1// Copyright 2015 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package lex
6
7import (
8	"text/scanner"
9
10	"cmd/internal/src"
11)
12
13// A Slice reads from a slice of Tokens.
14type Slice struct {
15	tokens []Token
16	base   *src.PosBase
17	line   int
18	pos    int
19}
20
21func NewSlice(base *src.PosBase, line int, tokens []Token) *Slice {
22	return &Slice{
23		tokens: tokens,
24		base:   base,
25		line:   line,
26		pos:    -1, // Next will advance to zero.
27	}
28}
29
30func (s *Slice) Next() ScanToken {
31	s.pos++
32	if s.pos >= len(s.tokens) {
33		return scanner.EOF
34	}
35	return s.tokens[s.pos].ScanToken
36}
37
38func (s *Slice) Text() string {
39	return s.tokens[s.pos].text
40}
41
42func (s *Slice) File() string {
43	return s.base.Filename()
44}
45
46func (s *Slice) Base() *src.PosBase {
47	return s.base
48}
49
50func (s *Slice) SetBase(base *src.PosBase) {
51	// Cannot happen because we only have slices of already-scanned text,
52	// but be prepared.
53	s.base = base
54}
55
56func (s *Slice) Line() int {
57	return s.line
58}
59
60func (s *Slice) Col() int {
61	// TODO: Col is only called when defining a macro and all it cares about is increasing
62	// position to discover whether there is a blank before the parenthesis.
63	// We only get here if defining a macro inside a macro.
64	// This imperfect implementation means we cannot tell the difference between
65	//	#define A #define B(x) x
66	// and
67	//	#define A #define B (x) x
68	// The first definition of B has an argument, the second doesn't. Because we let
69	// text/scanner strip the blanks for us, this is extremely rare, hard to fix, and not worth it.
70	return s.pos
71}
72
73func (s *Slice) Close() {
74}
75