[dpdk-dev] [PATCH v3] hash: added a new API to hash to query key id

[Kumar Amber <kumar.amber@intel.com>]

Adding new API function to query the maximum key ID
that could possibly returned by rte_hash_add_key and
rte_hash_add_key_with_hash. When RTE_HASH_EXTRA_FLAGS_MULTI_WRITER_ADD
is set, the maximum key id is larger than the entry count specified
by the user.

Signed-off-by: Kumar Amber <kumar.amber@intel.com>
---
 lib/librte_hash/rte_cuckoo_hash.c    | 15 +++++++++++++++
 lib/librte_hash/rte_hash.h           | 25 +++++++++++++++++++++++--
 lib/librte_hash/rte_hash_version.map |  1 +
 3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/lib/librte_hash/rte_cuckoo_hash.c b/lib/librte_hash/rte_cuckoo_hash.c
index 87a4c01f2..3a94f10b8 100644
--- a/lib/librte_hash/rte_cuckoo_hash.c
+++ b/lib/librte_hash/rte_cuckoo_hash.c
@@ -506,6 +506,21 @@ rte_hash_hash(const struct rte_hash *h, const void *key)
 	return h->hash_func(key, h->key_len, h->hash_func_init_val);
 }
 
+uint32_t
+rte_hash_max_key_id(const struct rte_hash *h)
+{
+	RETURN_IF_TRUE((h == NULL), -EINVAL);
+	if (h->use_local_cache)
+		/*
+		 * Increase number of slots by total number of indices
+		 * that can be stored in the lcore caches
+		 */
+		return (h->entries + ((RTE_MAX_LCORE - 1) *
+					(LCORE_CACHE_SIZE - 1)));
+	else
+		return h->entries;
+}
+
 int32_t
 rte_hash_count(const struct rte_hash *h)
 {
diff --git a/lib/librte_hash/rte_hash.h b/lib/librte_hash/rte_hash.h
index 0d73370dc..c87861e72 100644
--- a/lib/librte_hash/rte_hash.h
+++ b/lib/librte_hash/rte_hash.h
@@ -164,6 +164,23 @@ rte_hash_reset(struct rte_hash *h);
 int32_t
 rte_hash_count(const struct rte_hash *h);
 
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice
+ *
+ * Return  the maximum key value ID that could possibly be returned by
+ * rte_hash_add_key function.
+ *
+ * @param h
+ *  Hash table to query from
+ * @return
+ *   - -EINVAL if parameters are invalid
+ *   - A value indicating the max key Id  key slots present in the table.
+ */
+__rte_experimental
+uint32_t
+rte_hash_max_key_id(const struct rte_hash *h);
+
 /**
  * Add a key-value pair to an existing hash table.
  * This operation is not multi-thread safe
@@ -234,7 +251,9 @@ rte_hash_add_key_with_hash_data(const struct rte_hash *h, const void *key,
  *   - -EINVAL if the parameters are invalid.
  *   - -ENOSPC if there is no space in the hash for this key.
  *   - A positive value that can be used by the caller as an offset into an
- *     array of user data. This value is unique for this key.
+ *     array of user data. This value is unique for this key. This
+ *     unique key id may be larger than the user specified entry count
+ *     when RTE_HASH_EXTRA_FLAGS_MULTI_WRITER_ADD flag is set.
  */
 int32_t
 rte_hash_add_key(const struct rte_hash *h, const void *key);
@@ -256,7 +275,9 @@ rte_hash_add_key(const struct rte_hash *h, const void *key);
  *   - -EINVAL if the parameters are invalid.
  *   - -ENOSPC if there is no space in the hash for this key.
  *   - A positive value that can be used by the caller as an offset into an
- *     array of user data. This value is unique for this key.
+ *     array of user data. This value is unique for this key. This
+ *     unique key ID may be larger than the user specified entry count
+ *     when RTE_HASH_EXTRA_FLAGS_MULTI_WRITER_ADD flag is set.
  */
 int32_t
 rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key, hash_sig_t sig);
diff --git a/lib/librte_hash/rte_hash_version.map b/lib/librte_hash/rte_hash_version.map
index 734ae28b0..562ceb8bc 100644
--- a/lib/librte_hash/rte_hash_version.map
+++ b/lib/librte_hash/rte_hash_version.map
@@ -58,5 +58,6 @@ EXPERIMENTAL {
 	global:
 
 	rte_hash_free_key_with_position;
+    rte_hash_max_key_id;
 
 };
-- 
2.17.1