Topic: NSA Identified Satoshi Nakamoto - page 2. (Read 1689 times)

unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast)
{
    const unsigned int nTargetTimespan = 30 * 24 * 60 * 60;
    const unsigned int nTargetSpacing = 15 * 60;
    const unsigned int nIntervals = nTargetTimespan / nTargetSpacing;

    // Cache
    static const CBlockIndex* pindexLastCache;
    static unsigned int nBitsCache;
    static CCriticalSection cs_cache;
    CRITICAL_BLOCK(cs_cache)
        if (pindexLast && pindexLast == pindexLastCache)
            return nBitsCache;

    // Go back 30 days
    const CBlockIndex* pindexFirst = pindexLast;
    for (int i = 0; pindexFirst && i < nIntervals; i++)
        pindexFirst = pindexFirst->pprev;
    if (pindexFirst == NULL)
        return MINPROOFOFWORK;

    // Load first and last block
    CBlock blockFirst;
    if (!blockFirst.ReadFromDisk(pindexFirst, false))
        throw runtime_error("GetNextWorkRequired() : blockFirst.ReadFromDisk failed\n");
    CBlock blockLast;
    if (!blockLast.ReadFromDisk(pindexLast, false))
        throw runtime_error("GetNextWorkRequired() : blockLast.ReadFromDisk failed\n");

    // Limit one change per timespan
    unsigned int nBits = blockLast.nBits;
    if (blockFirst.nBits == blockLast.nBits)
    {
        unsigned int nTimespan = blockLast.nTime - blockFirst.nTime;
        if (nTimespan > nTargetTimespan * 2 && nBits >= MINPROOFOFWORK)
            nBits--;
        else if (nTimespan < nTargetTimespan / 2)
            nBits++;
    }

    CRITICAL_BLOCK(cs_cache)
    {
        pindexLastCache = pindexLast;
        nBitsCache = nBits;
    }
    return nBits;
}