improved circbuf

circbuf/README.md

@@ -4,48 +4,6 @@ Circular buffer
 This is a C implementation of a circular buffer, which can also be used
 as a queue or stack.
 
-Supported operations: `push`, `pop`, `append`.
-
 To achieve thread safety (to some extent) in a producent-consumer situation,
-there is no length variable, only write pointers.
-
-The buffer has a fixed size, values are copied when inserted. The buffer is created using `malloc`.
-If your platform does not support `malloc`, you will have to customize the initialization routine.
-
-Applications
-------------
-
-- Buffer for USARTs or similar communication interfaces
-- Event queue
-- Object stack
-
-Usage
------
-
-```c
-#include <stdint.h>
-#include "circbuf.h"
-
-CircBuf *cb; // buffer instance
-
-void main()
-{
-	cb = cbuf_create(32, sizeof(char)); // create a char buffer of size 32.
-
-	// now it's ready for use!
-
-    // write functions return true on success:
-	cbuf_append(cb, 'A'); // append A (using as a queue)
-	cbuf_push(cb, 'B');   // push B (using as a stack)
-
-	// read all
-	char c;
-	while (cbuf_pop(cb, &c)) {
-		printf("%c", c);
-	}
-
-	cbuf_destroy(cb); // free the buffer
-}
-```
-
-For details how to use each function, please read the header file.
+there is no length variable, only write pointers. Due to not using a length variable,
+one element in the buffer is always left unused.

circbuf/circbuf.c

@@ -1,7 +1,6 @@
 #include <stdint.h>
 #include <stdbool.h>
 #include <string.h>
-#include <malloc.h>
 
 #include "circbuf.h"
 
@@ -11,25 +10,15 @@
 #define PV_OFFS(pvBuf, elem_size, index) ((uint8_t*)(pvBuf) + ((elem_size)*(index)))
 
 
-// Instance structure
-struct circbuf_struct {
-	void *buf;
-	size_t elem_size;
-	size_t cap;
-	size_t lr; // last read pos
-	size_t nw; // next write pos
-};
-
-
 /**
  * @brief Write data to a CircBuf slot
  * @param cb     : circbuf
  * @param index  : slot index
  * @param source : data source
  */
-static void write_buffer(CircBuf *cb, size_t index, const void *source)
+static void write_buffer(CircBuf *cb, circbuf_size_t index, const void *source)
 {
-	memcpy(PV_OFFS(cb->buf, cb->elem_size, index), source, cb->elem_size);
+    memcpy(PV_OFFS(cb->buf, cb->elem_size, index), source, cb->elem_size);
 }
 
 
@@ -39,129 +28,170 @@ static void write_buffer(CircBuf *cb, size_t index, const void *source)
  * @param index  : slot index
  * @param dest   : destination buffer
  */
-static void read_buffer(const CircBuf *cb, size_t index, void *dest)
+static void read_buffer(const CircBuf *cb, circbuf_size_t index, void *dest)
 {
-	memcpy(dest, PV_OFFS(cb->buf, cb->elem_size, index), cb->elem_size);
+    memcpy(dest, PV_OFFS(cb->buf, cb->elem_size, index), cb->elem_size);
 }
 
 
-/** Create a cbuf */
-CircBuf *cbuf_create(size_t capacity, size_t elem_size)
+void cbuf_init(CircBuf *cb, void *buf, circbuf_size_t capacity, circbuf_size_t elem_size)
 {
-	// add one, because one is always unused.
-	capacity++;
-
-	// Allocate the structure
-	CircBuf *cb = malloc(sizeof(CircBuf));
-	if (cb == NULL) {
-		return NULL;
-	}
-
-	// allocate the buffer
-	cb->buf = malloc(capacity * elem_size);
-	if (cb->buf == NULL) {
-		free(cb); // fail - free structure.
-		return NULL;
-	}
-
-	// set capacity, clear state
-	cb->elem_size = elem_size;
-	cb->cap = capacity;
-	cbuf_clear(cb);
-
-	return cb;
-}
-
+    cb->buf = buf;
 
-/** Release cbuf memory */
-void cbuf_destroy(CircBuf *cb)
-{
-	if (cb != NULL) {
-		if (cb->buf != NULL) {
-			free(cb->buf);
-		}
+    // set capacity, clear state
+    cb->elem_size = elem_size;
+    cb->cap = capacity;
 
