beginning of pager decoder

decoder_modules/pager_decoder/src/pocsag/pocsag.h

@@ -0,0 +1,48 @@
+#pragma once
+#include <string>
+#include <stdint.h>
+#include <utils/new_event.h>
+
+#define POCSAG_SYNC_DIST            4
+#define POCSAG_BATCH_CODEWORD_COUNT 16
+
+namespace pocsag {
+    enum CodewordType {
+        CODEWORD_TYPE_IDLE      = -1,
+        CODEWORD_TYPE_ADDRESS   = 0,
+        CODEWORD_TYPE_MESSAGE   = 1
+    };
+
+    enum MessageType {
+        MESSAGE_TYPE_NUMERIC        = 0b00,
+        MESSAGE_TYPE_ALPHANUMERIC   = 0b11
+    };
+
+    using Codeword = uint32_t;
+    using Address = uint32_t;
+
+    class Decoder {
+    public:
+        void process(uint8_t* symbols, int count);
+
+        NewEvent<Address, MessageType, const std::string&> onMessage;
+
+    private:
+        static int distance(uint32_t a, uint32_t b);
+        bool correctCodeword(Codeword in, Codeword& out);
+        void flushMessage();
+        void decodeBatch();
+
+        uint32_t syncSR = 0;
+        bool synced = false;
+        int batchOffset = 0;
+
+        Codeword batch[POCSAG_BATCH_CODEWORD_COUNT];
+
+        Address addr;
+        MessageType msgType;
+        std::string msg;
+
+        uint32_t lastMsgData;
+    };
+}