gri3-wm/include/shmlog.h

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/*
* vim:ts=4:sw=4:expandtab
*
* i3 - an improved dynamic tiling window manager
* © 2009 Michael Stapelberg and contributors (see also: LICENSE)
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*
* The format of the shmlog data structure which i3 development versions use by
* default (ringbuffer for storing the debug log).
*
*/
#pragma once
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#include <stdint.h>
#include <pthread.h>
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/* Default shmlog size if not set by user. */
extern const int default_shmlog_size;
/*
* Header of the shmlog file. Used by i3/src/log.c and i3/i3-dump-log/main.c.
*
*/
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typedef struct i3_shmlog_header {
/* 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 occurred. */
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uint32_t offset_last_wrap;
/* The size of the logfile in bytes. Since the size is limited to 25 MiB
* an uint32_t is sufficient. */
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uint32_t size;
/* wrap counter. We need it to reliably signal to clients that we just
* wrapped (clients cannot use offset_last_wrap because that might
* coincidentally be exactly the same as previously). Overflows can happen
* and dont matter clients use an equality check (==). */
uint32_t wrap_count;
/* pthread condvar which will be broadcasted whenever there is a new
* message in the log. i3-dump-log uses this to implement -f (follow, like
* tail -f) in an efficient way. */
pthread_cond_t condvar;
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} i3_shmlog_header;