BitStreamReader.cpp

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#include <array>
#include <limits>
 
#include "zserio/BitStreamReader.h"
#include "zserio/CppRuntimeException.h"
#include "zserio/FloatUtil.h"
#include "zserio/RuntimeArch.h"
 
namespace zserio
{
 
namespace
{
 
// max size calculated to prevent "bitIndex + numBits" overflows
const size_t MAX_BUFFER_SIZE = std::numeric_limits<size_t>::max() / 8 - sizeof(size_t);
 
using BitPosType = BitStreamReader::BitPosType;
using ReaderContext = BitStreamReader::ReaderContext;
 
#ifdef ZSERIO_RUNTIME_64BIT
using BaseType = uint64_t;
using BaseSignedType = int64_t;
#else
using BaseType = uint32_t;
using BaseSignedType = int32_t;
#endif
 
#ifdef ZSERIO_RUNTIME_64BIT
const std::array<BaseType, 65> MASK_TABLE = {
        UINT64_C(0x00),
        UINT64_C(0x0001),
        UINT64_C(0x0003),
        UINT64_C(0x0007),
        UINT64_C(0x000f),
        UINT64_C(0x001f),
        UINT64_C(0x003f),
        UINT64_C(0x007f),
        UINT64_C(0x00ff),
        UINT64_C(0x01ff),
        UINT64_C(0x03ff),
        UINT64_C(0x07ff),
        UINT64_C(0x0fff),
        UINT64_C(0x1fff),
        UINT64_C(0x3fff),
        UINT64_C(0x7fff),
        UINT64_C(0xffff),
        UINT64_C(0x0001ffff),
        UINT64_C(0x0003ffff),
        UINT64_C(0x0007ffff),
        UINT64_C(0x000fffff),
        UINT64_C(0x001fffff),
        UINT64_C(0x003fffff),
        UINT64_C(0x007fffff),
        UINT64_C(0x00ffffff),
        UINT64_C(0x01ffffff),
        UINT64_C(0x03ffffff),
        UINT64_C(0x07ffffff),
        UINT64_C(0x0fffffff),
        UINT64_C(0x1fffffff),
        UINT64_C(0x3fffffff),
        UINT64_C(0x7fffffff),
        UINT64_C(0xffffffff),
 
        UINT64_C(0x00000001ffffffff),
        UINT64_C(0x00000003ffffffff),
        UINT64_C(0x00000007ffffffff),
        UINT64_C(0x0000000fffffffff),
        UINT64_C(0x0000001fffffffff),
        UINT64_C(0x0000003fffffffff),
        UINT64_C(0x0000007fffffffff),
        UINT64_C(0x000000ffffffffff),
        UINT64_C(0x000001ffffffffff),
        UINT64_C(0x000003ffffffffff),
        UINT64_C(0x000007ffffffffff),
        UINT64_C(0x00000fffffffffff),
        UINT64_C(0x00001fffffffffff),
        UINT64_C(0x00003fffffffffff),
        UINT64_C(0x00007fffffffffff),
        UINT64_C(0x0000ffffffffffff),
        UINT64_C(0x0001ffffffffffff),
        UINT64_C(0x0003ffffffffffff),
        UINT64_C(0x0007ffffffffffff),
        UINT64_C(0x000fffffffffffff),
        UINT64_C(0x001fffffffffffff),
        UINT64_C(0x003fffffffffffff),
        UINT64_C(0x007fffffffffffff),
        UINT64_C(0x00ffffffffffffff),
        UINT64_C(0x01ffffffffffffff),
        UINT64_C(0x03ffffffffffffff),
        UINT64_C(0x07ffffffffffffff),
        UINT64_C(0x0fffffffffffffff),
        UINT64_C(0x1fffffffffffffff),
        UINT64_C(0x3fffffffffffffff),
        UINT64_C(0x7fffffffffffffff),
        UINT64_C(0xffffffffffffffff),
};
#else
const std::array<BaseType, 33> MASK_TABLE = {
        UINT32_C(0x00),
        UINT32_C(0x0001),
        UINT32_C(0x0003),
        UINT32_C(0x0007),
        UINT32_C(0x000f),
        UINT32_C(0x001f),
        UINT32_C(0x003f),
        UINT32_C(0x007f),
        UINT32_C(0x00ff),
        UINT32_C(0x01ff),
        UINT32_C(0x03ff),
        UINT32_C(0x07ff),
        UINT32_C(0x0fff),
        UINT32_C(0x1fff),
        UINT32_C(0x3fff),
        UINT32_C(0x7fff),
        UINT32_C(0xffff),
        UINT32_C(0x0001ffff),
        UINT32_C(0x0003ffff),
        UINT32_C(0x0007ffff),
        UINT32_C(0x000fffff),
        UINT32_C(0x001fffff),
        UINT32_C(0x003fffff),
        UINT32_C(0x007fffff),
        UINT32_C(0x00ffffff),
        UINT32_C(0x01ffffff),
        UINT32_C(0x03ffffff),
        UINT32_C(0x07ffffff),
        UINT32_C(0x0fffffff),
        UINT32_C(0x1fffffff),
        UINT32_C(0x3fffffff),
        UINT32_C(0x7fffffff),
        UINT32_C(0xffffffff),
};
#endif
 
