Major circular buffer fix

esch_queue.c

@@ -7,13 +7,12 @@ esch_err esch_queue_create(esch_queue_t* queue)
 
     if (queue) {
         if (queue->buffer) {
-            queue->item_top = queue->buffer;
-            queue->item_current = NULL;
-            queue->item_end = (uint32_t*)queue->item_top + (queue->item_count) * queue->item_size;
+            queue->private._head = 0;
+            queue->private._tail = 0;
+            queue->private._count = 0;
 
-            if (queue->item_count > 0) {
-                queue->count = 0;
-                memset(queue->buffer, 0, queue->item_size * queue->item_count);
+            if (queue->item_count > 0 && queue->item_size) {
+                memset(queue->buffer, 0, (queue->item_size * queue->item_count));
                 err = ESCH_OK;
             }
         }
@@ -28,23 +27,17 @@ esch_err esch_queue_add(esch_queue_t* queue, void* item)
 
     if (queue) {
         if (queue->buffer) {
-            if (queue->count <= queue->item_count - 1) {
-                if (queue->item_current) {
-                    queue->item_current = (((uint32_t*)queue->item_current + queue->item_size) == queue->item_end)
-                        ? queue->buffer
-                        : ((uint32_t*)queue->item_current + queue->item_size);
-                } else {
-                    queue->item_current = queue->buffer;
-                }
-                memcpy(queue->item_current, item, queue->item_size);
-                queue->count++;
+            if (queue->private._head != ((queue->private._tail + 1) % queue->item_count)) {
+                uint32_t ptr = queue->private._tail * queue->item_size + (uint32_t)queue->buffer;
+                memcpy((void*)ptr, item, queue->item_size);
+                queue->private._tail = (queue->private._tail + 1) % queue->item_count;
+                queue->private._count++;
                 err = ESCH_OK;
             } else {
                 err = ESCH_QUEUE_FULL;
             }
         }
     }
-
     return err;
 }
 
@@ -53,12 +46,11 @@ esch_err esch_queue_get(esch_queue_t* queue, void* item)
     esch_err err = ESCH_FAIL;
     if (queue) {
         if (queue->buffer) {
-            if (queue->count > 0) {
-                memcpy(item, queue->item_top, queue->item_size);
-                queue->item_top = (((uint32_t*)queue->item_top + queue->item_size) == queue->item_end)
-                    ? queue->buffer
-                    : ((uint32_t*)queue->item_top + queue->item_size);
-                queue->count--;
+            if (queue->private._head != queue->private._tail) {
+                uint32_t ptr = queue->private._head * queue->item_size + (uint32_t)queue->buffer;
+                memcpy(item, (void*)ptr, queue->item_size);
+                queue->private._head = (queue->private._head + 1) % queue->item_count;
+                queue->private._count--;
                 err = ESCH_OK;
             } else {
                 err = ESCH_QUEUE_EMPTY;

include/esch_queue.h

@@ -1,12 +1,12 @@
 /**
  * @file esch_queue.h
  * @author Sergey Tkachenko ([email protected])
- * @brief 
+ * @brief
  * @version 0.1
  * @date 2021-07-18
- * 
+ *
  * @copyright Copyright (c) 2021
- * 
+ *
  */
 #pragma once
 
@@ -19,58 +19,59 @@ extern "C" {
 
 /**
  * @brief Queue handle/descriptor
- * 
+ *
  */
 typedef struct {
     const uint32_t item_size; /** User-defined item size */
     const uint32_t item_count; /** User-defined item count / queue length */
     void* buffer; /** User-defined pointer to queue memory. Should be (item_size * item_count) in size */
-    void* item_top; /** Top item pointer. Should not be accessed by user */
-    void* item_current; /** Current item pointer. Should not be accessed by user */
-    void* item_end; /** Address of last item. Should not be accessed by user */
-    uint32_t count; /** Quantity of items in queue. Should not be accessed by user */
+    struct {
+        uint32_t _head; /** Read item index. */
+        uint32_t _tail; /** Write item indexm. */
+        uint32_t _count; /** Quantity of items in queue. */
+    } private; /** Should not be accessed by user */
 } esch_queue_t;
 
 /**
  * @brief Initializes the queue
- * 
+ *
  * ```c
  * #define BUFF_SIZE 5
  * static uint32_t buff[BUFF_SIZE];
- * 
+ *
  * esch_queue_t queue = {
  *      .item_size = sizeof(uint32_t),
  *      .item_count = BUFF_SIZE,
  *      .buffer = buff
  *  };
- * 
+ *
  * esch_queue_create(&queue);
  * ```
- * 
+ *
  * @note Must be called before using esch_queue_add or esch_queue_get
- * 
+ *
  * @param queue Pointer to queue object
- * @return esch_err 
+ * @return esch_err
  */
 esch_err esch_queue_create(esch_queue_t* queue);
 
 /**
  * @brief Adds item to the queue
- * 
+ *
  * @note item is copied into user-provided buffer
- * 
+ *
  * @param queue Pointer to queue object
  * @param item Item pointer
  * @return esch_err
  */
 esch_err esch_queue_add(esch_queue_t* queue, void* item);
 
 /**
- * @brief Copies item and removes it from queue 
- * 
+ * @brief Copies item and removes it from queue
+ *
  * @param queue Pointer to queue object
  * @param item Item pointer
- * @return esch_err 
+ * @return esch_err
  */
 esch_err esch_queue_get(esch_queue_t* queue, void* item);