e68a8dd86c
This changes the SHM log format, it doesn’t use 0-bytes to separate entries anymore. Instead of using lots of printf() calls in i3-dump-log, we now do precisely one big write(). So, to be clear: i3-dump-log and i3 both need to be upgraded. Mismatching versions will lead to garbage output (no crashes of i3, just garbage output). The -f flag uses an inter-process pthread_cond_t in the shared memory header to broadcast the arrival of new messages to all i3-dump-log processes. This internally uses futexes and thus doesn’t even mean a kernel call in most cases. inter-process pthread_cond_ts require NPTL (the Native Posix Thread Library, introduce in Linux 2.6).
45 lines
1.4 KiB
C
45 lines
1.4 KiB
C
/*
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* vim:ts=4:sw=4:expandtab
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*
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* i3 - an improved dynamic tiling window manager
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* © 2009-2012 Michael Stapelberg and contributors (see also: LICENSE)
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*
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* The format of the shmlog data structure which i3 development versions use by
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* default (ringbuffer for storing the debug log).
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*
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*/
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#ifndef _I3_SHMLOG_H
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#define _I3_SHMLOG_H
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#include <stdint.h>
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#include <pthread.h>
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/*
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* Header of the shmlog file. Used by i3/src/log.c and i3/i3-dump-log/main.c.
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*
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*/
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typedef struct i3_shmlog_header {
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/* Byte offset where the next line will be written to. */
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uint32_t offset_next_write;
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/* Byte offset where the last wrap occured. */
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uint32_t offset_last_wrap;
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/* The size of the logfile in bytes. Since the size is limited to 25 MiB
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* an uint32_t is sufficient. */
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uint32_t size;
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/* wrap counter. We need it to reliably signal to clients that we just
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* wrapped (clients cannot use offset_last_wrap because that might
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* coincidentally be exactly the same as previously). Overflows can happen
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* and don’t matter — clients use an equality check (==). */
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uint32_t wrap_count;
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/* pthread condvar which will be broadcasted whenever there is a new
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* message in the log. i3-dump-log uses this to implement -f (follow, like
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* tail -f) in an efficient way. */
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pthread_cond_t condvar;
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} i3_shmlog_header;
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#endif
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