msousa@0: /*
msousa@0:  * Copyright (c) 2002,2016 Mario de Sousa (msousa@fe.up.pt)
msousa@0:  *
msousa@0:  * This file is part of the Modbus library for Beremiz and matiec.
msousa@0:  *
msousa@0:  * This Modbus library is free software: you can redistribute it and/or modify
msousa@0:  * it under the terms of the GNU Lesser General Public License as published by
msousa@0:  * the Free Software Foundation, either version 3 of the License, or
msousa@0:  * (at your option) any later version.
msousa@0:  *
msousa@0:  * This program is distributed in the hope that it will be useful, but
msousa@0:  * WITHOUT ANY WARRANTY; without even the implied warranty of
msousa@0:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser 
msousa@0:  * General Public License for more details.
msousa@0:  *
msousa@0:  * You should have received a copy of the GNU Lesser General Public License
msousa@0:  * along with this Modbus library.  If not, see <http://www.gnu.org/licenses/>.
msousa@0:  *
msousa@0:  * This code is made available on the understanding that it will not be
msousa@0:  * used in safety-critical situations without a full and competent review.
msousa@0:  */
msousa@0: 
msousa@0: 
msousa@0: 
msousa@0:  /* Data structures used by the modbus protocols... */
msousa@0: 
msousa@0: 
msousa@0: #ifndef __MODBUS_DS_UTIL_H
msousa@0: #define __MODBUS_DS_UTIL_H
msousa@0: 
msousa@0: 
msousa@0: #include "mb_types.h"  /* get the data types */
msousa@0: 
msousa@0: /**************************************/
msousa@0: /**                                  **/
msousa@0: /** A data structure - linear buffer **/
msousa@0: /**                                  **/
msousa@0: /**************************************/
msousa@0: 
msousa@0: /* An unbounded FIFO data structure.
msousa@0:  *
msousa@0:  * The user/caller writes and reads directly from the data structure's buffer,
msousa@0:  * which eliminates slow copying of bytes between the user's and the structure's
msousa@0:  * local memory.
msousa@0:  *
msousa@0:  * The data structure stores the current data linearly in a single memory array,
msousa@0:  * i.e. the current data is stored from start to finish from a low address
msousa@0:  * to a high address, and does *not* circle back to the bottom of the address
msousa@0:  * space as is usual in a circular buffer. This allows the user/caller to
msousa@0:  * pass the structure's own byte array on to other functions such as
msousa@0:  * read() and write() for file operations.
msousa@0:  *
msousa@0:  * The FIFO is implemented by allocating more memory than the maximum number
msousa@0:  * of bytes it will ever hold, and using the extra bytes at the top of the
msousa@0:  * array as the bottom data bytes are released. When we run out of extra bytes,
msousa@0:  * (actually, when the number of un-used bytes at the beginning is larger than
msousa@0:  * a configured maximum), the whole data is moved down, freeing once again the
msousa@0:  * extra bytes at the top of the array.
msousa@0:  *
msousa@0:  * Remember that we can optimize the data structure so that whenever it becomes
msousa@0:  * empty, we can reset it to start off at the bottom of the byte array, i.e. we
msousa@0:  * can set the start = end = 0; instead of simply setting the start = end, which
msousa@0:  * may point to any position in the array.
msousa@0:  *
msousa@0:  * Taking the above into consideration, it would probably be a little more efficient
msousa@0:  * to implement it as a circular buffer with an additional linearize() function
msousa@0:  * the user could call whenever (s)he required the data to be stored linearly.
msousa@0:  * Nevertheless, since it has already been implemented as a linear buffer, and since
msousa@0:  * under normal circumstances the start and end pointers will be reset to 0 quite
msousa@0:  * often (and therefore we get no additional benefit under normal circumstances),
msousa@0:  * we will leave it as it is for the time being...
msousa@0:  *
msousa@0:  *
msousa@0:  * The user is expected to call
msousa@0:  *   lb_init() -> to initialize the structure
msousa@0:  *   lb_done() -> to free the data structure's memory
msousa@0:  *
msousa@0:  * The user can store data starting off from...