-		free(cb);
-	}
+    cbuf_clear(cb);
 }
 
 
 /** Check if cbuf is full */
 bool cbuf_full(const CircBuf *cb)
 {
-	if (cb == NULL) return false;
+    if (cb == NULL) {
+        return false;
+    }
 
-	return (cb->lr == cb->nw);
+    return (cb->lr == cb->nw);
 }
 
 
 /** Check if cbuf is empty */
 bool cbuf_empty(const CircBuf *cb)
 {
-	if (cb == NULL) return true;
+    if (cb == NULL) {
+        return true;
+    }
 
-	return ((cb->lr + 1) % cb->cap) == cb->nw;
+    return ((cb->lr + 1) % cb->cap) == cb->nw;
 }
 
 
-/** Write a byte to the buffer, if space left */
-bool cbuf_append(CircBuf *cb, const void *source)
+bool cbuf_push(CircBuf *cb, const void *source)
 {
-	if (cb == NULL) return false;
-	if (source == NULL) return false;
-	if (cbuf_full(cb)) return false;
+    if (cb == NULL || source == NULL || cbuf_full(cb)) {
+        return false;
+    }
 
-	write_buffer(cb, cb->nw, source);
+    write_buffer(cb, cb->nw, source);
 
-	// increment
-	cb->nw++;
-	if (cb->nw == cb->cap) cb->nw = 0;
+    // increment
+    cb->nw++;
+    if (cb->nw == cb->cap) { cb->nw = 0; }
 
-	return true;
+    return true;
 }
 
 
-/** Push value to the end, like a stack. */
-bool cbuf_push(CircBuf *cb, const void *source)
+bool cbuf_pop(CircBuf *cb, void *dest)
 {
-	if (cb == NULL) return false;
-	if (source == NULL) return false;
-	if (cbuf_full(cb)) return false;
+    if (cb == NULL || dest == NULL || cbuf_empty(cb)) {
+        return false;
+    }
 
-	write_buffer(cb, cb->lr, source);
+    // increment
+    if (cb->nw == 0) {
+        cb->nw = cb->cap - 1;
+    } else {
+        cb->nw--;
+    }
 
-	// move lr back
-	if (cb->lr == 0) {
-		cb->lr = cb->cap - 1; // wrap to the end
-	} else {
-		cb->lr--;
-	}
+    read_buffer(cb, cb->nw, dest);
 
-	return true;
+#ifdef CIRCBUF_ZERO_FREE_SLOTS
+    memset(PV_OFFS(cb->buf, cb->elem_size, cb->nw), 0, cb->elem_size);
+#endif
+
+    return true;
 }
 
 
-/** Read one byte, if not empty. */
-bool cbuf_pop(CircBuf *cb, void *dest)
+bool cbuf_peek(const CircBuf *cb, void *dest) {
+    if (cb == NULL || dest == NULL || cbuf_empty(cb)) {
+        return false;
+    }
+
+    circbuf_size_t index = cb->nw;
+    if (index == 0) {
+        index = cb->cap - 1;
+    } else {
+        index--;
+    }
+
+    read_buffer(cb, index, dest);
+    return true;
+}
+
+
+bool cbuf_push_back(CircBuf *cb, const void *source)
 {
-	if (cb == NULL || dest == NULL) return false;
-	if (cbuf_empty(cb)) return false;
+    if (cb == NULL || source == NULL || cbuf_full(cb)) {
+        return false;
+    }
 
-	// increment
-	cb->lr++;
-	if (cb->lr == cb->cap) cb->lr = 0;
+    write_buffer(cb, cb->lr, source);
 
-	read_buffer(cb, cb->lr, dest);
+    // move lr back
+    if (cb->lr == 0) {
+        cb->lr = cb->cap - 1; // wrap to the end
+    } else {
+        cb->lr--;
+    }
 
