Sliding window array implementation

1 files changed, 43 insertions, 0 deletions

diff --git a/src/slidingwindow.c b/src/slidingwindow.c
new file mode 100644
index 0000000..883e852
--- /dev/null
+++ b/src/slidingwindow.c
@@ -0,0 +1,43 @@
+#include "slidingwindow.h"
+#include "common.h"
+#include "smrt_arena.h"
+
+#include <string.h>
+
+sliding_window_array_t *sw_create(smrt_arena_t *arena, u64 elem_size, u64 size) {
+    sliding_window_array_t *sw = smrt_arena_push(arena, sizeof(sliding_window_array_t) + 2 * elem_size * size, true);
+    sw->size = size;
+    sw->element_size_bytes = elem_size;
+
+    return sw;
+}
+
+void sw_insert(sliding_window_array_t *sw, void *x) {
+    if (sw->num_elements == sw->size) {
+        sw->start_idx++;
+    }
+
+    if ((sw->start_idx + sw->size) > (2 * sw->size)) {
+        u64 src_offset = SLIDING_WINDOW_BASE_POS + (sw->start_idx * sw->element_size_bytes);
+        u64 bytes_to_copy = (sw->size - 1) * sw->element_size_bytes;
+        memmove(
+            ((u8*)sw + SLIDING_WINDOW_BASE_POS),
+            ((u8*)sw + src_offset),
+            bytes_to_copy
+        );
+
+        sw->start_idx = 0;
+    }
+
+    u64 new_pos = sw->start_idx + sw->num_elements;
+
+    if (new_pos >= sw->start_idx + sw->size) {
+        new_pos = sw->start_idx + sw->size - 1;
+    }
+
+    memcpy(((u8*)sw + SLIDING_WINDOW_BASE_POS + (new_pos * sw->element_size_bytes)), x, sw->element_size_bytes);
+
+    if (sw->num_elements < sw->size) {
+        sw->num_elements++;
+    }
+}