/**
* mds — A micro-display server
* Copyright © 2014, 2015, 2016 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_LIBMDSCLIENT_INBOUND_H
#define MDS_LIBMDSCLIENT_INBOUND_H
/* This module is eerily similar to <libmdsserver/mds-message.h>,
* somethings have been removed, some things have been added. */
#include <stddef.h>
#include <semaphore.h>
/**
* Message passed between a server and a client or between two of either
*/
typedef struct libmds_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` but `headers` itself is `NULL` if there
* are no headers. The "Length" header is 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;
/**
* 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;
/**
* The number of bytes read from `buffer` (internal data)
*/
size_t buffer_off;
/**
* Zero unless the structure is flattend, otherwise
* the size of the object (internal data)
*
* Flattened means that all pointers are subpointers
* of the object itself
*/
size_t flattened;
/**
* 0 while reading headers, 1 while reading payload, and 2 when done (internal data)
*/
int stage;
} libmds_message_t;
/**
* Queue of spooled messages
*/
typedef struct libmds_mspool
{
/**
* Array of messages (internal data)
*/
libmds_message_t** messages;
/**
* The number of elements the current
* allocation of `messages` can hold (internal data)
*/
size_t size;
/**
* Push end (internal data)
*/
size_t head;
/**
* Poll end (internal data)
*/
size_t tail;
/**
* The total size of all spooled messages
* (internal data)
*/
size_t spooled_bytes;
/**
* Do not spool additional messages if
* `spooled_bytes` is equal to or exceeds
* to value
*/
size_t spool_limit_bytes;
/**
* Do not spool more than this amount
* of messages
*/
size_t spool_limit_messages;
/**
* If non-zero, `wait_semaphore` shall
* be incremented when a message is
* polled (internal data)
*/
int please_post;
/* POSIX semaphores are lighter weight than XSI semaphores, so we use POSIX here. */
/**
* Binary semaphore used to lock the spool whilst
* manipulating it (internal data)
*/
sem_t lock;
/**
* Semaphore used to signal addition of messages.
* Each time a message is spooled, this semaphore
* is increased, the polling thread decreases the
* semaphore before despooling a message, causing
* it to block when the spool is empty
* (internal data)
*/
sem_t semaphore;
/**
* If the spool is full, the semaphore is acquired
* so that the spool function blocks, it is then
* posted when a message is polled so that the
* spool function may try again (internal data)
*/
sem_t wait_semaphore;
} libmds_mspool_t;
/**
* Message pool (stack) for reusable message allocations
*/
typedef struct libmds_mpool
{
/**
* Array of messages (internal data)
*/
libmds_message_t** messages;
/**
* The number of elements the current
* allocation of 'messages` can hold (internal data)
*/
size_t size;
/**
* The tip of the stack (internal data)
*/
volatile size_t tip;
/**
* Binary semaphore used to lock the pool
* whilst manipulating it (internal data)
*/
sem_t lock;
} libmds_mpool_t;
/**
* Initialise a message slot so that it can
* be used by `libmds_message_read`
*
* @param this Memory slot in which to store the new message
* @return Zero on success, -1 error, `errno` will be set
* accordingly
*
* @throws ENOMEM Out of memory. Possibly, the process hit the RLIMIT_AS or
* RLIMIT_DATA limit described in getrlimit(2).
*/
__attribute__((nonnull, warn_unused_result))
int libmds_message_initialise(libmds_message_t* restrict this);
/**
* Release all resources in a message
*
* @param this The message
*/
__attribute__((nonnull))
void libmds_message_destroy(libmds_message_t* restrict this);
/**
* Release all resources in a message, should
* be done even if initialisation fails
*
* @param this The message
* @param pool Message allocation pool, may be `NULL`
* @return The duplicate, you do not need to call `libmds_message_destroy`
* on it before you call `free` on it. However, you cannot use
* this is an `libmds_message_t` array (libmds_message_t*), only
* in an `libmds_message_t*` array (libmds_message_t**).
*
* @throws ENOMEM Out of memory. Possibly, the process hit the RLIMIT_AS or
* RLIMIT_DATA limit described in getrlimit(2).
*/
__attribute__((nonnull(1), malloc, warn_unused_result))
libmds_message_t* libmds_message_duplicate(libmds_message_t* restrict this, libmds_mpool_t* restrict pool);
/**
* 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 Zero on success, -1 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.