const uint8_t VARINT_SIGN_1 = UINT8_C(0x80);
const uint8_t VARINT_BYTE_1 = UINT8_C(0x3f);
const uint8_t VARINT_BYTE_N = UINT8_C(0x7f);
const uint8_t VARINT_HAS_NEXT_1 = UINT8_C(0x40);
const uint8_t VARINT_HAS_NEXT_N = UINT8_C(0x80);
 
const uint8_t VARUINT_BYTE = UINT8_C(0x7f);
const uint8_t VARUINT_HAS_NEXT = UINT8_C(0x80);
 
const uint32_t VARSIZE_MAX_VALUE = (UINT32_C(1) << 31U) - 1;
 
#ifdef ZSERIO_RUNTIME_64BIT
inline BaseType parse64(Span<const uint8_t>::const_iterator bufferIt)
{
    return static_cast<BaseType>(*bufferIt) << 56U | static_cast<BaseType>(*(bufferIt + 1)) << 48U |
            static_cast<BaseType>(*(bufferIt + 2)) << 40U | static_cast<BaseType>(*(bufferIt + 3)) << 32U |
            static_cast<BaseType>(*(bufferIt + 4)) << 24U | static_cast<BaseType>(*(bufferIt + 5)) << 16U |
            static_cast<BaseType>(*(bufferIt + 6)) << 8U | static_cast<BaseType>(*(bufferIt + 7));
}
 
inline BaseType parse56(Span<const uint8_t>::const_iterator bufferIt)
{
    return static_cast<BaseType>(*bufferIt) << 48U | static_cast<BaseType>(*(bufferIt + 1)) << 40U |
            static_cast<BaseType>(*(bufferIt + 2)) << 32U | static_cast<BaseType>(*(bufferIt + 3)) << 24U |
            static_cast<BaseType>(*(bufferIt + 4)) << 16U | static_cast<BaseType>(*(bufferIt + 5)) << 8U |
            static_cast<BaseType>(*(bufferIt + 6));
}
 
inline BaseType parse48(Span<const uint8_t>::const_iterator bufferIt)
{
    return static_cast<BaseType>(*bufferIt) << 40U | static_cast<BaseType>(*(bufferIt + 1)) << 32U |
            static_cast<BaseType>(*(bufferIt + 2)) << 24U | static_cast<BaseType>(*(bufferIt + 3)) << 16U |
            static_cast<BaseType>(*(bufferIt + 4)) << 8U | static_cast<BaseType>(*(bufferIt + 5));
}
 
inline BaseType parse40(Span<const uint8_t>::const_iterator bufferIt)
{
    return static_cast<BaseType>(*bufferIt) << 32U | static_cast<BaseType>(*(bufferIt + 1)) << 24U |
            static_cast<BaseType>(*(bufferIt + 2)) << 16U | static_cast<BaseType>(*(bufferIt + 3)) << 8U |
            static_cast<BaseType>(*(bufferIt + 4));
}
#endif
inline BaseType parse32(Span<const uint8_t>::const_iterator bufferIt)
{
    return static_cast<BaseType>(*bufferIt) << 24U | static_cast<BaseType>(*(bufferIt + 1)) << 16U |
            static_cast<BaseType>(*(bufferIt + 2)) << 8U | static_cast<BaseType>(*(bufferIt + 3));
}
 
inline BaseType parse24(Span<const uint8_t>::const_iterator bufferIt)
{
    return static_cast<BaseType>(*bufferIt) << 16U | static_cast<BaseType>(*(bufferIt + 1)) << 8U |
            static_cast<BaseType>(*(bufferIt + 2));
}
 
inline BaseType parse16(Span<const uint8_t>::const_iterator bufferIt)
{
    return static_cast<BaseType>(*bufferIt) << 8U | static_cast<BaseType>(*(bufferIt + 1));
}
 
