… | |
… | |
2209 | Periodic watchers are also timers of a kind, but they are very versatile |
2209 | Periodic watchers are also timers of a kind, but they are very versatile |
2210 | (and unfortunately a bit complex). |
2210 | (and unfortunately a bit complex). |
2211 | |
2211 | |
2212 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2212 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2213 | relative time, the physical time that passes) but on wall clock time |
2213 | relative time, the physical time that passes) but on wall clock time |
2214 | (absolute time, the thing you can read on your calender or clock). The |
2214 | (absolute time, the thing you can read on your calendar or clock). The |
2215 | difference is that wall clock time can run faster or slower than real |
2215 | difference is that wall clock time can run faster or slower than real |
2216 | time, and time jumps are not uncommon (e.g. when you adjust your |
2216 | time, and time jumps are not uncommon (e.g. when you adjust your |
2217 | wrist-watch). |
2217 | wrist-watch). |
2218 | |
2218 | |
2219 | You can tell a periodic watcher to trigger after some specific point |
2219 | You can tell a periodic watcher to trigger after some specific point |
… | |
… | |
5300 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5300 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5301 | assumes that the same (machine) code can be used to call any watcher |
5301 | assumes that the same (machine) code can be used to call any watcher |
5302 | callback: The watcher callbacks have different type signatures, but libev |
5302 | callback: The watcher callbacks have different type signatures, but libev |
5303 | calls them using an C<ev_watcher *> internally. |
5303 | calls them using an C<ev_watcher *> internally. |
5304 | |
5304 | |
|
|
5305 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5306 | |
|
|
5307 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5308 | relies on this setting pointers and integers to null. |
|
|
5309 | |
5305 | =item pointer accesses must be thread-atomic |
5310 | =item pointer accesses must be thread-atomic |
5306 | |
5311 | |
5307 | Accessing a pointer value must be atomic, it must both be readable and |
5312 | Accessing a pointer value must be atomic, it must both be readable and |
5308 | writable in one piece - this is the case on all current architectures. |
5313 | writable in one piece - this is the case on all current architectures. |
5309 | |
5314 | |