File : i-cstrin.adb
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT COMPILER COMPONENTS --
4 -- --
5 -- I N T E R F A C E S . C . S T R I N G S --
6 -- --
7 -- B o d y --
8 -- --
9 -- Copyright (C) 1992-2010, Free Software Foundation, Inc. --
10 -- --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
17 -- --
18 -- --
19 -- --
20 -- --
21 -- --
22 -- You should have received a copy of the GNU General Public License and --
23 -- a copy of the GCC Runtime Library Exception along with this program; --
24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
25 -- <http://www.gnu.org/licenses/>. --
26 -- --
27 -- GNAT was originally developed by the GNAT team at New York University. --
28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
29 -- --
30 ------------------------------------------------------------------------------
31
32 with System; use System;
33 with System.Storage_Elements; use System.Storage_Elements;
34
35 with Ada.Unchecked_Conversion;
36
37 package body Interfaces.C.Strings is
38
39 -- Note that the type chars_ptr has a pragma No_Strict_Aliasing in the
40 -- spec, to prevent any assumptions about aliasing for values of this type,
41 -- since arbitrary addresses can be converted, and it is quite likely that
42 -- this type will in fact be used for aliasing values of other types.
43
44 function To_chars_ptr is
45 new Ada.Unchecked_Conversion (System.Parameters.C_Address, chars_ptr);
46
47 function To_Address is
48 new Ada.Unchecked_Conversion (chars_ptr, System.Parameters.C_Address);
49
50 -----------------------
51 -- Local Subprograms --
52 -----------------------
53
54 function Peek (From : chars_ptr) return char;
55 pragma Inline (Peek);
56 -- Given a chars_ptr value, obtain referenced character
57
58 procedure Poke (Value : char; Into : chars_ptr);
59 pragma Inline (Poke);
60 -- Given a chars_ptr, modify referenced Character value
61
62 function "+" (Left : chars_ptr; Right : size_t) return chars_ptr;
63 pragma Inline ("+");
64 -- Address arithmetic on chars_ptr value
65
66 function Position_Of_Nul (Into : char_array) return size_t;
67 -- Returns position of the first Nul in Into or Into'Last + 1 if none
68
69 -- We can't use directly System.Memory because the categorization is not
70 -- compatible, so we directly import here the malloc and free routines.
71
72 function Memory_Alloc (Size : size_t) return chars_ptr;
73 pragma Import (C, Memory_Alloc, System.Parameters.C_Malloc_Linkname);
74
75 procedure Memory_Free (Address : chars_ptr);
76 pragma Import (C, Memory_Free, "__gnat_free");
77
78 ---------
79 -- "+" --
80 ---------
81
82 function "+" (Left : chars_ptr; Right : size_t) return chars_ptr is
83 begin
84 return To_chars_ptr (To_Address (Left) + Storage_Offset (Right));
85 end "+";
86
87 ----------
88 -- Free --
89 ----------
90
91 procedure Free (Item : in out chars_ptr) is
92 begin
93 if Item = Null_Ptr then
94 return;
95 end if;
96
97 Memory_Free (Item);
98 Item := Null_Ptr;
99 end Free;
100
101 --------------------
102 -- New_Char_Array --
103 --------------------
104
105 function New_Char_Array (Chars : char_array) return chars_ptr is
106 Index : size_t;
107 Pointer : chars_ptr;
108
109 begin
110 -- Get index of position of null. If Index > Chars'Last,
111 -- nul is absent and must be added explicitly.
112
113 Index := Position_Of_Nul (Into => Chars);
114 Pointer := Memory_Alloc ((Index - Chars'First + 1));
115
116 -- If nul is present, transfer string up to and including nul
117
118 if Index <= Chars'Last then
119 Update (Item => Pointer,
120 Offset => 0,
121 Chars => Chars (Chars'First .. Index),
122 Check => False);
123 else
124 -- If original string has no nul, transfer whole string and add
125 -- terminator explicitly.
126
127 Update (Item => Pointer,
128 Offset => 0,
129 Chars => Chars,
130 Check => False);
131 Poke (nul, Into => Pointer + size_t'(Chars'Length));
132 end if;
133
134 return Pointer;
135 end New_Char_Array;
136
137 ----------------
138 -- New_String --
139 ----------------
140
141 function New_String (Str : String) return chars_ptr is
142
143 -- It's important that this subprogram uses the heap directly to compute
144 -- the result, and doesn't copy the string on the stack, otherwise its
145 -- use is limited when used from tasks on large strings.
