path: root/contrib/libs/apache/orc/c++/src/RleEncoderV2.cc

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with option work for additional information
 * regarding copyright ownership.  The ASF licenses option file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use option file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "Adaptor.hh"
#include "Compression.hh"
#include "RLEv2.hh"
#include "RLEV2Util.hh"

#define MAX_SHORT_REPEAT_LENGTH 10

namespace orc {

/**
 * Compute the bits required to represent pth percentile value
 * @param data - array
 * @param p - percentile value (>=0.0 to <=1.0)
 * @return pth percentile bits
 */
uint32_t RleEncoderV2::percentileBits(int64_t* data, size_t offset, size_t length, double p, bool reuseHist) {
    if ((p > 1.0) || (p <= 0.0)) {
        throw InvalidArgument("Invalid p value: " + to_string(p));
    }

    if (!reuseHist) {
        // histogram that store the encoded bit requirement for each values.
        // maximum number of bits that can encoded is 32 (refer FixedBitSizes)
        memset(histgram, 0, FixedBitSizes::SIZE * sizeof(int32_t));
        // compute the histogram
        for(size_t i = offset; i < (offset + length); i++) {
            uint32_t idx = encodeBitWidth(findClosestNumBits(data[i]));
            histgram[idx] += 1;
        }
    }

    int32_t perLen = static_cast<int32_t>(static_cast<double>(length) * (1.0 - p));

    // return the bits required by pth percentile length
    for(int32_t i = HIST_LEN - 1; i >= 0; i--) {
        perLen -= histgram[i];
        if (perLen < 0) {
            return decodeBitWidth(static_cast<uint32_t>(i));
        }
    }
    return 0;
}

RleEncoderV2::RleEncoderV2(std::unique_ptr<BufferedOutputStream> outStream,
                           bool hasSigned, bool alignBitPacking) :
        RleEncoder(std::move(outStream), hasSigned),
        alignedBitPacking(alignBitPacking),
        prevDelta(0){
    literals = new int64_t[MAX_LITERAL_SIZE];
    gapVsPatchList = new int64_t[MAX_LITERAL_SIZE];
    zigzagLiterals = hasSigned ? new int64_t[MAX_LITERAL_SIZE] : nullptr;
    baseRedLiterals = new int64_t[MAX_LITERAL_SIZE];
    adjDeltas = new int64_t[MAX_LITERAL_SIZE];
}

void RleEncoderV2::write(int64_t val) {
    if(numLiterals == 0) {
        initializeLiterals(val);
        return;
    }

    if(numLiterals == 1) {
        prevDelta = val - literals[0];
        literals[numLiterals++] = val;

        if(val == literals[0]) {
            fixedRunLength = 2;
            variableRunLength = 0;
        } else {
            fixedRunLength = 0;
            variableRunLength = 2;
        }
        return;
    }

    int64_t currentDelta = val - literals[numLiterals - 1];
    EncodingOption option = {};
    if (prevDelta == 0 && currentDelta == 0) {
        // case 1: fixed delta run
        literals[numLiterals++] = val;

        if (variableRunLength > 0) {
            // if variable run is non-zero then we are seeing repeating
            // values at the end of variable run in which case fixed Run
            // length is 2
            fixedRunLength = 2;
        }
        fixedRunLength++;

        // if fixed run met the minimum condition and if variable
        // run is non-zero then flush the variable run and shift the
        // tail fixed runs to start of the buffer
        if (fixedRunLength >= MIN_REPEAT && variableRunLength > 0) {
            numLiterals -= MIN_REPEAT;
            variableRunLength -= (MIN_REPEAT - 1);

            determineEncoding(option);
            writeValues(option);

            // shift tail fixed runs to beginning of the buffer
            for (size_t i = 0; i < MIN_REPEAT; ++i) {
                literals[i] = val;
            }
            numLiterals = MIN_REPEAT;
        }

        if (fixedRunLength == MAX_LITERAL_SIZE) {
            option.encoding = DELTA;
            option.isFixedDelta = true;
            writeValues(option);
        }
        return;
    }

    // case 2: variable delta run

    // if fixed run length is non-zero and if it satisfies the
    // short repeat conditions then write the values as short repeats
    // else use delta encoding
    if (fixedRunLength >= MIN_REPEAT) {
        if (fixedRunLength <= MAX_SHORT_REPEAT_LENGTH) {
            option.encoding = SHORT_REPEAT;
        } else {
            option.encoding = DELTA;
            option.isFixedDelta = true;
        }
        writeValues(option);
    }