inline BaseType parse8(Span<const uint8_t>::const_iterator bufferIt)
{
    return static_cast<BaseType>(*bufferIt);
}
 
inline void throwNumBitsIsNotValid(uint8_t numBits)
{
    throw CppRuntimeException("BitStreamReader: ReadBits #")
            << numBits << " is not valid, reading from stream failed!";
}
 
inline void checkNumBits(uint8_t numBits)
{
    if (numBits == 0 || numBits > 32)
    {
        throwNumBitsIsNotValid(numBits);
    }
}
 
inline void checkNumBits64(uint8_t numBits)
{
    if (numBits == 0 || numBits > 64)
    {
        throwNumBitsIsNotValid(numBits);
    }
}
 
inline void throwEof()
{
    throw CppRuntimeException("BitStreamReader: Reached eof(), reading from stream failed!");
}
 
inline void loadCacheNext(ReaderContext& ctx, uint8_t numBits)
{
    static const uint8_t cacheBitSize = sizeof(BaseType) * 8;
 
    // ctx.bitIndex is always byte aligned and ctx.cacheNumBits is always zero in this call
    const size_t byteIndex = ctx.bitIndex >> 3U;
    if (ctx.bufferBitSize >= ctx.bitIndex + cacheBitSize)
    {
        ctx.cache =
#ifdef ZSERIO_RUNTIME_64BIT
                parse64(ctx.buffer.begin() + byteIndex);
#else
                parse32(ctx.buffer.begin() + byteIndex);
#endif
        ctx.cacheNumBits = cacheBitSize;
    }
    else
    {
        if (ctx.bitIndex + numBits > ctx.bufferBitSize)
        {
            throwEof();
        }
 
        ctx.cacheNumBits = static_cast<uint8_t>(ctx.bufferBitSize - ctx.bitIndex);
 
        // buffer must be always available in full bytes, even if some last bits are not used
        const uint8_t alignedNumBits = static_cast<uint8_t>((ctx.cacheNumBits + 7U) & ~0x7U);
 
        switch (alignedNumBits)
        {
#ifdef ZSERIO_RUNTIME_64BIT
        case 64:
            ctx.cache = parse64(ctx.buffer.begin() + byteIndex);
            break;
        case 56:
            ctx.cache = parse56(ctx.buffer.begin() + byteIndex);
            break;
        case 48:
            ctx.cache = parse48(ctx.buffer.begin() + byteIndex);
            break;
        case 40:
            ctx.cache = parse40(ctx.buffer.begin() + byteIndex);
            break;
#endif
        case 32:
            ctx.cache = parse32(ctx.buffer.begin() + byteIndex);
            break;
        case 24:
            ctx.cache = parse24(ctx.buffer.begin() + byteIndex);
            break;
        case 16:
            ctx.cache = parse16(ctx.buffer.begin() + byteIndex);
            break;
        default: // 8
            ctx.cache = parse8(ctx.buffer.begin() + byteIndex);
            break;
        }
 
        ctx.cache >>= static_cast<uint8_t>(alignedNumBits - ctx.cacheNumBits);
    }
}
 
inline BaseType readBitsImpl(ReaderContext& ctx, uint8_t numBits)
{
    BaseType value = 0;
    if (ctx.cacheNumBits < numBits)
    {
        // read all remaining cache bits
        value = ctx.cache & MASK_TABLE[ctx.cacheNumBits];
        ctx.bitIndex += ctx.cacheNumBits;
        numBits = static_cast<uint8_t>(numBits - ctx.cacheNumBits);
 
        // load next piece of buffer into cache
        loadCacheNext(ctx, numBits);
 
        // add the remaining bits to the result
        // if numBits is sizeof(BaseType) * 8 here, value is already 0 (see MASK_TABLE[0])
        if (numBits < sizeof(BaseType) * 8)
        {
            value <<= numBits;
        }
    }
    value |= ((ctx.cache >> static_cast<uint8_t>(ctx.cacheNumBits - numBits)) & MASK_TABLE[numBits]);
    ctx.cacheNumBits = static_cast<uint8_t>(ctx.cacheNumBits - numBits);
    ctx.bitIndex += numBits;
 
    return value;
}
 
inline BaseSignedType readSignedBitsImpl(ReaderContext& ctx, uint8_t numBits)
{
    static const uint8_t typeSize = sizeof(BaseSignedType) * 8;
    BaseType value = readBitsImpl(ctx, numBits);
 