146
147 Result : constant chars_ptr := Memory_Alloc (Str'Length + 1);
148
149 Result_Array : char_array (1 .. Str'Length + 1);
150 for Result_Array'Address use To_Address (Result);
151 pragma Import (Ada, Result_Array);
152
153 Count : size_t;
154
155 begin
156 To_C
157 (Item => Str,
158 Target => Result_Array,
159 Count => Count,
160 Append_Nul => True);
161 return Result;
162 end New_String;
163
164 ----------
165 -- Peek --
166 ----------
167
168 function Peek (From : chars_ptr) return char is
169 begin
170 return char (From.all);
171 end Peek;
172
173 ----------
174 -- Poke --
175 ----------
176
177 procedure Poke (Value : char; Into : chars_ptr) is
178 begin
179 Into.all := Character (Value);
180 end Poke;
181
182 ---------------------
183 -- Position_Of_Nul --
184 ---------------------
185
186 function Position_Of_Nul (Into : char_array) return size_t is
187 begin
188 for J in Into'Range loop
189 if Into (J) = nul then
190 return J;
191 end if;
192 end loop;
193
194 return Into'Last + 1;
195 end Position_Of_Nul;
196
197 ------------
198 -- Strlen --
199 ------------
200
201 function Strlen (Item : chars_ptr) return size_t is
202 Item_Index : size_t := 0;
203
204 begin
205 if Item = Null_Ptr then
206 raise Dereference_Error;
207 end if;
208
209 loop
210 if Peek (Item + Item_Index) = nul then
211 return Item_Index;
212 end if;
213
214 Item_Index := Item_Index + 1;
215 end loop;
216 end Strlen;
217
218 ------------------
219 -- To_Chars_Ptr --
220 ------------------
221
222 function To_Chars_Ptr
223 (Item : char_array_access;
224 Nul_Check : Boolean := False) return chars_ptr
225 is
226 begin
227 if Item = null then
228 return Null_Ptr;
229 elsif Nul_Check
230 and then Position_Of_Nul (Into => Item.all) > Item'Last
231 then
232 raise Terminator_Error;
233 else
234 return To_chars_ptr (Item (Item'First)'Address);
235 end if;
236 end To_Chars_Ptr;
237
238 ------------
239 -- Update --
240 ------------
241
242 procedure Update
243 (Item : chars_ptr;
244 Offset : size_t;
245 Chars : char_array;
246 Check : Boolean := True)
247 is
248 Index : chars_ptr := Item + Offset;
249
250 begin
251 if Check and then Offset + Chars'Length > Strlen (Item) then
252 raise Update_Error;
253 end if;
254
255 for J in Chars'Range loop
256 Poke (Chars (J), Into => Index);
257 Index := Index + size_t'(1);
258 end loop;
259 end Update;
260
261 procedure Update
262 (Item : chars_ptr;
263 Offset : size_t;
264 Str : String;
265 Check : Boolean := True)
266 is
267 begin
268 -- Note: in RM 95, the Append_Nul => False parameter is omitted. But
269 -- this has the unintended consequence of truncating the string after
270 -- an update. As discussed in Ada 2005 AI-242, this was unintended,
271 -- and should be corrected. Since this is a clear error, it seems
272 -- appropriate to apply the correction in Ada 95 mode as well.
273
274 Update (Item, Offset, To_C (Str, Append_Nul => False), Check);
275 end Update;
276
277 -----------
278 -- Value --
279 -----------
280
281 function Value (Item : chars_ptr) return char_array is
282 Result : char_array (0 .. Strlen (Item));
283
284 begin
285 if Item = Null_Ptr then
286 raise Dereference_Error;
287 end if;
288
289 -- Note that the following loop will also copy the terminating Nul
290
291 for J in Result'Range loop
292 Result (J) := Peek (Item + J);
293 end loop;
294
295 return Result;
296 end Value;
297
298 function Value
299 (Item : chars_ptr;
300 Length : size_t) return char_array
301 is
302 begin
303 if Item = Null_Ptr then
304 raise Dereference_Error;
305 end if;
306
307 -- ACATS cxb3010 checks that Constraint_Error gets raised when Length
308 -- is 0. Seems better to check that Length is not null before declaring
309 -- an array with size_t bounds of 0 .. Length - 1 anyway.
310
311 if Length = 0 then
312 raise Constraint_Error;
313 end if;
314
315 declare
316 Result : char_array (0 .. Length - 1);
317
318 begin
319 for J in Result'Range loop
320 Result (J) := Peek (Item + J);
321
322 if Result (J) = nul then
323 return Result (0 .. J);
324 end if;
325 end loop;
326
327 return Result;
328 end;
329 end Value;
330
331 function Value (Item : chars_ptr) return String is
332 begin
333 return To_Ada (Value (Item));
334 end Value;
335
336 function Value (Item : chars_ptr; Length : size_t) return String is
337 Result : char_array (0 .. Length);
338
339 begin
340 -- As per AI-00177, this is equivalent to:
341
342 -- To_Ada (Value (Item, Length) & nul);
343
344 if Item = Null_Ptr then
345 raise Dereference_Error;
346 end if;
347
348 for J in 0 .. Length - 1 loop
349 Result (J) := Peek (Item + J);
350
351 if Result (J) = nul then
352 return To_Ada (Result (0 .. J));
353 end if;
354 end loop;
355
356 Result (Length) := nul;
357 return To_Ada (Result);
358 end Value;
359
360 end Interfaces.C.Strings;