1 files changed, 112 insertions, 0 deletions
diff --git a/lib/darr.c b/lib/darr.c
new file mode 100644
index 0000000..bef51b8
--- /dev/null
+++ b/lib/darr.c
@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * June 23 2023, Christian Hopps <chopps@labn.net>
+ *
+ * Copyright (c) 2023, LabN Consulting, L.L.C.
+ *
+ */
+#include <zebra.h>
+#include "darr.h"
+#include "memory.h"
+
+DEFINE_MTYPE_STATIC(LIB, DARR, "Dynamic Array");
+
+static uint _msb(uint count)
+{
+	uint bit = 0;
+	int msb = 0;
+
+	while (count) {
+		if (count & 1)
+			msb = bit;
+		count >>= 1;
+		bit += 1;
+	}
+	return msb;
+}
+
+static uint darr_next_count(uint count, size_t esize)
+{
+	uint ncount;
+
+	if (esize > sizeof(long long) && count == 1)
+		/* treat like a pointer */
+		ncount = 1;
+	else {
+		uint msb = _msb(count);
+
+		ncount = 1ull << msb;
+		/* if the users count wasn't a pow2 make it the next pow2. */
+		if (ncount != count) {
+			assert(ncount < count);
+			ncount <<= 1;
+			if (esize < sizeof(long long) && ncount < 8)
+				ncount = 8;
+		}
+	}
+	return ncount;
+}
+
+static size_t darr_size(uint count, size_t esize)
+{
+	return count * esize + sizeof(struct darr_metadata);
+}
+
+void *__darr_resize(void *a, uint count, size_t esize)
+{
+	uint ncount = darr_next_count(count, esize);
+	size_t osz = (a == NULL) ? 0 : darr_size(darr_cap(a), esize);
+	size_t sz = darr_size(ncount, esize);
+	struct darr_metadata *dm = XREALLOC(MTYPE_DARR,
+					    a ? _darr_meta(a) : NULL, sz);
+
+	if (sz > osz)
+		memset((char *)dm + osz, 0, sz - osz);
+	dm->cap = ncount;
+	return (void *)(dm + 1);
+}
+
+
+void *__darr_insert_n(void *a, uint at, uint count, size_t esize, bool zero)
+{
+
+	struct darr_metadata *dm;
+	uint olen, nlen;
+
+	if (!a)
+		a = __darr_resize(NULL, at + count, esize);
+	dm = (struct darr_metadata *)a - 1;
+	olen = dm->len;
+
+	// at == 1
+	// count == 100
+	// olen == 2
+
+	/* see if the user is expanding first using `at` */
+	if (at >= olen)
+		nlen = at + count;
+	else
+		nlen = olen + count;
+
+	if (nlen > dm->cap) {
+		a = __darr_resize(a, nlen, esize);
+		dm = (struct darr_metadata *)a - 1;
+	}
+
+#define _a_at(i) ((char *)a + ((i)*esize))
+	if (at < olen)
+		memmove(_a_at(at + count), _a_at(at), esize * (olen - at));
+
+	dm->len = nlen;
+
+	if (zero) {
+		if (at >= olen) {
+			at -= olen;
+			count += olen;
+		}
+		memset(_a_at(at), 0, esize * count);
+	}
+
+	return a;
+#undef _a_at
+}