[dpdk-dev] [PATCH 3/9] fbarray: reduce duplication in find_next_n code

[Anatoly Burakov <anatoly.burakov@intel.com>]

Mostly code move, aside from more quick checks done to avoid
doing computations in obviously hopeless cases.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
 lib/librte_eal/common/eal_common_fbarray.c | 63 ++++++++++++----------
 1 file changed, 36 insertions(+), 27 deletions(-)

diff --git a/lib/librte_eal/common/eal_common_fbarray.c b/lib/librte_eal/common/eal_common_fbarray.c
index e37fe1e4d..c5ee017dd 100644
--- a/lib/librte_eal/common/eal_common_fbarray.c
+++ b/lib/librte_eal/common/eal_common_fbarray.c
@@ -723,54 +723,63 @@ rte_fbarray_find_next_used(struct rte_fbarray *arr, unsigned int start)
 	return ret;
 }
 
-int __rte_experimental
-rte_fbarray_find_next_n_free(struct rte_fbarray *arr, unsigned int start,
-		unsigned int n)
+static int
+fbarray_find_n(struct rte_fbarray *arr, unsigned int start, unsigned int n,
+		bool used)
 {
 	int ret = -1;
 
-	if (arr == NULL || start >= arr->len || n > arr->len) {
+	if (arr == NULL || start >= arr->len || n > arr->len || n == 0) {
 		rte_errno = EINVAL;
 		return -1;
 	}
+	if (arr->len - start < n) {
+		rte_errno = used ? ENOENT : ENOSPC;
+		return -1;
+	}
 
 	/* prevent array from changing under us */
 	rte_rwlock_read_lock(&arr->rwlock);
 
-	if (arr->len == arr->count || arr->len - arr->count < n) {
-		rte_errno = ENOSPC;
-		goto out;
+	/* cheap checks to prevent doing useless work */
+	if (!used) {
+		if (arr->len == arr->count || arr->len - arr->count < n) {
+			rte_errno = ENOSPC;
+			goto out;
+		}
+		if (arr->count == 0) {
+			ret = start;
+			goto out;
+		}
+	} else {
+		if (arr->count < n) {
+			rte_errno = ENOENT;
+			goto out;
+		}
+		if (arr->count == arr->len) {
+			ret = start;
+			goto out;
+		}
 	}
 
-	ret = find_next_n(arr, start, n, false);
+	ret = find_next_n(arr, start, n, used);
 out:
 	rte_rwlock_read_unlock(&arr->rwlock);
 	return ret;
 }
 
 int __rte_experimental
-rte_fbarray_find_next_n_used(struct rte_fbarray *arr, unsigned int start,
+rte_fbarray_find_next_n_free(struct rte_fbarray *arr, unsigned int start,
 		unsigned int n)
 {
-	int ret = -1;
-
-	if (arr == NULL || start >= arr->len || n > arr->len) {
-		rte_errno = EINVAL;
-		return -1;
-	}
-
-	/* prevent array from changing under us */
-	rte_rwlock_read_lock(&arr->rwlock);
-
-	if (arr->count < n) {
-		rte_errno = ENOENT;
-		goto out;
-	}
+	return fbarray_find_n(arr, start, n, false);
+}
 
-	ret = find_next_n(arr, start, n, true);
-out:
-	rte_rwlock_read_unlock(&arr->rwlock);
-	return ret;
+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);
 }
 
 static int
-- 
2.17.1