utils/channel: Added an asynchronous I/O multiplexer.

A channel is a buffered pipe supporting multiple parallel readers and writers.

diff --git a/src/Makefile.am b/src/Makefile.am
index 3cdb58e906edbf36483dfb5c7beb81b05e6d7a30..48e77eb34071da3d5c1136a9c835c5dbf19205bc 100644 (file)
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -25,6 +25,7 @@ libsysdb_la_SOURCES = \
                core/store.c include/core/store.h \
                include/core/data.h \
                core/error.c include/core/error.h \
+               utils/channel.c include/utils/channel.h \
                utils/llist.c include/utils/llist.h \
                utils/strbuf.c include/utils/strbuf.h \
                core/time.c include/core/time.h \

diff --git a/src/include/utils/channel.h b/src/include/utils/channel.h
new file mode 100644 (file)
index 0000000..3eb7dc1
--- /dev/null
+++ b/src/include/utils/channel.h
@@ -0,0 +1,99 @@
+/*
+ * SysDB - src/include/utils/channel.h
+ * 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.
+ */
+
+#ifndef SDB_UTILS_CHANNEL_H
+#define SDB_UTILS_CHANNEL_H 1
+
+#include "core/object.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * A channel is an asynchronous I/O multiplexer supporting multiple parallel
+ * readers and writers. A channel may be buffered (depending on its 'size'
+ * attribute). Writing fails unless buffer space is available and reading
+ * fails if no data is available.
+ */
+
+struct sdb_channel;
+typedef struct sdb_channel sdb_channel_t;
+
+/*
+ * sdb_channel_create:
+ * Create a new channel for elements of size 'elem_size'. At most, 'size'
+ * elements can be buffered in the channel (default: 1).
+ *
+ * Returns:
+ *  - a channel object on success
+ *  - a negative value else
+ */
+sdb_channel_t *
+sdb_channel_create(size_t size, size_t elem_size);
+
+/*
+ * sdb_channel_destroy:
+ * Removing all pending data and destroy the specified channel freeing its
+ * memory.
+ */
+void
+sdb_channel_destroy(sdb_channel_t *chan);
+
+/*
+ * sdb_channel_write:
+ * Write an element to a channel. The memory pointed to by 'data' is copied to
+ * the buffer based on the channel's element size.
+ *
+ * Returns:
+ *  - 0 on success
+ *  - a negative value else
+ */
+int
+sdb_channel_write(sdb_channel_t *chan, const void *data);
+
+/*
+ * sdb_channel_read:
+ * Read an element from a channel. The element is copied to the location
+ * pointed to by 'data' which needs to be large enough to store a whole
+ * element based on the channel's element size.
+ *
+ * Returns:
+ *  - 0 on success
+ *  - a negative value else
+ */
+int
+sdb_channel_read(sdb_channel_t *chan, void *data);
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif /* ! SDB_UTILS_CHANNEL_H */
+
+/* vim: set tw=78 sw=4 ts=4 noexpandtab : */
+

diff --git a/src/utils/channel.c b/src/utils/channel.c
new file mode 100644 (file)
index 0000000..1b68784
--- /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 : */
+