SHA256

local hash; do
    local MOD = 2^32
    local MODM = MOD-1
    local bxor = bit32.bxor;
    local band = bit32.band;
    local bnot = bit32.bnot;
    local rshift1 = bit32.rshift;
    local rshift = bit32.rshift;
    local lshift = bit32.lshift;
    local rrotate = bit32.rrotate;

    local str_gsub = string.gsub;
    local str_fmt = string.format;
    local str_byte = string.byte;
    local str_char = string.char;
    local str_rep = string.rep;

    local k = {
        0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
        0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
        0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
        0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
        0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
        0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
        0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
        0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
        0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
        0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
        0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
        0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
        0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
        0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
        0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
        0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
    }
    local function str2hexa(s)
        return (str_gsub(s, ".", function(c) return str_fmt("%02x", str_byte(c)) end))
    end
    local function num2s(l, n)
        local s = ""
        for i = 1, n do
            local rem = l % 256
            s = str_char(rem) .. s
            l = (l - rem) / 256
        end
        return s
    end
    local function s232num(s, i)
        local n = 0
        for i = i, i + 3 do n = n*256 + str_byte(s, i) end
        return n
        end
        local function preproc(msg, len)
        local extra = 64 - ((len + 9) % 64)
        len = num2s(8 * len, 8)
        msg = msg .. "\128" .. str_rep("\0", extra) .. len
        assert(#msg % 64 == 0)
        return msg
    end
    local function initH256(H)
        H[1] = 0x6a09e667
        H[2] = 0xbb67ae85
        H[3] = 0x3c6ef372
        H[4] = 0xa54ff53a
        H[5] = 0x510e527f
        H[6] = 0x9b05688c
        H[7] = 0x1f83d9ab
        H[8] = 0x5be0cd19
        return H
    end
    local function digestblock(msg, i, H)
        local w = {}
        for j = 1, 16 do w[j] = s232num(msg, i + (j - 1)*4) end
        for j = 17, 64 do
            local v = w[j - 15]
            local s0 = bxor(rrotate(v, 7), rrotate(v, 18), rshift(v, 3))
            v = w[j - 2]
            w[j] = w[j - 16] + s0 + w[j - 7] + bxor(rrotate(v, 17), rrotate(v, 19), rshift(v, 10))
        end
        local a, b, c, d, e, f, g, h = H[1], H[2], H[3], H[4], H[5], H[6], H[7], H[8]
        for i = 1, 64 do
            local s0 = bxor(rrotate(a, 2), rrotate(a, 13), rrotate(a, 22))
            local maj = bxor(band(a, b), band(a, c), band(b, c))
            local t2 = s0 + maj
            local s1 = bxor(rrotate(e, 6), rrotate(e, 11), rrotate(e, 25))
            local ch = bxor(band(e, f), band(bnot(e), g))
            local t1 = h + s1 + ch + k[i] + w[i]
            h, g, f, e, d, c, b, a = g, f, e, d + t1, c, b, a, t1 + t2
        end
        H[1] = band(H[1] + a)
        H[2] = band(H[2] + b)
        H[3] = band(H[3] + c)
        H[4] = band(H[4] + d)
        H[5] = band(H[5] + e)
        H[6] = band(H[6] + f)
        H[7] = band(H[7] + g)
        H[8] = band(H[8] + h)
    end
    function hash(msg, t)
        msg = preproc(msg, #msg)
        local H = initH256({})
        for i = 1, #msg, 64 do digestblock(msg, i, H) end
        return str2hexa(num2s(H[1], 4) .. num2s(H[2], 4) .. num2s(H[3], 4) .. num2s(H[4], 4) .. num2s(H[5], 4) .. num2s(H[6], 4) .. num2s(H[7], 4) .. num2s(H[8], 4))
    end
end