1 files changed, 74 insertions, 0 deletions
diff --git a/src/cmd/asm/internal/lex/slice.go b/src/cmd/asm/internal/lex/slice.go
new file mode 100644
index 0000000..61b15dd
--- /dev/null
+++ b/src/cmd/asm/internal/lex/slice.go
@@ -0,0 +1,74 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package lex
+
+import (
+	"text/scanner"
+
+	"cmd/internal/src"
+)
+
+// A Slice reads from a slice of Tokens.
+type Slice struct {
+	tokens []Token
+	base   *src.PosBase
+	line   int
+	pos    int
+}
+
+func NewSlice(base *src.PosBase, line int, tokens []Token) *Slice {
+	return &Slice{
+		tokens: tokens,
+		base:   base,
+		line:   line,
+		pos:    -1, // Next will advance to zero.
+	}
+}
+
+func (s *Slice) Next() ScanToken {
+	s.pos++
+	if s.pos >= len(s.tokens) {
+		return scanner.EOF
+	}
+	return s.tokens[s.pos].ScanToken
+}
+
+func (s *Slice) Text() string {
+	return s.tokens[s.pos].text
+}
+
+func (s *Slice) File() string {
+	return s.base.Filename()
+}
+
+func (s *Slice) Base() *src.PosBase {
+	return s.base
+}
+
+func (s *Slice) SetBase(base *src.PosBase) {
+	// Cannot happen because we only have slices of already-scanned text,
+	// but be prepared.
+	s.base = base
+}
+
+func (s *Slice) Line() int {
+	return s.line
+}
+
+func (s *Slice) Col() int {
+	// TODO: Col is only called when defining a macro and all it cares about is increasing
+	// position to discover whether there is a blank before the parenthesis.
+	// We only get here if defining a macro inside a macro.
+	// This imperfect implementation means we cannot tell the difference between
+	//	#define A #define B(x) x
+	// and
+	//	#define A #define B (x) x
+	// The first definition of B has an argument, the second doesn't. Because we let
+	// text/scanner strip the blanks for us, this is extremely rare, hard to fix, and not worth it.
+	return s.pos
+}
+
+func (s *Slice) Close() {
+}