--- /dev/null
+/**************************************************************************//**
+ * @file
+ * A ring buffer with multi-threaded synchronization.
+ *
+ * License
+ * -------
+ *
+ * Copyright(c) <2016>, AT&T Intellectual Property. All other 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.
+ * 3. All advertising materials mentioning features or use of this software
+ * must display the following acknowledgement: This product includes
+ * software developed by the AT&T.
+ * 4. Neither the name of AT&T nor the names of its contributors may be used to
+ * endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY AT&T INTELLECTUAL PROPERTY ''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 AT&T INTELLECTUAL PROPERTY 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 <assert.h>
+#include <malloc.h>
+
+#include "ring_buffer.h"
+#include "evel.h"
+
+/**************************************************************************//**
+ * Ring buffer initialization.
+ *
+ * Initialize the buffer supplied to the specified size.
+ *
+ * @param buffer Pointer to the ring-buffer to be initialized.
+ * @param size How many elements to be stored in the ring-buffer.
+ *
+ * @returns Nothing
+******************************************************************************/
+void ring_buffer_initialize(ring_buffer * buffer, int size)
+{
+ int pthread_rc = 0;
+
+ EVEL_ENTER();
+
+ /***************************************************************************/
+ /* Check assumptions. */
+ /***************************************************************************/
+ assert(buffer != NULL);
+ assert(size > 0);
+
+ /***************************************************************************/
+ /* Initialize the synchronization objects. */
+ /***************************************************************************/
+ pthread_rc = pthread_mutex_init(&buffer->ring_mutex, NULL);
+ assert(pthread_rc == 0);
+ pthread_rc = pthread_cond_init(&buffer->ring_cv, NULL);
+ assert(pthread_rc == 0);
+
+ /***************************************************************************/
+ /* Allocate the ring buffer itself. */
+ /***************************************************************************/
+ buffer->ring = malloc(size * sizeof(void *));
+ assert(buffer->ring != NULL);
+
+ /***************************************************************************/
+ /* Initialize the ring as empty. */
+ /***************************************************************************/
+ buffer->next_write = 0;
+ buffer->next_read = 0;
+ buffer->size = size;
+
+ EVEL_EXIT();
+}
+
+/**************************************************************************//**
+ * Read an element from a ring_buffer.
+ *
+ * Reads an element from the ring_buffer, advancing the next-read position.
+ * Operation is synchronized and therefore MT-safe. Blocks if no data is
+ * available.
+ *
+ * @param buffer Pointer to the ring-buffer to be read.
+ *
+ * @returns Pointer to the element read from the buffer.
+******************************************************************************/
+void * ring_buffer_read(ring_buffer * buffer)
+{
+ void *msg = NULL;
+ EVEL_DEBUG("RBR: Ring buffer read");
+
+ pthread_mutex_lock(&buffer->ring_mutex);
+ while (1)
+ {
+ EVEL_DEBUG("RBR: got lock. NR=%d NW=%d",
+ buffer->next_read,
+ buffer->next_write);
+ if(buffer->next_read != buffer->next_write)
+ {
+ EVEL_DEBUG("RBR: buffer has item available");
+ msg = (buffer->ring)[buffer->next_read];
+ buffer->ring[buffer->next_read] = NULL;
+ buffer->next_read = (buffer->next_read + 1) % buffer->size;
+ EVEL_DEBUG("RBR: next read location is %d", buffer->next_read);
+ pthread_mutex_unlock(&buffer->ring_mutex);
+ break;
+ }
+ else
+ {
+ EVEL_DEBUG("RBR: Waiting for condition variable");
+ pthread_cond_wait(&buffer->ring_cv, &buffer->ring_mutex);
+ EVEL_DEBUG("RBR: Condition variable wait completed");
+ }
+ }
+ EVEL_DEBUG("RBR: Ring buffer read returning data at %lp", msg);
+ return msg;
+}
+
+/**************************************************************************//**
+ * Write an element into a ring_buffer.
+ *
+ * Writes an element into the ring_buffer, advancing the next-write position.
+ * Operation is synchronized and therefore MT-safe. Fails if the buffer is
+ * full without blocking.
+ *
+ * @param buffer Pointer to the ring-buffer to be written.
+ * @param msg Pointer to data to be stored in the ring_buffer.
+ *
+ * @returns Number of items written.
+ * @retval 1 The data was written successfully.
+ * @retval 0 The ring_buffer was full so no data written.
+******************************************************************************/
+int ring_buffer_write(ring_buffer * buffer, void * msg)
+{
+ int item_count = 0;
+ int items_written = 0;
+ EVEL_DEBUG("RBW: Ring Buffer Write message at %lp", msg);
+
+ pthread_mutex_lock(&buffer->ring_mutex);
+ EVEL_DEBUG("RBW: got lock. NR=%d NW=%d SZ=%d",
+ buffer->next_read,
+ buffer->next_write,
+ buffer->size);
+
+ item_count = (buffer->next_write - buffer->next_read) % buffer->size;
+ if (item_count < 0)
+ {
+ item_count += buffer->size;
+ }
+ if (item_count < buffer->size - 1)
+ {
+ EVEL_DEBUG("RBW: %d items in buffer", item_count);
+ buffer->ring[buffer->next_write] = msg;
+ buffer->next_write = (buffer->next_write + 1) % buffer->size;
+ EVEL_DEBUG("RBW: next write location is %d", buffer->next_write);
+ items_written = 1;
+ }
+ else
+ {
+ EVEL_ERROR("RBW: ring buffer full - unable to write event");
+ }
+
+ pthread_mutex_unlock(&buffer->ring_mutex);
+ EVEL_DEBUG("RBW: released lock");
+ pthread_cond_signal(&buffer->ring_cv);
+
+ return items_written;
+}
+
+/**************************************************************************//**
+ * Tests whether there is data in the ring_buffer.
+ *
+ * Tests whether there is currently data in the ring_buffer without blocking.
+ *
+ * @param buffer Pointer to the ring-buffer to be tested.
+ *
+ * @returns Whether there is data in the ring_buffer.
+ * @retval 0 There isn't any data in the ring_buffer.
+ * @retval 1 There is data in the ring_buffer.
+******************************************************************************/
+int ring_buffer_is_empty(ring_buffer * buffer)
+{
+ int is_empty = 0;
+ EVEL_DEBUG("RBE: Ring empty check");
+
+ pthread_mutex_lock(&buffer->ring_mutex);
+ is_empty = (buffer->next_read == buffer->next_write);
+ pthread_mutex_unlock(&buffer->ring_mutex);
+
+ EVEL_DEBUG("RBE: Ring state= %d", is_empty);
+ return is_empty;
+}
+
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