39934deb |
1 | /* |
2 | * timing.c |
3 | * |
4 | * This module tracks any timers set up by schedule_timer(). It |
5 | * keeps all the currently active timers in a list; it informs the |
6 | * front end of when the next timer is due to go off if that |
7 | * changes; and, very importantly, it tracks the context pointers |
8 | * passed to schedule_timer(), so that if a context is freed all |
9 | * the timers associated with it can be immediately annulled. |
10 | */ |
11 | |
12 | #include <assert.h> |
13 | #include <stdio.h> |
14 | |
15 | #include "putty.h" |
16 | #include "tree234.h" |
17 | |
18 | struct timer { |
19 | timer_fn_t fn; |
20 | void *ctx; |
21 | long now; |
22 | }; |
23 | |
24 | static tree234 *timers = NULL; |
1605c493 |
25 | static tree234 *timer_contexts = NULL; |
39934deb |
26 | static long now = 0L; |
27 | |
28 | static int compare_timers(void *av, void *bv) |
29 | { |
30 | struct timer *a = (struct timer *)av; |
31 | struct timer *b = (struct timer *)bv; |
32 | long at = a->now - now; |
33 | long bt = b->now - now; |
34 | |
35 | if (at < bt) |
36 | return -1; |
37 | else if (at > bt) |
38 | return +1; |
39 | |
40 | /* |
41 | * Failing that, compare on the other two fields, just so that |
42 | * we don't get unwanted equality. |
43 | */ |
8136216b |
44 | #ifdef __LCC__ |
45 | /* lcc won't let us compare function pointers. Legal, but annoying. */ |
46 | { |
47 | int c = memcmp(&a->fn, &b->fn, sizeof(a->fn)); |
48 | if (c < 0) |
49 | return -1; |
50 | else if (c > 0) |
51 | return +1; |
52 | } |
53 | #else |
39934deb |
54 | if (a->fn < b->fn) |
55 | return -1; |
56 | else if (a->fn > b->fn) |
57 | return +1; |
8136216b |
58 | #endif |
39934deb |
59 | |
60 | if (a->ctx < b->ctx) |
61 | return -1; |
62 | else if (a->ctx > b->ctx) |
63 | return +1; |
64 | |
65 | /* |
66 | * Failing _that_, the two entries genuinely are equal, and we |
67 | * never have a need to store them separately in the tree. |
68 | */ |
69 | return 0; |
70 | } |
71 | |
72 | static int compare_timer_contexts(void *av, void *bv) |
73 | { |
1605c493 |
74 | char *a = (char *)av; |
75 | char *b = (char *)bv; |
39934deb |
76 | if (a < b) |
77 | return -1; |
78 | else if (a > b) |
79 | return +1; |
80 | return 0; |
81 | } |
82 | |
83 | static void init_timers(void) |
84 | { |
85 | if (!timers) { |
86 | timers = newtree234(compare_timers); |
1605c493 |
87 | timer_contexts = newtree234(compare_timer_contexts); |
39934deb |
88 | now = GETTICKCOUNT(); |
89 | } |
90 | } |
91 | |
92 | long schedule_timer(int ticks, timer_fn_t fn, void *ctx) |
93 | { |
94 | long when; |
95 | struct timer *t, *first; |
96 | |
97 | init_timers(); |
98 | |
99 | when = ticks + GETTICKCOUNT(); |
2ac3322e |
100 | |
101 | /* |
102 | * Just in case our various defences against timing skew fail |
103 | * us: if we try to schedule a timer that's already in the |
104 | * past, we instead schedule it for the immediate future. |
105 | */ |
106 | if (when - now <= 0) |
107 | when = now + 1; |
39934deb |
108 | |
109 | t = snew(struct timer); |
110 | t->fn = fn; |
111 | t->ctx = ctx; |
112 | t->now = when; |
113 | |
114 | if (t != add234(timers, t)) { |
115 | sfree(t); /* identical timer already exists */ |
1605c493 |
116 | } else { |
117 | add234(timer_contexts, t->ctx);/* don't care if this fails */ |
39934deb |
118 | } |
119 | |
120 | first = (struct timer *)index234(timers, 0); |
121 | if (first == t) { |
122 | /* |
123 | * This timer is the very first on the list, so we must |
124 | * notify the front end. |
125 | */ |
126 | timer_change_notify(first->now); |
127 | } |
128 | |
129 | return when; |
130 | } |
131 | |
132 | /* |
133 | * Call to run any timers whose time has reached the present. |
