Import of the watch repository from Pebble

src/fw/applib/app_outbox.h

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <stdint.h>
+#include <stddef.h>
+
+typedef enum {
+  AppOutboxStatusSuccess,
+  AppOutboxStatusConsumerDoesNotExist,
+  AppOutboxStatusOutOfResources,
+  AppOutboxStatusOutOfMemory,
+
+  // Clients of app outbox can use this range for use-case specific status codes:
+  AppOutboxStatusUserRangeStart,
+  AppOutboxStatusUserRangeEnd = 0xff,
+} AppOutboxStatus;
+
+typedef void (*AppOutboxSentHandler)(AppOutboxStatus status, void *cb_ctx);
+
+//! Sends a message to the outbox.
+//! If the outbox is not registered, the `sent_handler` will be called immediately with
+//! status AppOutboxStatusConsumerDoesNotExist, *after* this function returns.
+//! @param data The message data. The caller is responsible for keeping this buffer around until
+//! `sent_handler` is called. Don't write to this buffer after calling this either, or the sent
+//! data might get corrupted.
+//! @param length Size of `data` in number of bytes.
+//! @param sent_handler Pointer to the function to call when the kernel has consumed the message,
+//! after which the `data` buffer will be no longer in use. Note that the `sent_handler` MUST be
+//! white-listed in app_outbox_service.c.
+//! @param cb_ctx Pointer to user data that will be passed into the `sent_handler`
+void app_outbox_send(const uint8_t *data, size_t length,
+                     AppOutboxSentHandler sent_handler, void *cb_ctx);
+
+//! To be called once per app launch by the system.
+void app_outbox_init(void);