swimtracker-firmware/lib/session/StreamingMsgPackEncoder.h

#pragma once

template<typename T> struct TypeToMsgPackCode{};
template<> struct TypeToMsgPackCode<uint8_t> { static const char CODE; };
template<> struct TypeToMsgPackCode<uint16_t>{ static const char CODE; };
template<> struct TypeToMsgPackCode<uint32_t>{ static const char CODE; };
template<> struct TypeToMsgPackCode<int8_t>  { static const char CODE; };
template<> struct TypeToMsgPackCode<int16_t> { static const char CODE; };
template<> struct TypeToMsgPackCode<int32_t> { static const char CODE; };

const char TypeToMsgPackCode<uint8_t>::CODE  = '\xcc';
const char TypeToMsgPackCode<uint16_t>::CODE = '\xcd';
const char TypeToMsgPackCode<uint32_t>::CODE = '\xce';
const char TypeToMsgPackCode<int8_t>::CODE  = '\xd0';
const char TypeToMsgPackCode<int16_t>::CODE = '\xd1';
const char TypeToMsgPackCode<int32_t>::CODE = '\xd2';

struct DummyWriter {
    void write(const void*, uint32_t) {}
};

class CopyWriter {
public:
    CopyWriter(uint8_t * bufferToWrite)
        : bufferToWrite_( bufferToWrite )
    {}

    void write(const void* data, uint32_t length) {
        memcpy(bufferToWrite_, data, length);
        bufferToWrite_ += length;
    }

private:
    uint8_t * bufferToWrite_;
};

template<typename Writer>
class StreamingMsgPackEncoder
{
public:
    StreamingMsgPackEncoder(Writer * writer_)
            : writer(writer_), contentLength(0), sizeCountMode(false)
    {}

    void sendMap16(byte size)
    {
        if( sizeCountMode )
        {
            contentLength += 1;
        }
        else
        {
            size |= 0b10000000;
            writer->write((const char*)(&size), 1);
        }
    }

    void sendString255(PGM_P s)
    {
        auto len = strlen_P(s);
        if( len >= 255 ) {
            Serial.println(F("ERROR: StreamingMsgPackEncoder::string255 - string too long"));
            return;
        }
        byte castedLen = (byte)(len);

        if( sizeCountMode )
        {
            contentLength += 2 + castedLen;
        }
        else
        {
            writer->write("\xd9", 1);
            writer->write((const char*)&castedLen, 1);
            writer->write(s, len);
        }
    }

    template<typename T>
    void sendInt(T value)
    {
        if( sizeCountMode )
        {
            contentLength += 1 + sizeof(T);
        }
        else
        {
            if( sizeof(T) == 4 )
                value = htonl(value);
            else if( sizeof(T) == 2)
                value = htons(value);
            writer->write(&TypeToMsgPackCode<T>::CODE, 1);
            writer->write((const char*)&value, sizeof(T));
        }
    }

    template<typename T>
    void sendArray(const T * data, uint32_t length)
    {
        sendArrayHeader<T>(length);
        sendArrayPartialContents(data, length);
    }

    template<typename T>
    void sendArrayHeader(uint32_t length)
    {
        if( sizeCountMode )
        {
            contentLength += 1 + sizeof(uint32_t) + 1;
        }
        else
        {
            uint32_t nlength = htonl(length * sizeof(T));
            writer->write("\xc9", 1); // ext dtype since typed arrays are not supported by msgpack
            writer->write((char*)(&nlength), sizeof(uint32_t) );
            writer->write(&TypeToMsgPackCode<T>::CODE, 1); // put code for type here, this is not part of msgpack but custom
        }
    }

    template<typename T>
    void sendArrayPartialContents(T * data, uint32_t length)
    {
        if( !sizeCountMode ) {
            writer->write((char*)(data), length * sizeof(T));
        } else {
            contentLength += sizeof(T) * length;
        }
    }

