BitStreamWriter.cpp

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#include "zserio/BitStreamWriter.h"
#include "zserio/FloatUtil.h"
 
namespace zserio
{
 
static const std::array<uint32_t, 33> MAX_U32_VALUES = {
        0x00U,
        0x0001U,
        0x0003U,
        0x0007U,
        0x000fU,
        0x001fU,
        0x003fU,
        0x007fU,
        0x00ffU,
        0x01ffU,
        0x03ffU,
        0x07ffU,
        0x0fffU,
        0x1fffU,
        0x3fffU,
        0x7fffU,
        0xffffU,
        0x0001ffffU,
        0x0003ffffU,
        0x0007ffffU,
        0x000fffffU,
        0x001fffffU,
        0x003fffffU,
        0x007fffffU,
        0x00ffffffU,
        0x01ffffffU,
        0x03ffffffU,
        0x07ffffffU,
        0x0fffffffU,
        0x1fffffffU,
        0x3fffffffU,
        0x7fffffffU,
        0xffffffffU,
};
 
static const std::array<int32_t, 33> MIN_I32_VALUES = {
        0,
        -0x0001,
        -0x0002,
        -0x0004,
        -0x0008,
        -0x0010,
        -0x0020,
        -0x0040,
        -0x0080,
        -0x0100,
        -0x0200,
        -0x0400,
        -0x0800,
        -0x1000,
        -0x2000,
        -0x4000,
        -0x8000,
        -0x00010000,
        -0x00020000,
        -0x00040000,
        -0x00080000,
        -0x00100000,
        -0x00200000,
        -0x00400000,
        -0x00800000,
        -0x01000000,
        -0x02000000,
        -0x04000000,
        -0x08000000,
        -0x10000000,
        -0x20000000,
        -0x40000000,
        INT32_MIN,
};
 
static const std::array<int32_t, 33> MAX_I32_VALUES = {
        0x00,
        0x0000,
        0x0001,
        0x0003,
        0x0007,
        0x000f,
        0x001f,
        0x003f,
        0x007f,
        0x00ff,
        0x01ff,
        0x03ff,
        0x07ff,
        0x0fff,
        0x1fff,
        0x3fff,
        0x7fff,
        0x0000ffff,
        0x0001ffff,
        0x0003ffff,
        0x0007ffff,
        0x000fffff,
        0x001fffff,
        0x003fffff,
        0x007fffff,
        0x00ffffff,
        0x01ffffff,
        0x03ffffff,
        0x07ffffff,
        0x0fffffff,
        0x1fffffff,
        0x3fffffff,
        0x7fffffff,
};
 
static const std::array<uint64_t, 65> MAX_U64_VALUES = {
        0x00ULL,
        0x0001ULL,
        0x0003ULL,
        0x0007ULL,
        0x000fULL,
        0x001fULL,
        0x003fULL,
        0x007fULL,
        0x00ffULL,
        0x01ffULL,
        0x03ffULL,
        0x07ffULL,
        0x0fffULL,
        0x1fffULL,
        0x3fffULL,
        0x7fffULL,
        0xffffULL,
        0x0001ffffULL,
        0x0003ffffULL,
        0x0007ffffULL,
        0x000fffffULL,
        0x001fffffULL,
        0x003fffffULL,
        0x007fffffULL,
        0x00ffffffULL,
        0x01ffffffULL,
        0x03ffffffULL,
        0x07ffffffULL,
        0x0fffffffULL,
        0x1fffffffULL,
        0x3fffffffULL,
        0x7fffffffULL,
        0xffffffffULL,
        0x0001ffffffffULL,
        0x0003ffffffffULL,
        0x0007ffffffffULL,
        0x000fffffffffULL,
        0x001fffffffffULL,
        0x003fffffffffULL,
        0x007fffffffffULL,
        0x00ffffffffffULL,
        0x01ffffffffffULL,
        0x03ffffffffffULL,
        0x07ffffffffffULL,
        0x0fffffffffffULL,
        0x1fffffffffffULL,
        0x3fffffffffffULL,
        0x7fffffffffffULL,
        0xffffffffffffULL,
        0x0001ffffffffffffULL,
        0x0003ffffffffffffULL,
        0x0007ffffffffffffULL,
        0x000fffffffffffffULL,
        0x001fffffffffffffULL,
        0x003fffffffffffffULL,
        0x007fffffffffffffULL,
        0x00ffffffffffffffULL,
        0x01ffffffffffffffULL,
        0x03ffffffffffffffULL,
        0x07ffffffffffffffULL,
        0x0fffffffffffffffULL,
        0x1fffffffffffffffULL,
        0x3fffffffffffffffULL,
        0x7fffffffffffffffULL,
        0xffffffffffffffffULL,
};
 
