libcamera: Add ByteStreamBuffer

The ByteStreamBuffer class wraps a memory area, expected to be allocated
by the user of the class and provides operations to perform sequential
access in read and write modes.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/libcamera/include/byte_stream_buffer.h

@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * byte_stream_buffer.h - Byte stream buffer
+ */
+#ifndef __LIBCAMERA_BYTE_STREAM_BUFFER_H__
+#define __LIBCAMERA_BYTE_STREAM_BUFFER_H__
+
+#include <stddef.h>
+#include <stdint.h>
+
+namespace libcamera {
+
+class ByteStreamBuffer
+{
+public:
+	ByteStreamBuffer(const uint8_t *base, size_t size);
+	ByteStreamBuffer(uint8_t *base, size_t size);
+	ByteStreamBuffer(ByteStreamBuffer &&other);
+	ByteStreamBuffer &operator=(ByteStreamBuffer &&other);
+
+	const uint8_t *base() const { return base_; }
+	uint32_t offset() const { return (write_ ? write_ : read_) - base_; }
+	size_t size() const { return size_; }
+	bool overflow() const { return overflow_; }
+
+	ByteStreamBuffer carveOut(size_t size);
+	int skip(size_t size);
+
+	template<typename T>
+	int read(T *t)
+	{
+		return read(reinterpret_cast<uint8_t *>(t), sizeof(*t));
+	}
+	template<typename T>
+	int write(const T *t)
+	{
+		return write(reinterpret_cast<const uint8_t *>(t), sizeof(*t));
+	}
+
+private:
+	ByteStreamBuffer(const ByteStreamBuffer &other) = delete;
+	ByteStreamBuffer &operator=(const ByteStreamBuffer &other) = delete;
+
+	void setOverflow();
+
+	int read(uint8_t *data, size_t size);
+	int write(const uint8_t *data, size_t size);
+
+	ByteStreamBuffer *parent_;
+
+	const uint8_t *base_;
+	size_t size_;
+	bool overflow_;
+
+	const uint8_t *read_;
+	uint8_t *write_;
+};
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_BYTE_STREAM_BUFFER_H__ */