static inline int sha256_base_do_finalize(struct shash_desc *desc,
            sha256_block_fn *block_fn)
{
  const int bit_offset = SHA256_BLOCK_SIZE - sizeof(__be64);
  struct sha256_state *sctx = shash_desc_ctx(desc);
  __be64 *bits = (__be64 *)(sctx->buf + bit_offset);
  unsigned int partial = sctx->count % SHA256_BLOCK_SIZE;

  sctx->buf[partial++] = 0x80;
  if (partial > bit_offset) {
    memset(sctx->buf + partial, 0x0, SHA256_BLOCK_SIZE - partial);
    partial = 0;

    block_fn(sctx, sctx->buf, 1);
  }

  memset(sctx->buf + partial, 0x0, bit_offset - partial);
  *bits = cpu_to_be64(sctx->count << 3);
  block_fn(sctx, sctx->buf, 1);

  return 0;
}