    void setSizeCountMode(bool sizeCountMode_=true)
    {
        sizeCountMode = sizeCountMode_;
    }

    bool getSizeCountMode() const {
        return sizeCountMode;
    }

    uint32_t getContentLength() const {
        return contentLength;
    }

    void resetContentLength() {
        contentLength = 0;
    }
private:
    Writer * writer;
    uint32_t contentLength;
    bool sizeCountMode;
};



template<typename Writer>
class ChunkedStreamingMsgPackEncoder
{
public:
    ChunkedStreamingMsgPackEncoder(Writer * writer_, uint32_t offset, uint32_t maxSize)
            : encoder_(writer_), sentBytes_(0), maxBytes_(maxSize), offsetToStart_(offset), sendingFinished_(false)
    {}

    void sendMap16(byte size) {
        sendIfSpaceLeft([&]() { encoder_.sendMap16(size); });
    }

    void sendString255(PGM_P s) {
        sendIfSpaceLeft([&]() { encoder_.sendString255(s); });
    }

    template<typename T>
    void sendInt(T value) {
        sendIfSpaceLeft([&]() { encoder_.template sendInt<T>(value); });
    }

    template<typename T>
    void sendArray(const T * data, uint32_t length)
    {
        sendArrayHeader<T>(length);
        sendArrayPartialContents(data, length);
    }

    template<typename T>
    void sendArrayHeader(uint32_t length) {
        sendIfSpaceLeft([&]() { encoder_.template sendArrayHeader<T>(length); });
    }

    template<typename T>
    void sendArrayPartialContents(T * data, uint32_t length) {
        if(  sendingFinished_ ) {
            return;
        }

        uint32_t elementsToSkip = 0;
        if( sentBytes_ < offsetToStart_ ) {
            elementsToSkip = (offsetToStart_ - sentBytes_) / sizeof(T);
            assert((offsetToStart_ - sentBytes_) % sizeof(T) == 0,
                    "Looks like previous sent operation send fraction of an element.");
        }
        if( elementsToSkip >= length) {
            sentBytes_ += sizeof(T) * length;
            return;
        } else {
            sentBytes_ += sizeof(T) * elementsToSkip;
            const uint32_t elementsRemaining = length - elementsToSkip;
            const uint32_t maxElementsToSend = (maxBytes_ - sentBytes_) / sizeof(T);
            const uint32_t elementsToSend = min(elementsRemaining, maxElementsToSend);
            if( elementsToSend == 0 ) {
                sendingFinished_ = true;
                return;
            } else {
                encoder_.sendArrayPartialContents(data + elementsToSkip, elementsToSend);
                sentBytes_ += sizeof(T) * elementsToSend;
                if( elementsRemaining > elementsToSend ) {
                    sendingFinished_ = true;
                }
            }
        }
    }

    uint32_t sentBytes() const {
        return sentBytes_;
    }

    bool getSizeCountMode() const {
        return false;
    }

private:
    template<typename T, typename... Args>
    void sendIfSpaceLeft(T sendFunction) {
        if(  sendingFinished_ ) {
            return;
        }

        encoder_.setSizeCountMode(true);
        encoder_.resetContentLength();
        sendFunction();
        auto sizeRequired = encoder_.getContentLength();
        encoder_.setSizeCountMode(false);

        if( sentBytes_ < offsetToStart_ ) {
            // already sent
            sentBytes_ += sizeRequired;
            assert( sentBytes_ <= offsetToStart_, "Partial sending not supported by this function" );
            return;
        }

        if( sentBytes_ + sizeRequired <= maxBytes_ ) {
            sendFunction();
            sentBytes_ += sizeRequired;
        } else {
            sendingFinished_ = true;
        }
    }

    StreamingMsgPackEncoder<Writer> encoder_;
    uint32_t sentBytes_;
    uint32_t maxBytes_;
    uint32_t offsetToStart_;
    bool sendingFinished_;
};