JUCE/modules/juce_midi_ci/detail/juce_CIMarshalling.h

/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2022 - Raw Material Software Limited

   JUCE is an open source library subject to commercial or open-source
   licensing.

   By using JUCE, you agree to the terms of both the JUCE 7 End-User License
   Agreement and JUCE Privacy Policy.

   End User License Agreement: www.juce.com/juce-7-licence
   Privacy Policy: www.juce.com/juce-privacy-policy

   Or: You may also use this code under the terms of the GPL v3 (see
   www.gnu.org/licenses).

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

/*
    Utilities for converting sequences of bytes to and from
    C++ struct types.
*/
namespace juce::midi_ci::detail::Marshalling
{

template <uint8_t> struct IntForNumBytes;
template <> struct IntForNumBytes<1> { using Type = uint8_t; };
template <> struct IntForNumBytes<2> { using Type = uint16_t; };
template <> struct IntForNumBytes<4> { using Type = uint32_t; };

template <uint8_t NumBytes> using IntForNumBytesT = typename IntForNumBytes<NumBytes>::Type;

//==============================================================================
/*
    Reads a sequence of bytes representing a MIDI-CI message, and populates
    structs with the information contained in the message.
*/
class Reader
{
public:
    /*  Constructs a reader that will parse the provided buffer, using the most
        recent known MIDI-CI version.
    */
    explicit Reader (Span<const std::byte> b)
        : Reader (b, static_cast<uint8_t> (MessageMeta::implementationVersion)) {}

    /*  Constructs a reader for the provided MIDI-CI version that will parse
        the provided buffer. Fields introduced in later versions will be ignored,
        and so left with their default values.
    */
    Reader (Span<const std::byte> b, int v)
        : bytes (b), version (v) {}

    std::optional<int> getVersion() const { return version; }

    /*  Attempts to interpret the byte sequence passed to the constructor
        as a sequence of structs 'T'.

        Returns true if parsing succeeds, otherwise returns false.
    */
    template <typename... T>
    bool operator() (T&&... t)
    {
        return (doArchiveChecked (std::forward<T> (t)) && ...);
    }

private:
    template <typename T>
    bool doArchiveChecked (T&& t)
    {
        if (failed)
            return false;

        doArchive (t);
        return ! failed;
    }

    void doArchive (ChannelInGroup& x)
    {
        if (const auto popped = popBytes (1))
        {
            const auto p = *popped;
            x = ChannelInGroup (p[0] & std::byte { 0x7f });
            return;
        }

        failed = true;
    }

    // If we're trying to parse into a constant, then we should check that the next byte(s)
    // match that constant.
    void doArchive (const std::byte& x)
    {
        std::byte temp{};

        if (! doArchiveChecked (temp))
            return;

        failed |= x != temp;
    }

    void doArchive (std::byte& x)
    {
        if (const auto popped = popBytes (1))
        {
            const auto p = *popped;
            x = p[0] & std::byte { 0x7f };
            return;
        }

        failed = true;
    }

    void doArchive (const uint16_t& x)
    {
        uint16_t temp{};

        if (! doArchiveChecked (temp))
            return;

        failed |= temp != x;
    }

    void doArchive (uint16_t& x)
    {
        if (const auto popped = popBytes (2))
        {
            const auto p = *popped;
            x = (uint16_t) (((uint16_t) p[0] & 0x7f) << 0x00)
              | (uint16_t) (((uint16_t) p[1] & 0x7f) << 0x07);
            return;
        }

        failed = true;
    }

    void doArchive (const uint32_t& x)
    {
        uint32_t temp{};

        if (! doArchiveChecked (temp))
            return;

        failed |= temp != x;
    }

    void doArchive (uint32_t& x)
    {
        if (const auto popped = popBytes (4))
        {
            const auto p = *popped;
            x = (((uint32_t) p[0] & 0x7f) << 0x00)
              | (((uint32_t) p[1] & 0x7f) << 0x07)
              | (((uint32_t) p[2] & 0x7f) << 0x0e)
              | (((uint32_t) p[3] & 0x7f) << 0x15);
            return;
        }

        failed = true;
    }

    template <uint8_t NumBytes, bool B>
    void doArchive (MessageMeta::SpanWithSizeBytes<NumBytes, Span<const std::byte>, B> x)
    {
        IntForNumBytesT<NumBytes> numBytes{};

        // Read the number of bytes in the field
        if (! doArchiveChecked (numBytes))
            return;

        // Attempt to pop that many bytes
        if (const auto popped = popBytes (numBytes))
        {
            x.span = *popped;
            return;
        }

        failed = true;
    }

    template <uint8_t NumBytes, size_t N>
    void doArchive (MessageMeta::SpanWithSizeBytes<NumBytes, Span<const std::array<std::byte, N>>> x)
    {
        IntForNumBytesT<NumBytes> numItems{};

