*
* PURPOSE: Ring buffer management
* Description: Support and management functions for ring buffers
+ * All synchronization must be provided by the user.
*
* $Id:$
**********************************************************************/
* dapls_rbuf_alloc
*
* Given a DAPL_RING_BUFFER, initialize it and provide memory for
- * the ringbuf itself. A passed in size will be adjusted to the next
- * largest power of two number to simplify management.
+ * the ringbuf itself.
*
* Input:
* rbuf pointer to DAPL_RING_BUFFER
*/
DAT_RETURN dapls_rbuf_alloc(INOUT DAPL_RING_BUFFER * rbuf, IN DAT_COUNT size)
{
- unsigned int rsize; /* real size */
-
/* The circular buffer must be allocated one too large.
* This eliminates any need for a distinct counter, as
* having the two pointers equal always means "empty" -- never "full"
*/
size++;
- /* Put size on a power of 2 boundary */
- rsize = 1;
- while ((DAT_COUNT) rsize < size) {
- rsize <<= 1;
- }
-
- rbuf->base = (void *)dapl_os_alloc(rsize * sizeof(void *));
- if (rbuf->base != NULL) {
- rbuf->lim = rsize - 1;
- dapl_os_atomic_set(&rbuf->head, 0);
- dapl_os_atomic_set(&rbuf->tail, 0);
- } else {
+ rbuf->base = (void *)dapl_os_alloc(size * sizeof(void *));
+ if (rbuf->base == NULL)
return DAT_INSUFFICIENT_RESOURCES | DAT_RESOURCE_MEMORY;
- }
+ rbuf->size = size;
+ rbuf->head = 0;
+ rbuf->tail = 0;
return DAT_SUCCESS;
}
/*
* dapls_rbuf_realloc
*
- * Resizes a DAPL_RING_BUFFER. This function is not thread safe;
- * adding or removing elements from a ring buffer while resizing
- * will have indeterminate results.
+ * Resizes a DAPL_RING_BUFFER.
*
* Input:
* rbuf pointer to DAPL_RING_BUFFER
*/
DAT_RETURN dapls_rbuf_realloc(INOUT DAPL_RING_BUFFER * rbuf, IN DAT_COUNT size)
{
- DAPL_RING_BUFFER new_rbuf;
- void *entry;
- DAT_RETURN dat_status;
-
- dat_status = DAT_SUCCESS;
+ void **base;
/* decreasing the size or retaining the old size is not allowed */
- if (size <= rbuf->lim + 1) {
- dat_status = DAT_ERROR(DAT_INVALID_PARAMETER, DAT_INVALID_ARG2);
- goto bail;
- }
+ if (size <= rbuf->size + 1)
+ return DAT_ERROR(DAT_INVALID_PARAMETER, DAT_INVALID_ARG2);
- /*
- * !This is NOT ATOMIC!
- * Simple algorithm: Allocate a new ring buffer, take everything
- * out of the old one and put it in the new one, and release the
- * old base buffer.
- */
- dat_status = dapls_rbuf_alloc(&new_rbuf, size);
- if (dat_status != DAT_SUCCESS) {
- goto bail;
- }
+ base = (void *) dapl_os_alloc(size * sizeof(void *));
+ if (base == NULL)
+ return DAT_INSUFFICIENT_RESOURCES | DAT_RESOURCE_MEMORY;
- while ((entry = dapls_rbuf_remove(rbuf)) != NULL) {
- /* We know entries will fit so ignore the return code */
- (void)dapls_rbuf_add(&new_rbuf, entry);
+ if (rbuf->head > rbuf->tail) {
+ memcpy(&base[rbuf->tail], &rbuf->base[rbuf->tail],
+ (rbuf->head - rbuf->tail) * sizeof(void *));
+ } else if (rbuf->head < rbuf->tail) {
+ memcpy(&base[0], &rbuf->base[rbuf->tail],
+ (rbuf->size - rbuf->tail) * sizeof(void *));
+ memcpy(&base[rbuf->size - rbuf->tail], &rbuf->base[0],
+ rbuf->head * sizeof(void *));
+ rbuf->head = rbuf->size - rbuf->tail + rbuf->head;
+ rbuf->tail = 0;
}
- /* release the old base buffer */
