meta

Store definition

// SPDX-FileCopyrightText: 2020-2023 Jochem Rutgers
//
// SPDX-License-Identifier: CC0-1.0

int32=42 some int
double=1.618 a double
string:7="hello" world

Application

// SPDX-FileCopyrightText: 2020-2023 Jochem Rutgers
//
// SPDX-License-Identifier: CC0-1.0

/*!
 * \file
 * \brief Example to show how to use generated *Meta.py for further store
 *	processing.
 *
 * This example uses the generated meta data to generate another wrapper for a
 * store.  In this case, a wrapper that prints changes to the store of every
 * variable.
 *
 * The generator used for this example, takes libstored/doc/ExampleMetaMeta.py
 * and the jinja2 template input LoggingWrapper.h.tmpl, and generates the
 * store-specific output file LoggingExampleMeta.h.
 */

#include "ExampleMeta.h"
#include "LoggingExampleMeta.h"

#include <stored>

// Create an ExampleMeta store, which uses the generated LoggingExampleMeta as
// a wrapper.
class ExampleMeta : public STORE_T(ExampleMeta, LoggingExampleMeta, stored::ExampleMetaBase) {
	STORE_CLASS(ExampleMeta, LoggingExampleMeta, stored::ExampleMetaBase)
public:
	ExampleMeta() is_default
};

int main()
{
	ExampleMeta store;

	// No change expected, no output.
	store.some_int = 42;

	// Expect some logging output.
	store.a_double = 2.718;
	store.world.set("hi");
}

Output

'a double' changed to 2.718
'world' changed to "hi"

Store reference

template<typename Base_, typename Implementation_> class ExampleMetaObjects

All ExampleMetaBase’s objects.

Public Types

typedef Base_ Base

typedef Implementation_ Implementation

Public Members

impl::StoreVariable<Base, Implementation, double, 0u, 8> a_double: a double

impl::StoreVariable<Base, Implementation, int32_t, 16u, 4> some_int: some int

impl::StoreVariantV<Base, Implementation, Type::String, 8u, 7u> world: world

template<typename Implementation_> class ExampleMetaBase : public stored::ExampleMetaObjects<ExampleMetaBase<Implementation_>, Implementation_>

Base class with default interface of all ExampleMeta implementations.

Although there are no virtual functions in the base class, subclasses can override them. The (lowest) subclass must pass the Implementation_ template paramater to its base, such that all calls from the base class can be directed to the proper overridden implementation.

The base class cannot be instantiated. If a default implementation is required, which does not have side effects to functions, instantiate stored::ExampleMeta. This class contains all data of all variables, so it can be large. So, be aware when instantiating it on the stack. Heap is fine. Static allocations is fine too, as the constructor and destructor are trivial.

To inherit the base class, you can use the following template:

class ExampleMeta : public stored::store<ExampleMeta, ExampleMetaBase>::type {
    STORE_CLASS(ExampleMeta, ExampleMetaBase)
public:
    // Your class implementation, such as:
    ExampleMeta() is_default
    // ...
};

Some compilers or tools may get confused by the inheritance using stored::store or stored::store_t. Alternatively, use STORE_T(...) instead, providing the template parameters of stored::store as macro arguments.

See also

stored::ExampleMeta

See also

stored::ExampleMetaData

Subclassed by LoggingExampleMeta< stored::ExampleMetaBase< ExampleMeta > >, stored::ExampleMetaDefaultFunctions< ExampleMetaBase< ExampleMeta > >

Public Types

enum [anonymous]

Values:

enumerator ObjectCount: Number of objects in the store.

enumerator VariableCount: Number of variables in the store.

enumerator FunctionCount: Number of functions in the store.

enumerator BufferSize: Buffer size.

typedef Implementation_ Implementation: Type of the actual implementation, which is the (lowest) subclass.

typedef uintptr_t Key

Type of a key.

See also

bufferToKey()

typedef Map<String::type, Variant<Implementation>>::type ObjectMap: Map as generated by map().

typedef ExampleMetaObjects<ExampleMetaBase, Implementation_> Objects

typedef ExampleMetaBase root: We are the root, as used by STORE_CLASS.

typedef ExampleMetaBase self: Define self for stored::store.

