/*******************************************************************************
 * This file is part of SWIFT.
 * Copyright (c) 2017 Pedro Gonnet (pedro.gonnet@durham.ac.uk)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 ******************************************************************************/
#ifndef SWIFT_LOGGER_H
#define SWIFT_LOGGER_H

/* Includes. */
#include "part.h"

/* Forward declaration */
struct dump;

/**
 * Logger entries contain messages representing the particle data at a given
 * point in time during the simulation.
 *
 * The logger messages always start with an 8-byte header structured as
 * follows:
 *
 *   data: [ mask |                     offset                     ]
 *   byte: [  01  |  02  |  03  |  04  |  05  |  06  |  07  |  08  ]
 *
 * I.e. a first "mask" byte followed by 7 "offset" bytes. The mask contains
 * information on what kind of data is packed after the header. The mask
 * bits correspond to the following data:
 *
 *   bit | name   | size | comment
 *   -------------------------------------------------------------------------
 *   0   | x      | 24   | The particle position, in absolute coordinates,
 *       |        |      | stored as three doubles.
 *   1   | v      | 12   | Particle velocity, stored as three floats.
 *   2   | a      | 12   | Particle acceleration, stored as three floats.
 *   3   | u      | 4    | Particle internal energy (or entropy, if Gadget-SPH
 *       |        |      | is used), stored as a single float.
 *   4   | h      | 4    | Particle smoothing length (or epsilon, if a gpart),
 *       |        |      | stored as a single float.
 *   5   | rho    | 4    | Particle density, stored as a single float.
 *   6   | consts | 12   | Particle constants, i.e. mass and ID.
 *   7   | time   | 8    | Timestamp, not associated with a particle, just
 *       |        |      | marks the transitions from one timestep to another.
 *
 * There is no distinction between gravity and SPH particles.
 *
 * The offset refers to the relative location of the previous message for the
 * same particle or for the previous timestamp (if mask bit 7 is set). I.e.
 * the previous log entry will be at the address of the current mask byte minus
 * the unsigned value stored in the offset. An offset of zero indicates that
 * this is the first message for the given particle/timestamp.
 */

/* Some constants. */
#define logger_mask_x 1
#define logger_mask_v 2
#define logger_mask_a 4
#define logger_mask_u 8
#define logger_mask_h 16
#define logger_mask_rho 32
#define logger_mask_consts 64
#define logger_mask_timestamp 128

/* Function prototypes. */
int logger_size(unsigned int mask);
void logger_log_part(struct part *p, unsigned int mask, size_t *offset,
                     struct dump *dump);
void logger_log_gpart(struct gpart *p, unsigned int mask, size_t *offset,
                      struct dump *dump);
void logger_log_timestamp(unsigned long long int t, size_t *offset,
                          struct dump *dump);
int logger_read_part(struct part *p, size_t *offset, const char *buff);
int logger_read_gpart(struct gpart *p, size_t *offset, const char *buff);
int logger_read_timestamp(unsigned long long int *t, size_t *offset,
                          const char *buff);

#endif /* SWIFT_LOGGER_H */
