SHA256Transform
SHA256Transform(H, (uint8_t *)buf + i);
SHA256Transform(H, pad + i);
static void SHA256Transform(SHA2_CTX *, const uint8_t *);
SHA256Transform(ctx, ctx->buf_un.buf8);
SHA256Transform(ctx, &input[i]);
SHA256Transform(H, (uint8_t *)buf + i);
SHA256Transform(H, pad + i);