protocol.h

#pragma once
#include <stdint.h>
#include <sys/ipc.h>

#define MAX_DAEMON_PACKET_DATA_SIZE 4096

#define MSG_QUEUE_KEY "/var/run/sibyl"
#define MSG_QUEUE_PROJ_ID 69

/**
 * typedef daemon_measurement_datatype_t - Enum of possible datatypes for `daemon_measurement_t`.
 */
typedef enum {
    CHAR,
    INT64,
    UINT64,
    FLOAT64
} __attribute__ ((__packed__)) daemon_measurement_datatype_t;

/**
 * typedef daemon_measurement_t - Structure to hold a userspace measurement.
 * @measurement_id: The id of the measurement. Every sender should have a unique id.
 * @daemon_measurement_datatype: Datatype of the data. All values in `data` must be of this type.
 * @length: How many types of `datatype` are in `data`. Must not exceed (`length` * daemon_measurement_datatype_size(`datatype`)) > MAX_DAEMON_PACKET_DATA_SIZE.
 * @data: The measurement data.
 */
typedef struct {
    uint8_t measurement_id;
    daemon_measurement_datatype_t datatype;
    uint16_t length;
    uint8_t data[MAX_DAEMON_PACKET_DATA_SIZE];
} daemon_measurement_t;

/**
 * daemon_measurement_datatype_size() - Get the size of a `daemon_measurement_datatype_t`.
 * @arg1: The datatype to get the size of.
 *
 * Returns the size.
 */
int daemon_measurement_datatype_size(daemon_measurement_datatype_t datatype);
/**
 * daemon_measurement_check() - Check if a `daemon_measurement_t` is correct.
 * @arg1: Measurement to check.
 *
 * Checks if the datatype size * length not exceeds MAX_DAEMON_PACKET_DATA_SIZE.
 *
 * Returns 0 on success, -1 on error.
 */
int daemon_measurement_check(daemon_measurement_t* daemon_measurement);

/**
 * msg_queue_key() - Return the message queue key for the userspace communication.
 *
 * Returns the key of the message queue or -1 on error.
 */
key_t msg_queue_key();