params: add helper to provide default initialization.

@wythe points out that many cases want a default value, not NULL.
Nicer to do it in the param_parse() call.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/params.c

@@ -10,13 +10,14 @@
 struct param {
 	const char *name;
 	bool is_set;
+	bool required;
 	param_cb cb;
 	void *arg;
 	size_t argsize;
 };
 
 static void param_add(struct param **params,
-		      const char *name, param_cb cb, void *arg,
+		      const char *name, bool required, param_cb cb, void *arg,
 		      size_t argsize)
 {
 #if DEVELOPER
@@ -31,6 +32,7 @@ static void param_add(struct param **params,
 
 	last->is_set = false;
 	last->name = name;
+	last->required = required;
 	last->cb = cb;
 	last->arg = arg;
 	last->argsize = argsize;
@@ -101,7 +103,7 @@ static struct param *post_check(struct command *cmd, struct param *params)
 	struct param *last = first + tal_count(params);
 
 	/* Make sure required params were provided. */
-	while (first != last && first->argsize == 0) {
+	while (first != last && first->required) {
 		if (!first->is_set) {
 			command_fail(cmd, JSONRPC2_INVALID_PARAMS,
 				     "missing required parameter: '%s'",
@@ -214,7 +216,7 @@ static int comp_by_arg(const struct param *a, const struct param *b,
 static int comp_req_order(const struct param *a, const struct param *b,
 			  void *unused)
 {
-	if (a->argsize != 0 && b->argsize == 0)
+	if (!a->required && b->required)
 		return 0;
 	return 1;
 }
@@ -294,10 +296,11 @@ bool param_parse(struct command *cmd, const char *buffer,
 
 	va_start(ap, tokens);
 	while ((name = va_arg(ap, const char *)) != NULL) {
+		bool required = va_arg(ap, int);
 		param_cb cb = va_arg(ap, param_cb);
 		void *arg = va_arg(ap, void *);
 		size_t argsize = va_arg(ap, size_t);
-		param_add(&params, name, cb, arg, argsize);
+		param_add(&params, name, required, cb, arg, argsize);
 	}
 	va_end(ap);
 

lightningd/params.h

@@ -60,6 +60,7 @@ typedef bool(*param_cb)(const char *buffer, const jsmntok_t *tok, void *arg);
  */
 #define param_req(name, cb, arg)					\
 		  name"",						\
+		  true,							\
 		  (cb),							\
 		  (arg) + 0*sizeof((cb)((const char *)NULL,		\
 					(const jsmntok_t *)NULL,	\
@@ -72,12 +73,27 @@ typedef bool(*param_cb)(const char *buffer, const jsmntok_t *tok, void *arg);
  */
 #define param_opt(name, cb, arg)				\
 		  name"",					\
+		  false,					\
 		  (cb),						\
 		  (arg) + 0*sizeof((cb)((const char *)NULL,	\
 					(const jsmntok_t *)NULL,\
 					*(arg)) == true),	\
 		  sizeof(**(arg))
 
+/*
+ * Similar to param_req but for optional parameters.
+ * If not found during parsing, @arg will be set to @def.
+ * allocated, otherwise it will be set to NULL.
+ */
+#define param_opt_default(name, cb, arg, def)				\
+		  name"",						\
+		  false,						\
+		  (cb),							\
+		  (arg) + 0*sizeof((cb)((const char *)NULL,		\
+					(const jsmntok_t *)NULL,	\
+					(arg)) == true),		\
+		  ((void)((*arg) = (def)), 0)
+
 /*
  * For when you want an optional raw token.
  *
@@ -85,6 +101,7 @@ typedef bool(*param_cb)(const char *buffer, const jsmntok_t *tok, void *arg);
  */
 #define param_opt_tok(name, arg)					\
 		      name"",						\
+		      false,						\
 		      json_tok_tok,					\
 		      (arg) + 0*sizeof(*(arg) == (jsmntok_t *)NULL),	\
 		      sizeof(const jsmntok_t *)

lightningd/test/run-params.c

@@ -198,12 +198,12 @@ static void dup_names(void)
 
 static void null_params(void)
 {
-	uint64_t *ints = tal_arr(cmd, uint64_t, 4);
+	uint64_t *ints = tal_arr(cmd, uint64_t, 5);
-	uint64_t **intptrs = tal_arr(cmd, uint64_t *, 3);
+	uint64_t **intptrs = tal_arr(cmd, uint64_t *, 2);
 	/* no null params */
 	struct json *j =
 	    json_parse(cmd, "[ '10', '11', '12', '13', '14', '15', '16']");
-	for (int i = 0; i < tal_count(ints); ++i)
+	for (int i = 0; i < tal_count(ints) - 1; ++i)
 		ints[i] = i;
 
 	assert(param_parse(cmd, j->buffer, j->toks,
@@ -211,9 +211,9 @@ static void null_params(void)
 			   param_req("1", json_tok_u64, &ints[1]),
 			   param_req("2", json_tok_u64, &ints[2]),
 			   param_req("3", json_tok_u64, &ints[3]),
-			   param_opt("4", json_tok_u64, &intptrs[0]),
+			   param_opt_default("4", json_tok_u64, &ints[4], 999),
-			   param_opt("5", json_tok_u64, &intptrs[1]),
+			   param_opt("5", json_tok_u64, &intptrs[0]),
-			   param_opt("6", json_tok_u64, &intptrs[2]),
+			   param_opt("6", json_tok_u64, &intptrs[1]),
 			   NULL));
 	for (int i = 0; i < tal_count(ints); ++i)
 		assert(ints[i] == i + 10);
@@ -234,11 +234,11 @@ static void null_params(void)
 			   param_req("3", json_tok_u64, &ints[3]),
 			   param_opt("4", json_tok_u64, &intptrs[0]),
 			   param_opt("5", json_tok_u64, &intptrs[1]),
-			   param_opt("6", json_tok_u64, &intptrs[2]),
+			   param_opt_default("6", json_tok_u64, &ints[4], 888),
 			   NULL));
 	assert(*intptrs[0] == 14);
 	assert(intptrs[1] == NULL);
-	assert(intptrs[2] == NULL);
+	assert(ints[4] == 888);
 }
 
 #if DEVELOPER
@@ -337,13 +337,13 @@ static void bad_programmer(void)
 		/* Add required param after optional */
 		struct json *j =
 		    json_parse(cmd, "[ '25', '546', '26', '1.1' ]");
-		unsigned int *msatoshi;
+		unsigned int msatoshi;
 		double riskfactor;
 		param_parse(cmd, j->buffer, j->toks,
 			    param_req("u64", json_tok_u64, &ival),
 			    param_req("double", json_tok_double, &dval),
-			    param_opt("msatoshi",
+			    param_opt_default("msatoshi",
-				      json_tok_number, &msatoshi),
+					      json_tok_number, &msatoshi, 100),
 			    param_req("riskfactor", json_tok_double,
 				      &riskfactor), NULL);
 		restore_assert(old_stderr);
@@ -361,7 +361,7 @@ static void add_members(struct param **params,
 		char *name = tal_fmt(tmpctx, "%i", i);
 		json_add_num(obj, name, i);
 		json_add_num(arr, NULL, i);
-		param_add(params, name,
+		param_add(params, name, true,
 			  typesafe_cb_preargs(bool, void *,
 					      json_tok_number,
 					      &ints[i],