JUCE/modules/juce_midi_ci/detail/juce_CIPropertyDataMessageChunker.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.

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   Agreement and JUCE Privacy Policy.

   End User License Agreement: www.juce.com/juce-7-licence
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   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.

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

namespace juce::midi_ci::detail
{

/*
    Breaks up a large property exchange message into chunks of the requested size.

    Note that the header *must* fit inside the first block, so you must ensure
    that the header is small enough to fit inside the requested chunk size.
*/
class PropertyDataMessageChunker
{
    auto tie() const { return std::tie (storage, body, source, dest, chunkSize, messageKind, requestId); }

public:
    /*  Constructs a chunker instance.

        @param storageIn        backing storage where each chunk will be written
        @param chunkSizeIn      the maximum size of each chunk
        @param messageKindIn    the subID2 byte identifying the type of message in each chunk
        @param requestIdIn      the id that should be included in all messages that are part of the same property exchange transaction
        @param headerIn         the header bytes of the message. This is always JSON encoded as 7-bit ASCII text, see the MIDI-CI spec for full details
        @param sourceIn         the MUID of the device sending the chunked messages
        @param destIn           the MUID of the recipient of the chunked messages
        @param bodyIn           a stream that can supply the data payload for this chunk sequence. All payload bytes *must* be 7-bit (MSB not set).
    */
    PropertyDataMessageChunker (std::vector<std::byte>& storageIn,
                                int chunkSizeIn,
                                const std::byte messageKindIn,
                                const std::byte requestIdIn,
                                Span<const std::byte> headerIn,
                                MUID sourceIn,
                                MUID destIn,
                                InputStream& bodyIn);

    /*  Returns true if this chunker hasn't finished producing chunks. */
    explicit operator bool() const { return *this != PropertyDataMessageChunker(); }

    /*  Allowing foreach usage. */
    auto begin() const { return *this; }

    /*  Allow foreach usage. */
    auto end()   const { return PropertyDataMessageChunker{}; }

    /*  Writes the bytes of the next chunk, if any, into the storage buffer. */
    PropertyDataMessageChunker& operator++() noexcept;

    /*  Checks whether the state of this chunker matches the state of another chunker, enabling foreach usage. */
    bool operator== (const PropertyDataMessageChunker& other) const noexcept { return tie() == other.tie(); }
    bool operator!= (const PropertyDataMessageChunker& other) const noexcept { return tie() != other.tie(); }

    /*  Returns a span over the valid bytes in the output buffer. */
    Span<const std::byte> operator*() const noexcept;

private:
    PropertyDataMessageChunker() = default;

    Span<const std::byte> getHeaderForBlock() const;
    int getRoomForBody() const;
    bool hasRoomForBody() const;
    void populateStorage() const;

    Span<const std::byte> header;
    std::vector<std::byte>* storage{};
    InputStream* body{};
    MUID source = MUID::makeUnchecked (0), dest = MUID::makeUnchecked (0);
    int chunkSize{};
    uint16_t thisChunk { 0x01 };
    std::byte messageKind{};
    std::byte requestId{};
};

} // namespace juce::midi_ci::detail