    // Skip the signed overflow correction if numBits == typeSize.
    // In that case, the value that comes out the readBits function
    // is already correct.
    if (numBits != 0 && numBits < typeSize &&
            (value >= (static_cast<BaseType>(1) << static_cast<uint8_t>(numBits - 1))))
    {
        value -= static_cast<BaseType>(1) << numBits;
    }
 
    return static_cast<BaseSignedType>(value);
}
 
#ifndef ZSERIO_RUNTIME_64BIT
inline uint64_t readBits64Impl(ReaderContext& ctx, uint8_t numBits)
{
    // read the first 32 bits
    numBits = static_cast<uint8_t>(numBits - 32);
    uint64_t value = readBitsImpl(ctx, 32);
 
    // add the remaining bits
    value <<= numBits;
    value |= readBitsImpl(ctx, numBits);
 
    return value;
}
#endif
 
} // namespace
 
BitStreamReader::ReaderContext::ReaderContext(
        Span<const uint8_t> readBuffer, size_t readBufferBitSize, size_t maxArrayPrealloc) :
        buffer(readBuffer),
        bufferBitSize(readBufferBitSize),
        cache(0),
        cacheNumBits(0),
        bitIndex(0),
        maxArrayPreallocation(maxArrayPrealloc)
{
    if (buffer.size() > MAX_BUFFER_SIZE)
    {
        throw CppRuntimeException("BitStreamReader: Buffer size exceeded limit '")
                << MAX_BUFFER_SIZE << "' bytes!";
    }
}
 
BitStreamReader::BitStreamReader(
        const uint8_t* buffer, size_t bufferByteSize, ArrayPreallocation maxArrayPrealloc) :
        BitStreamReader(Span<const uint8_t>(buffer, bufferByteSize), maxArrayPrealloc)
{}
 
BitStreamReader::BitStreamReader(Span<const uint8_t> buffer, ArrayPreallocation maxArrayPrealloc) :
        m_context(buffer, buffer.size() * 8, maxArrayPrealloc)
{}
 
BitStreamReader::BitStreamReader(
        Span<const uint8_t> buffer, size_t bufferBitSize, ArrayPreallocation maxArrayPrealloc) :
        m_context(buffer, bufferBitSize, maxArrayPrealloc)
{
    if (buffer.size() < (bufferBitSize + 7) / 8)
    {
        throw CppRuntimeException("BitStreamReader: Wrong buffer bit size ('")
                << buffer.size() << "' < '" << (bufferBitSize + 7) / 8 << "')!";
    }
}
 
BitStreamReader::BitStreamReader(
        const uint8_t* buffer, size_t bufferBitSize, BitsTag, ArrayPreallocation maxArrayPrealloc) :
        m_context(Span<const uint8_t>(buffer, (bufferBitSize + 7) / 8), bufferBitSize, maxArrayPrealloc)
{}
 
uint32_t BitStreamReader::readBits(uint8_t numBits)
{
    checkNumBits(numBits);
 
    return static_cast<uint32_t>(readBitsImpl(m_context, numBits));
}
 
uint64_t BitStreamReader::readBits64(uint8_t numBits)
{
    checkNumBits64(numBits);
 
#ifdef ZSERIO_RUNTIME_64BIT
    return readBitsImpl(m_context, numBits);
#else
    if (numBits <= 32)
    {
        return readBitsImpl(m_context, numBits);
    }
 
    return readBits64Impl(m_context, numBits);
#endif
}
 
int64_t BitStreamReader::readSignedBits64(uint8_t numBits)
{
    checkNumBits64(numBits);
 
#ifdef ZSERIO_RUNTIME_64BIT
    return readSignedBitsImpl(m_context, numBits);
#else
    if (numBits <= 32)
    {
        return readSignedBitsImpl(m_context, numBits);
    }
 
    int64_t value = static_cast<int64_t>(readBits64Impl(m_context, numBits));
 
