Implemented a dynamically sized byte array

Pretty simple, want to ensure amortised constant big O so I use a
REALLOC_MULT, which can be redefined if wished.

src/darr.c

@@ -0,0 +1,58 @@
+/* Copyright (C) 2023 Aryadev Chavali
+
+ * You may distribute and modify this code under the terms of the
+ * GPLv2 license.  You should have received a copy of the GPLv2
+ * license with this file.  If not, please write to:
+ * aryadev@aryadevchavali.com.
+
+ * Created: 2023-10-15
+ * Author: Aryadev Chavali
+ * Description: Dynamically sized byte array
+ */
+
+#include <malloc.h>
+#include <string.h>
+
+#include "./darr.h"
+
+void darr_init(darr_t *darr, size_t size)
+{
+  if (size == 0)
+    size = DARR_DEFAULT_SIZE;
+  *darr = (darr_t){
+      .data      = calloc(size, 1),
+      .used      = 0,
+      .available = size,
+  };
+}
+
+void darr_ensure_capacity(darr_t *darr, size_t requested)
+{
+  if (darr->used + requested >= darr->available)
+  {
+    darr->available =
+        MAX(darr->used + requested, darr->available * DARR_REALLOC_MULT);
+    darr->data = realloc(darr->data, darr->available);
+  }
+}
+
+void darr_append_byte(darr_t *darr, byte byte)
+{
+  darr_ensure_capacity(darr, 1);
+  darr->data[darr->used++] = byte;
+}
+
+void darr_append_bytes(darr_t *darr, byte *bytes, size_t n)
+{
+  darr_ensure_capacity(darr, n);
+  memcpy(darr->data + darr->used, bytes, n);
+  darr->used += n;
+}
+
+byte darr_at(darr_t *darr, size_t index)
+{
+  if (index >= darr->used)
+    // TODO: Error (index is out of bounds)
+    return 0;
+  return darr->data[index];
+}