From 4d8cdaaf8e8b663b050509d64a45bd5a55ce220b Mon Sep 17 00:00:00 2001
From: Dirk Hohndel <dirk@hohndel.org>
Date: Wed, 5 Oct 2022 14:40:46 -0700
Subject: [PATCH] Garmin: attempt to parse big endian .FIT files

The only examples I have seen so far are small incomplete files that
don't contain the dive profile, so I'm unsure if this is sufficient (and
why there are big endian files in the first place).

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
---
 src/garmin_parser.c | 48 ++++++++++++++++++++++++++++++---------------
 1 file changed, 32 insertions(+), 16 deletions(-)

diff --git a/src/garmin_parser.c b/src/garmin_parser.c
index 06fd73d..1ce4952 100644
--- a/src/garmin_parser.c
+++ b/src/garmin_parser.c
@@ -139,6 +139,7 @@ typedef struct garmin_parser_t {
 	} gps;
 
 	struct dc_field_cache cache;
+	unsigned char is_big_endian; // instead of bool
 } garmin_parser_t;
 
 typedef int (*garmin_data_cb_t)(unsigned char type, const unsigned char *data, int len, void *user);
@@ -390,6 +391,19 @@ struct field_desc {
 	void (*parse)(struct garmin_parser_t *, unsigned char base_type, const unsigned char *data);
 };
 
+static inline int base_type_is_integer(unsigned char base_type)
+{
+	return !memcmp(base_type_info[base_type].type_name + 1, "INT", 3);
+}
+
+static inline unsigned int array_uint_endian(const unsigned char *p, unsigned int type_size, unsigned char bigendian)
+{
+	if (bigendian)
+		return array_uint_be(p, type_size);
+	else
+		return array_uint_le(p, type_size);
+}
+
 #define DECLARE_FIELD(msg, name, type) __DECLARE_FIELD(msg##_##name, type)
 #define __DECLARE_FIELD(name, type) \
 	static void parse_##name(struct garmin_parser_t *, const type); \
@@ -397,10 +411,14 @@ struct field_desc {
 	{ \
 		if (strcmp(#type, base_type_info[base_type].type_name)) \
 			fprintf(stderr, "%s: %s should be %s\n", #name, #type, base_type_info[base_type].type_name); \
-		type val = *(type *)p; \
+		type val; \
+		if (base_type_info[base_type].type_size > 1 && base_type_is_integer(base_type)) \
+			val = (type)array_uint_endian(p, base_type_info[base_type].type_size, g->is_big_endian); \
+		else \
+			val = *(type *)p; \
 		if (val == type##_INVAL) return; \
 		DEBUG(g->base.context, "%s (%s): %lld", #name, #type, (long long)val); \
-		parse_##name(g, *(type *)p); \
+		parse_##name(g, val); \
 	} \
 	static const struct field_desc name##_field_##type = { #name, parse_##name##_##type }; \
 	static void parse_##name(struct garmin_parser_t *garmin, type data)
@@ -1217,18 +1235,13 @@ static int traverse_definition(struct garmin_parser_t *garmin,
 	struct type_desc *desc = garmin->type_desc + type;
 	int fields, devfields, len;
 
-	msg = array_uint16_le(data+2);
+	// data[1] tells us if this is big or little endian
+	garmin->is_big_endian = data[1] != 0;
+	msg = array_uint_endian(data + 2, 2, garmin->is_big_endian);
 	desc->msg_desc = lookup_msg_desc(msg, type, &desc->msg_name);
 	fields = data[4];
-
-	DEBUG(garmin->base.context, "Define local type %d: %02x %02x %04x %02x %s",
-		type, data[0], data[1], msg, fields, desc->msg_name);
-
-	if (data[1]) {
-		ERROR(garmin->base.context, "Only handling little-endian definitions\n");
-		return -1;
-	}
-
+	DEBUG(garmin->base.context, "Define local type %d: %02x %s %04x %02x %s",
+		type, data[0], data[1] ? "big-endian" : "little-endian", msg, fields, desc->msg_name);
 	if (fields > MAXFIELDS) {
 		ERROR(garmin->base.context, "Too many fields in description: %d (max %d)\n", fields, MAXFIELDS);
 		return -1;
@@ -1280,13 +1293,16 @@ traverse_data(struct garmin_parser_t *garmin)
 
 	hdrsize = data[0];
 	protocol = data[1];
-	profile = array_uint16_le(data+2);
+	profile = array_uint16_le(data+2);  // these two fields are always little endian
 	datasize = array_uint32_le(data+4);
-	if (memcmp(data+8, ".FIT", 4))
+	if (memcmp(data+8, ".FIT", 4)) {
+		DEBUG(garmin->base.context, " missing .FIT marker");
 		return DC_STATUS_IO;
-	if (hdrsize < 12 || datasize > len || datasize + hdrsize + 2 > len)
+	}
+	if (hdrsize < 12 || datasize > len || datasize + hdrsize + 2 > len) {
+		DEBUG(garmin->base.context, " inconsistent size information hdrsize %d datasize %d len %d", hdrsize, datasize, len);
 		return DC_STATUS_IO;
-
+	}
 	garmin->dive.protocol = protocol;
 	garmin->dive.profile = profile;