        // Read the number of items in the field
        if (! doArchiveChecked (numItems))
            return;

        if (const auto popped = popBytes (numItems * N))
        {
            x.span = Span (unalignedPointerCast<const std::array<std::byte, N>*> (popped->data()), numItems);
            return;
        }

        failed = true;
    }

    template <size_t N>
    void doArchive (Span<const std::byte, N>& x)
    {
        if (const auto popped = popBytes (bytes.size()))
        {
            x = *popped;
            return;
        }

        failed = true;
    }

    template <size_t N>
    void doArchive (std::array<std::byte, N>& x)
    {
        if (const auto popped = popBytes (x.size()))
        {
            const auto p = *popped;
            std::transform (p.begin(), p.end(), x.begin(), [] (std::byte b)
            {
                return b & std::byte { 0x7f };
            });
            return;
        }

        failed = true;
    }

    template <typename T>
    void doArchive (T& t)
    {
        juce::detail::doLoad (*this, t);
    }

    template <typename T>
    void doArchive (Named<T> named)
    {
        doArchiveChecked (named.value);
    }

    std::optional<Span<const std::byte>> popBytes (size_t num)
    {
        if (bytes.size() < num)
            return {};

        const Span result { bytes.data(), num };
        bytes = Span { bytes.data() + num, bytes.size() - num };
        return result;
    }

    Span<const std::byte> bytes;    /*   Bytes making up a CI message. */
    int version{};                  /*   The version to assume when parsing the message, specified in the message header. */
    bool failed = false;
};

//==============================================================================
/*
    Converts one or more structs into a byte sequence suitable for transmission
    as a MIDI-CI message.
*/
class Writer
{
public:
    /*  Constructs a writer that will write into the provided buffer. */
    explicit Writer (std::vector<std::byte>& b)
        : Writer (b, static_cast<uint8_t> (MessageMeta::implementationVersion)) {}

    /*  Constructs a writer that will write a MIDI-CI message of the requested
        version to the provided buffer.

        Fields introduced in later MIDI-CI versions will be ignored.
    */
    Writer (std::vector<std::byte>& b, int v)
        : bytes (b), version (v) {}

    std::optional<int> getVersion() const { return version; }

    /*  Formats the information contained in the provided structs into a
        MIDI-CI message, and returns a bool indicating success or failure.
    */
    template <typename... T>
    bool operator() (const T&... t)
    {
        return (doArchiveChecked (t) && ...);
    }

private:
    template <typename T>
    bool doArchiveChecked (T&& t)
    {
        if (failed)
            return false;

        doArchive (t);
        return ! failed;
    }

    void doArchive (ChannelInGroup x)
    {
        doArchiveChecked (std::byte (x));
    }

    void doArchive (std::byte x)
    {
        bytes.push_back (x);
    }

    void doArchive (uint16_t x)
    {
        bytes.insert (bytes.end(), { (std::byte) ((x >> 0x00) & 0x7f),
                                     (std::byte) ((x >> 0x07) & 0x7f) });
    }

    void doArchive (uint32_t x)
    {
        bytes.insert (bytes.end(), { (std::byte) ((x >> 0x00) & 0x7f),
                                     (std::byte) ((x >> 0x07) & 0x7f),
                                     (std::byte) ((x >> 0x0e) & 0x7f),
                                     (std::byte) ((x >> 0x15) & 0x7f) });
    }

    template <uint8_t NumBytes, typename T, bool B>
    void doArchive (MessageMeta::SpanWithSizeBytes<NumBytes, T, B> x)
    {
        if (x.span.size() >= (1 << (7 * NumBytes)))
        {
            // Unable to express the size of the field in the requested number of bytes
            jassertfalse;
            failed = true;
            return;
        }

        // Write the number of bytes, followed by the bytes themselves.
        const auto numBytes = (IntForNumBytesT<NumBytes>) x.span.size();
        doArchiveChecked (numBytes);
        doArchiveChecked (x.span);
    }

    template <typename T, size_t N>
    void doArchive (Span<const T, N> x)
    {
        failed = ! std::all_of (x.begin(), x.end(), [&] (const auto& item)
        {
            return doArchiveChecked (item);
        });
    }

    template <size_t N>
    void doArchive (const std::array<std::byte, N>& x)
    {
        bytes.insert (bytes.end(), x.begin(), x.end());
    }

    template <typename T>
    void doArchive (const T& t)
    {
        juce::detail::doSave (*this, t);
    }

    template <typename T>
    void doArchive (Named<T> named)
    {
        doArchiveChecked (named.value);
    }

    std::vector<std::byte>& bytes;    /*   The buffer that will hold the completed message. */
    int version{};                    /*   The version to assume when writing the message, specified in the message header. */
    bool failed = false;
};

} // namespace juce::midi_ci::detail::Marshalling