An on-disk ring buffer for persistent, fixed-sized logs.
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.gitignore
Makefile
README.md
example.c
ring_log.c
ring_log.h
ring_log_arch_freertos.c
ring_log_arch_posix.c
ring_log_config.c
test.c

README.md

For Linux systems, there is logrotate. For embedded systems, there's ring_log.

Specify how many total logs you want to keep (in bytes), and then use ring_log's API to add new log entries.

ring_log will manage the on-disk log storage such that only the N most recent log entries are kept. It will use the amount of disk space that you allow it to, and no more.

How to use:

Copy over ring_log.c, ring_log.h, and the ring_log_arch_*.c matching your OS.

Copy and edit ring_log_config.c. Important values such as the total log size, the number of logs, etc, are defined there.

Start up ring_log and write a few entries (see example.c):

if (!ring_log_init()) {
    puts("ring_log_init failed");
    exit(1);
}

ring_log_write_tail("log_a", "one", 3);
ring_log_write_tail_complete("log_a");

ring_log_write_tail("log_a", "two", 3);
ring_log_write_tail_complete("log_a");

ring_log_write_tail("log_a", "three", 5);
ring_log_write_tail_complete("log_a");

Read all the entries out:

while (ring_log_has_unread("log_a")) {
    int read_now;
    char buffer[8];
    size_t read_total = 0;
    printf("entry: ");
    while ((read_now = ring_log_read_head("log_a", &buffer, sizeof(buffer), &read_total))) {
        printf("%.*s", read_now, (char *)&buffer);
    };
    puts("");
    ring_log_read_head_success("log_a");
}