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1c1af145 | 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; | |
25 | static tree234 *timer_contexts = NULL; | |
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 | */ | |
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 | |
54 | if (a->fn < b->fn) | |
55 | return -1; | |
56 | else if (a->fn > b->fn) | |
57 | return +1; | |
58 | #endif | |
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 | { | |
74 | char *a = (char *)av; | |
75 | char *b = (char *)bv; | |
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); | |
87 | timer_contexts = newtree234(compare_timer_contexts); | |
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(); | |
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; | |
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 */ | |
116 | } else { | |
117 | add234(timer_contexts, t->ctx);/* don't care if this fails */ | |
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 | ||
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 | ||
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 | ||
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) { | |
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 | { | |
234 | init_timers(); | |
235 | ||
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); | |
243 | } |