-	return true;
+    return true;
+}
+
+
+bool cbuf_peek_back(const CircBuf *cb, void *dest) {
+    if (cb == NULL || dest == NULL || cbuf_empty(cb)) {
+        return false;
+    }
+
+    circbuf_size_t index = cb->lr;
+    if (index == cb->cap - 1) {
+        index = 0;
+    } else {
+        index++;
+    }
+
+    read_buffer(cb, index, dest);
+    return true;
+}
+
+
+bool cbuf_pop_back(CircBuf *cb, void *dest)
+{
+    if (cb == NULL || dest == NULL || cbuf_empty(cb)) {
+        return false;
+    }
+
+    // increment
+    cb->lr++;
+    if (cb->lr == cb->cap) {
+        cb->lr = 0;
+    }
+
+    read_buffer(cb, cb->lr, dest);
+
+#ifdef CIRCBUF_ZERO_FREE_SLOTS
+    memset(PV_OFFS(cb->buf, cb->elem_size, cb->lr), 0, cb->elem_size);
+#endif
+
+    return true;
 }
 
 
-/** Clear a cbuf */
 void cbuf_clear(CircBuf *cb)
 {
-	if (cb == NULL) return;
+    if (cb == NULL) {
+        return;
+    }
+
+    cb->lr = cb->cap - 1;
+    cb->nw = 0;
 
-	cb->lr = cb->cap - 1;
-	cb->nw = 0;
+#ifdef CIRCBUF_ZERO_FREE_SLOTS
+    memset(PV_OFFS(cb->buf, cb->elem_size, 0), 0, cb->cap * cb->elem_size);
+#endif
 }

circbuf/circbuf.h

@@ -1,9 +1,8 @@
 /**
  * @file circbuf.h
- * @author Ondřej Hruška, 2016
+ * @author Ondřej Hruška, 2016,2023
  *
  * Circular buffer / queue / stack.
- * Slots are pre-allocated, values are copied into the buffer.
  *
  * The buffer may be used as a stack, event queue or a simple buffer.
  *
@@ -21,35 +20,39 @@
  * MIT license
  */
 
-#pragma once
+#ifndef CIRCBUF_H
+#define CIRCBUF_H
 
 #include <stdint.h>
 #include <stdbool.h>
 #include <stdlib.h>
 
+// Enable to zero a freed slots after pop, useful for debugging
+#define CIRCBUF_ZERO_FREE_SLOTS
 
-typedef struct circbuf_struct CircBuf;
 
+typedef uint32_t circbuf_size_t;
 
-/**
- * @brief Initialize a circular buffer. The buffer is malloc'd.
- * @param capacity  : buffer capacity
- * @param elem_size : size of one element
- * @return pointer to the buffer instance
- */
-CircBuf *cbuf_create(size_t capacity, size_t elem_size);
+/** Instance structure - public to allow static allocation, but consider the structure internal matter */
+struct circbuf_struct {
+  void *buf;
+  circbuf_size_t elem_size;
+  circbuf_size_t cap;
+  circbuf_size_t lr; // last read pos
+  circbuf_size_t nw; // next write pos
+};
 
+typedef struct circbuf_struct CircBuf;
 
 /**
- * @brief Destroy a buffer, freeing used memory.
- *
- * @attention
- * If the buffer items have malloc'd members, you have
- * to free them manually to avoid a memory leak.
+ * @brief Initialize a circular buffer
  *
- * @param cb : buffer
+ * @param[in,out] cb - pointer to the buffer to init, can be statically or dynamically allocated
+ * @param buf  : backing buffer, can be statically or dynamically allocated
+ * @param capacity  : buffer capacity
+ * @param elem_size : size of one element
  */
-void cbuf_destroy(CircBuf *cb);
+void cbuf_init(CircBuf *cb, void *buf, circbuf_size_t capacity, circbuf_size_t elem_size);
 
 
 /** Test for full buffer */
@@ -61,33 +64,61 @@ bool cbuf_empty(const CircBuf *cb);
 
 
 /**
- * @brief Append a value to the buffer (FIFO)
+ * @brief Push to front
  * @param cb     : buffer
  * @param source : pointer to a value (will be copied)
  * @return success
  */
-bool cbuf_append(CircBuf *cb, const void *source);
+bool cbuf_push(CircBuf *cb, const void *source);
 
 
 /**
- * @brief Push a value into the circbuf (LIFO).
- *
+ * @brief Pop from front
+ * @param cb   : buffer
+ * @param dest : read destination. If NULL, value is discarded.
+ * @return success
+ */
+bool cbuf_pop(CircBuf *cb, void *dest);
+
+
+/**
+ * @brief Push to end
  * @param cb     : buffer
  * @param source : pointer to a value (will be copied)
  * @return success
  */
-bool cbuf_push(CircBuf *cb, const void *source);
+bool cbuf_push_back(CircBuf *cb, const void *source);
 
