4 files changed, 101 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++;
+    }
+}
diff --git a/src/slidingwindow.h b/src/slidingwindow.h
new file mode 100644
index 0000000..3cfe821
--- /dev/null
+++ b/src/slidingwindow.h
@@ -0,0 +1,19 @@
+#pragma once
+
+#include "common.h"
+#include "smrt_arena.h"
+
+#define SLIDING_WINDOW_BASE_POS (sizeof(sliding_window_array_t))
+
+typedef struct {
+     u64               size;
+     u64       num_elements;
+     u64          start_idx;
+     u64 element_size_bytes;
+} sliding_window_array_t;
+
+#define SMRTA_ALLOC_SLIDINGWINDOW(arena, T, n) (sliding_window_array_t*)sw_create(arena, sizeof(T), (n))
+#define SLIDINGWINDOW_GET(w, T) ((T*)((u8*)(w) + SLIDING_WINDOW_BASE_POS) + (w)->start_idx)
+
+sliding_window_array_t *sw_create(smrt_arena_t *arena, u64 elem_size, u64 size);
+void sw_insert(sliding_window_array_t *sw, void *x);
diff --git a/src/vec2sw.c b/src/vec2sw.c
new file mode 100644
index 0000000..0e1aec0
--- /dev/null
+++ b/src/vec2sw.c
@@ -0,0 +1,23 @@
+#include "vec2sw.h"
+#include "slidingwindow.h"
+#include "vec2.h"
+
+vec2d_sw_soa_t vec2d_sw_soa(smrt_arena_t *arena, u64 size) {
+    vec2d_sw_soa_t vs = { .size=size };
+    vs.xs = SMRTA_ALLOC_SLIDINGWINDOW(arena, f64, size);
+    vs.ys = SMRTA_ALLOC_SLIDINGWINDOW(arena, f64, size);
+    return vs;
+}
+
+void vec2d_sw_soa_insert(vec2d_sw_soa_t sw_vs, vec2d_t v) {
+    sw_insert(sw_vs.xs, (void*)&v.x);
+    sw_insert(sw_vs.ys, (void*)&v.y);
+}
+
+vec2d_soa_t vec2d_sw_soa_get(vec2d_sw_soa_t sw_vs) {
+    return (vec2d_soa_t){
+        .size = sw_vs.xs->num_elements,
+        .xs = SLIDINGWINDOW_GET(sw_vs.xs, f64),
+        .ys = SLIDINGWINDOW_GET(sw_vs.ys, f64),
+    };
+}
diff --git a/src/vec2sw.h b/src/vec2sw.h
new file mode 100644
index 0000000..cbf8e6d
--- /dev/null
+++ b/src/vec2sw.h
@@ -0,0 +1,16 @@
+#pragma once
+
+#include "common.h"
+#include "smrt_arena.h"
+#include "vec2.h"
+#include "slidingwindow.h"
+
+typedef struct {
+    sliding_window_array_t  *xs;
+    sliding_window_array_t  *ys;
+                       u64 size;
+} vec2d_sw_soa_t;
+
+vec2d_sw_soa_t        vec2d_sw_soa(smrt_arena_t *arena, u64 size);
+          void vec2d_sw_soa_insert(vec2d_sw_soa_t sw_vs, vec2d_t v);
+   vec2d_soa_t    vec2d_sw_soa_get(vec2d_sw_soa_t sw_vs);