    // if fixed run length is <MIN_REPEAT and current value is
    // different from previous then treat it as variable run
    if (fixedRunLength > 0 && fixedRunLength < MIN_REPEAT && val != literals[numLiterals - 1]) {
        variableRunLength = fixedRunLength;
        fixedRunLength = 0;
    }

    // after writing values re-initialize the variables
    if (numLiterals == 0) {
        initializeLiterals(val);
    } else {
        prevDelta = val - literals[numLiterals - 1];
        literals[numLiterals++] = val;
        variableRunLength++;

        if (variableRunLength == MAX_LITERAL_SIZE) {
            determineEncoding(option);
            writeValues(option);
        }
    }
}

void RleEncoderV2::computeZigZagLiterals(EncodingOption &option) {
    assert (isSigned);
    for (size_t i = 0; i < numLiterals; i++) {
        zigzagLiterals[option.zigzagLiteralsCount++] = zigZag(literals[i]);
    }
}

void RleEncoderV2::preparePatchedBlob(EncodingOption& option) {
    // mask will be max value beyond which patch will be generated
    int64_t mask = static_cast<int64_t>(static_cast<uint64_t>(1) << option.brBits95p) - 1;

    // since we are considering only 95 percentile, the size of gap and
    // patch array can contain only be 5% values
    option.patchLength = static_cast<uint32_t>(std::ceil((numLiterals / 20)));

    // #bit for patch
    option.patchWidth = option.brBits100p - option.brBits95p;
    option.patchWidth = getClosestFixedBits(option.patchWidth);

    // if patch bit requirement is 64 then it will not possible to pack
    // gap and patch together in a long. To make sure gap and patch can be
    // packed together adjust the patch width
    if (option.patchWidth == 64) {
        option.patchWidth = 56;
        option.brBits95p = 8;
        mask = static_cast<int64_t>(static_cast<uint64_t>(1) << option.brBits95p) - 1;
    }

    uint32_t gapIdx = 0;
    uint32_t patchIdx = 0;
    size_t prev = 0;
    size_t maxGap = 0;

    std::vector<int64_t> gapList;
    std::vector<int64_t> patchList;

    for(size_t i = 0; i < numLiterals; i++) {
        // if value is above mask then create the patch and record the gap
        if (baseRedLiterals[i] > mask) {
            size_t gap = i - prev;
            if (gap > maxGap) {
                maxGap = gap;
            }

            // gaps are relative, so store the previous patched value index
            prev = i;
            gapList.push_back(static_cast<int64_t>(gap));
            gapIdx++;

            // extract the most significant bits that are over mask bits
            int64_t patch = baseRedLiterals[i] >> option.brBits95p;
            patchList.push_back(patch);
            patchIdx++;

            // strip off the MSB to enable safe bit packing
            baseRedLiterals[i] &= mask;
        }
    }

    // adjust the patch length to number of entries in gap list
    option.patchLength = gapIdx;

    // if the element to be patched is the first and only element then
    // max gap will be 0, but to store the gap as 0 we need atleast 1 bit
    if (maxGap == 0 && option.patchLength != 0) {
        option.patchGapWidth = 1;
    } else {
        option.patchGapWidth = findClosestNumBits(static_cast<int64_t>(maxGap));
    }

    // special case: if the patch gap width is greater than 256, then
    // we need 9 bits to encode the gap width. But we only have 3 bits in
    // header to record the gap width. To deal with this case, we will save
    // two entries in patch list in the following way
    // 256 gap width => 0 for patch value
    // actual gap - 256 => actual patch value
    // We will do the same for gap width = 511. If the element to be patched is
    // the last element in the scope then gap width will be 511. In this case we
    // will have 3 entries in the patch list in the following way
    // 255 gap width => 0 for patch value
    // 255 gap width => 0 for patch value
    // 1 gap width => actual patch value
    if (option.patchGapWidth > 8) {
        option.patchGapWidth = 8;
        // for gap = 511, we need two additional entries in patch list
        if (maxGap == 511) {
            option.patchLength += 2;
        } else {
            option.patchLength += 1;
        }
    }

    // create gap vs patch list
    gapIdx = 0;
    patchIdx = 0;
    for(size_t i = 0; i < option.patchLength; i++) {
        int64_t g = gapList[gapIdx++];
        int64_t p = patchList[patchIdx++];
        while (g > 255) {
            gapVsPatchList[option.gapVsPatchListCount++] = (255L << option.patchWidth);
            i++;
            g -= 255;
        }

