From 712950db5e0c08d7b31a5074765d507f73da423c Mon Sep 17 00:00:00 2001
From: Daniel Friesel <derf@finalrewind.org>
Date: Fri, 12 Feb 2016 20:46:34 +0100
Subject: quick&dirty hamming buffer implementation.

---
 src/fecmodem.cc | 28 ++++++++++++++++++++++++++++
 src/fecmodem.h  | 11 +++++++++++
 src/modem.cc    | 10 ++++++++++
 src/modem.h     |  5 ++++-
 4 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/src/fecmodem.cc b/src/fecmodem.cc
index bd0d58c..52271fd 100644
--- a/src/fecmodem.cc
+++ b/src/fecmodem.cc
@@ -48,4 +48,32 @@ uint8_t FECModem::hamming2416(uint8_t *byte1, uint8_t *byte2, uint8_t parity)
 	return 0;
 }
 
+uint8_t FECModem::buffer_available()
+{
+	if (rxWasReset())
+		hammingState = FIRST_BYTE;
+	if (this->Modem::buffer_available() >= 3)
+		return 2;
+	if (hammingState == SECOND_BYTE)
+		return 1;
+	return 0;
+}
+
+uint8_t FECModem::buffer_get()
+{
+	uint8_t byte1, parity;
+	if (hammingState == SECOND_BYTE) {
+		hammingState = FIRST_BYTE;
+		return buf_byte;
+	}
+	hammingState = SECOND_BYTE;
+	byte1 = this->Modem::buffer_get();
+	buf_byte = this->Modem::buffer_get();
+	parity = this->Modem::buffer_get();
+
+	hamming2416(&byte1, &buf_byte, parity);
+
+	return byte1;
+}
+
 FECModem modem;
diff --git a/src/fecmodem.h b/src/fecmodem.h
index dd36f68..00487ee 100644
--- a/src/fecmodem.h
+++ b/src/fecmodem.h
@@ -9,10 +9,21 @@
 
 class FECModem : public Modem {
 	private:
+		enum HammingState : uint8_t {
+			FIRST_BYTE,
+			SECOND_BYTE
+		};
+		HammingState hammingState;
+		uint8_t buf_byte;
+
 		uint8_t parity128(uint8_t byte);
 		uint8_t parity2416(uint8_t byte1, uint8_t byte2);
 		uint8_t correct128(uint8_t *byte, uint8_t parity);
 		uint8_t hamming2416(uint8_t *byte1, uint8_t *byte2, uint8_t parity);
+	public:
+		FECModem() : Modem() { hammingState = FIRST_BYTE; };
+		uint8_t buffer_available(void);
+		uint8_t buffer_get(void);
 };
 
 extern FECModem modem;
diff --git a/src/modem.cc b/src/modem.cc
index 472fe04..dc183b1 100644
--- a/src/modem.cc
+++ b/src/modem.cc
@@ -14,6 +14,15 @@
 
 extern FECModem modem;
 
+bool Modem::rxWasReset()
+{
+	if (new_transmission) {
+		new_transmission = false;
+		return true;
+	}
+	return false;
+}
+
 /*
  * Returns number of available bytes in ringbuffer or 0 if empty
  */
@@ -84,6 +93,7 @@ void Modem::receive() {
 	if (modem_pulselen > MODEM_SYNC_LEN) {
 		modem_bitlen = (modem_pulselen >> 2);
 		modem_bit = 0;
+		new_transmission = true;
 		return;
 	}
 
diff --git a/src/modem.h b/src/modem.h
index 4040c92..284edeb 100644
--- a/src/modem.h
+++ b/src/modem.h
@@ -32,9 +32,12 @@ class Modem {
 		uint8_t buffer_head;
 		uint8_t buffer_tail;
 		uint8_t buffer[MODEM_BUFFER_SIZE];
+		bool new_transmission;
 		void buffer_put(const uint8_t c);
 	public:
-		Modem() {};
+		Modem() {new_transmission = false;};
+
+		bool rxWasReset();
 
 		/**
 		 * Checks if there are unprocessed bytes in the modem receive buffer.
-- 
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