common/json_parse_simple: make convenience functions inline

json_tok_streq(…) and json_get_member(…) are convenience wrappers for
json_tok_strneq(…) and json_get_membern(…) respectively. Unfortunately, using
them incurs a performance penalty in the common case where they are called with
a string literal argument because the compiler is unable to substitute a
compile-time constant in place of the buried call to strlen(…).

For example,

	json_get_member(buf, tok, "example");

…will have worse performance than…

	json_get_membern(buf, tok, "example", strlen("example"));

…because the former is forced to scan over "example" at run-time to count its
length whereas the latter is able to elide the strlen(…) call at compile time.

Hoist these convenience functions up into common/json_parse_simple.h and mark
them as inline so that the compiler can elide the strlen(…) call in the common
case of calling these functions with a string literal argument.

Changelog-None

Author: whitslack

common/json_parse_simple.c

@@ -33,11 +33,6 @@ bool json_tok_strneq(const char *buffer, const jsmntok_t *tok,
 	return memeq(buffer + tok->start, tok->end - tok->start, str, len);
 }
 
-bool json_tok_streq(const char *buffer, const jsmntok_t *tok, const char *str)
-{
-	return json_tok_strneq(buffer, tok, str, strlen(str));
-}
-
 bool json_tok_startswith(const char *buffer, const jsmntok_t *tok,
 			 const char *prefix)
 {
@@ -217,12 +212,6 @@ const jsmntok_t *json_get_membern(const char *buffer,
 	return NULL;
 }
 
-const jsmntok_t *json_get_member(const char *buffer, const jsmntok_t tok[],
-				 const char *label)
-{
-	return json_get_membern(buffer, tok, label, strlen(label));
-}
-
 const jsmntok_t *json_get_arr(const jsmntok_t tok[], size_t index)
 {
 	const jsmntok_t *t;

common/json_parse_simple.h

@@ -14,13 +14,17 @@ const char *json_tok_full(const char *buffer, const jsmntok_t *t);
 /* Include " if it's a string. */
 int json_tok_full_len(const jsmntok_t *t);
 
-/* Is this a string equal to str? */
-bool json_tok_streq(const char *buffer, const jsmntok_t *tok, const char *str);
-
 /* Is this a string equal to str of length len? */
 bool json_tok_strneq(const char *buffer, const jsmntok_t *tok,
 		     const char *str, size_t len);
 
+/* Is this a string equal to str? */
+static inline bool json_tok_streq(const char *buffer, const jsmntok_t *tok,
+				  const char *str)
+{
+	return json_tok_strneq(buffer, tok, str, strlen(str));
+}
+
 /* Does this string token start with prefix? */
 bool json_tok_startswith(const char *buffer, const jsmntok_t *tok,
 			 const char *prefix);
@@ -66,8 +70,12 @@ const jsmntok_t *json_get_membern(const char *buffer,
 				  const char *label, size_t len);
 
 /* Get top-level member. */
-const jsmntok_t *json_get_member(const char *buffer, const jsmntok_t tok[],
-				 const char *label);
+static inline const jsmntok_t *json_get_member(const char *buffer,
+					       const jsmntok_t tok[],
+					       const char *label)
+{
+	return json_get_membern(buffer, tok, label, strlen(label));
+}
 
 /* Get index'th array member. */
 const jsmntok_t *json_get_arr(const jsmntok_t tok[], size_t index);