 
 /**
- * @brief Read a value from the buffer, return susccess.
- *
+ * @brief Pop from end
  * @param cb   : buffer
- * @param dest : read destionation. If NULL, value is discarded.
+ * @param dest : read destination. If NULL, value is discarded.
  * @return success
  */
-bool cbuf_pop(CircBuf *cb, void *dest);
+bool cbuf_pop_back(CircBuf *cb, void *dest);
+
+
+/**
+ * @brief Copy the frontmost element without changing the buffer
+ * @param cb   : buffer
+ * @param dest : read destination
+ * @return success
+ */
+bool cbuf_peek(const CircBuf *cb, void *dest);
+
+
+/**
+ * @brief Copy the backmost element without changing the buffer
+ * @param cb   : buffer
+ * @param dest : read destination
+ * @return success
+ */
+bool cbuf_peek_back(const CircBuf *cb, void *dest);
 
 
 /** @brief Remove all data from buffer */
 void cbuf_clear(CircBuf *cb);
+
+
+#endif // CIRCBUF_H

circbuf_deque/README.md

@@ -0,0 +1,10 @@
+Circular buffer (enhanced)
+==========================
+
+This variant of a circular buffer uses static allocation.
+
+This buffer is not meant for producer-consumer synchronization, it's geared towards use cases where the buffer is accessed from a single thread, such as to keep a running average.
+
+The full capacity is utilized thanks to internally storing its length. The buffer has both front and back sets of push/pop/peek functions, as well as a way to iterate and mutate its elements.
+
+See the header for usage details.

