JUCE/modules/juce_blocks_basics/protocol/juce_BitPackingUtilities.h

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

   This file is part of the JUCE library.
   Copyright (c) 2016 - ROLI Ltd.

   Permission is granted to use this software under the terms of either:
   a) the GPL v2 (or any later version)
   b) the Affero GPL v3

   Details of these licenses can be found at: www.gnu.org/licenses

   JUCE is distributed in the hope that it will be useful, but WITHOUT ANY
   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

   ------------------------------------------------------------------------------

   To release a closed-source product which uses JUCE, commercial licenses are
   available: visit www.juce.com for more information.

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


/**
    All sysex messages to or from a BLOCKS device begin with these header bytes.
    The next byte that follows indicates the device index within the topology, where
    the 0x40 bit is set for device->host messages, and clear for host->device messages.
    The lower 6 bits contain the topology index of the destination or source device.
*/
static const uint8 roliSysexHeader[] = { 0xf0, 0x00, 0x21, 0x10, 0x77 };


static uint8 calculatePacketChecksum (const uint8* data, uint32 size) noexcept
{
    uint8 checksum = (uint8) size;

    for (uint32 i = 0; i < size; ++i)
        checksum += checksum * 2 + data[i];

    return checksum & 0x7f;
}


//==============================================================================
template <int numBits>
struct IntegerWithBitSize
{
    IntegerWithBitSize() noexcept = default;
    IntegerWithBitSize (const IntegerWithBitSize&) noexcept = default;
    IntegerWithBitSize& operator= (const IntegerWithBitSize&) noexcept = default;

    IntegerWithBitSize (uint32 v) noexcept : value (v)
    {
        static_assert (numBits <= 32, "numBits must be <= 32");
        jassert (v >= 0 && v <= maxValue);
    }

    enum
    {
        bits = numBits,
        maxValue = static_cast<uint32> ((1ULL << numBits) - 1ULL)
    };

    operator uint32() const noexcept            { return value; }
    uint32 get() const noexcept                 { return value; }

    uint8 getScaledToByte() const noexcept
    {
        return (uint8) (numBits < 8 ? (uint32) (value << (8 - numBits))
                                    : (uint32) (value >> (numBits - 8)));
    }

    float toUnipolarFloat() const noexcept      { return value / (float) maxValue; }
    float toBipolarFloat() const noexcept       { return static_cast<int32> (value << (32 - numBits)) / (float) 0x80000000u; }

    static IntegerWithBitSize fromUnipolarFloat (float value) noexcept
    {
        static_assert (numBits <= 31, "numBits must be <= 31");
        return IntegerWithBitSize ((uint32) jlimit (0, (int) maxValue, (int) (value * maxValue)));
    }

    static IntegerWithBitSize fromBipolarFloat (float value) noexcept
    {
        static_assert (numBits <= 31, "numBits must be <= 31");
        return IntegerWithBitSize (maxValue & (uint32) jlimit ((int) -(maxValue / 2), (int) (maxValue / 2), (int) (value * (maxValue / 2))));
    }

    uint32 value = 0;
};

//==============================================================================
/**
    This helper class allocates a block of 7-bit bytes and can push sequences of bits into it.
    @see Packed7BitArrayReader
*/
template <int allocatedBytes>
struct Packed7BitArrayBuilder
{
    const void* getData() const noexcept        { return data; }
    int size() const noexcept                   { return bytesWritten + (bitsInCurrentByte > 0 ? 1 : 0); }

    bool hasCapacity (int bitsNeeded) const noexcept
    {
        return ((bytesWritten + 2) * 7 + bitsInCurrentByte + bitsNeeded) <= allocatedBytes * 7;
    }

    void writeHeaderSysexBytes (uint8 deviceIndex) noexcept
    {
        jassert (bytesWritten + bitsInCurrentByte == 0);

        for (int i = 0; i < (int) sizeof (roliSysexHeader); ++i)
            data[bytesWritten++] = roliSysexHeader[i];

        jassert (deviceIndex < 128);
        data[bytesWritten++] = deviceIndex & 0x7f;
    }