134 | * Returns the time (in ticks) expected until the next timer after |
135 | * that triggers. |
136 | */ |
137 | int run_timers(long anow, long *next) |
138 | { |
139 | struct timer *first; |
140 | |
141 | init_timers(); |
142 | |
2ac3322e |
143 | #ifdef TIMING_SYNC |
144 | /* |
145 | * In this ifdef I put some code which deals with the |
146 | * possibility that `anow' disagrees with GETTICKCOUNT by a |
147 | * significant margin. Our strategy for dealing with it differs |
148 | * depending on platform, because on some platforms |
149 | * GETTICKCOUNT is more likely to be right whereas on others |
150 | * `anow' is a better gold standard. |
151 | */ |
152 | { |
153 | long tnow = GETTICKCOUNT(); |
154 | |
155 | if (tnow + TICKSPERSEC/50 - anow < 0 || |
156 | anow + TICKSPERSEC/50 - tnow < 0 |
157 | ) { |
158 | #if defined TIMING_SYNC_ANOW |
159 | /* |
160 | * If anow is accurate and the tick count is wrong, |
161 | * this is likely to be because the tick count is |
162 | * derived from the system clock which has changed (as |
163 | * can occur on Unix). Therefore, we resolve this by |
164 | * inventing an offset which is used to adjust all |
165 | * future output from GETTICKCOUNT. |
166 | * |
167 | * A platform which defines TIMING_SYNC_ANOW is |
168 | * expected to have also defined this offset variable |
169 | * in (its platform-specific adjunct to) putty.h. |
170 | * Therefore we can simply reference it here and assume |
171 | * that it will exist. |
172 | */ |
173 | tickcount_offset += anow - tnow; |
174 | #elif defined TIMING_SYNC_TICKCOUNT |
175 | /* |
176 | * If the tick count is more likely to be accurate, we |
177 | * simply use that as our time value, which may mean we |
178 | * run no timers in this call (because we got called |
179 | * early), or alternatively it may mean we run lots of |
180 | * timers in a hurry because we were called late. |
181 | */ |
182 | anow = tnow; |
183 | #else |
184 | /* |
185 | * Any platform which defines TIMING_SYNC must also define one of the two |
186 | * auxiliary symbols TIMING_SYNC_ANOW and TIMING_SYNC_TICKCOUNT, to |
187 | * indicate which measurement to trust when the two disagree. |
188 | */ |
189 | #error TIMING_SYNC definition incomplete |
190 | #endif |
191 | } |
192 | } |
193 | #endif |
194 | |
39934deb |
195 | now = anow; |
196 | |
197 | while (1) { |
198 | first = (struct timer *)index234(timers, 0); |
199 | |
200 | if (!first) |
201 | return FALSE; /* no timers remaining */ |
202 | |
1605c493 |
203 | if (find234(timer_contexts, first->ctx, NULL) == NULL) { |
204 | /* |
205 | * This timer belongs to a context that has been |
206 | * expired. Delete it without running. |
207 | */ |
208 | delpos234(timers, 0); |
209 | sfree(first); |
210 | } else if (first->now - now <= 0) { |
39934deb |
211 | /* |
212 | * This timer is active and has reached its running |
213 | * time. Run it. |
214 | */ |
215 | delpos234(timers, 0); |
216 | first->fn(first->ctx, first->now); |
217 | sfree(first); |
218 | } else { |
219 | /* |
220 | * This is the first still-active timer that is in the |
221 | * future. Return how long it has yet to go. |
222 | */ |
223 | *next = first->now; |
224 | return TRUE; |
225 | } |
226 | } |
227 | } |
228 | |
229 | /* |
230 | * Call to expire all timers associated with a given context. |
231 | */ |
232 | void expire_timer_context(void *ctx) |
233 | { |
1605c493 |
234 | init_timers(); |
5e376138 |
235 | |
1605c493 |
236 | /* |
237 | * We don't bother to check the return value; if the context |
238 | * already wasn't in the tree (presumably because no timers |
239 | * ever actually got scheduled for it) then that's fine and we |
240 | * simply don't need to do anything. |
241 | */ |
242 | del234(timer_contexts, ctx); |
39934deb |
243 | } |