Add client support, use it to dump json to stdout first.

json.c

@@ -0,0 +1,64 @@
+#include <assert.h>
+#include <stdio.h>
+
+#include "client.h"
+#include "json.h"
+
+
+// Hobo JSON to avoid overhead. Assumes that we can't get quotes in the data.
+
+void json_init() {
+}
+
+static size_t json_hello(char *buf) {
+	int len = snprintf(buf, SERIALIZE_LEN,
+	                   "{\"mlat_timestamp_mhz\":%ju,\"mlat_timestamp_max\":%ju,\"rssi_max\":%ju}\n",
+					       		 (uintmax_t) MLAT_MHZ,
+							       (uintmax_t) MLAT_MAX,
+						         (uintmax_t) RSSI_MAX);
+	assert(len < SERIALIZE_LEN);
+	return len;
+}
+
+static size_t json_serialize_mode_s_short(struct packet *packet, char *buf) {
+	char hexbuf[14];
+	hex_from_bin(hexbuf, packet->data, 7);
+	int len = snprintf(buf, SERIALIZE_LEN,
+	                   "{\"payload\":\"%.14s\",\"mlat_timestamp\":%ju,\"rssi\":%ju}\n",
+					           hexbuf,
+					           (uintmax_t) packet->mlat_timestamp,
+					           (uintmax_t) packet->rssi);
+	assert(len < SERIALIZE_LEN);
+	return len;
+}
+
+static size_t json_serialize_mode_s_long(struct packet *packet, char *buf) {
+	char hexbuf[28];
+	hex_from_bin(hexbuf, packet->data, 14);
+	int len = snprintf(buf, SERIALIZE_LEN,
+	                   "{\"payload\":\"%.28s\",\"mlat_timestamp\":%ju,\"rssi\":%ju}\n",
+					           hexbuf,
+					           (uintmax_t) packet->mlat_timestamp,
+					           (uintmax_t) packet->rssi);
+	assert(len < SERIALIZE_LEN);
+	return len;
+}
+
+size_t json_serialize(struct packet *packet, char *buf) {
+	if (!packet) {
+		return json_hello(buf);
+	}
+
+	switch (packet->type) {
+		case MODE_AC:
+			return 0;
+
+		case MODE_S_SHORT:
+			return json_serialize_mode_s_short(packet, buf);
+
+		case MODE_S_LONG:
+			return json_serialize_mode_s_long(packet, buf);
+	}
+	
+	return 0;
+}