shared: add ring buffer

New "struct ring" object that implements a basic ring buffer for arbitrary
byte-streams. A new basic runtime test is also added.

This will be needed for our pty helpers for systemd-console and friends.

1 files changed, 135 insertions, 0 deletions

diff --git a/src/test/test-ring.c b/src/test/test-ring.c
new file mode 100644
index 0000000000..880815811c
--- /dev/null
+++ b/src/test/test-ring.c
@@ -0,0 +1,135 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 David Herrmann <dh.herrmann@gmail.com>
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <locale.h>
+#include <errno.h>
+
+#include "def.h"
+#include "ring.h"
+#include "util.h"
+
+static void test_ring(void) {
+        static const char buf[8192];
+        struct ring r;
+        size_t l;
+        struct iovec vec[2];
+        int s;
+
+        memset(&r, 0, sizeof(r));
+
+        l = ring_peek(&r, vec);
+        assert_se(l == 0);
+
+        s = ring_push(&r, buf, 2048);
+        assert_se(!s);
+        assert_se(ring_get_size(&r) == 2048);
+
+        l = ring_peek(&r, vec);
+        assert_se(l == 1);
+        assert_se(vec[0].iov_len == 2048);
+        assert_se(!memcmp(vec[0].iov_base, buf, vec[0].iov_len));
+        assert_se(ring_get_size(&r) == 2048);
+
+        ring_pull(&r, 2048);
+        assert_se(ring_get_size(&r) == 0);
+
+        l = ring_peek(&r, vec);
+        assert_se(l == 0);
+        assert_se(ring_get_size(&r) == 0);
+
+        s = ring_push(&r, buf, 2048);
+        assert_se(!s);
+        assert_se(ring_get_size(&r) == 2048);
+
+        l = ring_peek(&r, vec);
+        assert_se(l == 1);
+        assert_se(vec[0].iov_len == 2048);
+        assert_se(!memcmp(vec[0].iov_base, buf, vec[0].iov_len));
+        assert_se(ring_get_size(&r) == 2048);
+
+        s = ring_push(&r, buf, 1);
+        assert_se(!s);
+        assert_se(ring_get_size(&r) == 2049);
+
+        l = ring_peek(&r, vec);
+        assert_se(l == 2);
+        assert_se(vec[0].iov_len == 2048);
+        assert_se(vec[1].iov_len == 1);
+        assert_se(!memcmp(vec[0].iov_base, buf, vec[0].iov_len));
+        assert_se(!memcmp(vec[1].iov_base, buf, vec[1].iov_len));
+        assert_se(ring_get_size(&r) == 2049);
+
+        ring_pull(&r, 2048);
+        assert_se(ring_get_size(&r) == 1);
+
+        l = ring_peek(&r, vec);
+        assert_se(l == 1);
+        assert_se(vec[0].iov_len == 1);
+        assert_se(!memcmp(vec[0].iov_base, buf, vec[0].iov_len));
+        assert_se(ring_get_size(&r) == 1);
+
+        ring_pull(&r, 1);
+        assert_se(ring_get_size(&r) == 0);
+
+        s = ring_push(&r, buf, 2048);
+        assert_se(!s);
+        assert_se(ring_get_size(&r) == 2048);
+
+        s = ring_push(&r, buf, 2049);
+        assert_se(!s);
+        assert_se(ring_get_size(&r) == 4097);
+
+        l = ring_peek(&r, vec);
+        assert_se(l == 1);
+        assert_se(vec[0].iov_len == 4097);
+        assert_se(!memcmp(vec[0].iov_base, buf, vec[0].iov_len));
+        assert_se(ring_get_size(&r) == 4097);
+
+        ring_pull(&r, 1);
+        assert_se(ring_get_size(&r) == 4096);
+
+        s = ring_push(&r, buf, 4096);
+        assert_se(!s);
+        assert_se(ring_get_size(&r) == 8192);
+
+        l = ring_peek(&r, vec);
+        assert_se(l == 2);
+        assert_se(vec[0].iov_len == 8191);
+        assert_se(vec[1].iov_len == 1);
+        assert_se(!memcmp(vec[0].iov_base, buf, vec[0].iov_len));
+        assert_se(!memcmp(vec[1].iov_base, buf, vec[1].iov_len));
+        assert_se(ring_get_size(&r) == 8192);
+
+        ring_clear(&r);
+        assert_se(ring_get_size(&r) == 0);
+}
+
+int main(int argc, char *argv[]) {
+        log_parse_environment();
+        log_open();
+
+        test_ring();
+
+        return 0;
+}