Public Functions

inline ~ExampleMetaBase()

inline Key bufferToKey(void const *buffer) const noexcept

Converts a variable’s buffer to a key.

A key is unique for all variables of the same store, but identical for the same variables across different instances of the same store class. Therefore, the key can be used to synchronize between instances of the same store. A key does not contain meta data, such as type or length. It is up to the synchronization library to make sure that these properties are handled well.

For synchronization, when hookEntryX() or hookEntryRO() is invoked, one can compute the key of the object that is accessed. The key can be used, for example, in a key-to-Variant map. When data arrives from another party, the key can be used to find the proper Variant in the map.

This way, data exchange is type-safe, as the Variant can check if the data format matches the expected type. However, one cannot process data if the key is not set yet in the map.

inline Type::type bufferToType(void const *buffer) noexcept: Return the type of the variable, given its buffer.

inline Variant<Implementation> find(char const *name, size_t len = std::numeric_limits<size_t>::max()) noexcept

Finds an object with the given name.

Returns:: the object, or an invalid stored::Variant if not found.

template<typename T> inline Function<T, Implementation> function(char const *name, size_t len = std::numeric_limits<size_t>::max()) noexcept

Finds a function with the given name.

The function, when it exists, must have the given (fixed) type.

inline Implementation const &implementation() const noexcept: Returns the reference to the implementation.

inline Implementation &implementation() noexcept: Returns the reference to the implementation.

template<typename F> inline void list(F &&f) noexcept

Calls a callback for every object in the longDirectory().

See also

stored::list()

template<typename F> inline void list(F f, void *arg, char const *prefix, String::type *nameBuffer) noexcept

Calls a callback for every object in the longDirectory().

See also

stored::list()

template<typename F> inline void list(F f, void *arg, char const *prefix = nullptr) noexcept

Calls a callback for every object in the longDirectory().

See also

stored::list()

inline uint8_t const *longDirectory() const noexcept

Retuns the long directory.

When not available, the short directory is returned.

inline ObjectMap map(char const *prefix = nullptr)

Create a name to Variant map for the store.

Generating the map may be expensive and the result is not cached.

inline char const *name() const noexcept: Returns the name of store, which can be used as prefix for stored::Debugger.

inline uint8_t const *shortDirectory() const noexcept: Returns the short directory.

template<typename T> inline Variable<T, Implementation> variable(char const *name, size_t len = std::numeric_limits<size_t>::max()) noexcept

Finds a variable with the given name.

The variable, when it exists, must have the given (fixed) type.

Public Members

impl::StoreVariable<Base, Implementation, double, 0u, 8> a_double: a double

impl::StoreVariable<Base, Implementation, int32_t, 16u, 4> some_int: some int

impl::StoreVariantV<Base, Implementation, Type::String, 8u, 7u> world: world

Public Static Functions

template<typename T> static inline constexpr FreeFunction<T, Implementation> freeFunction(char const *name, size_t len = std::numeric_limits<size_t>::max()) noexcept

Finds a function with the given name.

The function, when it exists, must have the given (fixed) type. It is returned as a free function; it is not bound yet to a specific store instance. This function is constexpr for C++14.

template<typename T> static inline constexpr FreeVariable<T, Implementation> freeVariable(char const *name, size_t len = std::numeric_limits<size_t>::max()) noexcept

Finds a variable with the given name.

The variable, when it exists, must have the given (fixed) type. It is returned as a free variable; it is not bound yet to a specific store instance. This function is constexpr for C++14.

static inline constexpr char const *hash() noexcept: Returns a unique hash of the store.

Friends

friend class impl::StoreFunction

friend class impl::StoreVariable

friend class impl::StoreVariantF

friend class impl::StoreVariantV

friend class stored::FreeVariable

friend class stored::Variant< void >

class ExampleMeta : public LoggingExampleMeta<stored::ExampleMetaBase<ExampleMeta>>

Public Functions

ExampleMeta() = default