func ExampleScanner_Scan() {
// src is the input that we want to tokenize.
src := []byte(`[profile "A"]
color = blue ; Comment`)
// Initialize the scanner.
var s scanner.Scanner
fset := token.NewFileSet() // positions are relative to fset
file := fset.AddFile("", fset.Base(), len(src)) // register input "file"
s.Init(file, src, nil /* no error handler */, scanner.ScanComments)
// Repeated calls to Scan yield the token sequence found in the input.
for {
pos, tok, lit := s.Scan()
if tok == token.EOF {
break
}
fmt.Printf("%s\t%q\t%q\n", fset.Position(pos), tok, lit)
}
// output:
// 1:1 "[" ""
// 1:2 "IDENT" "profile"
// 1:10 "STRING" "\"A\""
// 1:13 "]" ""
// 1:14 "\n" ""
// 2:1 "IDENT" "color"
// 2:7 "=" ""
// 2:9 "STRING" "blue"
// 2:14 "COMMENT" "; Comment"
}
func readInto(config interface{}, fset *token.FileSet, file *token.File, src []byte) error {
var s scanner.Scanner
var errs scanner.ErrorList
s.Init(file, src, func(p token.Position, m string) { errs.Add(p, m) }, 0)
sect, sectsub := "", ""
pos, tok, lit := s.Scan()
errfn := func(msg string) error {
return fmt.Errorf("%s: %s", fset.Position(pos), msg)
}
for {
if errs.Len() > 0 {
return errs.Err()
}
switch tok {
case token.EOF:
return nil
case token.EOL, token.COMMENT:
pos, tok, lit = s.Scan()
case token.LBRACK:
pos, tok, lit = s.Scan()
if errs.Len() > 0 {
return errs.Err()
}
if tok != token.IDENT {
return errfn("expected section name")
}
sect, sectsub = lit, ""
pos, tok, lit = s.Scan()
if errs.Len() > 0 {
return errs.Err()
}
if tok == token.STRING {
sectsub = unquote(lit)
if sectsub == "" {
return errfn("empty subsection name")
}
pos, tok, lit = s.Scan()
if errs.Len() > 0 {
return errs.Err()
}
}
if tok != token.RBRACK {
if sectsub == "" {
return errfn("expected subsection name or right bracket")
}
return errfn("expected right bracket")
}
pos, tok, lit = s.Scan()
if tok != token.EOL && tok != token.EOF && tok != token.COMMENT {
return errfn("expected EOL, EOF, or comment")
}
case token.IDENT:
if sect == "" {
return errfn("expected section header")
}
n := lit
pos, tok, lit = s.Scan()
if errs.Len() > 0 {
return errs.Err()
}
blank, v := tok == token.EOF || tok == token.EOL || tok == token.COMMENT, ""
if !blank {
if tok != token.ASSIGN {
return errfn("expected '='")
}
pos, tok, lit = s.Scan()
if errs.Len() > 0 {
return errs.Err()
}
if tok != token.STRING {
return errfn("expected value")
}
v = unquote(lit)
pos, tok, lit = s.Scan()
if errs.Len() > 0 {
return errs.Err()
}
if tok != token.EOL && tok != token.EOF && tok != token.COMMENT {
return errfn("expected EOL, EOF, or comment")
}
}
err := set(config, sect, sectsub, n, blank, v)
if err != nil {
return errfn(err.Error())
}
default:
if sect == "" {
return errfn("expected section header")
}
return errfn("expected section header or variable declaration")
}
}
panic("never reached")
}