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/*
* Usurpataion --- client-server protocol interface.
*
* Copyright (C) 2019 Ramūnas Mažeikis
*
* 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; version 2.1
* of the License.
*
* 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 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, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
*/
#ifndef PROTOCOL_H_INCLUDED
#define PROTOCOL_H_INCLUDED
#include <errno.h>
#define E_TLV_OVERFLOW (1 << 0)
#define E_UNKNOWN_TYPE (1 << 1)
#define E_IVALID_DESCRIPTOR (1 << 2)
/**
* Regular packets contain tlv's defined by tlv_type.
*
* Hearbeat packet tell daemon that device is still alive and listening.
*
* Discovery packets are used for what they say.
*/
enum packet_type {
REGURAL,
HEARTBEAT,
DISCOVERY
};
/**
* Connection descriptor.
*/
typedef unsigned int cd_t;
/**
* Message sequence number since beggining of sesssion.
*
* Mainly used for identifying lost messages.
*/
typedef unsigned int msg_idx_t;
enum tlv_type {
/**
* NULL-terminated string. To be put in a queue to display on the
* screen.
*/
TEXT,
/** Fixed point. 1 decimal digit of precision. */
FPI1,
/** Literally time_t */
TIMESTAMP,
/** Represents a request for lost message. Data is unsigned integer
* that uniquely identifies the message.
*/
REQUEST,
/**
* Response to request. Begins with unsigned integer that represents
* which message is being repeated and the actual null-terminated
* message after that.
*/
REPLY,
/**
* UUID that represents a particular device.
*/
UUID
};
/**
* Packet data itself is a special type of tlv. A packet is either regular,
* hearbeat or discovery.
*/
struct packet_data {
enum packet_type type;
size_t packet_size;
char *data; /* Bytes representing tlv's */
};
/**
* Literally type-length-value
* */
struct tlv {
enum tlv_type type;
size_t length;
void *data;
};
/**
* Reads last packets received, parses and stores them to be later retreived
* via get_tlv.
* */
int get_last_data(cd_t connection);
/** Returns tlv's parsed by get_last_data. Returned tlv is only valid until
* next call to get_tlv.
* */
struct tlv * get_tlv(cd_t cd);
/**
* Any modifications made to the pending outgoing packet are nullified.
* */
void clear_data(cd_t connection);
/**
* Appends data to the next packet to be sent. Type of data is determined by
* enum tlv_type.
* */
int push_data(cd_t connection, const char *data, enum tlv_type);
/**
* Sends packet towards the other end.
* */
void flush_data(cd_t connection);
cd_t protocol_init(void);
#endif /* PROTOCOL_H_INCLUDED */
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