    // Skip the signed overflow correction if numBits == 64.
    // In that case, the value that comes out the readBits function
    // is already correct.
    const bool needsSignExtension =
            numBits < 64 && (static_cast<uint64_t>(value) >= (UINT64_C(1) << (numBits - 1)));
    if (needsSignExtension)
    {
        value = static_cast<int64_t>(static_cast<uint64_t>(value) - (UINT64_C(1) << numBits));
    }
 
    return value;
#endif
}
 
int32_t BitStreamReader::readSignedBits(uint8_t numBits)
{
    checkNumBits(numBits);
 
    return static_cast<int32_t>(readSignedBitsImpl(m_context, numBits));
}
 
int64_t BitStreamReader::readVarInt64()
{
    uint8_t byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 1
    const bool sign = (byte & VARINT_SIGN_1) != 0;
    uint64_t result = byte & VARINT_BYTE_1;
    if ((byte & VARINT_HAS_NEXT_1) == 0)
    {
        return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 2
    result = result << 7U | static_cast<uint8_t>(byte & VARINT_BYTE_N);
    if ((byte & VARINT_HAS_NEXT_N) == 0)
    {
        return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 3
    result = static_cast<uint64_t>(result) << 7U | static_cast<uint8_t>(byte & VARINT_BYTE_N);
    if ((byte & VARINT_HAS_NEXT_N) == 0)
    {
        return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 4
    result = result << 7U | static_cast<uint8_t>(byte & VARINT_BYTE_N);
    if ((byte & VARINT_HAS_NEXT_N) == 0)
    {
        return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 5
    result = result << 7U | static_cast<uint8_t>(byte & VARINT_BYTE_N);
    if ((byte & VARINT_HAS_NEXT_N) == 0)
    {
        return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 6
    result = result << 7U | static_cast<uint8_t>(byte & VARINT_BYTE_N);
    if ((byte & VARINT_HAS_NEXT_N) == 0)
    {
        return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 7
    result = result << 7U | static_cast<uint8_t>(byte & VARINT_BYTE_N);
    if ((byte & VARINT_HAS_NEXT_N) == 0)
    {
        return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
    }
 
    result = result << 8U | static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 8
    return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
}
 
int32_t BitStreamReader::readVarInt32()
{
    uint8_t byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 1
    const bool sign = (byte & VARINT_SIGN_1) != 0;
    uint32_t result = byte & VARINT_BYTE_1;
    if ((byte & VARINT_HAS_NEXT_1) == 0)
    {
        return sign ? -static_cast<int32_t>(result) : static_cast<int32_t>(result);
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 2
    result = result << 7U | static_cast<uint8_t>(byte & VARINT_BYTE_N);
    if ((byte & VARINT_HAS_NEXT_N) == 0)
    {
        return sign ? -static_cast<int32_t>(result) : static_cast<int32_t>(result);
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 3
    result = result << 7U | static_cast<uint8_t>(byte & VARINT_BYTE_N);
    if ((byte & VARINT_HAS_NEXT_N) == 0)
    {
        return sign ? -static_cast<int32_t>(result) : static_cast<int32_t>(result);
    }
 
    result = result << 8U | static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 4
    return sign ? -static_cast<int32_t>(result) : static_cast<int32_t>(result);
}
 
int16_t BitStreamReader::readVarInt16()
{
    uint8_t byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 1
    const bool sign = (byte & VARINT_SIGN_1) != 0;
    uint16_t result = byte & VARINT_BYTE_1;
    if ((byte & VARINT_HAS_NEXT_1) == 0)
    {
        return sign ? static_cast<int16_t>(-result) : static_cast<int16_t>(result);
    }
 
    result = static_cast<uint16_t>(result << 8U);
    result = static_cast<uint16_t>(result | readBitsImpl(m_context, 8)); // byte 2
    return sign ? static_cast<int16_t>(-result) : static_cast<int16_t>(result);
}
 
uint64_t BitStreamReader::readVarUInt64()
{
    uint8_t byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 1
    uint64_t result = byte & VARUINT_BYTE;
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 2
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 3
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 4
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 5
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 6
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 7
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    result = result << 8U | static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 8
    return result;
}
 
uint32_t BitStreamReader::readVarUInt32()
{
    uint8_t byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 1
    uint32_t result = byte & VARUINT_BYTE;
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 2
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 3
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    result = result << 8U | static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 4
    return result;
}
 
uint16_t BitStreamReader::readVarUInt16()
{
    uint8_t byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 1
    uint16_t result = byte & VARUINT_BYTE;
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    result = static_cast<uint16_t>(result << 8U);
    result = static_cast<uint16_t>(result | readBitsImpl(m_context, 8)); // byte 2
    return result;
}
 
