diff options
Diffstat (limited to 'VES5.0/evel/evel-library/code/evel_library/ring_buffer.c')
| -rw-r--r-- | VES5.0/evel/evel-library/code/evel_library/ring_buffer.c | 206 |
1 files changed, 206 insertions, 0 deletions
diff --git a/VES5.0/evel/evel-library/code/evel_library/ring_buffer.c b/VES5.0/evel/evel-library/code/evel_library/ring_buffer.c new file mode 100644 index 00000000..3795ed36 --- /dev/null +++ b/VES5.0/evel/evel-library/code/evel_library/ring_buffer.c @@ -0,0 +1,206 @@ +/**************************************************************************//** + * @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; +} + |