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/**
* mds — A micro-display server
* Copyright © 2014 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU 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 General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef MDS_LIBMDSSERVER_MDS_MESSAGE_H
#define MDS_LIBMDSSERVER_MDS_MESSAGE_H
#include <stddef.h>
#define MDS_MESSAGE_T_VERSION 0
/**
* Message passed between a server and a client or between two of either
*/
typedef struct mds_message
{
/**
* The headers in the message, each element in this list
* as an unparsed header, it consists of both the header
* name and its associated value, joined by ": ". A header
* cannot be `NULL` (unless its memory allocation failed,)
* but `headers` itself is NULL if there are no headers.
* The "Length" should be included in this list.
*/
char** headers;
/**
* The number of headers in the message
*/
size_t header_count;
/**
* The payload of the message, `NULL` if none (of zero-length)
*/
char* payload;
/**
* The size of the payload
*/
size_t payload_size;
/**
* How much of the payload that has been stored (internal data)
*/
size_t payload_ptr;
/**
* Internal buffer for the reading function (internal data)
*/
char* buffer;
/**
* The size allocated to `buffer` (internal data)
*/
size_t buffer_size;
/**
* The number of bytes used in `buffer` (internal data)
*/
size_t buffer_ptr; /* TODO: would it be better to use a circular buffer? */
/**
* 0 while reading headers, 1 while reading payload, and 2 when done (internal data)
*/
int stage;
} mds_message_t;
/**
* Initialise a message slot so that it can
* be used by `mds_message_read`
*
* @param this Memory slot in which to store the new message
* @return Non-zero on error, errno will be set accordingly.
* Destroy the message on error.
*/
int mds_message_initialise(mds_message_t* restrict this);
/**
* Zero initialise a message slot
*
* @param this Memory slot in which to store the new message
*/
void mds_message_zero_initialise(mds_message_t* restrict this);
/**
* Release all resources in a message, should
* be done even if initialisation fails
*
* @param this The message
*/
void mds_message_destroy(mds_message_t* restrict this);
/**
* Extend the header list's allocation
*
* @param this The message
* @param extent The number of additional entries
* @return Zero on success, -1 on error
*/
int mds_message_extend_headers(mds_message_t* restrict this, size_t extent);
/**
* Read the next message from a file descriptor
*
* @param this Memory slot in which to store the new message
* @param fd The file descriptor
* @return Non-zero on error or interruption, errno will be
* set accordingly. Destroy the message on error,
* be aware that the reading could have been
* interrupted by a signal rather than canonical error.
* If -2 is returned errno will not have been set,
* -2 indicates that the message is malformated,
* which is a state that cannot be recovered from.
*/
int mds_message_read(mds_message_t* restrict this, int fd);
/**
* Get the required allocation size for `data` of the
* function `mds_message_marshal`
*
* @param this The message
* @return The size of the message when marshalled
*/
size_t mds_message_marshal_size(const mds_message_t* restrict this) __attribute__((pure));
/**
* Marshal a message for state serialisation
*
* @param this The message
* @param data Output buffer for the marshalled data
*/
void mds_message_marshal(const mds_message_t* restrict this, char* restrict data);
/**
* Unmarshal a message for state deserialisation
*
* @param this Memory slot in which to store the new message
* @param data In buffer with the marshalled data
* @return Non-zero on error, errno will be set accordingly.
* Destroy the message on error.
*/
int mds_message_unmarshal(mds_message_t* restrict this, char* restrict data);
/**
* Get the required allocation size for `data` of the
* function `mds_message_compose`
*
* @param this The message
* @return The size of the message when marshalled
*/
size_t mds_message_compose_size(const mds_message_t* restrict this) __attribute__((pure));
/**
* Marshal a message for communication
*
* @param this The message
* @param data Output buffer for the marshalled data
*/
void mds_message_compose(const mds_message_t* restrict this, char* restrict data);
#endif
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