Collect more garbage!

1 files changed, 63 insertions, 0 deletions

diff --git a/src/utils.c b/src/utils.c
index ebff4a7..5f9d49e 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -18,3 +18,66 @@ void pit_debug(const char *format, ...) {
     vfprintf(stderr, format, vargs);
     va_end(vargs);
 }
+
+static uintptr_t pit_align_down(uintptr_t addr, uintptr_t align) {
+    return addr & ~(align - 1); /* easy! just zero the low bits */
+}
+static uintptr_t pit_align_up(uintptr_t addr, uintptr_t align) {
+    return (addr + align - 1) /* increment past the next aligned address... */
+        & ~(align - 1); /* ...and then zero the low bits */
+}
+
+pit_arena *pit_arena_new(i64 capacity, i64 elem_size) {
+    i64 byte_len = 0;
+    pit_mul(&byte_len, elem_size, capacity);
+    pit_arena *a = (pit_arena *) malloc(sizeof(pit_arena) + (size_t) byte_len);
+    if (!a || byte_len <= 0) return NULL;
+    a->elem_size = elem_size;
+    a->capacity = byte_len / elem_size;
+    a->next = 0;
+    a->back = byte_len;
+    return a;
+}
+void pit_arena_reset(pit_arena *a) {
+    a->next = 0;
+    pit_mul(&a->back, a->elem_size, a->capacity);
+}
+static i64 pit_arena_byte_idx(pit_arena *a, i64 idx) {
+    i64 byte_idx = 0; pit_mul(&byte_idx, a->elem_size, idx);
+    return byte_idx;
+}
+i64 pit_arena_alloc_idx(pit_arena *a) {
+    i64 ret = a->next;
+    i64 byte_idx = pit_arena_byte_idx(a, ret);
+    if (byte_idx + a->elem_size >= a->back) { return -1; }
+    a->next += 1;
+    return ret;
+}
+i64 pit_arena_alloc_bulk_idx(pit_arena *a, i64 num) {
+    i64 ret = a->next;
+    i64 byte_idx = pit_arena_byte_idx(a, ret);
+    i64 byte_len = 0; pit_mul(&byte_len, a->elem_size, num);
+    if (byte_idx + byte_len > a->back) { return -1; }
+    a->next += num;
+    return ret;
+}
+void *pit_arena_get(pit_arena *a, i64 idx) {
+    i64 byte_idx = pit_arena_byte_idx(a, idx);
+    if (byte_idx < 0 || byte_idx + a->elem_size >= a->back) { return NULL; }
+    return &a->data[byte_idx];
+}
+void *pit_arena_alloc(pit_arena *a) {
+    i64 idx = pit_arena_alloc_idx(a);
+    return pit_arena_get(a, idx);
+}
+void *pit_arena_alloc_bulk(pit_arena *a, i64 num) {
+    i64 idx = pit_arena_alloc_bulk_idx(a, num);
+    return pit_arena_get(a, idx);
+}
+void *pit_arena_alloc_back(pit_arena *a, i64 sz) {
+    i64 next_byte = pit_arena_byte_idx(a, a->next);
+    i64 back_byte = (i64) pit_align_down((uintptr_t) (a->back - sz), sizeof(void *));
+    if (back_byte < next_byte) return NULL;
+    a->back = back_byte;
+    return &a->data[a->back];
+}