/tutorial/external/C/example2.e

  1class EXAMPLE2
  2   --
  3   -- How to use the Eiffel $ operator which can be used to pass the address of
  4   -- an Eiffel feature (to be called later from C).
  5   --
  6   -- To compile this file:
  7   --
  8   --       compile example2 c_glue2.c
  9   --
 10   -- You may also prefer:
 11   --
 12   --       gcc -c c_glue.c
 13   --       compile example2 c_glue2.o
 14   --
 15
 16create {ANY}
 17   make
 18
 19feature {ANY}
 20   make
 21      local
 22         v: INTEGER
 23      do
 24         -- When a C function need to write some attribute:
 25         io.put_string("Example #0%N")
 26         write_integer_attribute($integer_attribute)
 27         io.put_integer(integer_attribute)
 28         io.put_new_line
 29         -- Call back of `procedure_1':
 30         io.put_string("Example #1%N")
 31         call_back_1(Current, $procedure_1)
 32         -- Call back of `function_1':
 33         io.put_string("Example #2%N")
 34         io.put_integer(call_back_2(Current, $function_1))
 35         io.put_new_line
 36         -- Call back of `function_2':
 37         io.put_string("Example #3%N")
 38         io.put_integer(call_back_3(Current, $function_2, "Eiffel STRING%N"))
 39         io.put_new_line
 40         -- Call back of `function_3':
 41         io.put_string("Example #4%N")
 42         io.put_integer(call_back_4(Current, $function_3, "Eiffel STRIN"))
 43         io.put_new_line
 44         -- Call back of `routine5':
 45         io.put_string("Example #5%N")
 46         call_back_5(Current, $routine5)
 47         io.put_new_line
 48         -- Call back of `once_routine6':
 49         io.put_string("Example #6%N")
 50         call_back_6(Current, $once_routine6)
 51         call_back_6(Current, $once_routine6)
 52         call_back_6(Current, $once_routine6)
 53         call_back_6(Current, $once_routine6)
 54         check
 55            integer_attribute = 6
 56         end
 57         -- Call back of `once_routine7':
 58         io.put_string("Example #7%N")
 59         v := call_back_7(Current, $once_routine7)
 60         check
 61            v = 10
 62         end
 63         v := call_back_7(Current, $once_routine7)
 64         check
 65            v = 10
 66         end
 67         io.put_integer(v)
 68         io.put_new_line
 69         -- Call back of `once_routine8':
 70         io.put_string("Example #8%N")
 71         v := call_back_7(Current, $once_routine8)
 72         check
 73            v = 10
 74         end
 75         v := call_back_7(Current, $once_routine8)
 76         check
 77            v = 10
 78         end
 79         io.put_integer(v)
 80         io.put_new_line
 81      end
 82
 83feature {ANY}
 84   integer_attribute: INTEGER
 85
 86feature {}
 87   write_integer_attribute (integer_pointer: POINTER)
 88         -- (Corresponding C function defined in c_glue2.c)
 89      external "C"
 90      end
 91
 92   procedure_1
 93         -- A procedure which only needs `Current'.
 94      do
 95         io.put_string("From `procedure_1' :%N")
 96         io.put_integer(integer_attribute)
 97         io.put_new_line
 98      end
 99
100   call_back_1 (c: like Current; a_routine: POINTER)
101         -- (Corresponding C function defined in c_glue2.c)
102      external "C"
103      end
104
105   function_1: INTEGER
106         -- A function which only needs `Current'.
107      do
108         Result := integer_attribute + 1
109      end
110
111   call_back_2 (c: like Current; a_routine: POINTER): INTEGER
112         -- (Corresponding C function defined in c_glue2.c)
113      external "C"
114      end
115
116   function_2 (s: STRING): INTEGER
117         -- A function which needs `Current' and a STRING as argument.
118      require
119         s.count > 0
120      do
121         io.put_string(s)
122         Result := integer_attribute + s.count
123      end
124
125   call_back_3 (c: like Current; a_routine: POINTER; str: STRING): INTEGER
126         -- (Corresponding C function defined in c_glue2.c)
127      external "C"
128      end
129
130   function_3 (s: STRING; c: CHARACTER): INTEGER
131         -- A function which needs two arguments.
132      require
133         s.count > 0
134      do
135         s.extend(c)
136         s.extend('%N')
137         io.put_string(s)
138         Result := s.count
139      end
140
141   call_back_4 (c: like Current; a_routine: POINTER; str: STRING): INTEGER
142         -- (Corresponding C function defined in c_glue2.c)
143      external "C"
144      end
145
146   routine5 (other: like Current)
147         -- A procedure.
148      require
149         other = Current
150      do
151         io.put_integer(integer_attribute + other.integer_attribute)
152      end
153
154   call_back_5 (c: like Current; a_routine: POINTER)
155         -- (Corresponding C function defined in c_glue2.c)
156      external "C"
157      end
158
159   once_routine6
160      once
161         integer_attribute := integer_attribute + 4
162         io.put_string("Only once routine6.%N")
163      end
164
165   call_back_6 (c: like Current; a_routine: POINTER)
166         -- (Corresponding C function defined in c_glue2.c)
167      external "C"
168      end
169
170   once_routine7: INTEGER
171      once
172         Result := integer_attribute + 4
173      end
174
175   call_back_7 (c: like Current; a_routine: POINTER): INTEGER
176         -- (Corresponding C function defined in c_glue2.c)
177      external "C"
178      end
179
180   once_routine8: INTEGER
181         -- Just to check that such a pre-computable once
182         -- function causes no pain.
183      once
184         Result := 10
185      end
186
187end -- class EXAMPLE2