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726f6388 JA |
1 | /* I can't stand it anymore! Please can't we just write the |
2 | whole Unix system in lisp or something? */ | |
3 | ||
4 | /* Copyright (C) 1987,1989 Free Software Foundation, Inc. | |
5 | ||
6 | This file is part of GNU Bash, the Bourne Again SHell. | |
7 | ||
8 | Bash is free software; you can redistribute it and/or modify it under | |
9 | the terms of the GNU General Public License as published by the Free | |
10 | Software Foundation; either version 1, or (at your option) any later | |
11 | version. | |
12 | ||
13 | Bash is distributed in the hope that it will be useful, but WITHOUT ANY | |
14 | WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
15 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
16 | for more details. | |
17 | ||
18 | You should have received a copy of the GNU General Public License along | |
19 | with Bash; see the file COPYING. If not, write to the Free Software | |
20 | Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */ | |
21 | ||
22 | /* **************************************************************** */ | |
23 | /* */ | |
24 | /* Unwind Protection Scheme for Bash */ | |
25 | /* */ | |
26 | /* **************************************************************** */ | |
27 | #include "bashtypes.h" | |
28 | #include <signal.h> | |
29 | #include "config.h" | |
30 | #include "command.h" | |
31 | #include "general.h" | |
32 | #include "unwind_prot.h" | |
33 | #include "quit.h" | |
34 | ||
35 | /* If CLEANUP is null, then ARG contains a tag to throw back to. */ | |
36 | typedef struct _uwp { | |
37 | struct _uwp *next; | |
38 | Function *cleanup; | |
39 | char *arg; | |
40 | } UNWIND_ELT; | |
41 | ||
42 | static void | |
43 | unwind_frame_discard_internal (), unwind_frame_run_internal (), | |
44 | add_unwind_protect_internal (), remove_unwind_protect_internal (), | |
45 | run_unwind_protects_internal (), without_interrupts (); | |
46 | ||
47 | static UNWIND_ELT *unwind_protect_list = (UNWIND_ELT *)NULL; | |
48 | ||
49 | extern int interrupt_immediately; | |
50 | ||
51 | /* Run a function without interrupts. This relies on the fact that the | |
52 | FUNCTION cannot change the value of interrupt_immediately. (I.e., does | |
53 | not call QUIT (). */ | |
54 | static void | |
55 | without_interrupts (function, arg1, arg2) | |
56 | VFunction *function; | |
57 | char *arg1, *arg2; | |
58 | { | |
59 | int old_interrupt_immediately; | |
60 | ||
61 | old_interrupt_immediately = interrupt_immediately; | |
62 | interrupt_immediately = 0; | |
63 | ||
64 | (*function)(arg1, arg2); | |
65 | ||
66 | interrupt_immediately = old_interrupt_immediately; | |
67 | } | |
68 | ||
69 | /* Start the beginning of a region. */ | |
70 | void | |
71 | begin_unwind_frame (tag) | |
72 | char *tag; | |
73 | { | |
74 | add_unwind_protect ((Function *)NULL, tag); | |
75 | } | |
76 | ||
77 | /* Discard the unwind protects back to TAG. */ | |
78 | void | |
79 | discard_unwind_frame (tag) | |
80 | char *tag; | |
81 | { | |
82 | if (unwind_protect_list) | |
83 | without_interrupts (unwind_frame_discard_internal, tag, (char *)NULL); | |
84 | } | |
85 | ||
86 | /* Run the unwind protects back to TAG. */ | |
87 | void | |
88 | run_unwind_frame (tag) | |
89 | char *tag; | |
90 | { | |
91 | if (unwind_protect_list) | |
92 | without_interrupts (unwind_frame_run_internal, tag, (char *)NULL); | |
93 | } | |
94 | ||
95 | /* Add the function CLEANUP with ARG to the list of unwindable things. */ | |
96 | void | |
97 | add_unwind_protect (cleanup, arg) | |
98 | Function *cleanup; | |
99 | char *arg; | |
100 | { | |
101 | without_interrupts (add_unwind_protect_internal, (char *)cleanup, arg); | |
102 | } | |
103 | ||
104 | /* Remove the top unwind protect from the list. */ | |
105 | void | |
106 | remove_unwind_protect () | |
107 | { | |
108 | if (unwind_protect_list) | |
109 | without_interrupts | |
110 | (remove_unwind_protect_internal, (char *)NULL, (char *)NULL); | |
111 | } | |
112 | ||
113 | /* Run the list of cleanup functions in unwind_protect_list. */ | |
114 | void | |
115 | run_unwind_protects () | |
116 | { | |
117 | if (unwind_protect_list) | |
118 | without_interrupts | |
119 | (run_unwind_protects_internal, (char *)NULL, (char *)NULL); | |
120 | } | |
121 | ||
122 | /* **************************************************************** */ | |
123 | /* */ | |