        // store patch value in LSBs and gap in MSBs
        gapVsPatchList[option.gapVsPatchListCount++] = ((g << option.patchWidth) | p);
    }
}

/**
 * Prepare for Direct or PatchedBase encoding
 * compute zigZagLiterals and zzBits100p (Max number of encoding bits required)
 * @return zigzagLiterals
 */
int64_t* RleEncoderV2::prepareForDirectOrPatchedBase(EncodingOption& option) {
    if (isSigned) {
        computeZigZagLiterals(option);
    }
    int64_t* currentZigzagLiterals = isSigned ? zigzagLiterals : literals;
    option.zzBits100p = percentileBits(currentZigzagLiterals, 0, numLiterals, 1.0);
    return currentZigzagLiterals;
}

void RleEncoderV2::determineEncoding(EncodingOption& option) {
    // We need to compute zigzag values for DIRECT and PATCHED_BASE encodings,
    // but not for SHORT_REPEAT or DELTA. So we only perform the zigzag
    // computation when it's determined to be necessary.

    // not a big win for shorter runs to determine encoding
    if (numLiterals <= MIN_REPEAT) {
        // we need to compute zigzag values for DIRECT encoding if we decide to
        // break early for delta overflows or for shorter runs
        prepareForDirectOrPatchedBase(option);
        option.encoding = DIRECT;
        return;
    }

    // DELTA encoding check

    // for identifying monotonic sequences
    bool isIncreasing = true;
    bool isDecreasing = true;
    option.isFixedDelta = true;

    option.min = literals[0];
    int64_t max = literals[0];
    int64_t initialDelta = literals[1] - literals[0];
    int64_t currDelta = 0;
    int64_t deltaMax = 0;
    adjDeltas[option.adjDeltasCount++] = initialDelta;

    for (size_t i = 1; i < numLiterals; i++) {
        const int64_t l1 = literals[i];
        const int64_t l0 = literals[i - 1];
        currDelta = l1 - l0;
        option.min = std::min(option.min, l1);
        max = std::max(max, l1);

        isIncreasing &= (l0 <= l1);
        isDecreasing &= (l0 >= l1);

        option.isFixedDelta &= (currDelta == initialDelta);
        if (i > 1) {
            adjDeltas[option.adjDeltasCount++] = std::abs(currDelta);
            deltaMax = std::max(deltaMax, adjDeltas[i - 1]);
        }
    }

    // it's faster to exit under delta overflow condition without checking for
    // PATCHED_BASE condition as encoding using DIRECT is faster and has less
    // overhead than PATCHED_BASE
    if (!isSafeSubtract(max, option.min)) {
        prepareForDirectOrPatchedBase(option);
        option.encoding = DIRECT;
        return;
    }

    // invariant - subtracting any number from any other in the literals after
    // option point won't overflow

    // if min is equal to max then the delta is 0, option condition happens for
    // fixed values run >10 which cannot be encoded with SHORT_REPEAT
    if (option.min == max) {
        if (!option.isFixedDelta) {
            throw InvalidArgument(to_string(option.min) + "==" +
              to_string(max) + ", isFixedDelta cannot be false");
        }

        if(currDelta != 0) {
            throw InvalidArgument(to_string(option.min) + "==" +
            to_string(max) + ", currDelta should be zero");
        }
        option.fixedDelta = 0;
        option.encoding = DELTA;
        return;
    }

    if (option.isFixedDelta) {
        if (currDelta != initialDelta) {
            throw InvalidArgument("currDelta should be equal to initialDelta for fixed delta encoding");
        }

        option.encoding = DELTA;
        option.fixedDelta = currDelta;
        return;
    }

    // if initialDelta is 0 then we cannot delta encode as we cannot identify
    // the sign of deltas (increasing or decreasing)
    if (initialDelta != 0) {
        // stores the number of bits required for packing delta blob in
        // delta encoding
        option.bitsDeltaMax = findClosestNumBits(deltaMax);

        // monotonic condition
        if (isIncreasing || isDecreasing) {
            option.encoding = DELTA;
            return;
        }
    }

    // PATCHED_BASE encoding check

    // percentile values are computed for the zigzag encoded values. if the
    // number of bit requirement between 90th and 100th percentile varies
    // beyond a threshold then we need to patch the values. if the variation
    // is not significant then we can use direct encoding

    int64_t* currentZigzagLiterals = prepareForDirectOrPatchedBase(option);
    option.zzBits90p = percentileBits(currentZigzagLiterals, 0, numLiterals, 0.9, true);
    uint32_t diffBitsLH = option.zzBits100p - option.zzBits90p;

