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

[Anatoly Burakov]

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

Signed-off-by: Anatoly Burakov <anatoly.bura...@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