return result;
}
+static int
+find_prev_n(const struct rte_fbarray *arr, unsigned int start, unsigned int n,
+ bool used)
+{
+ const struct used_mask *msk = get_used_mask(arr->data, arr->elt_sz,
+ arr->len);
+ unsigned int msk_idx, lookbehind_idx, first, first_mod;
+ uint64_t ignore_msk;
+
+ /*
+ * mask only has granularity of MASK_ALIGN, but start may not be aligned
+ * on that boundary, so construct a special mask to exclude anything we
+ * don't want to see to avoid confusing ctz.
+ */
+ first = MASK_LEN_TO_IDX(start);
+ first_mod = MASK_LEN_TO_MOD(start);
+ /* we're going backwards, so mask must start from the top */
+ ignore_msk = first_mod == MASK_ALIGN - 1 ?
+ -1ULL : /* prevent overflow */
+ ~(-1ULL << (first_mod + 1));
+
+ /* go backwards, include zero */
+ msk_idx = first;
+ do {
+ uint64_t cur_msk, lookbehind_msk;
+ unsigned int run_start, run_end, ctz, left;
+ bool found = false;
+ /*
+ * The process of getting n consecutive bits from the top for
+ * arbitrary n is a bit involved, but here it is in a nutshell:
+ *
+ * 1. let n be the number of consecutive bits we're looking for
+ * 2. check if n can fit in one mask, and if so, do n-1
+ * lshift-ands to see if there is an appropriate run inside
+ * our current mask
+ * 2a. if we found a run, bail out early
+ * 2b. if we didn't find a run, proceed
+ * 3. invert the mask and count trailing zeroes (that is, count
+ * how many consecutive set bits we had starting from the
+ * start of current mask) as k
+ * 3a. if k is 0, continue to next mask
+ * 3b. if k is not 0, we have a potential run
+ * 4. to satisfy our requirements, next mask must have n-k
+ * consecutive set bits at the end, so we will do (n-k-1)
+ * lshift-ands and check if last bit is set.
+ *
+ * Step 4 will need to be repeated if (n-k) > MASK_ALIGN until
+ * we either run out of masks, lose the run, or find what we
+ * were looking for.
+ */
+ cur_msk = msk->data[msk_idx];
+ left = n;
+
+ /* if we're looking for free spaces, invert the mask */
+ if (!used)
+ cur_msk = ~cur_msk;
+
+ /* if we have an ignore mask, ignore once */
+ if (ignore_msk) {
+ cur_msk &= ignore_msk;
+ ignore_msk = 0;
+ }
+
+ /* if n can fit in within a single mask, do a search */
+ if (n <= MASK_ALIGN) {
+ uint64_t tmp_msk = cur_msk;
+ unsigned int s_idx;
+ for (s_idx = 0; s_idx < n - 1; s_idx++)
+ tmp_msk &= tmp_msk << 1ULL;
+ /* we found what we were looking for */
+ if (tmp_msk != 0) {
+ /* clz will give us offset from end of mask, and
+ * we only get the end of our run, not start,
+ * so adjust result to point to where start
+ * would have been.
+ */
+ run_start = MASK_ALIGN -
+ __builtin_clzll(tmp_msk) - n;
+ return MASK_GET_IDX(msk_idx, run_start);
+ }
+ }
+
+ /*
+ * we didn't find our run within the mask, or n > MASK_ALIGN,
+ * so we're going for plan B.
