![[tokkee]](http://tokkee.org/images/avatar.png){kind=avatar}
diff --git a/src/utils/channel.c b/src/utils/channel.c
--- /dev/null
+++ b/src/utils/channel.c
@@ -0,0 +1,177 @@
+/*
+ * SysDB - src/utils/channel.c
+ * Copyright (C) 2013 Sebastian 'tokkee' Harl <sh@tokkee.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "utils/channel.h"
+
+#include <assert.h>
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <pthread.h>
+
+/*
+ * private data types
+ */
+
+struct sdb_channel {
+ pthread_rwlock_t lock;
+
+ /* maybe TODO: add support for 'nil' values using a boolean area */
+
+ void *data;
+ size_t data_len;
+ size_t elem_size;
+
+ size_t head;
+ size_t tail;
+ _Bool full;
+};
+
+/*
+ * private helper functions
+ */
+
+#define NEXT_WRITE(chan) (((chan)->tail + 1) % (chan)->data_len)
+#define NEXT_READ(chan) (((chan)->head + 1) % (chan)->data_len)
+
+#define ELEM(chan, i) \
+ (void *)((char *)(chan)->data + (i) * (chan)->elem_size)
+#define TAIL(chan) ELEM(chan, (chan)->tail)
+#define HEAD(chan) ELEM(chan, (chan)->head)
+
+/* Insert a new element at the end. */
+static int
+channel_write(sdb_channel_t *chan, const void *data)
+{
+ assert(chan && data);
+
+ if (chan->full)
+ return -1;
+
+ memcpy(TAIL(chan), data, chan->elem_size);
+ chan->tail = NEXT_WRITE(chan);
+
+ chan->full = chan->tail == chan->head;
+ return 0;
+} /* channel_write */
+
+/* retrieve the first element */
+static int
+channel_read(sdb_channel_t *chan, void *data)
+{
+ assert(chan && data);
+
+ if ((chan->head == chan->tail) && (! chan->full))
+ return -1;
+
+ memcpy(data, HEAD(chan), chan->elem_size);
+ chan->head = NEXT_READ(chan);
+
+ chan->full = 0;
+ return 0;
+} /* channel_read */
+
+/*
+ * public API
+ */
+
+sdb_channel_t *
+sdb_channel_create(size_t size, size_t elem_size)
+{
+ sdb_channel_t *chan;
+
+ if (! elem_size)
+ return NULL;
+ if (! size)
+ size = 1;
+
+ chan = calloc(1, sizeof(*chan));
+ if (! chan)
+ return NULL;
+
+ chan->data = calloc(size, elem_size);
+ if (! chan->data) {
+ sdb_channel_destroy(chan);
+ return NULL;
+ }
+
+ chan->data_len = size;
+ chan->elem_size = elem_size;
+
+ pthread_rwlock_init(&chan->lock, /* attr = */ NULL);
+
+ chan->head = chan->tail = 0;
+ return chan;
+} /* sdb_channel_create */
+
+void
+sdb_channel_destroy(sdb_channel_t *chan)
+{
+ if (! chan)
+ return;
+
+ pthread_rwlock_wrlock(&chan->lock);
+ free(chan->data);
+ chan->data = NULL;
+ chan->data_len = 0;
+
+ pthread_rwlock_unlock(&chan->lock);
+ pthread_rwlock_destroy(&chan->lock);
+ free(chan);
+} /* sdb_channel_destroy */
+
+int
+sdb_channel_write(sdb_channel_t *chan, const void *data)
+{
+ int status;
+
+ if ((! chan) || (! data))
+ return -1;
+
+ pthread_rwlock_wrlock(&chan->lock);
+ status = channel_write(chan, data);
+ pthread_rwlock_unlock(&chan->lock);
+ return status;
+} /* sdb_channel_write */
+
+int
+sdb_channel_read(sdb_channel_t *chan, void *data)
+{
+ int status;
+
+ if ((! chan) || (! data))
+ return -1;
+
+ pthread_rwlock_wrlock(&chan->lock);
+ status = channel_read(chan, data);
+ pthread_rwlock_unlock(&chan->lock);
+ return status;
+} /* sdb_channel_read */
+
+/* vim: set tw=78 sw=4 ts=4 noexpandtab : */
+