blake2s_compress
blake2s_compress(c, c->buf, BLAKE2S_BLOCKBYTES);
blake2s_compress(c, in, datalen);
blake2s_compress(c, c->buf, c->buflen);
blake2s_compress(state, state->buf, 1, BLAKE2S_BLOCK_SIZE);
blake2s_compress(state, in, nblocks - 1, BLAKE2S_BLOCK_SIZE);
blake2s_compress(state, state->buf, 1, state->buflen);