msousa@0:  *   lb_free() -> pointer to address of free memory
msousa@0:  *   lb_free_count() -> number of free bytes available
msousa@0:  * and then call
msousa@0:  *   lb_data_add()
msousa@0:  * to add the data to the data structure
msousa@0:  *
msousa@0:  * Likewise, the user can read the data directly from
msousa@0:  *   lb_data() -> pointer to address of data location
msousa@0:  *   lb_free_count() -> number of data bytes available
msousa@0:  * and free the data using
msousa@0:  *   lb_data_purge()
msousa@0:  * to remove the data from the data structure
msousa@0:  */
msousa@0: 
msousa@0: 
msousa@0: typedef struct {
msousa@0:         u8 *data;
msousa@0:         int data_size;      /* size of the *data buffer                   */
msousa@0:         int data_start;     /* offset within *data were valid data starts */
msousa@0:         int data_end;       /* offset within *data were valid data ends   */
msousa@0:         int max_data_start; /* optimization parameter! When should it be normalised? */
msousa@0:         } lb_buf_t;
msousa@0: 
msousa@0: /* NOTE: lb = Linear Buffer */
msousa@0: 
msousa@0: static inline u8 *lb_init(lb_buf_t *buf, int size, int max_data_start) {
msousa@0:   if (size <= 0)
msousa@0:     return NULL;
msousa@0: 
msousa@0:   if (max_data_start >= size)
msousa@0:     max_data_start = size - 1;
msousa@0: 
msousa@0:   buf->data_size  = size;
msousa@0:   buf->data_start = 0;
msousa@0:   buf->data_end   = 0;
msousa@0:   buf->max_data_start = max_data_start;
msousa@0:   buf->data = (u8 *)malloc(size);
msousa@0:   return buf->data;
msousa@0: }
msousa@0: 
msousa@0: static inline void lb_done(lb_buf_t *buf) {
msousa@0:   free(buf->data);
msousa@0:   buf->data = NULL;
msousa@0: }
msousa@0: 
msousa@0: static inline u8 *lb_normalize(lb_buf_t *buf) {
msousa@0:   return (u8 *)memmove(buf->data,
msousa@0:                        buf->data + buf->data_start,
msousa@0:                        buf->data_end - buf->data_start);
msousa@0: }
msousa@0: 
msousa@0: static inline u8 *lb_data(lb_buf_t *buf) {
msousa@0:   return buf->data + buf->data_start;
msousa@0: }
msousa@0: 
msousa@0: static inline int lb_data_count(lb_buf_t *buf) {
msousa@0:   return buf->data_end - buf->data_start;
msousa@0: }
msousa@0: 
msousa@0: static inline void lb_data_add(lb_buf_t *buf, int count) {
msousa@0:   if ((buf->data_end += count) >= buf->data_size)
msousa@0:     buf->data_end = buf->data_size - 1;
msousa@0: }
msousa@0: 
msousa@0: static inline u8 *lb_data_purge(lb_buf_t *buf, int count) {
msousa@0:   buf->data_start += count;
msousa@0:   if (buf->data_start > buf->data_end)
msousa@0:     buf->data_start = buf->data_end;
msousa@0: 
msousa@0:   if ((buf->data_end == buf->data_size) || (buf->data_start >= buf->max_data_start))
msousa@0:     return lb_normalize(buf);
msousa@0: 
msousa@0:   return buf->data + buf->data_start;
msousa@0: }
msousa@0: 
msousa@0: static inline void lb_data_purge_all(lb_buf_t *buf) {
msousa@0:   buf->data_start = buf->data_end = 0;
msousa@0: }
msousa@0: 
msousa@0: static inline u8 *lb_free(lb_buf_t *buf) {
msousa@0:   return buf->data + buf->data_end;
msousa@0: }
msousa@0: 
msousa@0: static inline int lb_free_count(lb_buf_t *buf) {
msousa@0:   return buf->data_size - buf->data_end;
msousa@0: }
msousa@0: 
msousa@0: 
msousa@0: 
msousa@0: 
msousa@0: #endif  /* __MODBUS_DS_UTIL_H */