124 | /* The Actual Functions */ | |
125 | /* */ | |
126 | /* **************************************************************** */ | |
127 | ||
128 | static void | |
129 | add_unwind_protect_internal (cleanup, arg) | |
130 | Function *cleanup; | |
131 | char *arg; | |
132 | { | |
133 | UNWIND_ELT *elt; | |
134 | ||
135 | elt = (UNWIND_ELT *)xmalloc (sizeof (UNWIND_ELT)); | |
136 | elt->cleanup = cleanup; | |
137 | elt->arg = arg; | |
138 | elt->next = unwind_protect_list; | |
139 | unwind_protect_list = elt; | |
140 | } | |
141 | ||
142 | static void | |
143 | remove_unwind_protect_internal () | |
144 | { | |
145 | UNWIND_ELT *elt = unwind_protect_list; | |
146 | ||
147 | if (elt) | |
148 | { | |
149 | unwind_protect_list = unwind_protect_list->next; | |
150 | free (elt); | |
151 | } | |
152 | } | |
153 | ||
154 | static void | |
155 | run_unwind_protects_internal () | |
156 | { | |
157 | UNWIND_ELT *t, *elt = unwind_protect_list; | |
158 | ||
159 | while (elt) | |
160 | { | |
161 | /* This function can be run at strange times, like when unwinding | |
162 | the entire world of unwind protects. Thus, we may come across | |
163 | an element which is simply a label for a catch frame. Don't call | |
164 | the non-existant function. */ | |
165 | if (elt->cleanup) | |
166 | (*(elt->cleanup)) (elt->arg); | |
167 | ||
168 | t = elt; | |
169 | elt = elt->next; | |
170 | free (t); | |
171 | } | |
172 | unwind_protect_list = elt; | |
173 | } | |
174 | ||
175 | static void | |
176 | unwind_frame_discard_internal (tag) | |
177 | char *tag; | |
178 | { | |
179 | UNWIND_ELT *elt; | |
180 | ||
181 | while (elt = unwind_protect_list) | |
182 | { | |
183 | unwind_protect_list = unwind_protect_list->next; | |
184 | if (!elt->cleanup && (STREQ (elt->arg, tag))) | |
185 | { | |
186 | free (elt); | |
187 | break; | |
188 | } | |
189 | else | |
190 | free (elt); | |
191 | } | |
192 | } | |
193 | ||
194 | static void | |
195 | unwind_frame_run_internal (tag) | |
196 | char *tag; | |
197 | { | |
198 | UNWIND_ELT *elt; | |
199 | ||
200 | while (elt = unwind_protect_list) | |
201 | { | |
202 | unwind_protect_list = elt->next; | |
203 | ||
204 | /* If tag, then compare. */ | |
205 | if (!elt->cleanup) | |
206 | { | |
207 | if (STREQ (elt->arg, tag)) | |
208 | { | |
209 | free (elt); | |
210 | break; | |
211 | } | |
212 | free (elt); | |
213 | continue; | |
214 | } | |
215 | else | |
216 | { | |
217 | (*(elt->cleanup)) (elt->arg); | |
218 | free (elt); | |
219 | } | |
220 | } | |
221 | } | |
222 | ||
223 | /* Structure describing a saved variable and the value to restore it to. */ | |
224 | typedef struct { | |
225 | int *variable; | |
226 | char *desired_setting; | |
227 | int size; | |
228 | } SAVED_VAR; | |
229 | ||
230 | /* Restore the value of a variable, based on the contents of SV. If | |
231 | sv->size is greater than sizeof (int), sv->desired_setting points to | |
232 | a block of memory SIZE bytes long holding the value, rather than the | |
233 | value itself. This block of memory is copied back into the variable. */ | |
234 | static void | |
235 | restore_variable (sv) | |
236 | SAVED_VAR *sv; | |
237 | { | |
238 | if (sv->size > sizeof (int)) | |
239 | { | |
240 | bcopy ((char *)sv->desired_setting, (char *)sv->variable, sv->size); | |
241 | free (sv->desired_setting); | |
242 | } | |
243 | else | |
244 | *(sv->variable) = (int)sv->desired_setting; | |
245 | ||
246 | free (sv); | |
247 | } | |
248 | ||
249 | /* Save the value of a variable so it will be restored when unwind-protects | |
250 | are run. VAR is a pointer to the variable. VALUE is the value to be | |
251 | saved. SIZE is the size in bytes of VALUE. If SIZE is bigger than what | |
252 | can be saved in an int, memory will be allocated and the value saved | |
253 | into that using bcopy (). */ | |
254 | void | |
255 | unwind_protect_var (var, value, size) | |
256 | int *var; | |
257 | char *value; | |
258 | int size; | |
259 | { | |
260 | SAVED_VAR *s = (SAVED_VAR *)xmalloc (sizeof (SAVED_VAR)); | |
261 | ||
262 | s->variable = var; | |
263 | if (size > sizeof (int)) | |
264 | { | |
265 | s->desired_setting = (char *)xmalloc (size); | |
266 | bcopy (value, (char *)s->desired_setting, size); | |
267 | } | |
268 | else | |
269 | s->desired_setting = value; | |
270 | s->size = size; | |
271 | add_unwind_protect ((Function *)restore_variable, (char *)s); | |
272 | } |