+ */
+
+ /* count trailing zeroes on inverted mask */
+ if (~cur_msk == 0)
+ ctz = sizeof(cur_msk) * 8;
+ else
+ ctz = __builtin_ctzll(~cur_msk);
+
+ /* if there aren't any runs at the start either, just
+ * continue
+ */
+ if (ctz == 0)
+ continue;
+
+ /* we have a partial run at the start, so try looking behind */
+ run_end = MASK_GET_IDX(msk_idx, ctz);
+ left -= ctz;
+
+ /* go backwards, include zero */
+ lookbehind_idx = msk_idx - 1;
+
+ /* we can't lookbehind as we've run out of masks, so stop */
+ if (msk_idx == 0)
+ break;
+
+ do {
+ const uint64_t last_bit = 1ULL << (MASK_ALIGN - 1);
+ unsigned int s_idx, need;
+
+ lookbehind_msk = msk->data[lookbehind_idx];
+
+ /* if we're looking for free space, invert the mask */
+ if (!used)
+ lookbehind_msk = ~lookbehind_msk;
+
+ /* figure out how many consecutive bits we need here */
+ need = RTE_MIN(left, MASK_ALIGN);
+
+ for (s_idx = 0; s_idx < need - 1; s_idx++)
+ lookbehind_msk &= lookbehind_msk << 1ULL;
+
+ /* if last bit is not set, we've lost the run */
+ if ((lookbehind_msk & last_bit) == 0) {
+ /*
+ * we've scanned this far, so we know there are
+ * no runs in the space we've lookbehind-scanned
+ * as well, so skip that on next iteration.
+ */
+ ignore_msk = -1ULL << need;
+ msk_idx = lookbehind_idx;
+ break;
+ }
+
+ left -= need;
+
+ /* check if we've found what we were looking for */
+ if (left == 0) {
+ found = true;
+ break;
+ }
+ } while ((lookbehind_idx--) != 0); /* decrement after check to
+ * include zero
+ */
+
+ /* we didn't find anything, so continue */
+ if (!found)
+ continue;
+
+ /* we've found what we were looking for, but we only know where
+ * the run ended, so calculate start position.
+ */
+ return run_end - n;
+ } while (msk_idx-- != 0); /* decrement after check to include zero */
+ /* we didn't find anything */
+ rte_errno = used ? ENOENT : ENOSPC;
+ return -1;
+}
+
static int
find_prev(const struct rte_fbarray *arr, unsigned int start, bool used)
{
static int
fbarray_find_n(struct rte_fbarray *arr, unsigned int start, unsigned int n,
- bool used)
+ bool next, bool used)
{
int ret = -1;
rte_errno = EINVAL;
return -1;
}
- if (arr->len - start < n) {
+ if (next && (arr->len - start) < n) {
+ rte_errno = used ? ENOENT : ENOSPC;
+ return -1;
+ }
+ if (!next && start < (n - 1)) {
rte_errno = used ? ENOENT : ENOSPC;
return -1;
}
goto out;
}
if (arr->count == 0) {
- ret = start;
+ ret = next ? start : start - n + 1;
goto out;
}
} else {
goto out;
}
if (arr->count == arr->len) {
- ret = start;
+ ret = next ? start : start - n + 1;
goto out;
}
}
- ret = find_next_n(arr, start, n, used);
+ if (next)
+ ret = find_next_n(arr, start, n, used);
+ else
+ ret = find_prev_n(arr, start, n, used);
out:
rte_rwlock_read_unlock(&arr->rwlock);
return ret;
rte_fbarray_find_next_n_free(struct rte_fbarray *arr, unsigned int start,
unsigned int n)
{
- return fbarray_find_n(arr, start, n, false);
+ return fbarray_find_n(arr, start, n, true, false);
}
int __rte_experimental
rte_fbarray_find_next_n_used(struct rte_fbarray *arr, unsigned int start,
unsigned int n)
{
- return fbarray_find_n(arr, start, n, true);
+ return fbarray_find_n(arr, start, n, true, true);
+}
+
+int __rte_experimental
+rte_fbarray_find_prev_n_free(struct rte_fbarray *arr, unsigned int start,
+ unsigned int n)
+{
+ return fbarray_find_n(arr, start, n, false, false);
+}
+
+int __rte_experimental
+rte_fbarray_find_prev_n_used(struct rte_fbarray *arr, unsigned int start,
+ unsigned int n)
+{
+ return fbarray_find_n(arr, start, n, false, true);
}
static int
git.droids-corp.org / dpdk.git / commitdiff