Class: Lexer

Inherits:
Object
  • Object
show all
Defined in:
lib/xmk/lexer.rb

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Lexer

Returns a new instance of Lexer.



3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
 
# File 'lib/xmk/lexer.rb', line 3

def initialize
  @tokens = Array.new
  @start = 0
  @current = -1
  @line = 0
  @string = ""
  @file = nil
  @in_label = false
  @assignment_type = ""

  if File.exists?("xmkfile")
    @file = File.open("xmkfile", "r")
  else 
    puts "No xmkfile found"
  end
end

Instance Method Details

#advance(n = 1) ⇒ Object 



176
177
178
179
180
181
182
183
184
185
186
187
 
# File 'lib/xmk/lexer.rb', line 176

def advance(n = 1)
  c = ""
  i = n
  @current += n
  loop do
    c = self.consume
    @string << c if c
    i -= 1
    break if i == 0
  end
  c
end

#consume ⇒ Object 



195
196
197
198
199
200
 
# File 'lib/xmk/lexer.rb', line 195

def consume
  if self.terminates?(@string[@current])
    @line += 1
  end
  @file.getc
end

#end_line ⇒ Object 



216
217
218
219
220
221
222
 
# File 'lib/xmk/lexer.rb', line 216

def end_line
  # strips away characters until line break
  loop do
    c = self.advance
    break if self.terminates?(c)
  end
end

#find(c) ⇒ Object 



100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
 
# File 'lib/xmk/lexer.rb', line 100

def find(c)
  # check if char occurs before comment or newline
  res = false
  i = 0
  backup = Array.new
  loop do
    d = self.consume 
    backup.push(d)
    i += 1
    res = true if d == c
    break if d == "#"
    break if self.terminates?(d)
  end
  i.times do |j|
    self.push_back(backup[i-j-1])
  end
  res
end

#get_value(t) ⇒ Object 



119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
 
# File 'lib/xmk/lexer.rb', line 119

def get_value(t)
  if self.terminates?(@string[@current])
    return @tokens.push(Token.new(Token::LBR, "", @line))
  end
  @start = @current
  loop do 
    c = self.advance
    c = self.handle_comment_backslash(c)
    break if self.terminates?(c)
  end
  str = @string[@start .. @current-1].rstrip
  if t == Token::VAL && @assignment_type == "assign"
      str = str.lstrip
  end
  @tokens.push(Token.new(t, str, @line))
end

#handle_comment_backslash(c) ⇒ Object 



147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
 
# File 'lib/xmk/lexer.rb', line 147

def handle_comment_backslash(c)
  if c == "\\"
    loop do
      if self.terminates?(self.peek)
        @string[@current] = self.consume
        break
      else
        @string[@current] = self.consume
      end
    end
    while self.terminates?(@string[@current])
      @string[@current] = self.consume
    end
    while @string[@current] == " "
      @string[@current] = self.consume
    end
  elsif c == "#"
    loop do
      @string[@current] = self.consume
      if self.terminates?(self.peek)
        @string[@current] = self.consume
        c = @string[@current]
        break
      end
    end
  end
  c
end

#handle_label ⇒ Object 



136
137
138
139
140
141
142
143
144
145
 
# File 'lib/xmk/lexer.rb', line 136

def handle_label
  @in_label = true
  loop do
    self.advance
    break if self.peek == ":"
  end
  @tokens.push(Token.new(Token::LAB, @string[@start .. @current],
    @line))
  self.end_line
end

#peek ⇒ Object 



189
190
191
192
193
 
# File 'lib/xmk/lexer.rb', line 189

def peek
  c = self.consume
  self.push_back(c)
  c
end

#push_back(c) ⇒ Object 



202
203
204
205
206
207
 
# File 'lib/xmk/lexer.rb', line 202

def push_back(c)
  if self.terminates?(c)
    @line -= 1
  end
  @file.ungetc(c)
end

#scan ⇒ Object 



20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
 
# File 'lib/xmk/lexer.rb', line 20

def scan
  while (c = self.advance) != nil
    @start = @current
    case c
    when "#" # comment
      self.end_line
    when "+" # append/declaration
      if self.peek == "=" 
        @assignment_type = "append"
        @tokens.push(Token.new(Token::ADD, '+=', @line))
        self.advance(2)
        self.get_value(Token::VAL)
      end
    when "=" # declaration
      @assignment_type = "assign"
      @tokens.push(Token.new(Token::SET, '=', @line))
      self.advance
      self.get_value(Token::VAL)
    when "@" # target
      loop do
        c = self.advance
        c = self.handle_comment_backslash(c)
        break if self.terminates?(c)
      end
      @tokens.push(Token.new(Token::TAR, @string[@start+1 .. @current].strip,
        @line))
    when "$" # cmd
      self.get_value(Token::CMD)
    when "_" # label
      self.handle_label
    else 
      if self.terminates?(c)
        @in_label = false
        @tokens.push(Token.new(Token::LBR, c, @line))
      elsif c.match?(/[A-Z]/) # var
        loop do
          self.advance
          break unless self.peek.match?(/[A-Z_]/)
        end
        @tokens.push(Token.new(
          Token::VAR, @string[@start .. @current].strip, @line))
      elsif c.match?(/[a-z]/) # cmd / label / platform
        if @in_label # cmd
          self.get_value(Token::CMD)
        else # label || platform
          if self.find("@") # platform
            loop do
              self.advance
              break if self.peek == ":"
            end
            @tokens.push(Token.new(Token::PLAT, @string[@start .. @current],
              @line))
            parse_target = false
            loop do
              c = self.advance
              if c == "@"
                self.advance
                parse_target = true
                @start = @current
              end
              if (c == " " || self.terminates?(c)) && parse_target
                parse_target = false
                @tokens.push(Token.new(Token::TARLINK,
                  @string[@start .. @current-1], @line))
              end
              break if self.terminates?(c)
            end
          else 
            self.handle_label
          end
        end
      end
    end
  end
  @file.close
  @tokens.push(Token.new(Token::LBR, "", @line))
  @tokens.push(Token.new(Token::EOF, "end_of_file", @line))
  @tokens
end

#terminates?(c) ⇒ Boolean

Returns:

  • (Boolean) 


209
210
211
212
213
214
 
# File 'lib/xmk/lexer.rb', line 209

def terminates?(c)
  return true if c == "\n"
  return true if c.nil?
  return true if c == "\r"
  return false
end