From 9a8beb4020f6b3de0dfabcb36048d5bb5c1ce4ad Mon Sep 17 00:00:00 2001
From: Warwick <warwick.l.e.new@gmail.com>
Date: Wed, 18 Dec 2024 17:03:08 +0000
Subject: [PATCH] Shrink array when capacity is double length

---
 src/dyn_arr.c | 18 ++++++++++++++----
 src/dyn_arr.h |  2 +-
 src/main.c    |  4 ++--
 3 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/src/dyn_arr.c b/src/dyn_arr.c
index af74613..bb99774 100644
--- a/src/dyn_arr.c
+++ b/src/dyn_arr.c
@@ -6,6 +6,7 @@
 #include <string.h>
 
 #define ARRAY_GROWTH_MULTIPLIER 1.3
+#define ARRAY_SHRINK_TRIGGER 2
 
 void *dyn_arr_init(size_t item_size, size_t capacity) {
   void *dyna_ptr = NULL;
@@ -27,16 +28,25 @@ void *dyna_ensure_capacity(void *array, int64_t item_count) {
   dyna_header *header = dyna_get_header(array);
   size_t minimum_capacity = header->length + item_count;
   size_t maximum_capacity =
-      header->length + item_count * ARRAY_GROWTH_MULTIPLIER;
+      (header->length + item_count) * ARRAY_SHRINK_TRIGGER;
 
+  printf("%zu %zu %zu\n", header->capacity, minimum_capacity, maximum_capacity);
+
+  // Return if capacity is in acceptable range.
   if (header->capacity > minimum_capacity &&
       header->capacity < maximum_capacity) {
+    printf("AAAAA\n");
     return header + 1;
   }
 
-  size_t new_capacity = header->capacity * ARRAY_GROWTH_MULTIPLIER;
-  while (new_capacity < minimum_capacity) {
-    new_capacity *= ARRAY_GROWTH_MULTIPLIER;
+  size_t new_capacity = minimum_capacity * ARRAY_GROWTH_MULTIPLIER;
+  printf("%zu\n", new_capacity);
+
+  // Return if the array is valid and so small it's not worth reallocating
+  if (header->capacity > minimum_capacity &&
+      header->capacity <= ARRAY_INITIAL_CAPACITY) {
+    printf("pfft\n");
+    return header + 1;
   }
 
   size_t new_size = sizeof(dyna_header) + new_capacity * item_size;
diff --git a/src/dyn_arr.h b/src/dyn_arr.h
index fb38171..414572b 100644
--- a/src/dyn_arr.h
+++ b/src/dyn_arr.h
@@ -3,7 +3,7 @@
 #include <stdbool.h>
 #include <stdlib.h>
 
-#define ARRAY_INITIAL_CAPACITY 4
+#define ARRAY_INITIAL_CAPACITY 10
 
 /* TODO:
  * Functions to implement to match what I want:
diff --git a/src/main.c b/src/main.c
index efb2672..c8a3035 100644
--- a/src/main.c
+++ b/src/main.c
@@ -6,13 +6,13 @@
 int main() {
   uint64_t *dyna_array = dyna_init(uint64_t);
 
-  for (uint64_t i = 0; i < 19; i++) {
+  for (uint64_t i = 0; i < 100; i++) {
     dyna_append(dyna_array, i);
     printf("length: %zu capacity: %zu value: %lu\n", dyna_length(dyna_array),
            dyna_capacity(dyna_array), dyna_array[i - 1]);
   }
 
-  for (uint64_t i = 19; i > 0; i--) {
+  for (uint64_t i = 100; i > 0; i--) {
     printf("length: %zu capacity: %zu value: %lu\n", dyna_length(dyna_array),
            dyna_capacity(dyna_array), dyna_array[i - 1]);
     dyna_pop(dyna_array);