stack.go

     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  
     5  package lex
     6  
     7  import (
     8  	"text/scanner"
     9  
    10  	"cmd/internal/src"
    11  )
    12  
    13  // A Stack is a stack of TokenReaders. As the top TokenReader hits EOF,
    14  // it resumes reading the next one down.
    15  type Stack struct {
    16  	tr []TokenReader
    17  }
    18  
    19  // Push adds tr to the top (end) of the input stack. (Popping happens automatically.)
    20  func (s *Stack) Push(tr TokenReader) {
    21  	s.tr = append(s.tr, tr)
    22  }
    23  
    24  func (s *Stack) Next() ScanToken {
    25  	tos := s.tr[len(s.tr)-1]
    26  	tok := tos.Next()
    27  	for tok == scanner.EOF && len(s.tr) > 1 {
    28  		tos.Close()
    29  		// Pop the topmost item from the stack and resume with the next one down.
    30  		s.tr = s.tr[:len(s.tr)-1]
    31  		tok = s.Next()
    32  	}
    33  	return tok
    34  }
    35  
    36  func (s *Stack) Text() string {
    37  	return s.tr[len(s.tr)-1].Text()
    38  }
    39  
    40  func (s *Stack) File() string {
    41  	return s.Base().Filename()
    42  }
    43  
    44  func (s *Stack) Base() *src.PosBase {
    45  	return s.tr[len(s.tr)-1].Base()
    46  }
    47  
    48  func (s *Stack) SetBase(base *src.PosBase) {
    49  	s.tr[len(s.tr)-1].SetBase(base)
    50  }
    51  
    52  func (s *Stack) Line() int {
    53  	return s.tr[len(s.tr)-1].Line()
    54  }
    55  
    56  func (s *Stack) Col() int {
    57  	return s.tr[len(s.tr)-1].Col()
    58  }
    59  
    60  func (s *Stack) Close() { // Unused.
    61  }
    62
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