    void writePacketSysexFooter() noexcept
    {
        if (bitsInCurrentByte != 0)
        {
            bitsInCurrentByte = 0;
            ++bytesWritten;
        }

        jassert (hasCapacity (0));

        uint32 headerBytes = (uint32) sizeof (roliSysexHeader) + 1;
        data[bytesWritten] = calculatePacketChecksum (data + headerBytes, (uint32) bytesWritten - headerBytes);
        ++bytesWritten;

        data[bytesWritten++] = 0xf7;
    }

    template <int numBits>
    Packed7BitArrayBuilder& operator<< (IntegerWithBitSize<numBits> value) noexcept
    {
        writeBits (value.value, numBits);
        return *this;
    }

    void writeBits (uint32 value, int numBits) noexcept
    {
        jassert (numBits <= 32);
        jassert (hasCapacity (numBits));
        jassert (numBits == 32 || (value >> numBits) == 0);

        while (numBits > 0)
        {
            if (bitsInCurrentByte == 0)
            {
                if (numBits < 7)
                {
                    data[bytesWritten] = (uint8) value;
                    bitsInCurrentByte = numBits;
                    return;
                }

                if (numBits == 7)
                {
                    data[bytesWritten++] = (uint8) value;
                    return;
                }

                data[bytesWritten++] = (uint8) (value & 0x7f);
                value >>= 7;
                numBits -= 7;
            }
            else
            {
                const int bitsToDo = jmin (7 - bitsInCurrentByte, numBits);

                data[bytesWritten] |= ((value & ((1 << bitsToDo) - 1)) << bitsInCurrentByte);
                value >>= bitsToDo;
                numBits -= bitsToDo;
                bitsInCurrentByte += bitsToDo;

                if (bitsInCurrentByte == 7)
                {
                    bitsInCurrentByte = 0;
                    ++bytesWritten;
                }
            }
        }
    }

    struct State
    {
        int bytesWritten, bitsInCurrentByte;
    };

    State getState() const noexcept
    {
        return { bytesWritten, bitsInCurrentByte };
    }

    void restore (State state) noexcept
    {
        bytesWritten = state.bytesWritten;
        bitsInCurrentByte = state.bitsInCurrentByte;
    }

private:
    uint8 data[allocatedBytes];
    int bytesWritten = 0, bitsInCurrentByte = 0;
};


//==============================================================================
/**
    This helper class reads from a block of 7-bit bytes as sequences of bits.
    @see Packed7BitArrayBuilder
*/
struct Packed7BitArrayReader
{
    Packed7BitArrayReader (const void* sourceData, int numBytes) noexcept
        : data (static_cast<const uint8*> (sourceData)), totalBits (numBytes * 7)
    {
    }

    int getRemainingBits() const noexcept
    {
        return totalBits - bitsReadInCurrentByte;
    }

    template <typename Target>
    Target read() noexcept
    {
        return Target (readBits (Target::bits));
    }

    uint32 readBits (int numBits) noexcept
    {
        jassert (numBits <= 32);
        jassert (getRemainingBits() >= numBits);

        uint32 value = 0;
        int bitsSoFar = 0;

        while (numBits > 0)
        {
            const uint32 valueInCurrentByte = (*data >> bitsReadInCurrentByte);

            const int bitsAvailable = 7 - bitsReadInCurrentByte;

            if (bitsAvailable > numBits)
            {
                value |= ((valueInCurrentByte & ((1 << numBits) - 1)) << bitsSoFar);
                bitsReadInCurrentByte += numBits;
                break;
            }

            value |= (valueInCurrentByte << bitsSoFar);
            numBits -= bitsAvailable;
            bitsSoFar += bitsAvailable;
            bitsReadInCurrentByte = 0;
            ++data;
            totalBits -= 7;
        }

        return value;
    }

    static bool checksumIsOK (const uint8* data, uint32 size) noexcept
    {
        return size > 1 && calculatePacketChecksum (data, size - 1) == data[size - 1];
    }

private:
    const uint8* data;
    int totalBits, bitsReadInCurrentByte = 0;
};