- dapl_os_free(rbuf->base, (rbuf->lim + 1) * sizeof(void *));
-
- *rbuf = new_rbuf;
+ dapl_os_free(rbuf->base, rbuf->size * sizeof(void *));
+ rbuf->base = base;
+ rbuf->size = size;
- bail:
- return dat_status;
+ return DAT_SUCCESS;
}
/*
*/
void dapls_rbuf_destroy(IN DAPL_RING_BUFFER * rbuf)
{
- if ((NULL == rbuf) || (NULL == rbuf->base)) {
- return;
- }
-
- dapl_os_free(rbuf->base, (rbuf->lim + 1) * sizeof(void *));
- rbuf->base = NULL;
- rbuf->lim = 0;
-
- return;
+ dapl_os_free(rbuf->base, rbuf->size * sizeof(void *));
}
/*
*/
DAT_RETURN dapls_rbuf_add(IN DAPL_RING_BUFFER * rbuf, IN void *entry)
{
- int pos;
- int val;
+ DAT_RETURN ret;
- while (((dapl_os_atomic_read(&rbuf->head) + 1) & rbuf->lim) !=
- (dapl_os_atomic_read(&rbuf->tail) & rbuf->lim)) {
- pos = dapl_os_atomic_read(&rbuf->head);
- val = dapl_os_atomic_assign(&rbuf->head, pos, pos + 1);
- if (val == pos) {
- pos = (pos + 1) & rbuf->lim; /* verify in range */
- rbuf->base[pos] = entry;
- return DAT_SUCCESS;
- }
+ if (dapls_rbuf_count(rbuf) < rbuf->size - 1) {
+ rbuf->base[rbuf->head++] = entry;
+ if (rbuf->head == rbuf->size)
+ rbuf->head = 0;
+ ret = DAT_SUCCESS;
+ } else {
+ ret = DAT_ERROR(DAT_INSUFFICIENT_RESOURCES, DAT_RESOURCE_MEMORY);
}
- return DAT_ERROR(DAT_INSUFFICIENT_RESOURCES, DAT_RESOURCE_MEMORY);
-
+ return ret;
}
/*
*/
void *dapls_rbuf_remove(IN DAPL_RING_BUFFER * rbuf)
{
- int pos;
- int val;
-
- while (dapl_os_atomic_read(&rbuf->head) !=
- dapl_os_atomic_read(&rbuf->tail)) {
- pos = dapl_os_atomic_read(&rbuf->tail);
- val = dapl_os_atomic_assign(&rbuf->tail, pos, pos + 1);
- if (val == pos) {
- pos = (pos + 1) & rbuf->lim; /* verify in range */
+ void *entry;
- return (rbuf->base[pos]);
- }
+ if (!dapls_rbuf_empty(rbuf)) {
+ entry = rbuf->base[rbuf->tail++];
+ if (rbuf->tail == rbuf->size)
+ rbuf->tail = 0;
+ } else {
+ entry = NULL;
}
- return NULL;
+ return entry;
}
/*
- * dapli_rbuf_count
+ * dapls_rbuf_count
*
* Return the number of entries in use in the ring buffer
*
*/
DAT_COUNT dapls_rbuf_count(IN DAPL_RING_BUFFER * rbuf)
{
- DAT_COUNT count;
- int head;
- int tail;
-
- head = dapl_os_atomic_read(&rbuf->head) & rbuf->lim;
- tail = dapl_os_atomic_read(&rbuf->tail) & rbuf->lim;
- if (head > tail) {
- count = head - tail;
- } else {
- /* add 1 to lim as it is a mask, number of entries - 1 */
- count = (rbuf->lim + 1 - tail + head) & rbuf->lim;
- }
-
- return count;
+ if (rbuf->head >= rbuf->tail)
+ return rbuf->head - rbuf->tail;
+ else
+ return rbuf->size - rbuf->tail + rbuf->head;
}
/*
*/
void dapls_rbuf_adjust(IN DAPL_RING_BUFFER * rbuf, IN intptr_t offset)
{
- int pos;
+ int i;
- pos = dapl_os_atomic_read(&rbuf->head);
- while (pos != dapl_os_atomic_read(&rbuf->tail)) {
- rbuf->base[pos] = (void *)((char *)rbuf->base[pos] + offset);
- pos = (pos + 1) & rbuf->lim; /* verify in range */
- }
+ for (i = 0; i < rbuf->size; i++)
+ rbuf->base[i] = (void *) ((char *)rbuf->base[i] + offset);
}
-/*
- * Local variables:
- * c-indent-level: 4
- * c-basic-offset: 4
- * tab-width: 8
- * End:
- */
+int dapls_rbuf_empty(IN DAPL_RING_BUFFER * rbuf)
+{
+ return rbuf->head == rbuf->tail;
+}
projects / ~shefty / rdma-win.git / commitdiff