[OpenWrt-Devel] [PATCH uqmi] Fix character "@" added at end of received messages

[Sławomir Demeszko]

If 7 bit message encoded on 8 bit cells has one last bit occupying
whole byte it need to be padded with 7 zero bits. To not mistake
these last 7 bits with a character with code 0 (@) we need to check
length from User Data Length field and not rely on actual length
of received data. An example can be message "abcdefg" encoded
as "61 f1 98 5c 36 9f 01", it is decoded as "abcdefg@".

Signed-off-by: Sławomir Demeszko <s.demeszko at wireless-instruments.com>
---
It depends on my last patches from today.

 commands-wms.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/commands-wms.c b/commands-wms.c
index 74f50aa..47d4d76 100644
--- a/commands-wms.c
+++ b/commands-wms.c
@@ -1,5 +1,8 @@
 #include "qmi-message.h"
 
+#define MIN(a,b) (((a)<(b))?(a):(b))
+#define CEILDIV(x,y) (((x) + (y) - 1) / (y))
+
 static void cmd_wms_list_messages_cb(struct qmi_dev *qmi, struct qmi_request *req, struct qmi_msg *msg)
 {
 	struct qmi_wms_list_messages_response res;
@@ -191,8 +194,9 @@ static int decode_udh(const unsigned char *data)
 
 static void decode_7bit_field(char *name, const unsigned char *data, int data_len, int bit_offset)
 {
-	char *dest = blobmsg_alloc_string_buffer(&status, name, 3 * (data_len * 8 / 7) + 2);
-	pdu_decode_7bit_str(dest, data, data_len, bit_offset);
+	char *dest = blobmsg_alloc_string_buffer(&status, name, 3 * data_len + 2);
+	pdu_decode_7bit_str(dest, data, CEILDIV(data_len * 7, 8), bit_offset);
+	dest[data_len] = 0;
 	blobmsg_add_string_buffer(&status);
 }
 
@@ -366,12 +370,13 @@ static void cmd_wms_get_message_cb(struct qmi_dev *qmi, struct qmi_request *req,
 		data += 7;
 	}
 
-	data++;
+	int message_len = *(data++);
+	int udh_len = 0;
 	int bit_offset = 0;
 
 	/* User Data Header */
 	if (first & 0x40) {
-		int udh_len = decode_udh(data);
+		udh_len = decode_udh(data);
 		data += udh_len;
 		bit_offset = udh_len % 7;
 		}
@@ -382,15 +387,19 @@ static void cmd_wms_get_message_cb(struct qmi_dev *qmi, struct qmi_request *req,
 	switch(dcs & 0x0c) {
 		case 0x00:
 			/* 7 bit GSM alphabet */
-			decode_7bit_field("text", data, end - data, bit_offset);
+			message_len = message_len - CEILDIV(udh_len * 8, 7);
+			message_len = MIN(message_len, CEILDIV((end - data) * 8, 7));
+			decode_7bit_field("text", data, message_len, bit_offset);
 			break;
 		case 0x04:
 			/* 8 bit data */
-			blobmsg_add_hex(&status, "data", data, end - data);
+			message_len = MIN(message_len - udh_len, end - data);
+			blobmsg_add_hex(&status, "data", data, message_len);
 			break;
 		case 0x08:
 			/* 16 bit UCS-2 string */
-			blobmsg_add_hex(&status, "ucs-2", data, end - data);
+			message_len = MIN(message_len - udh_len, end - data);
+			blobmsg_add_hex(&status, "ucs-2", data, message_len);
 			break;
 		default:
 			goto error;
-- 
1.9.1
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