From a11eca1c28b4e0cdfd317ed6ae549de1b896043a Mon Sep 17 00:00:00 2001
From: sq8vps <sq8vps@gmail.com>
Date: Sun, 3 Sep 2023 10:49:47 +0200
Subject: [PATCH] kiss escape chars handling

---
 Src/ax25.c     | 39 +++++++++++++++++++++++++++++++++++----
 Src/terminal.c | 22 ++++++++++++++++++----
 2 files changed, 53 insertions(+), 8 deletions(-)

diff --git a/Src/ax25.c b/Src/ax25.c
index 3dbce4e..ed69a64 100644
--- a/Src/ax25.c
+++ b/Src/ax25.c
@@ -154,9 +154,10 @@ void Ax25TxKiss(uint8_t *buf, uint16_t len)
 	}
 	for(uint16_t i = 0; i < len; i++)
 	{
-		if(buf[i] == 0xC0) //frame start marker
+		if((buf[i] == 0xC0) && ((buf[i + 1] & 0xF) == 0)) //frame start marker and type is data frame
 		{
-			uint16_t end = i + 1;
+			i += 2; //skip 0xC0 and type
+			uint16_t end = i;
 			while(end < len)
 			{
 				if(buf[end] == 0xC0)
@@ -165,8 +166,38 @@ void Ax25TxKiss(uint8_t *buf, uint16_t len)
 			}
 			if(end == len) //no frame end marker found
 				return;
-			Ax25WriteTxFrame(&buf[i + 2], end - (i + 2)); //skip modem number and send frame
-			DigiStoreDeDupe(&buf[i + 2], end - (i + 2));
+
+			uint16_t modifiedEnd = end;
+
+			for(uint16_t j = i; j < modifiedEnd; j++)
+			{
+				if(buf[j] == 0xDB) //escape character
+				{
+					if(buf[j + 1] == 0xDC) //transposed frame end
+					{
+						buf[j] = 0xC0;
+					}
+					else if(buf[j + 1] == 0xDD) //transposed frame escape
+					{
+						buf[j] = 0xDB;
+					}
+					else
+					{
+						j++;
+						continue;
+					}
+
+					j++;
+					modifiedEnd--;
+					for(uint16_t k = j; k < modifiedEnd; k++)
+					{
+						buf[k] = buf[k + 1];
+					}
+				}
+			}
+
+			Ax25WriteTxFrame(&buf[i], modifiedEnd - i); //skip modem number and send frame
+			DigiStoreDeDupe(&buf[i], modifiedEnd - i);
 			i = end; //move pointer to the next byte if there are more consecutive frames
 		}
 	}
diff --git a/Src/terminal.c b/Src/terminal.c
index f4ef73f..08aa0a3 100644
--- a/Src/terminal.c
+++ b/Src/terminal.c
@@ -62,12 +62,26 @@ void TermHandleSpecial(Uart *u)
 
 static void sendKiss(Uart *port, uint8_t *buf, uint16_t len)
 {
-	if(port->mode == MODE_KISS) //check if KISS mode
+	if(port->mode == MODE_KISS)
 	{
-		UartSendByte(port, 0xc0); //send data in kiss format
+		UartSendByte(port, 0xC0);
 		UartSendByte(port, 0x00);
-		UartSendString(port, buf, len);
-		UartSendByte(port, 0xc0);
+		for(uint16_t i = 0; i < len; i++)
+		{
+			if(buf[i] == 0xC0) //frame end in data
+			{
+				UartSendByte(port, 0xDB); //frame escape
+				UartSendByte(port, 0xDC); //transposed frame end
+			}
+			else if(buf[i] == 0xDB) //frame escape in data
+			{
+				UartSendByte(port, 0xDB); //frame escape
+				UartSendByte(port, 0xDD); //transposed frame escape
+			}
+			else
+				UartSendByte(port, buf[i]);
+		}
+		UartSendByte(port, 0xC0);
 	}
 }