Add KeepAlive support for all TCP sockets.
/*
* Copyright (c) 2002,2016 Mario de Sousa (msousa@fe.up.pt)
*
* This file is part of the Modbus library for Beremiz and matiec.
*
* This Modbus library 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, 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
* General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this Modbus library. If not, see <http://www.gnu.org/licenses/>.
*
* This code is made available on the understanding that it will not be
* used in safety-critical situations without a full and competent review.
*/
/* Data structures used by the modbus protocols... */
#ifndef __MODBUS_DS_UTIL_H
#define __MODBUS_DS_UTIL_H
#include "mb_types.h" /* get the data types */
/**************************************/
/** **/
/** A data structure - linear buffer **/
/** **/
/**************************************/
/* An unbounded FIFO data structure.
*
* The user/caller writes and reads directly from the data structure's buffer,
* which eliminates slow copying of bytes between the user's and the structure's
* local memory.
*
* The data structure stores the current data linearly in a single memory array,
* i.e. the current data is stored from start to finish from a low address
* to a high address, and does *not* circle back to the bottom of the address
* space as is usual in a circular buffer. This allows the user/caller to
* pass the structure's own byte array on to other functions such as
* read() and write() for file operations.
*
* The FIFO is implemented by allocating more memory than the maximum number
* of bytes it will ever hold, and using the extra bytes at the top of the
* array as the bottom data bytes are released. When we run out of extra bytes,
* (actually, when the number of un-used bytes at the beginning is larger than
* a configured maximum), the whole data is moved down, freeing once again the
* extra bytes at the top of the array.
*
* Remember that we can optimize the data structure so that whenever it becomes
* empty, we can reset it to start off at the bottom of the byte array, i.e. we
* can set the start = end = 0; instead of simply setting the start = end, which
* may point to any position in the array.
*
* Taking the above into consideration, it would probably be a little more efficient
* to implement it as a circular buffer with an additional linearize() function
* the user could call whenever (s)he required the data to be stored linearly.
* Nevertheless, since it has already been implemented as a linear buffer, and since
* under normal circumstances the start and end pointers will be reset to 0 quite
* often (and therefore we get no additional benefit under normal circumstances),
* we will leave it as it is for the time being...
*
*
* The user is expected to call
* lb_init() -> to initialize the structure
* lb_done() -> to free the data structure's memory
*
* The user can store data starting off from...
* lb_free() -> pointer to address of free memory
* lb_free_count() -> number of free bytes available
* and then call
* lb_data_add()
* to add the data to the data structure
*
* Likewise, the user can read the data directly from
* lb_data() -> pointer to address of data location
* lb_free_count() -> number of data bytes available
* and free the data using
* lb_data_purge()
* to remove the data from the data structure
*/
typedef struct {
u8 *data;
int data_size; /* size of the *data buffer */
int data_start; /* offset within *data were valid data starts */
int data_end; /* offset within *data were valid data ends */
int max_data_start; /* optimization parameter! When should it be normalised? */
} lb_buf_t;
/* NOTE: lb = Linear Buffer */
static inline u8 *lb_init(lb_buf_t *buf, int size, int max_data_start) {
if (size <= 0)
return NULL;
if (max_data_start >= size)
max_data_start = size - 1;
buf->data_size = size;
buf->data_start = 0;
buf->data_end = 0;
buf->max_data_start = max_data_start;
buf->data = (u8 *)malloc(size);
return buf->data;
}
static inline void lb_done(lb_buf_t *buf) {
free(buf->data);
buf->data = NULL;
}
static inline u8 *lb_normalize(lb_buf_t *buf) {
return (u8 *)memmove(buf->data,
buf->data + buf->data_start,
buf->data_end - buf->data_start);
}
static inline u8 *lb_data(lb_buf_t *buf) {
return buf->data + buf->data_start;
}
static inline int lb_data_count(lb_buf_t *buf) {
return buf->data_end - buf->data_start;
}
static inline void lb_data_add(lb_buf_t *buf, int count) {
if ((buf->data_end += count) >= buf->data_size)
buf->data_end = buf->data_size - 1;
}
static inline u8 *lb_data_purge(lb_buf_t *buf, int count) {
buf->data_start += count;
if (buf->data_start > buf->data_end)
buf->data_start = buf->data_end;
if ((buf->data_end == buf->data_size) || (buf->data_start >= buf->max_data_start))
return lb_normalize(buf);
return buf->data + buf->data_start;
}
static inline void lb_data_purge_all(lb_buf_t *buf) {
buf->data_start = buf->data_end = 0;
}
static inline u8 *lb_free(lb_buf_t *buf) {
return buf->data + buf->data_end;
}
static inline int lb_free_count(lb_buf_t *buf) {
return buf->data_size - buf->data_end;
}
#endif /* __MODBUS_DS_UTIL_H */