static const std::array<int64_t, 65> MIN_I64_VALUES = {
        0LL,
        -0x0001LL,
        -0x0002LL,
        -0x0004LL,
        -0x0008LL,
        -0x0010LL,
        -0x0020LL,
        -0x0040LL,
        -0x0080LL,
        -0x0100LL,
        -0x0200LL,
        -0x0400LL,
        -0x0800LL,
        -0x1000LL,
        -0x2000LL,
        -0x4000LL,
        -0x8000LL,
        -0x00010000LL,
        -0x00020000LL,
        -0x00040000LL,
        -0x00080000LL,
        -0x00100000LL,
        -0x00200000LL,
        -0x00400000LL,
        -0x00800000LL,
        -0x01000000LL,
        -0x02000000LL,
        -0x04000000LL,
        -0x08000000LL,
        -0x10000000LL,
        -0x20000000LL,
        -0x40000000LL,
        -0x80000000LL,
        -0x000100000000LL,
        -0x000200000000LL,
        -0x000400000000LL,
        -0x000800000000LL,
        -0x001000000000LL,
        -0x002000000000LL,
        -0x004000000000LL,
        -0x008000000000LL,
        -0x010000000000LL,
        -0x020000000000LL,
        -0x040000000000LL,
        -0x080000000000LL,
        -0x100000000000LL,
        -0x200000000000LL,
        -0x400000000000LL,
        -0x800000000000LL,
        -0x0001000000000000LL,
        -0x0002000000000000LL,
        -0x0004000000000000LL,
        -0x0008000000000000LL,
        -0x0010000000000000LL,
        -0x0020000000000000LL,
        -0x0040000000000000LL,
        -0x0080000000000000LL,
        -0x0100000000000000LL,
        -0x0200000000000000LL,
        -0x0400000000000000LL,
        -0x0800000000000000LL,
        -0x1000000000000000LL,
        -0x2000000000000000LL,
        -0x4000000000000000LL,
        INT64_MIN,
};
 
static const std::array<int64_t, 65> MAX_I64_VALUES = {
        0x00LL,
        0x0000LL,
        0x0001LL,
        0x0003LL,
        0x0007LL,
        0x000fLL,
        0x001fLL,
        0x003fLL,
        0x007fLL,
        0x00ffLL,
        0x01ffLL,
        0x03ffLL,
        0x07ffLL,
        0x0fffLL,
        0x1fffLL,
        0x3fffLL,
        0x7fffLL,
        0x0000ffffLL,
        0x0001ffffLL,
        0x0003ffffLL,
        0x0007ffffLL,
        0x000fffffLL,
        0x001fffffLL,
        0x003fffffLL,
        0x007fffffLL,
        0x00ffffffLL,
        0x01ffffffLL,
        0x03ffffffLL,
        0x07ffffffLL,
        0x0fffffffLL,
        0x1fffffffLL,
        0x3fffffffLL,
        0x7fffffffLL,
        0x0000ffffffffLL,
        0x0001ffffffffLL,
        0x0003ffffffffLL,
        0x0007ffffffffLL,
        0x000fffffffffLL,
        0x001fffffffffLL,
        0x003fffffffffLL,
        0x007fffffffffLL,
        0x00ffffffffffLL,
        0x01ffffffffffLL,
        0x03ffffffffffLL,
        0x07ffffffffffLL,
        0x0fffffffffffLL,
        0x1fffffffffffLL,
        0x3fffffffffffLL,
        0x7fffffffffffLL,
        0x0000ffffffffffffLL,
        0x0001ffffffffffffLL,
        0x0003ffffffffffffLL,
        0x0007ffffffffffffLL,
        0x000fffffffffffffLL,
        0x001fffffffffffffLL,
        0x003fffffffffffffLL,
        0x007fffffffffffffLL,
        0x00ffffffffffffffLL,
        0x01ffffffffffffffLL,
        0x03ffffffffffffffLL,
        0x07ffffffffffffffLL,
        0x0fffffffffffffffLL,
        0x1fffffffffffffffLL,
        0x3fffffffffffffffLL,
        0x7fffffffffffffffLL,
};
 
