsing keyvalue. Was expecting a literal or a name but got %q at line %d offset %d.\n", p.cur.Lit, p.cur.LineNr, p.cur.Offset)
}
tok, err := p.s.Peek()
if err != nil {
fmt.Fprintf(os.Stderr, "error when parsing keyvalue. Got an error when checking if there are more keyvalues: %v.\n", err)
return false
}
fmt.Fprintf(os.Stderr, "peeked %q (type %d) at line %d offset %d.\n", tok.Lit, tok.Type, tok.LineNr, tok.Offset)
if tok.Type == ObjectDelimiter {
p.advanceOneToken("keyvaluelast")
return false
}
return true
}
|
