[dpdk-dev] [PATCH 2/9] fbarray: reduce duplication in find_contig code

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

Mostly a code move, to have all code related to find_contig in
one place. This slightly changes the API in that previously,
calling find_contig_free() on a full fbarray would've been
an error, but equivalent call to find_contig_used() on an empty
array does not return an error, leading to an inconsistency in
the API.

The decision was made to not treat this condition as an error,
because it is equivalent to calling find_contig() on an index
that just happens to be used/free, which is not an error and
will return 0.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
 lib/librte_eal/common/eal_common_fbarray.c | 52 ++++++++++++----------
 1 file changed, 28 insertions(+), 24 deletions(-)

diff --git a/lib/librte_eal/common/eal_common_fbarray.c b/lib/librte_eal/common/eal_common_fbarray.c
index 9ae942bfe..e37fe1e4d 100644
--- a/lib/librte_eal/common/eal_common_fbarray.c
+++ b/lib/librte_eal/common/eal_common_fbarray.c
@@ -773,8 +773,8 @@ rte_fbarray_find_next_n_used(struct rte_fbarray *arr, unsigned int start,
 	return ret;
 }
 
-int __rte_experimental
-rte_fbarray_find_contig_free(struct rte_fbarray *arr, unsigned int start)
+static int
+fbarray_find_contig(struct rte_fbarray *arr, unsigned int start, bool used)
 {
 	int ret = -1;
 
@@ -786,14 +786,25 @@ rte_fbarray_find_contig_free(struct rte_fbarray *arr, unsigned int start)
 	/* prevent array from changing under us */
 	rte_rwlock_read_lock(&arr->rwlock);
 
-	if (arr->len == arr->count) {
-		rte_errno = ENOSPC;
-		goto out;
-	}
-
-	if (arr->count == 0) {
-		ret = arr->len - start;
-		goto out;
+	/* cheap checks to prevent doing useless work */
+	if (used) {
+		if (arr->count == 0) {
+			ret = 0;
+			goto out;
+		}
+		if (arr->len == arr->count) {
+			ret = arr->len - start;
+			goto out;
+		}
+	} else {
+		if (arr->len == arr->count) {
+			ret = 0;
+			goto out;
+		}
+		if (arr->count == 0) {
+			ret = arr->len - start;
+			goto out;
+		}
 	}
 
 	ret = find_contig(arr, start, false);
@@ -803,22 +814,15 @@ rte_fbarray_find_contig_free(struct rte_fbarray *arr, unsigned int start)
 }
 
 int __rte_experimental
-rte_fbarray_find_contig_used(struct rte_fbarray *arr, unsigned int start)
+rte_fbarray_find_contig_free(struct rte_fbarray *arr, unsigned int start)
 {
-	int ret = -1;
-
-	if (arr == NULL || start >= arr->len) {
-		rte_errno = EINVAL;
-		return -1;
-	}
-
-	/* prevent array from changing under us */
-	rte_rwlock_read_lock(&arr->rwlock);
-
-	ret = find_contig(arr, start, true);
+	return fbarray_find_contig(arr, start, false);
+}
 
-	rte_rwlock_read_unlock(&arr->rwlock);
-	return ret;
+int __rte_experimental
+rte_fbarray_find_contig_used(struct rte_fbarray *arr, unsigned int start)
+{
+	return fbarray_find_contig(arr, start, true);
 }
 
 int __rte_experimental
-- 
2.17.1