    // if the difference between 90th percentile and 100th percentile fixed
    // bits is > 1 then we need patch the values
    if (diffBitsLH > 1) {

        // patching is done only on base reduced values.
        // remove base from literals
        for (size_t i = 0; i < numLiterals; i++) {
            baseRedLiterals[option.baseRedLiteralsCount++] = (literals[i] - option.min);
        }

        // 95th percentile width is used to determine max allowed value
        // after which patching will be done
        option.brBits95p = percentileBits(baseRedLiterals, 0, numLiterals, 0.95);

        // 100th percentile is used to compute the max patch width
        option.brBits100p = percentileBits(baseRedLiterals, 0, numLiterals, 1.0, true);

        // after base reducing the values, if the difference in bits between
        // 95th percentile and 100th percentile value is zero then there
        // is no point in patching the values, in which case we will
        // fallback to DIRECT encoding.
        // The decision to use patched base was based on zigzag values, but the
        // actual patching is done on base reduced literals.
        if ((option.brBits100p - option.brBits95p) != 0) {
            option.encoding = PATCHED_BASE;
            preparePatchedBlob(option);
            return;
        } else {
            option.encoding = DIRECT;
            return;
        }
    } else {
        // if difference in bits between 95th percentile and 100th percentile is
        // 0, then patch length will become 0. Hence we will fallback to direct
        option.encoding = DIRECT;
        return;
    }
}

uint64_t RleEncoderV2::flush() {
    if (numLiterals != 0) {
        EncodingOption option = {};
        if (variableRunLength != 0) {
            determineEncoding(option);
            writeValues(option);
        } else if (fixedRunLength != 0) {
            if (fixedRunLength < MIN_REPEAT) {
                variableRunLength = fixedRunLength;
                fixedRunLength = 0;
                determineEncoding(option);
                writeValues(option);
            } else if (fixedRunLength >= MIN_REPEAT
                       && fixedRunLength <= MAX_SHORT_REPEAT_LENGTH) {
                option.encoding = SHORT_REPEAT;
                writeValues(option);
            } else {
                option.encoding = DELTA;
                option.isFixedDelta = true;
                writeValues(option);
            }
        }
    }

    outputStream->BackUp(static_cast<int>(bufferLength - bufferPosition));
    uint64_t dataSize = outputStream->flush();
    bufferLength = bufferPosition = 0;
    return dataSize;
}

void RleEncoderV2::writeValues(EncodingOption& option) {
    if (numLiterals != 0) {
        switch (option.encoding) {
            case SHORT_REPEAT:
                writeShortRepeatValues(option);
                break;
            case DIRECT:
                writeDirectValues(option);
                break;
            case PATCHED_BASE:
                writePatchedBasedValues(option);
                break;
            case DELTA:
                writeDeltaValues(option);
                break;
            default:
                throw NotImplementedYet("Not implemented yet");
        }

        numLiterals = 0;
        prevDelta = 0;
    }
}

void RleEncoderV2::writeShortRepeatValues(EncodingOption&) {
    int64_t repeatVal;
    if (isSigned) {
        repeatVal = zigZag(literals[0]);
    } else {
        repeatVal = literals[0];
    }

    const uint32_t numBitsRepeatVal = findClosestNumBits(repeatVal);
    const uint32_t numBytesRepeatVal = numBitsRepeatVal % 8 == 0 ? (numBitsRepeatVal >> 3) : ((numBitsRepeatVal >> 3) + 1);

    uint32_t header = getOpCode(SHORT_REPEAT);

    fixedRunLength -= MIN_REPEAT;
    header |= fixedRunLength;
    header |= ((numBytesRepeatVal - 1) << 3);

    writeByte(static_cast<char>(header));

    for(int32_t i = static_cast<int32_t>(numBytesRepeatVal - 1); i >= 0; i--) {
        int64_t b = ((repeatVal >> (i * 8)) & 0xff);
        writeByte(static_cast<char>(b));
    }

    fixedRunLength = 0;
}

void RleEncoderV2::writeDirectValues(EncodingOption& option) {
    // write the number of fixed bits required in next 5 bits
    uint32_t fb = option.zzBits100p;
    if (alignedBitPacking) {
        fb = getClosestAlignedFixedBits(fb);
    }

    const uint32_t efb = encodeBitWidth(fb) << 1;

    // adjust variable run length
    variableRunLength -= 1;

    // extract the 9th bit of run length
    const uint32_t tailBits = (variableRunLength & 0x100) >> 8;

    // create first byte of the header
    const char headerFirstByte = static_cast<char>(getOpCode(DIRECT) | efb | tailBits);

    // second byte of the header stores the remaining 8 bits of runlength
    const char headerSecondByte = static_cast<char>(variableRunLength & 0xff);

    // write header
    writeByte(headerFirstByte);
    writeByte(headerSecondByte);

    // bit packing the zigzag encoded literals
    int64_t* currentZigzagLiterals = isSigned ? zigzagLiterals : literals;
    writeInts(currentZigzagLiterals, 0, numLiterals, fb);

    // reset run length
    variableRunLength = 0;
}

void RleEncoderV2::writePatchedBasedValues(EncodingOption& option) {
    // NOTE: Aligned bit packing cannot be applied for PATCHED_BASE encoding
    // because patch is applied to MSB bits. For example: If fixed bit width of
    // base value is 7 bits and if patch is 3 bits, the actual value is
    // constructed by shifting the patch to left by 7 positions.
    // actual_value = patch << 7 | base_value
    // So, if we align base_value then actual_value can not be reconstructed.

    // write the number of fixed bits required in next 5 bits
    const uint32_t efb = encodeBitWidth(option.brBits95p) << 1;

    // adjust variable run length, they are one off
    variableRunLength -= 1;

    // extract the 9th bit of run length
    const uint32_t tailBits = (variableRunLength & 0x100) >> 8;

    // create first byte of the header
    const char headerFirstByte = static_cast<char>(getOpCode(PATCHED_BASE) | efb | tailBits);

    // second byte of the header stores the remaining 8 bits of runlength
    const char headerSecondByte = static_cast<char>(variableRunLength & 0xff);

    // if the min value is negative toggle the sign
    const bool isNegative = (option.min < 0);
    if (isNegative) {
        option.min = -option.min;
    }

    // find the number of bytes required for base and shift it by 5 bits
    // to accommodate patch width. The additional bit is used to store the sign
    // of the base value.
    const uint32_t baseWidth = findClosestNumBits(option.min) + 1;
    const uint32_t baseBytes = baseWidth % 8 == 0 ? baseWidth / 8 : (baseWidth / 8) + 1;
    const uint32_t bb = (baseBytes - 1) << 5;

    // if the base value is negative then set MSB to 1
    if (isNegative) {
        option.min |= (1LL << ((baseBytes * 8) - 1));
    }

    // third byte contains 3 bits for number of bytes occupied by base
    // and 5 bits for patchWidth
    const char headerThirdByte = static_cast<char>(bb | encodeBitWidth(option.patchWidth));

    // fourth byte contains 3 bits for page gap width and 5 bits for
    // patch length
    const char headerFourthByte = static_cast<char>((option.patchGapWidth - 1) << 5 | option.patchLength);

    // write header
    writeByte(headerFirstByte);
    writeByte(headerSecondByte);
    writeByte(headerThirdByte);
    writeByte(headerFourthByte);

    // write the base value using fixed bytes in big endian order
    for(int32_t i = static_cast<int32_t>(baseBytes - 1); i >= 0; i--) {
        char b = static_cast<char>(((option.min >> (i * 8)) & 0xff));
        writeByte(b);
    }

    // base reduced literals are bit packed
    uint32_t closestFixedBits = getClosestFixedBits(option.brBits95p);

    writeInts(baseRedLiterals, 0, numLiterals, closestFixedBits);

    // write patch list
    closestFixedBits = getClosestFixedBits(option.patchGapWidth + option.patchWidth);

    writeInts(gapVsPatchList, 0, option.patchLength, closestFixedBits);

    // reset run length
    variableRunLength = 0;
}

void RleEncoderV2::writeDeltaValues(EncodingOption& option) {
    uint32_t len = 0;
    uint32_t fb = option.bitsDeltaMax;
    uint32_t efb = 0;

    if (alignedBitPacking) {
        fb = getClosestAlignedFixedBits(fb);
    }

    if (option.isFixedDelta) {
        // if fixed run length is greater than threshold then it will be fixed
        // delta sequence with delta value 0 else fixed delta sequence with
        // non-zero delta value
        if (fixedRunLength > MIN_REPEAT) {
            // ex. sequence: 2 2 2 2 2 2 2 2
            len = fixedRunLength - 1;
            fixedRunLength = 0;
        } else {
            // ex. sequence: 4 6 8 10 12 14 16
            len = variableRunLength - 1;
            variableRunLength = 0;
        }
    } else {
        // fixed width 0 is used for long repeating values.
        // sequences that require only 1 bit to encode will have an additional bit
        if (fb == 1) {
            fb = 2;
        }
        efb = encodeBitWidth(fb) << 1;
        len = variableRunLength - 1;
        variableRunLength = 0;
    }