*
* @throws ENOMEM Out of memory. Possibly, the process hit the RLIMIT_AS or
* RLIMIT_DATA limit described in getrlimit(2).
* @throws Any error specified for recv(3)
*/
__attribute__((nonnull, warn_unused_result))
int libmds_message_read(libmds_message_t* restrict this, int fd);
/**
* Initialise a message spool
*
* @param this The message spool
* @return Zero on success, -1 on error, `errno` will be set accordingly
*
* @throws ENOMEM Out of memory. Possibly, the process hit the RLIMIT_AS or
* RLIMIT_DATA limit described in getrlimit(2).
*/
__attribute__((nonnull, warn_unused_result))
int libmds_mspool_initialise(libmds_mspool_t* restrict this);
/**
* Destroy a message spool, deallocate its resources
*
* @param this The message spool
*/
__attribute__((nonnull))
void libmds_mspool_destroy(libmds_mspool_t* restrict this);
/**
* Spool a message
*
* @param this The message spool
* @param message The message to spool, must be flat (created with `libmds_message_duplicate`)
* @return Zero on success, -1 on error, `errno` will be set accordingly
*
* @throws EINTR If interrupted
* @throws ENOMEM Out of memory. Possibly, the process hit the RLIMIT_AS or
* RLIMIT_DATA limit described in getrlimit(2).
*/
__attribute__((nonnull, warn_unused_result))
int libmds_mspool_spool(libmds_mspool_t* restrict this, libmds_message_t* restrict message);
/**
* Poll a message from a spool, wait if empty
*
* @param this The message spool
* @return A spooled message, `NULL`on error, `errno` will be set accordingly
*
* @throws EINTR If interrupted
*/
__attribute__((nonnull, warn_unused_result, malloc))
libmds_message_t* libmds_mspool_poll(libmds_mspool_t* restrict this);
/**
* Poll a message from a spool, wait for a limited time
* or return unsuccessfully if empty
*
* @param this The message spool
* @param deadline The CLOCK_REALTIME time the function must return,
* `NULL` to return immediately if it would block
* @return A spooled message, `NULL`on error, `errno` will be set accordingly
*
* @throws EINTR If interrupted
* @throws EAGAIN If `deadline` is `NULL` and the spool is empty
* @throws EINVAL If `deadline->tv_nsecs` is outside [0, 1 milliard[
* @throws ETIMEDOUT If the time specified `deadline` passed and the spool was till empty
*/
__attribute__((nonnull(1), warn_unused_result, malloc))
libmds_message_t* libmds_mspool_poll_try(libmds_mspool_t* restrict this,
const struct timespec* restrict deadline);
/**
* Initialise a pool of reusable message allocations
*
* @param this The message allocation pool
* @param size The number of allocations that may be pooled
* @return Zero on success, -1 on error, `errno` will be set accordingly
*
* @throws ENOMEM Out of memory. Possibly, the process hit the RLIMIT_AS or
* RLIMIT_DATA limit described in getrlimit(2).
*/
__attribute__((nonnull, warn_unused_result))
int libmds_mpool_initialise(libmds_mpool_t* restrict this, size_t size);
/**
* Destroy a pool of reusable message allocations,
* deallocate its resources and pooled allocations
*
* @param this The message allocation pool
*/
__attribute__((nonnull))
void libmds_mpool_destroy(libmds_mpool_t* restrict this);
/**
* Add a message allocation to a pool
*
* @param this The message allocation pool
* @param message Message allocation to pool, must be flat (created with
* `libmds_message_duplicate` or fetched with `libmds_mspool_poll`
* or `libmds_mspool_poll_try`)
* @return Zero on success, -1 on error, `errno` will be set accordingly
*/
__attribute__((nonnull, warn_unused_result))
int libmds_mpool_offer(libmds_mpool_t* restrict this, libmds_message_t* restrict message);
/**
* Fetch a message allocation from a pool
*
* @param this The message allocation pool
* @return An offered message allocation, `NULL` on error or if none
* are available. If `NULL` is returned, `errno` is set to zero,
* if the pool was empty, otherwise `errno` will describe the error.
*/
__attribute__((nonnull, warn_unused_result, malloc))
libmds_message_t* libmds_mpool_poll(libmds_mpool_t* restrict this);
#endif
