Import of the watch repository from Pebble

src/fw/util/buffer.h

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+/*
+ * 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>
+#include <stdbool.h>
+
+typedef struct {
+  size_t length;
+  size_t bytes_written;
+  uint8_t data[];
+} Buffer;
+
+//! Atomically add and return `length` bytes or add none and return 0
+size_t buffer_add(Buffer* const buffer, const uint8_t* const data, const size_t length);
+
+//! Remove `length` starting at `offset`.
+//! The combination of length and offset must not exceed the written bytes.
+size_t buffer_remove(Buffer* const b, const size_t offset, const size_t length);
+
+//! Create buffer with a data region of size_bytes
+Buffer* buffer_create(const size_t size_bytes);
+
+//! Initializes Buffer with a given `length`.
+//! Make sure that `buffer`'s data is can store `length` bytes.
+void buffer_init(Buffer * const buffer, const size_t length);
+
+//! Returns the number of remaining bytes that can be filled with `buffer_add`
+size_t buffer_get_bytes_remaining(Buffer *b);
+
+//! Empty buffer
+void buffer_clear(Buffer * const buffer);
+
+//! Return true if buffer is empty
+bool buffer_is_empty(Buffer * const buffer);