/*
 * Copyright © 2010 Stéphane Raimbault <stephane.raimbault@gmail.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser 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 Lesser Public License for more details.
 *
 * You should have received a copy of the GNU Lesser Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef _MODBUS_PRIVATE_H_
#define _MODBUS_PRIVATE_H_

#include "modbus.h"

MODBUS_BEGIN_DECLS

/* It's not really the minimal length (the real one is report slave ID
 * in RTU (4 bytes)) but it's a convenient size to use in RTU or TCP
 * communications to read many values or write a single one.
 * Maximum between :
 * - HEADER_LENGTH_TCP (7) + function (1) + address (2) + number (2)
 * - HEADER_LENGTH_RTU (1) + function (1) + address (2) + number (2) + CRC (2)
 */
#define _MIN_REQ_LENGTH           12

#define _REPORT_SLAVE_ID_LENGTH   75

#define _MODBUS_EXCEPTION_RSP_LENGTH  5

/* Time out between trames in microsecond */
#define _TIME_OUT_BEGIN_OF_TRAME    500000
#define _TIME_OUT_END_OF_TRAME      500000

/* Function codes */
#define _FC_READ_COILS                0x01
#define _FC_READ_DISCRETE_INPUTS      0x02
#define _FC_READ_HOLDING_REGISTERS    0x03
#define _FC_READ_INPUT_REGISTERS      0x04
#define _FC_WRITE_SINGLE_COIL         0x05
#define _FC_WRITE_SINGLE_REGISTER     0x06
#define _FC_READ_EXCEPTION_STATUS     0x07
#define _FC_WRITE_MULTIPLE_COILS      0x0F
#define _FC_WRITE_MULTIPLE_REGISTERS  0x10
#define _FC_REPORT_SLAVE_ID           0x11
#define _FC_READ_AND_WRITE_REGISTERS  0x17

typedef enum {
    _MODBUS_BACKEND_TYPE_RTU=0,
    _MODBUS_BACKEND_TYPE_TCP
} modbus_bakend_type_t;

/* This structure reduces the number of params in functions and so
 * optimizes the speed of execution (~ 37%). */
typedef struct _sft {
    int slave;
    int function;
    int t_id;
} sft_t;

typedef struct _modbus_backend {
    unsigned int backend_type;
    unsigned int header_length;
    unsigned int checksum_length;
    unsigned int max_adu_length;
    int (*set_slave) (modbus_t *ctx, int slave);
    int (*build_request_basis) (modbus_t *ctx, int function, int addr,
                                int nb, uint8_t *req);
    int (*build_response_basis) (sft_t *sft, uint8_t *rsp);
    int (*prepare_response_tid) (const uint8_t *req, int *req_length);
    int (*send_msg_pre) (uint8_t *req, int req_length);
    ssize_t (*send) (int s, const uint8_t *req, int req_length);
    ssize_t (*recv) (int s, uint8_t *rsp, int rsp_length);
    int (*check_integrity) (modbus_t *ctx, uint8_t *msg,
                            const int msg_length);
    int (*connect) (modbus_t *ctx);
    void (*close) (modbus_t *ctx);
    int (*flush) (modbus_t *ctx);
    int (*listen) (modbus_t *ctx, int nb_connection);
    int (*accept) (modbus_t *ctx, int *socket);
    int (*filter_request) (modbus_t *ctx, int slave);
} modbus_backend_t;

struct _modbus {
    /* Slave address */
    int slave;
    /* Socket or file descriptor */
    int s;
    int debug;
    int error_recovery;
    struct timeval timeout_begin;
    struct timeval timeout_end;
    const modbus_backend_t *backend;
    void *backend_data;
};

void _modbus_init_common(modbus_t *ctx);

MODBUS_END_DECLS

#endif  /* _MODBUS_PRIVATE_H_ */