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lex.go
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lex.go
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// Copyright 2017 The Cockroach Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied. See the License for the specific language governing
// permissions and limitations under the License.
package parser
import (
"errors"
"fmt"
"io"
"strconv"
scn "text/scanner"
)
//go:generate make
// Pos represents a position in the input.
type Pos struct {
pos scn.Position
}
func (pos Pos) String() string {
return pos.pos.String()
}
// PosError wraps an error that occurred at a specific position in the input.
type PosError struct {
Pos Pos
Err error
}
func (e PosError) Error() string {
return fmt.Sprintf("%s: %s", e.Pos.String(), e.Err.Error())
}
type lexer struct {
scn scn.Scanner
defs []Def
firstErr error
}
func newLexer(filename string, src io.Reader) *lexer {
var l lexer
l.scn.Init(src)
l.scn.Error = func(s *scn.Scanner, msg string) {
if l.firstErr == nil {
l.firstErr = PosError{Pos{pos: s.Pos()}, errors.New(msg)}
}
}
l.scn.Filename = filename
return &l
}
func (l *lexer) pos() Pos {
return Pos{pos: l.scn.Position}
}
// Error implements the irgenLexer interface.
func (l *lexer) Error(e string) {
if l.firstErr == nil {
l.firstErr = PosError{l.pos(), errors.New(e)}
}
}
// Lex implements the irgenLexer interface.
func (l *lexer) Lex(lval *irgenSymType) int {
tok := l.scn.Scan()
if l.firstErr != nil {
return ERROR
}
s := l.scn.TokenText()
switch tok {
case scn.EOF:
return 0
case scn.Ident:
switch l.scn.TokenText() {
case "enum":
return ENUM
case "format":
return FORMAT
case "prim":
return PRIM
case "reserved":
return RESERVED
case "struct":
return STRUCT
case "sum":
return SUM
default:
lval.str = strOccur{Str: s, Pos: l.pos()}
return IDENT
}
case scn.Int:
tag, err := strconv.Atoi(s)
if err != nil {
l.Error(err.Error())
return ERROR
}
if tag < 1 || (19000 <= tag && tag <= 19999) || tag > (1<<29)-1 {
l.Error(fmt.Sprintf("invalid tag number: %d", tag))
return ERROR
}
lval.tag = TagOccur{Tag: Tag(tag), Pos: l.pos()}
return TAG
case scn.String, scn.RawString:
lval.str = strOccur{Str: s, Pos: l.pos()}
return STR
case '*', '.', ';', '=', '[', ']', '{', '}':
return int(tok)
default:
l.Error(fmt.Sprintf("invalid token: %q", s))
return ERROR
}
}