addition/refactor: Made ADT design and added grow/shrink

So, added private functions made to grow and shrink the array in a
multiple of 2, 2 as a factro is fine, at least that is Rust does it that
way. Also changed the design to ADT, forgot i liked that, probably will
be changing that to apply also to my Arena implementation, i will see if
fits --probably--.

include/arraylist.h

@@ -5,15 +5,10 @@
 #include <stddef.h>
 #include <stdbool.h>
 
-typedef struct {
-    void *data;
-    size_t capacity;
-    size_t len;
-    size_t elem_size;
-} ArrayList;
+typedef struct ArrayList ArrayList;
 
 typedef struct {
-    ArrayList array;
+    ArrayList *array;
     size_t offset;
 } ArrayListSlice;
 
@@ -27,21 +22,13 @@ typedef enum {
     ARRLIST_INVALID_ELEM_SIZE,
 } ArrayListErr;
 
-typedef struct {
-    bool is_valid;
-    union {
-        ArrayListErr err;
-        ArrayList array;
-    };
-} ArrayListResult;
-
-ArrayListResult arraylist_init(size_t capacity, size_t elem_size);
+ArrayList *arraylist_init(size_t capacity, size_t elem_size);
 ArrayListErr arraylist_destroy(ArrayList *arr);
 ArrayListErr arraylist_clear(ArrayList *arr);
 
-size_t arraylist_size(ArrayList *arr);
-size_t arraylist_capacity(ArrayList *arr);
-bool arraylist_is_empty(ArrayList *arr);
+size_t arraylist_size(const ArrayList *arr);
+size_t arraylist_capacity(const ArrayList *arr);
+bool arraylist_is_empty(const ArrayList *arr);
 
 ArrayListErr arraylist_push_back(ArrayList *arr, void *data);
 ArrayListErr arraylist_insert(ArrayList*arr, size_t index, void *data);
@@ -52,7 +39,7 @@ ArrayListErr arraylist_pop_back(ArrayList *arr, void *out);
 ArrayListErr arraylist_remove_at(ArrayList *arr, size_t index, void *out);
 ArrayListErr arraylist_pop_front(ArrayList *arr, void *out);
 
-ArrayListErr arraylist_get(ArrayList *arr, size_t index, void *out);
+ArrayListErr arraylist_get(const ArrayList *arr, size_t index, void *out);
 ArrayListErr arraylist_set(ArrayList *arr, size_t index, void *data);
 
 ArrayListErr arraylist_resize(ArrayList *arr, size_t new_capacity);

src/arraylist.c

@@ -1,37 +1,45 @@
 #include "arraylist.h"
+#include <stdatomic.h>
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
 
-ArrayListResult arraylist_init(size_t capacity, size_t elem_size) {
+struct ArrayList{
+    void *data;
+    size_t capacity;
+    size_t len;
+    size_t elem_size;
+};
+
+// