void KeccakP1600times4_OverwriteBytes()

in src/sha3/keccak4x/KeccakP-1600-times4-SIMD256.c [168:197]

• 27 lines of code
• 6 McCabe index (conditional complexity)

void KeccakP1600times4_OverwriteBytes(void *states, unsigned int instanceIndex, const unsigned char *data, unsigned int offset, unsigned int length)
{
    unsigned int sizeLeft = length;
    unsigned int lanePosition = offset/SnP_laneLengthInBytes;
    unsigned int offsetInLane = offset%SnP_laneLengthInBytes;
    const unsigned char *curData = data;
    UINT64 *statesAsLanes = (UINT64 *)states;

    if ((sizeLeft > 0) && (offsetInLane != 0)) {
        unsigned int bytesInLane = SnP_laneLengthInBytes - offsetInLane;
        if (bytesInLane > sizeLeft)
            bytesInLane = sizeLeft;
        memcpy( ((unsigned char *)&statesAsLanes[laneIndex(instanceIndex, lanePosition)]) + offsetInLane, curData, bytesInLane);
        sizeLeft -= bytesInLane;
        lanePosition++;
        curData += bytesInLane;
    }

    while(sizeLeft >= SnP_laneLengthInBytes) {
        UINT64 lane = *((const UINT64*)curData);
        statesAsLanes[laneIndex(instanceIndex, lanePosition)] = lane;
        sizeLeft -= SnP_laneLengthInBytes;
        lanePosition++;
        curData += SnP_laneLengthInBytes;
    }

    if (sizeLeft > 0) {
        memcpy(&statesAsLanes[laneIndex(instanceIndex, lanePosition)], curData, sizeLeft);
    }
}