kvargs: add get by key

Adds a new function to get value of a specific key from kvargs list.

Signed-off-by: Xueming Li <xuemingl@nvidia.com>
Reviewed-by: Gaetan Rivet <grive@u256.net>

lib/librte_kvargs/rte_kvargs.c

@@ -203,6 +203,21 @@ rte_kvargs_free(struct rte_kvargs *kvlist)
 	free(kvlist);
 }
 
+/* Lookup a value in an rte_kvargs list by its key. */
+const char *
+rte_kvargs_get(const struct rte_kvargs *kvlist, const char *key)
+{
+	unsigned int i;
+
+	if (kvlist == NULL || key == NULL)
+		return NULL;
+	for (i = 0; i < kvlist->count; ++i) {
+		if (strcmp(kvlist->pairs[i].key, key) == 0)
+			return kvlist->pairs[i].value;
+	}
+	return NULL;
+}
+
 /*
  * Parse the arguments "key=value,key=value,..." string and return
  * an allocated structure that contains a key/value list. Also

lib/librte_kvargs/rte_kvargs.h

@@ -114,6 +114,26 @@ struct rte_kvargs *rte_kvargs_parse_delim(const char *args,
  */
 void rte_kvargs_free(struct rte_kvargs *kvlist);
 
+/**
+ * Get the value associated with a given key.
+ *
+ * If multiple key matches, the value of the first one is returned.
+ *
+ * The memory returned is allocated as part of the rte_kvargs structure,
+ * it must never be modified.
+ *
+ * @param kvlist
+ *   A list of rte_kvargs pair of 'key=value'.
+ * @param key
+ *   The matching key.
+
+ * @return
+ *   NULL if no key matches the input,
+ *   a value associated with a matching key otherwise.
+ */
+__rte_experimental
+const char *rte_kvargs_get(const struct rte_kvargs *kvlist, const char *key);
+
 /**
  * Call a handler function for each key/value matching the key
  *

lib/librte_kvargs/version.map

@@ -15,4 +15,6 @@ EXPERIMENTAL {
 	rte_kvargs_parse_delim;
 	rte_kvargs_strcmp;
 
+	# added in 21.05
+	rte_kvargs_get;
 };