1 files changed, 50 insertions, 0 deletions
diff --git a/packet.c b/packet.c
new file mode 100644
index 0000000..663778e
--- /dev/null
+++ b/packet.c
@@ -0,0 +1,50 @@
+#include "casio-get.h"
+#include <string.h>
+
+
+/*****************************************************************************
+ * Calculate the checksum of the data area of a packet
+ *****************************************************************************/
+unsigned char calculate_checksum(const char *start, const char *stop)
+{
+	unsigned char sum = 0;
+	while (start != stop)
+		sum += *(start++);
+
+	return 1 + ~(sum);
+}
+
+
+unsigned short calculate_checksum_word(const char *start, const char *stop)
+{
+	unsigned short sum = 0;
+	while (start != stop)
+		sum += (unsigned char)(*(start++));
+
+	return 1 + ~(sum);
+}
+
+/*****************************************************************************
+ * Returns the type of packet as determined from the packet header
+ *****************************************************************************/
+enum packet_types get_packet_type(const unsigned char* data)
+{
+	if (strncmp((char*)data, ":END", 4) == 0)
+		return PKT_END;
+	if (strncmp((char*)data, ":VAL", 4) == 0)
+		return PKT_VALUE_HEADER;
+	if (strncmp((char*)data, ":DD", 3) == 0)
+		return PKT_SCREEN_HEADER_BW;
+	if (strncmp((char*)data, ":DC", 3) == 0)
+		return PKT_SCREEN_HEADER_COL;
+	if (strncmp((char*)data, ":MEM", 4) == 0)
+		return PKT_BACKUP_HEADER;
+	if (strncmp((char*)data, ":FNC", 4) == 0)
+		return PKT_FUNCTION_HEADER;
+	if (strncmp((char*)data, ":TXT", 4) == 0)
+		return PKT_PROGRAM_HEADER;
+	if (strncmp((char*)data, ":\x00\x01\x00\x01", 4) == 0)
+		return PKT_VAL;
+
+	return PKT_UNKNOWN;
+}