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/* SPDX-License-Identifier: BSD-2-Clause */
/*
* Copyright (C) 2019-2021, Raspberry Pi (Trading) Limited
*
* metadata.hpp - general metadata class
*/
#pragma once
// A simple class for carrying arbitrary metadata, for example about an image.
#include <any>
#include <map>
#include <memory>
#include <mutex>
#include <string>
namespace RPiController {
class Metadata
{
public:
template<typename T>
void Set(std::string const &tag, T const &value)
{
std::scoped_lock lock(mutex_);
data_[tag] = value;
}
template<typename T>
int Get(std::string const &tag, T &value) const
{
std::scoped_lock lock(mutex_);
auto it = data_.find(tag);
if (it == data_.end())
return -1;
value = std::any_cast<T>(it->second);
return 0;
}
void Clear()
{
std::scoped_lock lock(mutex_);
data_.clear();
}
Metadata &operator=(Metadata const &other)
{
std::scoped_lock lock(mutex_, other.mutex_);
data_ = other.data_;
return *this;
}
template<typename T>
T *GetLocked(std::string const &tag)
{
// This allows in-place access to the Metadata contents,
// for which you should be holding the lock.
auto it = data_.find(tag);
if (it == data_.end())
return nullptr;
return std::any_cast<T>(&it->second);
}
template<typename T>
void SetLocked(std::string const &tag, T const &value)
{
// Use this only if you're holding the lock yourself.
data_[tag] = value;
}
// Note: use of (lowercase) lock and unlock means you can create scoped
// locks with the standard lock classes.
// e.g. std::lock_guard<RPiController::Metadata> lock(metadata)
void lock() { mutex_.lock(); }
void unlock() { mutex_.unlock(); }
private:
mutable std::mutex mutex_;
std::map<std::string, std::any> data_;
};
typedef std::shared_ptr<Metadata> MetadataPtr;
} // namespace RPiController
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