int64_t BitStreamReader::readVarInt()
{
    uint8_t byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 1
    const bool sign = (byte & VARINT_SIGN_1) != 0;
    uint64_t result = byte & VARINT_BYTE_1;
    if ((byte & VARINT_HAS_NEXT_1) == 0)
    {
        return sign ? (result == 0 ? INT64_MIN : -static_cast<int64_t>(result)) : static_cast<int64_t>(result);
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 2
    result = result << 7U | static_cast<uint8_t>(byte & VARINT_BYTE_N);
    if ((byte & VARINT_HAS_NEXT_N) == 0)
    {
        return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 3
    result = result << 7U | static_cast<uint8_t>(byte & VARINT_BYTE_N);
    if ((byte & VARINT_HAS_NEXT_N) == 0)
    {
        return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 4
    result = result << 7U | static_cast<uint8_t>(byte & VARINT_BYTE_N);
    if ((byte & VARINT_HAS_NEXT_N) == 0)
    {
        return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 5
    result = result << 7U | static_cast<uint8_t>(byte & VARINT_BYTE_N);
    if ((byte & VARINT_HAS_NEXT_N) == 0)
    {
        return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 6
    result = result << 7U | static_cast<uint8_t>(byte & VARINT_BYTE_N);
    if ((byte & VARINT_HAS_NEXT_N) == 0)
    {
        return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 7
    result = result << 7U | static_cast<uint8_t>(byte & VARINT_BYTE_N);
    if ((byte & VARINT_HAS_NEXT_N) == 0)
    {
        return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 8
    result = result << 7U | static_cast<uint8_t>(byte & VARINT_BYTE_N);
    if ((byte & VARINT_HAS_NEXT_N) == 0)
    {
        return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
    }
 
    result = result << 8U | static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 9
    return sign ? -static_cast<int64_t>(result) : static_cast<int64_t>(result);
}
 
uint64_t BitStreamReader::readVarUInt()
{
    uint8_t byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 1
    uint64_t result = byte & VARUINT_BYTE;
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 2
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 3
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 4
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 5
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 6
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 7
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 8
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    result = result << 8U | static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 9
    return result;
}
 
uint32_t BitStreamReader::readVarSize()
{
    uint8_t byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 1
    uint32_t result = byte & VARUINT_BYTE;
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 2
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 3
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    byte = static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 4
    result = result << 7U | static_cast<uint8_t>(byte & VARUINT_BYTE);
    if ((byte & VARUINT_HAS_NEXT) == 0)
    {
        return result;
    }
 
    result = result << 8U | static_cast<uint8_t>(readBitsImpl(m_context, 8)); // byte 5
    if (result > VARSIZE_MAX_VALUE)
    {
        throw CppRuntimeException("BitStreamReader: Read value '")
                << result << "' is out of range for varsize type!";
    }
 
    return result;
}
 
float BitStreamReader::readFloat16()
{
    const uint16_t halfPrecisionFloatValue = static_cast<uint16_t>(readBitsImpl(m_context, 16));
 
    return convertUInt16ToFloat(halfPrecisionFloatValue);
}
 
float BitStreamReader::readFloat32()
{
    const uint32_t singlePrecisionFloatValue = static_cast<uint32_t>(readBitsImpl(m_context, 32));
 
    return convertUInt32ToFloat(singlePrecisionFloatValue);
}
 
double BitStreamReader::readFloat64()
{
#ifdef ZSERIO_RUNTIME_64BIT
    const uint64_t doublePrecisionFloatValue = static_cast<uint64_t>(readBitsImpl(m_context, 64));
#else
    const uint64_t doublePrecisionFloatValue = readBits64Impl(m_context, 64);
#endif
 
    return convertUInt64ToDouble(doublePrecisionFloatValue);
}
 
bool BitStreamReader::readBool()
{
    return readBitsImpl(m_context, 1) != 0;
}
 
void BitStreamReader::setBitPosition(BitPosType position)
{
    if (position > m_context.bufferBitSize)
    {
        throw CppRuntimeException("BitStreamReader: Reached eof(), setting of bit position failed!");
    }
 
    m_context.bitIndex = (position / 8) * 8; // set to byte aligned position
    m_context.cacheNumBits = 0; // invalidate cache
    const uint8_t skip = static_cast<uint8_t>(position - m_context.bitIndex);
    if (skip != 0)
    {
        (void)readBits(skip);
    }
}
 
void BitStreamReader::alignTo(size_t alignment)
{
    const BitPosType offset = getBitPosition() % alignment;
    if (offset != 0)
    {
        const uint8_t skip = static_cast<uint8_t>(alignment - offset);
        (void)readBits64(skip);
    }
}
 
uint8_t BitStreamReader::readByte()
{
    return static_cast<uint8_t>(readBitsImpl(m_context, 8));
}
 
} // namespace zserio