android: Add CameraMetadata helper class

The new CameraMetadata helper class wraps the Android camera_metadata_t
to simplify its usage.

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

src/android/camera_metadata.cpp

@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * camera_metadata.cpp - libcamera Android Camera Metadata Helper
+ */
+
+#include "camera_metadata.h"
+
+#include "log.h"
+
+using namespace libcamera;
+
+LOG_DEFINE_CATEGORY(CameraMetadata);
+
+CameraMetadata::CameraMetadata(size_t entryCapacity, size_t dataCapacity)
+{
+	metadata_ = allocate_camera_metadata(entryCapacity, dataCapacity);
+	valid_ = metadata_ != nullptr;
+}
+
+CameraMetadata::~CameraMetadata()
+{
+	if (metadata_)
+		free_camera_metadata(metadata_);
+}
+
+bool CameraMetadata::addEntry(uint32_t tag, const void *data, size_t count)
+{
+	if (!valid_)
+		return false;
+
+	if (!add_camera_metadata_entry(metadata_, tag, data, count))
+		return true;
+
+	const char *name = get_camera_metadata_tag_name(tag);
+	if (name)
+		LOG(CameraMetadata, Error)
+			<< "Failed to add tag " << name;
+	else
+		LOG(CameraMetadata, Error)
+			<< "Failed to add unknown tag " << tag;
+
+	valid_ = false;
+
+	return false;
+}
+
+camera_metadata_t *CameraMetadata::get()
+{
+	return valid_ ? metadata_ : nullptr;
+}