circbuf_deque/circbuf.c

@@ -0,0 +1,255 @@
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+
+#include "circbuf.h"
+
+// --- Circbuf data structure ----
+
+/** Offset in void* buffer */
+#define PV_OFFS(pvBuf, elem_size, index) ((uint8_t*)(pvBuf) + ((elem_size)*(index)))
+
+
+/**
+ * @brief Write data to a CircBuf slot
+ * @param cb     : circbuf
+ * @param index  : slot index
+ * @param source : data source
+ */
+static inline void write_buffer(CircBuf *cb, circbuf_size_t index, const void *source)
+{
+    memcpy(PV_OFFS(cb->buf, cb->elem_size, index), source, cb->elem_size);
+}
+
+
+/**
+ * @brief Copy data from a CircBuf slot to a buffer
+ * @param cb     : circbuf
+ * @param index  : slot index
+ * @param dest   : destination buffer
+ */
+static inline void read_buffer(const CircBuf *cb, circbuf_size_t index, void *dest)
+{
+    memcpy(dest, PV_OFFS(cb->buf, cb->elem_size, index), cb->elem_size);
+}
+
+/** Get index of the front position (for write) */
+static inline circbuf_size_t front_writepos(const CircBuf *cb) {
+    return (cb->back + cb->num_used) % cb->cap;
+}
+
+
+void cbuf_init(CircBuf *cb, void *buf, circbuf_size_t capacity, circbuf_size_t elem_size)
+{
+    // allocate the buffer
+    cb->buf = buf;
+
+    // set capacity, clear state
+    cb->elem_size = elem_size;
+    cb->cap = capacity;
+
+    cbuf_clear(cb);
+}
+
+
+/** Check if cbuf is full */
+bool cbuf_full(const CircBuf *cb)
+{
+    if (cb == NULL) {
+        return false;
+    }
+
+    return cb->num_used == cb->cap;
+}
+
+
+/** Check if cbuf is empty */
+bool cbuf_empty(const CircBuf *cb)
+{
+    if (cb == NULL) {
+        return true;
+    }
+
+    return cb->num_used == 0;
+}
+
+
+/** Get the max capacity of the buffer */
+circbuf_size_t cbuf_capacity(const CircBuf *cb)
+{
+    return cb->cap;
+}
+
+
+/** Get the current number of items in the buffer */
+circbuf_size_t cbuf_count(const CircBuf *cb)
+{
+    return cb->num_used;
+}
+
+
+/** Push one element to the front_writepos */
+bool cbuf_push(CircBuf *cb, const void *source)
+{
+    if (cb == NULL || source == NULL || cb->num_used == cb->cap) {
+        return false;
+    }
+
+    write_buffer(cb, front_writepos(cb), source);
+
+    // increment
+    cb->num_used++;
+
+    return true;
+}
+
+
+/** Pop one element from the front_writepos */
+bool cbuf_pop(CircBuf *cb, void *dest)
+{
+    if (cb == NULL || dest == NULL || cb->num_used == 0) {
+        return false;
+    }
+
+    cb->num_used--;
+
+    circbuf_size_t f = front_writepos(cb);
+    read_buffer(cb, f, dest);
+
+#ifdef CIRCBUF_ZERO_FREE_SLOTS
+    memset(PV_OFFS(cb->buf, cb->elem_size, f), 0, cb->elem_size);
+#endif
+
+    return true;
+}
+
+
+/** Peek at the front_writepos element */
+bool cbuf_peek(const CircBuf *cb, void *dest)
+{
+    if (cb == NULL || dest == NULL || cb->num_used == 0) {
+        return false;
+    }
+
+    circbuf_size_t f = (cb->back + cb->num_used - 1) % cb->cap;
+    read_buffer(cb, f, dest);
+    return true;
+}
+
+
+void * cbuf_ptr(const CircBuf *cb)
+{
+    if (cb == NULL || dest == NULL || cb->num_used == 0) {
+        return NULL;
+    }
+
+    circbuf_size_t f = (cb->back + cb->num_used - 1) % cb->cap;
+    return PV_OFFS(cb->buf, cb->elem_size, f);
+}
+
+
+/** Peek at the nth element (counted from back) */
+bool cbuf_nth(const CircBuf *cb, circbuf_size_t num, void *dest)
+{
+    if (cb == NULL || dest == NULL || num > cb->num_used) {
+        return false;
+    }
+
+    circbuf_size_t index = (cb->back + num) % cb->cap;
+    read_buffer(cb, index, dest);
+    return true;
+}
+
+
+void *cbuf_ptr_nth(const CircBuf *cb, circbuf_size_t num)
+{
+    if (cb == NULL || dest == NULL || num > cb->num_used) {
+        return NULL;
+    }
+
+    circbuf_size_t index = (cb->back + num) % cb->cap;
+    return PV_OFFS(cb->buf, cb->elem_size, index);
+}
+
+
+/** Push one element to the back */
+bool cbuf_push_back(CircBuf *cb, const void *source)
+{
+    if (cb == NULL || source == NULL || cb->num_used == cb->cap) {
+        return false;
+    }
+
+    // move lr back
+    if (cb->back == 0) {
+        cb->back = cb->cap - 1; // wrap to the end
+    } else {
+        cb->back--;
+    }
+    cb->num_used++;
+
+    write_buffer(cb, cb->back, source);
+
+    return true;
+}
+
+
+/** Pop one element from the back */
+bool cbuf_pop_back(CircBuf *cb, void *dest)
+{
+    if (cb == NULL || dest == NULL || cb->num_used == 0) {
+        return false;
+    }
+
+    read_buffer(cb, cb->back, dest);
+
+#ifdef CIRCBUF_ZERO_FREE_SLOTS
+    memset(PV_OFFS(cb->buf, cb->elem_size, cb->back), 0, cb->elem_size);
+#endif
+
+    // increment
+    cb->back++;
+    if (cb->back == cb->cap) {
+        cb->back = 0;
+    }
+    cb->num_used--;
+
+    return true;
+}
+
+
+/** Pop one element from the back */
+bool cbuf_peek_back(const CircBuf *cb, void *dest)
+{
+    if (cb == NULL || dest == NULL || cb->num_used == 0) {
+        return false;
+    }
+
+    read_buffer(cb, cb->back, dest);
+    return true;
+}
+
+
+void* cbuf_ptr_back(const CircBuf *cb)
+{
+    if (cb == NULL || dest == NULL || cb->num_used == 0) {
+        return NULL;
+    }
+
+    return PV_OFFS(cb->buf, cb->elem_size, cb->back);
+}
+
+
+/** Clear a cbuf */
+void cbuf_clear(CircBuf *cb)
+{
+    if (cb == NULL) {
+        return;
+    }
+
+    cb->num_used = 0;
+    cb->back = 0;
+
+#ifdef CIRCBUF_ZERO_FREE_SLOTS
+    memset(PV_OFFS(cb->buf, cb->elem_size, 0), 0, cb->cap * cb->elem_size);
+#endif
+}

