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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; |
39934deb |
25 | static long now = 0L; |
26 | |
27 | static int compare_timers(void *av, void *bv) |
28 | { |
29 | struct timer *a = (struct timer *)av; |
30 | struct timer *b = (struct timer *)bv; |
31 | long at = a->now - now; |
32 | long bt = b->now - now; |
33 | |
34 | if (at < bt) |
35 | return -1; |
36 | else if (at > bt) |
37 | return +1; |
38 | |
39 | /* |
40 | * Failing that, compare on the other two fields, just so that |
41 | * we don't get unwanted equality. |
42 | */ |
8136216b |
43 | #ifdef __LCC__ |
44 | /* lcc won't let us compare function pointers. Legal, but annoying. */ |
45 | { |
46 | int c = memcmp(&a->fn, &b->fn, sizeof(a->fn)); |
47 | if (c < 0) |
48 | return -1; |
49 | else if (c > 0) |
50 | return +1; |
51 | } |
52 | #else |
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53 | if (a->fn < b->fn) |
54 | return -1; |
55 | else if (a->fn > b->fn) |
56 | return +1; |
8136216b |
57 | #endif |
39934deb |
58 | |
59 | if (a->ctx < b->ctx) |
60 | return -1; |
61 | else if (a->ctx > b->ctx) |
62 | return +1; |
63 | |
64 | /* |
65 | * Failing _that_, the two entries genuinely are equal, and we |
66 | * never have a need to store them separately in the tree. |
67 | */ |
68 | return 0; |
69 | } |
70 | |
71 | static int compare_timer_contexts(void *av, void *bv) |
72 | { |
5e376138 |
73 | struct timer *at = (struct timer *)av; |
74 | struct timer *bt = (struct timer *)bv; |
75 | char *a = (char *)at->ctx; |
76 | char *b = (char *)bt->ctx; |
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77 | if (a < b) |
78 | return -1; |
79 | else if (a > b) |
80 | return +1; |
81 | return 0; |
82 | } |
83 | |
84 | static void init_timers(void) |
85 | { |
86 | if (!timers) { |
87 | timers = newtree234(compare_timers); |
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; |
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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 */ |
39934deb |
116 | } |
117 | |
118 | first = (struct timer *)index234(timers, 0); |
119 | if (first == t) { |
120 | /* |
121 | * This timer is the very first on the list, so we must |
122 | * notify the front end. |
123 | */ |
124 | timer_change_notify(first->now); |
125 | } |
126 | |
127 | return when; |
128 | } |
129 | |
130 | /* |
131 | * Call to run any timers whose time has reached the present. |
132 | * Returns the time (in ticks) expected until the next timer after |
133 | * that triggers. |
134 | */ |
135 | int run_timers(long anow, long *next) |
136 | { |
137 | struct timer *first; |
138 | |
139 | init_timers(); |
140 | |
2ac3322e |
141 | #ifdef TIMING_SYNC |
142 | /* |
143 | * In this ifdef I put some code which deals with the |
144 | * possibility that `anow' disagrees with GETTICKCOUNT by a |
145 | * significant margin. Our strategy for dealing with it differs |
146 | * depending on platform, because on some platforms |
147 | * GETTICKCOUNT is more likely to be right whereas on others |
148 | * `anow' is a better gold standard. |
149 | */ |
150 | { |
151 | long tnow = GETTICKCOUNT(); |
152 | |
153 | if (tnow + TICKSPERSEC/50 - anow < 0 || |
154 | anow + TICKSPERSEC/50 - tnow < 0 |
155 | ) { |
156 | #if defined TIMING_SYNC_ANOW |
157 | /* |
158 | * If anow is accurate and the tick count is wrong, |
159 | * this is likely to be because the tick count is |
160 | * derived from the system clock which has changed (as |
161 | * can occur on Unix). Therefore, we resolve this by |
162 | * inventing an offset which is used to adjust all |
163 | * future output from GETTICKCOUNT. |
164 | * |
165 | * A platform which defines TIMING_SYNC_ANOW is |
166 | * expected to have also defined this offset variable |
167 | * in (its platform-specific adjunct to) putty.h. |
168 | * Therefore we can simply reference it here and assume |
169 | * that it will exist. |
170 | */ |
171 | tickcount_offset += anow - tnow; |
172 | #elif defined TIMING_SYNC_TICKCOUNT |
173 | /* |
174 | * If the tick count is more likely to be accurate, we |
175 | * simply use that as our time value, which may mean we |
176 | * run no timers in this call (because we got called |
177 | * early), or alternatively it may mean we run lots of |
178 | * timers in a hurry because we were called late. |
179 | */ |
180 | anow = tnow; |
181 | #else |
182 | /* |
183 | * Any platform which defines TIMING_SYNC must also define one of the two |
184 | * auxiliary symbols TIMING_SYNC_ANOW and TIMING_SYNC_TICKCOUNT, to |
185 | * indicate which measurement to trust when the two disagree. |
186 | */ |
187 | #error TIMING_SYNC definition incomplete |
188 | #endif |
189 | } |
190 | } |
191 | #endif |
192 | |
39934deb |
193 | now = anow; |
194 | |
195 | while (1) { |
196 | first = (struct timer *)index234(timers, 0); |
197 | |
198 | if (!first) |
199 | return FALSE; /* no timers remaining */ |
200 | |
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201 | if (first->now - now <= 0) { |
39934deb |
202 | /* |
203 | * This timer is active and has reached its running |
204 | * time. Run it. |
205 | */ |
206 | delpos234(timers, 0); |
207 | first->fn(first->ctx, first->now); |
208 | sfree(first); |
209 | } else { |
210 | /* |
211 | * This is the first still-active timer that is in the |
212 | * future. Return how long it has yet to go. |
213 | */ |
214 | *next = first->now; |
215 | return TRUE; |
216 | } |
217 | } |
218 | } |
219 | |
220 | /* |
221 | * Call to expire all timers associated with a given context. |
222 | */ |
223 | void expire_timer_context(void *ctx) |
224 | { |
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225 | struct timer *ptr; |
226 | struct timer exemplar; |
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227 | |
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228 | if (!timers) return; |
229 | |
230 | exemplar.ctx = ctx; |
231 | /* don't care about initialisation of other members */ |
232 | |
233 | /* Dispose of all timers with this context */ |
234 | while ((ptr = (struct timer *)find234(timers, &exemplar, |
235 | compare_timer_contexts))) { |
236 | del234(timers, ptr); |
237 | sfree(ptr); |
238 | } |
239 | |
240 | /* Dispose of timer tree itself if none are left */ |
241 | if (count234(timers) == 0) { |
242 | freetree234(timers); |
243 | timers = NULL; |
244 | } |
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245 | } |