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)
 *
 * The format of the shmlog data structure which i3 development versions use by
 * default (ringbuffer for storing the debug log).
 *
 */
#pragma once
 
#include <config.h>
 
#include <stdint.h>
#if !defined(__OpenBSD__)
#include <pthread.h>
#endif
 
/* Default shmlog size if not set by user. */
extern const int default_shmlog_size;
 
typedef struct i3_shmlog_header {
    /* Byte offset where the next line will be written to. */
    uint32_t offset_next_write;
 
    /* Byte offset where the last wrap occurred. */
    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. */
    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 don’t matter — clients use an equality check (==). */
    uint32_t wrap_count;
 
#if !defined(__OpenBSD__)
    /* 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;
#endif
} i3_shmlog_header;