circbuf_deque/circbuf.h

@@ -0,0 +1,150 @@
+/**
+ * @file circbuf.h
+ * @author Ondřej Hruška, 2016,2023
+ *
+ * Circular buffer / queue / stack.
+ * Slots are pre-allocated, values are copied into the buffer.
+ *
+ * The buffer may be used as a stack, event queue or a simple buffer.
+ *
+ * MIT license
+ */
+
+#ifndef CIRCBUF_H
+#define CIRCBUF_H
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
+// Enable to zero a freed slots after pop, useful for debugging
+#define CIRCBUF_ZERO_FREE_SLOTS
+
+typedef uint32_t circbuf_size_t;
+
+/** Instance structure - public to allow static allocation, but consider the structure internal matter */
+struct circbuf_struct {
+  void *buf;
+  circbuf_size_t num_used;
+  circbuf_size_t elem_size;
+  circbuf_size_t cap;
+  circbuf_size_t back;
+//  circbuf_size_t front;
+};
+
+typedef struct circbuf_struct CircBuf;
+
+/**
+ * @brief Initialize a circular buffer
+ *
+ * @param[in,out] cb - pointer to the buffer to init, can be statically or dynamically allocated
+ * @param buf  : backing buffer, can be statically or dynamically allocated
+ * @param capacity  : buffer capacity
+ * @param elem_size : size of one element
+ */
+void cbuf_init(CircBuf *cb, void *buf, circbuf_size_t capacity, circbuf_size_t elem_size);
+
+
+/** Test for full buffer */
+bool cbuf_full(const CircBuf *cb);
+
+
+/** Test for empty buffer */
+bool cbuf_empty(const CircBuf *cb);
+
+
+/** Get the max capacity of the buffer */
+circbuf_size_t cbuf_capacity(const CircBuf *cb);
+
+
+/** Get the current number of items in the buffer */
+circbuf_size_t cbuf_count(const CircBuf *cb);
+
+
+/** Peek at the nth element (counted from back) */
+bool cbuf_nth(const CircBuf *cb, circbuf_size_t num, void *dest);
+
+
+/** Get a mutable reference to nth element (counted from back) */
+void *cbuf_ptr_nth(const CircBuf *cb, circbuf_size_t num);
+
+
+/** @brief Remove all data from buffer */
+void cbuf_clear(CircBuf *cb);
+
+
+/**
+ * @brief Append a value to the buffer (FIFO)
+ * @param cb     : buffer
+ * @param source : pointer to a value (will be copied)
+ * @return success
+ */
+bool cbuf_push(CircBuf *cb, const void *source);
+
+
+/**
+ * @brief Read a value from the buffer, return susccess.
+ *
+ * @param cb   : buffer
+ * @param dest : read destination. If NULL, value is discarded.
+ * @return success
+ */
+bool cbuf_pop(CircBuf *cb, void *dest);
+
+
+/**
+ * @brief Copy the frontmost element without changing the buffer
+ * @param cb   : buffer
+ * @param dest : read destination
+ * @return success
+ */
+bool cbuf_peek(const CircBuf *cb, void *dest);
+
+
+/**
+ * @brief Get a mutable reference to the front element
+ * @param cb   : buffer
+ * @param dest : read destination
+ * @return reference or NULL
+ */
+void * cbuf_ptr(const CircBuf *cb);
+
+
+/**
+ * @brief Push a value into the circbuf (LIFO).
+ *
+ * @param cb     : buffer
+ * @param source : pointer to a value (will be copied)
+ * @return success
+ */
+bool cbuf_push_back(CircBuf *cb, const void *source);
+
+
+/**
+ * @brief Read a value from the buffer, return susccess.
+ *
+ * @param cb   : buffer
+ * @param dest : read destination. If NULL, value is discarded.
+ * @return success
+ */
+bool cbuf_pop_back(CircBuf *cb, void *dest);
+
+
+/**
+ * @brief Copy the backmost element without changing the buffer
+ * @param cb   : buffer
+ * @param dest : read destination
+ * @return success
+ */
+bool cbuf_peek_back(const CircBuf *cb, void *dest);
+
+
+/**
+ * @brief Get a mutable reference to the backmost element
+ * @param cb   : buffer
+ * @param dest : read destination
+ * @return reference or NULL
+ */
+void* cbuf_ptr_back(const CircBuf *cb);
+
+#endif // CIRCBUF_H