ParagonIE_Sodium_Core_BLAKE2b::update

    public static function update(SplFixedArray $ctx, SplFixedArray $p, $plen)
    {
        self::pseudoConstructor();

        $offset = 0;
        while ($plen > 0) {
            $left = $ctx[4];
            $fill = 256 - $left;

            if ($plen > $fill) {
                # memcpy( S->buf + left, in, fill ); /* Fill buffer */
                for ($i = $fill; $i--;) {
                    $ctx[3][$i + $left] = $p[$i + $offset];
                }

                # S->buflen += fill;
                $ctx[4] += $fill;

                # blake2b_increment_counter( S, BLAKE2B_BLOCKBYTES );
                self::increment_counter($ctx, 128);

                # blake2b_compress( S, S->buf ); /* Compress */
                self::compress($ctx, $ctx[3]);

                # memcpy( S->buf, S->buf + BLAKE2B_BLOCKBYTES, BLAKE2B_BLOCKBYTES ); /* Shift buffer left */
                for ($i = 128; $i--;) {
                    $ctx[3][$i] = $ctx[3][$i + 128];
                }

                # S->buflen -= BLAKE2B_BLOCKBYTES;
                $ctx[4] -= 128;

                # in += fill;
                $offset += $fill;

                # inlen -= fill;
                $plen -= $fill;
            } else {
                for ($i = $plen; $i--;) {
                    $ctx[3][$i + $left] = $p[$i + $offset];
                }
                $ctx[4] += $plen;
                $offset += $plen;
                $plen -= $plen;
            }
        }
    }