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/*
* Usurpation – clinet-server protocol implementation.
*
* Copyright (C) 2019 Ramūnas Mažeikis
* Copyright (C) 2019 Gediminas Jakutis
*
* 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 USURPATION_PROTOCOL_H_INCLUDED
#define USURPATION_PROTOCOL_H_INCLUDED
#include <errno.h>
#include <stdint.h>
#include <stddef.h>
#include <limits.h>
#define TLV_SZ_MAX (MTU - 64)
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
/**
* Message sequence number since beggining of sesssion.
*
* Mainly used for identifying lost messages.
*/
typedef unsigned int msg_idx_t;
enum tlv_type {
/**
* Explicitly states that this tlv is no longer valid for reading.
*/
INVALID = 0,
/**
* 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,
/**
* Says "I'm not dead yet.".
*/
HEARTBEAT,
};
struct tlv_header {
int32_t type;
uint32_t size;
};
struct tlv {
struct tlv_header head;
char *data;
};
/* for tlv to "raw" conversion */
struct tlv_packet {
size_t size;
ptrdiff_t cursor;
char *data;
};
/* used as a termninator */
#define tlv_none ((struct tlv) {{INVALID, 0}, NULL})
/**
* Fills tlv structure to represent the next tlv in the packet.
* If saveptr is non-NULL, saves the offset to the next field in saveptr.
* Returns NONEWDATA if once all tlvs were read.
*
* tlv data fields obtained through this function MUST NOT be given
* to free(), as they point to the offsets in the "in" buffer.
*/
int tlv_get(char *in, struct tlv *tlv, char **saveptr);
/* host<->network endianess conversion for the header */
struct tlv_header ntoh_tlvh(const struct tlv_header * const in);
struct tlv_header hton_tlvh(const struct tlv_header * const in);
/**
* Forms (packs up) a raw data packet from the given tlv by appending it to the
* packet. Returns E_TLV_OVERFLOW if pushing data would cause the final size
* (including the terminator tlv) to be greater than TLV_SZ_MAX_RAW. In case of
* such error the data is left untouched.
*/
int tlv_pack(struct tlv_packet *pack, struct tlv *tlv);
/* finalized the packet by placing tlv_none at the end */
int tlv_packet_finalize(struct tlv_packet *pack);
struct tlv *tlv_init(struct tlv *in, enum tlv_type type);
void tlv_destroy(struct tlv *in);
struct tlv_packet *tlv_packet_init(struct tlv_packet *in);
void tlv_packet_destroy(struct tlv_packet *in);
/* resets the packet to form a new one, without deallocating buffers */
struct tlv_packet *tlv_packet_reset(struct tlv_packet *in);
#ifdef __cplusplus
}
#endif /* __cplusplus */
#endif /* USURPATION_PROTOCOL_H_INCLUDED */
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