include/logging/log_backend.h

/*
 * Copyright (c) 2018 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: Apache-2.0
 */
#ifndef LOG_BACKEND_H
#define LOG_BACKEND_H

#include <logging/log_msg.h>
#include <assert.h>
#ifdef __cplusplus
extern "C" {
#endif

/**
 * @brief Logger backend interface
 * @defgroup log_backend Logger backend interface
 * @ingroup logger
 * @{
 */

/* Forward declaration of the log_backend type. */
struct log_backend;

/**
 * @brief Logger backend API.
 */
struct log_backend_api {
	void (*put)(const struct log_backend *const backend,
		    struct log_msg *msg);

	void (*panic)(const struct log_backend *const backend);
};

/**
 * @brief Logger backend control block.
 */
struct log_backend_control_block {
	void *ctx;
	u8_t id;
	bool active;
};

/**
 * @brief Logger backend structure.
 */
struct log_backend {
	const struct log_backend_api *api;
	struct log_backend_control_block *cb;
	const char *name;
};

extern const struct log_backend __log_backends_start[0];
extern const struct log_backend __log_backends_end[0];

/**
 * @brief Macro for creating a logger backend instance.
 *
 * @param _name  Name of the backend instance.
 * @param _api   Logger backend API.
 */
#define LOG_BACKEND_DEFINE(_name, _api)					       \
	static struct log_backend_control_block UTIL_CAT(backend_cb_, _name) = \
	{								       \
		.active = false,					       \
		.id = 0,						       \
	};								       \
	static const struct log_backend _name				       \
	__attribute__ ((section(".log_backends"))) __attribute__((used)) =     \
	{								       \
		.api = &_api,						       \
		.cb = &UTIL_CAT(backend_cb_, _name),			       \
		.name = STRINGIFY(_name)				       \
	}


/**
 * @brief Function for putting message with log entry to the backend.
 *
 * @param[in] backend  Pointer to the backend instance.
 * @param[in] msg      Pointer to message with log entry.
 */
static inline void log_backend_put(const struct log_backend *const backend,
				   struct log_msg *msg)
{
	assert(backend);
	assert(msg);
	backend->api->put(backend, msg);
}

/**
 * @brief Function for reconfiguring backend to panic mode.
 *
 * @param[in] backend  Pointer to the backend instance.
 */
static inline void log_backend_panic(const struct log_backend *const backend)
{
	assert(backend);
	backend->api->panic(backend);
}

/**
 * @brief Function for setting backend id.
 *
 * @note It is used internally by the logger.
 *
 * @param backend  Pointer to the backend instance.
 * @param id       ID.
 */
static inline void log_backend_id_set(const struct log_backend *const backend,
				      u8_t id)
{
	assert(backend);
	backend->cb->id = id;
}

/**
 * @brief Function for getting backend id.
 *
 * @note It is used internally by the logger.
 *
 * @param[in] backend  Pointer to the backend instance.
 * @return    Id.
 */
static inline u8_t log_backend_id_get(const struct log_backend *const backend)
{
	assert(backend);
	return backend->cb->id;
}

/**
 * @brief Function for getting backend.
 *
 * @param[in] idx  Pointer to the backend instance.
 *
 * @return    Pointer to the backend instance.
 */
static inline const struct log_backend *log_backend_get(u32_t idx)
{
	return &__log_backends_start[idx];
}

/**
 * @brief Function for getting number of backends.
 *
 * @return Number of backends.
 */
static inline int log_backend_count_get(void)
{
	return ((void *)__log_backends_end - (void *)__log_backends_start) /
			sizeof(struct log_backend);
}

/**
 * @brief Function for activating backend.
 *
 * @param[in] backend  Pointer to the backend instance.
 * @param[in] ctx      User context.
 */
static inline void log_backend_activate(const struct log_backend *const backend,
					void *ctx)
{
	assert(backend);
	backend->cb->ctx = ctx;
	backend->cb->active = true;
}

/**
 * @brief Function for deactivating backend.
 *
 * @param[in] backend  Pointer to the backend instance.
 */
static inline void log_backend_deactivate(
				const struct log_backend *const backend)
{
	assert(backend);
	backend->cb->active = false;
}

/**
 * @brief Function for checking state of the backend.
 *
 * @param[in] backend  Pointer to the backend instance.
 *
 * @return True if backend is active, false otherwise.
 */
static inline bool log_backend_is_active(
				const struct log_backend *const backend)
{
	assert(backend);
	return backend->cb->active;
}

/**
 * @}
 */

#ifdef __cplusplus
}
#endif

#endif /* LOG_BACKEND_H */