    // extract the 9th bit of run length
    const uint32_t tailBits = (len & 0x100) >> 8;

    // create first byte of the header
    const char headerFirstByte = static_cast<char>(getOpCode(DELTA) | efb | tailBits);

    // second byte of the header stores the remaining 8 bits of runlength
    const char headerSecondByte = static_cast<char>(len & 0xff);

    // write header
    writeByte(headerFirstByte);
    writeByte(headerSecondByte);

    // store the first value from zigzag literal array
    if (isSigned) {
        writeVslong(literals[0]);
    } else {
        writeVulong(literals[0]);
    }

    if (option.isFixedDelta) {
        // if delta is fixed then we don't need to store delta blob
        writeVslong(option.fixedDelta);
    } else {
        // store the first value as delta value using zigzag encoding
        writeVslong(adjDeltas[0]);

        // adjacent delta values are bit packed. The length of adjDeltas array is
        // always one less than the number of literals (delta difference for n
        // elements is n-1). We have already written one element, write the
        // remaining numLiterals - 2 elements here
        writeInts(adjDeltas, 1, numLiterals - 2, fb);
    }
}

void RleEncoderV2::writeInts(int64_t* input, uint32_t offset, size_t len, uint32_t bitSize) {
  if(input == nullptr || len < 1 || bitSize < 1) {
      return;
  }

  if (getClosestAlignedFixedBits(bitSize) == bitSize) {
    uint32_t numBytes;
    uint32_t endOffSet = static_cast<uint32_t>(offset + len);
    if (bitSize < 8 ) {
      char bitMask = static_cast<char>((1 << bitSize) - 1);
      uint32_t numHops = 8 / bitSize;
      uint32_t remainder = static_cast<uint32_t>(len % numHops);
      uint32_t endUnroll = endOffSet - remainder;
      for (uint32_t i = offset; i < endUnroll; i+=numHops) {
        char toWrite = 0;
        for (uint32_t j = 0; j < numHops; ++j) {
          toWrite |= static_cast<char>((input[i+j] & bitMask) << (8 - (j + 1) * bitSize));
        }
        writeByte(toWrite);
      }

      if (remainder > 0) {
        uint32_t startShift = 8 - bitSize;
        char toWrite = 0;
        for (uint32_t i = endUnroll; i < endOffSet; ++i) {
          toWrite |= static_cast<char>((input[i] & bitMask) << startShift);
          startShift -= bitSize;
        }
        writeByte(toWrite);
      }

    } else {
      numBytes = bitSize / 8;

      for (uint32_t i = offset; i < endOffSet; ++i) {
        for (uint32_t j = 0; j < numBytes; ++j) {
          char toWrite = static_cast<char>((input[i] >> (8 * (numBytes - j - 1))) & 255);
          writeByte(toWrite);
        }
      }
    }

    return;
  }

  // write for unaligned bit size
  uint32_t bitsLeft = 8;
  char current = 0;
  for(uint32_t i = offset; i < (offset + len); i++) {
    int64_t value = input[i];
    uint32_t bitsToWrite = bitSize;
    while (bitsToWrite > bitsLeft) {
      // add the bits to the bottom of the current word
      current |= static_cast<char>(value >> (bitsToWrite - bitsLeft));
      // subtract out the bits we just added
      bitsToWrite -= bitsLeft;
      // zero out the bits above bitsToWrite
      value &= (static_cast<uint64_t>(1) << bitsToWrite) - 1;
      writeByte(current);
      current = 0;
      bitsLeft = 8;
    }
    bitsLeft -= bitsToWrite;
    current |= static_cast<char>(value << bitsLeft);
    if (bitsLeft == 0) {
      writeByte(current);
      current = 0;
      bitsLeft = 8;
    }
  }

  // flush
  if (bitsLeft != 8) {
    writeByte(current);
  }
}

void RleEncoderV2::initializeLiterals(int64_t val) {
    literals[numLiterals++] = val;
    fixedRunLength = 1;
    variableRunLength = 1;
}
}