BitStreamWriter::BitStreamWriter(uint8_t* buffer, size_t bufferBitSize, BitsTag) :
        m_buffer(buffer, (bufferBitSize + 7) / 8),
        m_bitIndex(0),
        m_bufferBitSize(bufferBitSize)
{}
 
BitStreamWriter::BitStreamWriter(uint8_t* buffer, size_t bufferByteSize) :
        BitStreamWriter(Span<uint8_t>(buffer, bufferByteSize))
{}
 
BitStreamWriter::BitStreamWriter(Span<uint8_t> buffer) :
        m_buffer(buffer),
        m_bitIndex(0),
        m_bufferBitSize(buffer.size() * 8)
{}
 
BitStreamWriter::BitStreamWriter(Span<uint8_t> buffer, size_t bufferBitSize) :
        m_buffer(buffer),
        m_bitIndex(0),
        m_bufferBitSize(bufferBitSize)
{
    if (buffer.size() < (bufferBitSize + 7) / 8)
    {
        throw CppRuntimeException("BitStreamWriter: Wrong buffer bit size ('")
                << buffer.size() << "' < '" << (bufferBitSize + 7) / 8 << "')!";
    }
}
 
void BitStreamWriter::writeUnsignedBits32(uint32_t data, uint8_t numBits)
{
    if (numBits == 0 || numBits > sizeof(uint32_t) * 8 || data > MAX_U32_VALUES[numBits])
    {
        throw CppRuntimeException("BitStreamWriter: Writing of ")
                << numBits << "-bits value '" << data << "' failed!";
    }
 
    writeUnsignedBits32Impl(data, numBits);
}
 
void BitStreamWriter::writeUnsignedBits64(uint64_t data, uint8_t numBits)
{
    if (numBits == 0 || numBits > sizeof(uint64_t) * 8 || data > MAX_U64_VALUES[numBits])
    {
        throw CppRuntimeException("BitStreamWriter: Writing of ")
                << numBits << "-bits value '" << data << "' failed!";
    }
 
    writeUnsignedBits64Impl(data, numBits);
}
 
void BitStreamWriter::writeSignedBits32(int32_t data, uint8_t numBits)
{
    if (numBits == 0 || numBits > sizeof(int32_t) * 8 || data < MIN_I32_VALUES[numBits] ||
            data > MAX_I32_VALUES[numBits])
    {
        throw CppRuntimeException("BitStreamWriter: Writing of ")
                << numBits << "-bits value '" << data << "' failed!";
    }
 
    writeUnsignedBits32Impl(static_cast<uint32_t>(data) & MAX_U32_VALUES[numBits], numBits);
}
 
void BitStreamWriter::writeSignedBits64(int64_t data, uint8_t numBits)
{
    if (numBits == 0 || numBits > sizeof(int64_t) * 8 || data < MIN_I64_VALUES[numBits] ||
            data > MAX_I64_VALUES[numBits])
    {
        throw CppRuntimeException("BitStreamWriter: Writing of ")
                << numBits << "-bits value '" << data << "' failed!";
    }
 
    writeUnsignedBits64Impl(static_cast<uint64_t>(data) & MAX_U64_VALUES[numBits], numBits);
}
 
void BitStreamWriter::writeBool(Bool data)
{
    writeUnsignedBits32Impl((data ? 1 : 0), 1);
}
 
void BitStreamWriter::writeVarInt16(VarInt16 data)
{
    writeSignedVarNum(data, 2, detail::bitSizeOf(data) / 8);
}
 
void BitStreamWriter::writeVarInt32(VarInt32 data)
{
    writeSignedVarNum(data, 4, detail::bitSizeOf(data) / 8);
}
 
void BitStreamWriter::writeVarInt64(VarInt64 data)
{
    writeSignedVarNum(data, 8, detail::bitSizeOf(data) / 8);
}
 
void BitStreamWriter::writeVarInt(VarInt data)
{
    if (data == INT64_MIN)
    {
        writeUnsignedBits32Impl(0x80, 8); // INT64_MIN is encoded as -0
    }
    else
    {
        writeSignedVarNum(data, 9, detail::bitSizeOf(data) / 8);
    }
}
 
