From f7615efb642303cdfe2dff14416b1ee9bab2c4f9 Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Wed, 12 Aug 2020 16:51:54 +0200
Subject: Elemente an beiden Enden der Queue hinzufügen/entfernen
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 ringbuff.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 64 insertions(+), 9 deletions(-)

diff --git a/ringbuff.c b/ringbuff.c
index e101073..47d4cbf 100644
--- a/ringbuff.c
+++ b/ringbuff.c
@@ -1,3 +1,4 @@
+#include <assert.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -18,7 +19,21 @@ ring_init(struct ring_buffer *rb)
 }
 
 bool
-ring_put(struct ring_buffer *rb, T data)
+ring_push_front(struct ring_buffer *rb, T data)
+{
+	const size_t prev = (rb->tail + NELEM(rb->array) - 1) % NELEM(rb->array);
+
+	if ( prev == rb->head )
+		return false;
+
+	rb->array[prev] = data;
+	rb->tail        = prev;
+
+	return true;
+}
+
+bool
+ring_push_back(struct ring_buffer *rb, T data)
 {
 	const size_t next = (rb->head + 1) % NELEM(rb->array);
 
@@ -32,7 +47,7 @@ ring_put(struct ring_buffer *rb, T data)
 }
 
 bool
-ring_get(struct ring_buffer *rb, T *data)
+ring_pop_front(struct ring_buffer *rb, T *data)
 {
 	if ( rb->head == rb->tail )
 		return false;
@@ -45,12 +60,32 @@ ring_get(struct ring_buffer *rb, T *data)
 	return true;
 }
 
+bool
+ring_pop_back(struct ring_buffer *rb, T *data)
+{
+	if ( rb->head == rb->tail )
+		return false;
+
+	const size_t prev = (rb->head + NELEM(rb->array) - 1) % NELEM(rb->array);
+
+	*data    = rb->array[prev];
+	rb->head = prev;
+
+	return true;
+}
+
 void
 f()
 {
 	ERROR("");
 }
 
+void
+debug_print(const char *msg, struct ring_buffer *rb)
+{
+	printf("%s: head: %zu, tail: %zu\n", msg, rb->head, rb->tail);
+}
+
 int
 main(void)
 {
@@ -61,15 +96,35 @@ main(void)
 	struct ring_buffer rb = { .head = 0, .tail = 0 };
 #endif
 
-	for ( int i = 0; i != 30; ++i ) {
-		if ( !ring_put(&rb, i) )
-			break;
-	}
+	assert(ring_push_back(&rb, 1) == true); // 1
+	assert(ring_push_back(&rb, 2) == true); // 1, 2
+	assert(ring_push_back(&rb, 3) == true); // 1, 2, 3
+	assert(ring_push_back(&rb, 4) == true); // 1, 2, 3, 4
 
-	int j;
-	while ( ring_get(&rb, &j) ) {
-		printf("%d\n", j);
+	debug_print("Stand", &rb);
+
+	assert(ring_push_front(&rb, 0) == true);  // 0, 1, 2, 3, 4
+	assert(ring_push_front(&rb, -1) == true); // -1, 0, 1, 2, 3, 4
+
+	debug_print("Stand", &rb);
+
+	T temp;
+	assert(ring_pop_back(&rb, &temp) == true);  // -1, 0, 1, 2, 3
+	assert(ring_pop_front(&rb, &temp) == true); // 0, 1, 2, 3
+
+	debug_print("Stand", &rb);
+
+	assert(ring_push_back(&rb, 4) == true);   // 0, 1, 2, 3, 4
+	assert(ring_push_back(&rb, 5) == true);   // 0, 1, 2, 3, 4, 5
+	assert(ring_push_back(&rb, 6) == true);   // 0, 1, 2, 3, 4, 5, 6
+	assert(ring_push_back(&rb, 7) == false);  // 0, 1, 2, 3, 4, 5, 6
+	assert(ring_push_front(&rb, 7) == false); // 0, 1, 2, 3, 4, 5, 6
+
+	while ( ring_pop_back(&rb, &temp) ) {
+		printf("temp: %d\n", temp);
 	}
 
+	debug_print("Stand", &rb);
+
 	return EXIT_SUCCESS;
 }
-- 
cgit v1.3