SHA256REF_CTX *ctx = (SHA256REF_CTX*)ctxv;
memcpy(state, ctx->state, 256);
sha256_update(&ctx, data, size);
sha256_final(&ctx, (uint8_t*)hash);
memcpy(state, ctx->state, 256);
sha256_update(&ctx, data, size);
sha256_final(&ctx, (uint8_t*)hash);