void BitStreamWriter::writeVarUInt16(VarUInt16 data)
{
    writeUnsignedVarNum(data, 2, detail::bitSizeOf(data) / 8);
}
 
void BitStreamWriter::writeVarUInt32(VarUInt32 data)
{
    writeUnsignedVarNum(data, 4, detail::bitSizeOf(data) / 8);
}
 
void BitStreamWriter::writeVarUInt64(VarUInt64 data)
{
    writeUnsignedVarNum(data, 8, detail::bitSizeOf(data) / 8);
}
 
void BitStreamWriter::writeVarUInt(VarUInt data)
{
    writeUnsignedVarNum(data, 9, detail::bitSizeOf(data) / 8);
}
 
void BitStreamWriter::writeVarSize(VarSize data)
{
    writeUnsignedVarNum(data, 5, detail::bitSizeOf(data) / 8);
}
 
void BitStreamWriter::writeFloat16(Float16 data)
{
    const uint16_t halfPrecisionFloat = convertFloatToUInt16(data);
    writeUnsignedBits32Impl(halfPrecisionFloat, 16);
}
 
void BitStreamWriter::writeFloat32(Float32 data)
{
    const uint32_t singlePrecisionFloat = convertFloatToUInt32(data);
    writeUnsignedBits32Impl(singlePrecisionFloat, 32);
}
 
void BitStreamWriter::writeFloat64(Float64 data)
{
    const uint64_t doublePrecisionFloat = convertDoubleToUInt64(data);
    writeUnsignedBits64(doublePrecisionFloat, 64);
}
 
void BitStreamWriter::writeBytes(BytesView data)
{
    const VarSize len = fromCheckedValue<VarSize>(convertSizeToUInt32(data.size()));
    writeVarSize(len);
 
    const BitPosType beginBitPosition = getBitPosition();
    if ((beginBitPosition & 0x07U) != 0)
    {
        // we are not aligned to byte
        for (size_t i = 0; i < len; ++i)
        {
            writeUnsignedBits32Impl(data[i], 8);
        }
    }
    else
    {
        // we are aligned to bytes
        setBitPosition(beginBitPosition + len * 8);
        if (hasWriteBuffer())
        {
            (void)std::copy(data.begin(), data.end(), m_buffer.begin() + beginBitPosition / 8);
        }
    }
}
 
void BitStreamWriter::writeString(std::string_view data)
{
    const VarSize len = fromCheckedValue<VarSize>(convertSizeToUInt32(data.size()));
    writeVarSize(len);
 
    const BitPosType beginBitPosition = getBitPosition();
    if ((beginBitPosition & 0x07U) != 0)
    {
        // we are not aligned to byte
        for (size_t i = 0; i < len; ++i)
        {
            // TODO[Mi-L@]: can we use unchecked here?!
            writeUnsignedBits32(static_cast<uint8_t>(std::char_traits<char>::to_int_type(data[i])), 8);
        }
    }
    else
    {
        // we are aligned to bytes
        setBitPosition(beginBitPosition + len * 8);
        if (hasWriteBuffer())
        {
            (void)std::copy(data.begin(), data.begin() + len, m_buffer.data() + beginBitPosition / 8);
        }
    }
}
 
void BitStreamWriter::setBitPosition(BitPosType position)
{
    if (hasWriteBuffer())
    {
        checkCapacity(position);
    }
 
    m_bitIndex = position;
}
 
void BitStreamWriter::alignTo(size_t alignment)
{
    const BitPosType offset = getBitPosition() % alignment;
    if (offset != 0)
    {
        const uint8_t skip = static_cast<uint8_t>(alignment - offset);
        writeUnsignedBits64(0, skip);
    }
}
 
const uint8_t* BitStreamWriter::getWriteBuffer() const
{
    return m_buffer.data();
}
 
Span<const uint8_t> BitStreamWriter::getBuffer() const
{
    return m_buffer;
}
 
void BitStreamWriter::writeUnsignedBits32Impl(uint32_t data, uint8_t numBits)
{
    if (!hasWriteBuffer())
    {
        m_bitIndex += numBits;
        return;
    }
 
    checkCapacity(m_bitIndex + numBits);
 
    uint8_t restNumBits = numBits;
    const uint8_t bitsUsed = m_bitIndex & 0x07U;
    uint8_t bitsFree = static_cast<uint8_t>(8 - bitsUsed);
    size_t byteIndex = m_bitIndex / 8;
 
    if (restNumBits > bitsFree)
    {
        // first part
        const uint8_t shiftNum = static_cast<uint8_t>(restNumBits - bitsFree);
        const uint8_t maskedByte = static_cast<uint8_t>(m_buffer[byteIndex] & ~(0xFFU >> bitsUsed));
        m_buffer[byteIndex++] = static_cast<uint8_t>(maskedByte | (data >> shiftNum));
        restNumBits = static_cast<uint8_t>(restNumBits - bitsFree);
 
