Init new repository

examples/sandbox/arena.lc

@@ -0,0 +1,68 @@
+import "std_types";
+import libc "libc";
+
+PAGE_SIZE :: 4096;
+
+Arena :: struct {
+    data:     *u8;
+    len:       usize;
+    commit:    usize;
+    reserve:   usize;
+    alignment: usize;
+}
+
+GetAlignOffset :: proc(size: usize, align: usize): usize {
+    mask: usize = align - 1;
+    val:  usize = size & mask;
+    if val {
+        val = align - val;
+    }
+    return val;
+}
+
+AlignUp :: proc(size: usize, align: usize): usize {
+    result := size + GetAlignOffset(size, align);
+    return result;
+}
+
+InitArena :: proc(arena: *Arena, reserve: usize) {
+    aligned_reserve := AlignUp(reserve, PAGE_SIZE);
+    data := VReserve(aligned_reserve);
+    libc.assert(data != nil);
+
+    if data {
+        arena.data = data;
+        arena.reserve = aligned_reserve;
+        arena.alignment = 8;
+    }
+}
+
+PushSize :: proc(arena: *Arena, size: usize): *void {
+    libc.assert(arena.data != nil);
+
+    pointer := :usize(arena.data) + arena.len + size;
+    align := GetAlignOffset(pointer, arena.alignment);
+    aligned_size := size + align;
+
+    a := arena.len + aligned_size;
+    if a > arena.commit {
+        diff := a - arena.commit;
+        commit_size := AlignUp(diff, PAGE_SIZE*4);
+        libc.assert(commit_size + arena.commit <= arena.reserve);
+
+        if VCommit(&arena.data[arena.commit], commit_size) {
+            arena.commit += commit_size;
+        } else {
+            libc.assert(false && "commit failed"[0]);
+        }
+    }
+
+    arena.len += align;
+    result: *void = &arena.data[arena.len];
+    arena.len += size;
+    return result;
+}
+
+TestArena :: proc() {
+    arena: Arena;
+}