1 files changed, 97 insertions, 0 deletions
diff --git a/allocator.c b/allocator.c
new file mode 100644
index 0000000..7d1c6a7
--- /dev/null
+++ b/allocator.c
@@ -0,0 +1,97 @@
+typedef struct Page {
+	struct Page *next;
+	size_t used;
+	max_align_t data[];
+} Page;
+
+typedef struct {
+	Page *first;
+	Page *last;
+} Allocator;
+
+/* number of bytes a page hold, not including the header */
+#define PAGE_SIZE (16384 - sizeof(Page))
+
+static void allocr_create(Allocator *a) {
+	a->first = a->last = NULL;
+}
+
+static void *allocr_malloc(Allocator *a, size_t bytes) {
+	/* position in this page to return */
+	size_t pos = PAGE_SIZE;
+	if (a->last)
+		pos = (a->last->used + sizeof(max_align_t) - 1) / sizeof(max_align_t);
+	
+	if (pos * sizeof(max_align_t) + bytes > PAGE_SIZE) {
+		/* make a new page for this data */
+		Page *page = err_malloc(sizeof *page + (bytes > PAGE_SIZE ? bytes : PAGE_SIZE));
+		page->next = NULL;
+		page->used = bytes;
+		if (a->last)
+			a->last->next = page;
+		else
+			a->first = page;
+		a->last = page;
+		return page->data;
+	} else {
+		a->last->used += bytes;
+		return &a->last->data[pos];
+	}
+}
+
+static void *allocr_calloc(Allocator *a, size_t bytes) {
+	void *data = allocr_malloc(a, bytes);
+	memset(data, 0, bytes);
+	return data;
+}
+
+/* IMPORTANT: this can only be called with data which was originally allocated with allocr_realloc(a, NULL, x) */
+static void *allocr_realloc(Allocator *a, void *data, size_t new_size) {
+	if (!data) {
+		Page *page = err_malloc(sizeof *page + new_size);
+		page->used = PAGE_SIZE;	/* pretend we used all of this page */
+		page->next = NULL;
+		if (a->last)
+			a->last->next = page;
+		else
+			a->first = page;
+		a->last = page;
+		return page->data;
+	} else {
+		Page *page = (Page *)((char *)data - offsetof(Page, data));
+		page = err_realloc(page, sizeof *page + new_size);
+		return page->data;
+	}
+}
+
+static void allocr_free_all(Allocator *a) {
+	for (Page *page = a->first; page;) {
+		Page *next = page->next;
+		free(page);
+		page = next;
+	}
+}
+
+static void allocr_test(void) {
+	Allocator a;
+	allocr_create(&a);
+	for (int x = 1000; x <= 8000; x += 1000) {
+		size_t nfoos = x;
+		int *foos = allocr_malloc(&a, nfoos * sizeof(int));
+
+		for (size_t i = 0; i < nfoos; i++)
+			foos[i] = (int)i;
+		for (size_t i = 0; i < nfoos; i++)
+			assert(foos[i] == (int)i);
+		size_t nbars = x;
+		int *bars = allocr_calloc(&a, nbars * sizeof(int));
+		for (size_t i = 0; i < nbars; i++)
+			assert(bars[i] == 0);
+		for (size_t i = 0; i < nbars; i++)
+			bars[i] = (int)i;
+		for (size_t i = 0; i < nbars; i++)
+			assert(bars[i] == (int)i);
+	}
+	
+	allocr_free_all(&a);
+}