        // middle parts
        while (restNumBits >= 8)
        {
            restNumBits = static_cast<uint8_t>(restNumBits - 8);
            m_buffer[byteIndex++] = static_cast<uint8_t>((data >> restNumBits) & MAX_U32_VALUES[8]);
        }
 
        // reset bits free
        bitsFree = 8;
    }
 
    // last part
    if (restNumBits > 0)
    {
        const uint8_t shiftNum = static_cast<uint8_t>(bitsFree - restNumBits);
        const uint32_t mask = MAX_U32_VALUES[restNumBits];
        const uint8_t maskedByte =
                m_buffer[byteIndex] & static_cast<uint8_t>(~static_cast<uint8_t>(mask << shiftNum));
        m_buffer[byteIndex] = static_cast<uint8_t>(maskedByte | ((data & mask) << shiftNum));
    }
 
    m_bitIndex += numBits;
}
 
inline void BitStreamWriter::writeUnsignedBits64Impl(uint64_t data, uint8_t numBits)
{
    if (numBits <= 32)
    {
        writeUnsignedBits32Impl(static_cast<uint32_t>(data), numBits);
    }
    else
    {
        writeUnsignedBits32Impl(static_cast<uint32_t>(data >> 32U), static_cast<uint8_t>(numBits - 32));
        writeUnsignedBits32Impl(static_cast<uint32_t>(data), 32);
    }
}
 
inline void BitStreamWriter::writeSignedVarNum(int64_t value, size_t maxVarBytes, size_t numVarBytes)
{
    const uint64_t absValue = static_cast<uint64_t>(value < 0 ? -value : value);
    writeVarNum(absValue, true, value < 0, maxVarBytes, numVarBytes);
}
 
inline void BitStreamWriter::writeUnsignedVarNum(uint64_t value, size_t maxVarBytes, size_t numVarBytes)
{
    writeVarNum(value, false, false, maxVarBytes, numVarBytes);
}
 
inline void BitStreamWriter::writeVarNum(
        uint64_t value, bool hasSign, bool isNegative, size_t maxVarBytes, size_t numVarBytes)
{
    static const std::array<uint64_t, 8> bitMasks = {0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0xFF};
    const bool hasMaxByteRange = (numVarBytes == maxVarBytes);
 
    for (size_t i = 0; i < numVarBytes; i++)
    {
        uint8_t byte = 0x00;
        uint8_t numBits = 8;
        const bool hasNextByte = (i < numVarBytes - 1);
        const bool hasSignBit = (hasSign && i == 0);
        if (hasSignBit)
        {
            if (isNegative)
            {
                byte |= 0x80U;
            }
            numBits--;
        }
        if (hasNextByte)
        {
            numBits--;
            const uint8_t add = static_cast<uint8_t>(0x01U << numBits);
            byte = static_cast<uint8_t>(byte | add); // use bit 6 if signed bit is present, use bit 7 otherwise
        }
        else // this is the last byte
        {
            if (!hasMaxByteRange) // next byte indicator is not used in last byte in case of max byte range
            {
                numBits--;
            }
        }
 
        const size_t shiftBits = (numVarBytes - (i + 1)) * 7 + ((hasMaxByteRange && hasNextByte) ? 1 : 0);
        const uint8_t add = static_cast<uint8_t>((value >> shiftBits) & bitMasks[numBits - 1U]);
        byte = static_cast<uint8_t>(byte | add);
        writeUnsignedBits32Impl(byte, 8);
    }
}
 
inline void BitStreamWriter::throwInsufficientCapacityException() const
{
    throw InsufficientCapacityException("BitStreamWriter: Reached end of bit buffer!");
}
 
inline void BitStreamWriter::checkCapacity(size_t bitSize) const
{
    if (bitSize > m_bufferBitSize)
    {
        throwInsufficientCapacityException();
    }
}
 
} // namespace zserio