SDRPlusPlus/core/src/dsp/stream.h

#pragma once
#include <mutex>
#include <condition_variable>
#include <volk/volk.h>

// 1MB buffer
#define STREAM_BUFFER_SIZE 1000000

namespace dsp {
    class untyped_stream {
    public:
        virtual bool swap(int size) { return false; }
        virtual int read() { return -1; }
        virtual void flush() {}
        virtual void stopWriter() {}
        virtual void clearWriteStop() {}
        virtual void stopReader() {}
        virtual void clearReadStop() {}
    };

    template <class T>
    class stream : public untyped_stream {
    public:
        stream() {
            writeBuf = (T*)volk_malloc(STREAM_BUFFER_SIZE * sizeof(T), volk_get_alignment());
            readBuf = (T*)volk_malloc(STREAM_BUFFER_SIZE * sizeof(T), volk_get_alignment());
        }

        ~stream() {
            volk_free(writeBuf);
            volk_free(readBuf);
        }

        bool swap(int size) {
            {
                // Wait to either swap or stop
                std::unique_lock<std::mutex> lck(swapMtx);
                swapCV.wait(lck, [this] { return (canSwap || writerStop); });

                // If writer was stopped, abandon operation
                if (writerStop) { return false; }

                // Swap buffers
                dataSize = size;
                T* temp = writeBuf;
                writeBuf = readBuf;
                readBuf = temp;
                canSwap = false;
            }

            // Notify reader that some data is ready
            {
                std::lock_guard<std::mutex> lck(rdyMtx);
                dataReady = true;
            }
            rdyCV.notify_all();

            return true;
        }

        int read() {
            // Wait for data to be ready or to be stopped
            std::unique_lock<std::mutex> lck(rdyMtx);
            rdyCV.wait(lck, [this] { return (dataReady || readerStop); });

            return (readerStop ? -1 : dataSize);
        }

        void flush() {
            // Clear data ready
            {
                std::lock_guard<std::mutex> lck(rdyMtx);
                dataReady = false;
            }

            // Notify writer that buffers can be swapped
            {
                std::lock_guard<std::mutex> lck(swapMtx);
                canSwap = true;
            }

            swapCV.notify_all();
        }

        void stopWriter() {
            {
                std::lock_guard<std::mutex> lck(swapMtx);
                writerStop = true;
            }
            swapCV.notify_all();
        }

        void clearWriteStop() {
            writerStop = false;
        }

        void stopReader() {
            {
                std::lock_guard<std::mutex> lck(rdyMtx);
                readerStop = true;
            }
            rdyCV.notify_all();
        }

        void clearReadStop() {
            readerStop = false;
        }

        T* writeBuf;
        T* readBuf;

    private:
        std::mutex swapMtx;
        std::condition_variable swapCV;
        bool canSwap = true;

        std::mutex rdyMtx;
        std::condition_variable rdyCV;
        bool dataReady = false;

        bool readerStop = false;
        bool writerStop = false;

        int dataSize = 0;
    };
}