refactor: Increase buffer by explicit size

runtime/include/http_session.h

@@ -313,8 +313,6 @@ http_session_receive_request(struct http_session *session, http_session_receive_
 			goto err;
 		}
 
-		assert(bytes_parsed == bytes_received);
-
 		session->http_request.length_parsed += bytes_parsed;
 	}
 
@@ -353,8 +351,10 @@ http_session_write_response(struct http_session *session, const uint8_t *source,
 
 	int rc = 0;
 
-	if (session->response_buffer.capacity - session->response_buffer.length < n) {
+	size_t buffer_remaining = session->response_buffer.capacity - session->response_buffer.length;
-		rc = vec_u8_grow(&session->response_buffer);
+
+	if (buffer_remaining < n) {
+		rc = vec_u8_resize(&session->response_buffer, session->response_buffer.capacity + n - buffer_remaining);
 		if (rc != 0) goto DONE;
 	}
 

runtime/src/libc/wasi_impl_serverless.c

@@ -791,6 +791,19 @@ wasi_snapshot_preview1_backing_fd_write(wasi_context_t *context, __wasi_fd_t fd,
 		__wasi_size_t   nwritten         = 0;
 		int             rc               = 0;
 
+		/* Precompute required buffer size for entire iovec to call realloc at most once */
+		size_t total_size_to_copy = 0;
+		for (size_t i = 0; i < iovs_len; i++) { total_size_to_copy += iovs[i].buf_len; }
+		buffer_remaining = s->http->response_buffer.capacity - s->http->response_buffer.length;
+
+		if (buffer_remaining < total_size_to_copy) {
+			rc = vec_u8_resize(&s->http->response_buffer,
+			                   s->http->response_buffer.capacity + total_size_to_copy - buffer_remaining);
+			assert(rc == 0);
+		}
+
+		assert(s->http->response_buffer.capacity - s->http->response_buffer.length >= total_size_to_copy);
+
 		for (size_t i = 0; i < iovs_len; i++) {
 #ifdef LOG_SANDBOX_STDERR
 			if (fd == STDERR_FILENO) {