--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/mb_ds_util.h Sun Mar 05 00:05:46 2017 +0000
@@ -0,0 +1,169 @@
+/*
+ * 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 */