json: Fix handling for long integers

This patch adds the "enable_long_quoting" modparam (default: OFF), which
causes larger integers to be returned as strings, in order to avoid the
integer overflow and data loss.

modules/json/doc/json_admin.xml

@@ -56,9 +56,32 @@
 	<section id="exported_parameters" xreflabel="Exported Parameters">
 	<title>Exported Parameters</title>
 
+	<section id="param_enable_long_quoting" xreflabel="enable_long_quoting">
+		<title><varname>enable_long_quoting</varname> (boolean)</title>
 		<para>
-		The module does not export any parameters.
+		Enable this parameter if your input JSONs contain signed integers which
+		do not fit into 4 bytes (e.g. larger than 2147483647, etc.).  If the
+		parameter is enabled, 4-byte integers will continue to be returned as
+		integers, while larger values will be returned as strings, in order to
+		avoid the integer overflow.
 		</para>
+		<para>
+		<emphasis>
+			Default value is <emphasis>false</emphasis>.
+		</emphasis>
+		</para>
+		<example>
+		<title>Set <varname>enable_long_quoting</varname> parameter</title>
+		<programlisting format="linespecific">
+...
+modparam("json", "enable_long_quoting", true)
+...
+# normalize the "gateway_id" int/string value to be always a string
+$var(gateway_id) = "" + $json(body/gateway_id);
+...
+</programlisting>
+		</example>
+	</section>
 
 	</section>
 

modules/json/json.c

@@ -99,6 +99,7 @@ typedef struct _json_name
 
 pv_json_t * all;
 char buff[JSON_FILE_BUF_SIZE];
+int json_long_quoting;
 
 static int mod_init(void);
 static int child_init(int );
@@ -128,6 +129,12 @@ static const cmd_export_t cmds[]={
 	{0,0,{{0,0,0}},0}
 };
 
+static const param_export_t mod_params[]={
+	{ "enable_long_quoting",         INT_PARAM, &json_long_quoting       },
+	{ 0,0,0 }
+};
+
+
 static const pv_export_t mod_items[] = {
 	{ str_const_init("json"),    PVT_JSON, pv_get_json,
 		pv_set_json, pv_parse_json_name, pv_parse_json_index, 0, 0},
@@ -143,15 +150,15 @@ struct module_exports exports= {
 	MOD_TYPE_DEFAULT,/* class of this module */
 	MODULE_VERSION,
 	DEFAULT_DLFLAGS, /* dlopen flags */
-	0,				 /* load function */
+	0,               /* load function */
 	NULL,            /* OpenSIPS module dependencies */
 	cmds,            /* exported functions */
 	0,               /* exported async functions */
-	0,      /* param exports */
-	0,       /* exported statistics */
-	0,         /* exported MI functions */
+	mod_params,      /* param exports */
+	0,               /* exported statistics */
+	0,               /* exported MI functions */
 	mod_items,       /* exported pseudo-variables */
-	0,			 	 /* exported transformations */
+	0,               /* exported transformations */
 	0,               /* extra processes */
 	0,               /* module pre-initialization function */
 	mod_init,        /* module initialization function */
@@ -460,7 +467,8 @@ int pv_get_json_ext(struct sip_msg* msg,  pv_param_t* pvp, pv_value_t* val, int
 	{
 		int_value = json_object_get_int64(obj);
 		val->rs.s = sint2str(int_value, &val->rs.len);
-		if (int_value<=INT_MAX && int_value>=INT_MIN) {
+
+		if (!json_long_quoting || (int_value>=INT_MIN && int_value<=INT_MAX)) {
 			/* safe to store it as an INT in the pvar */
 			val->ri = int_value;
 			val->flags |= PV_VAL_INT|PV_TYPE_INT|PV_VAL_STR;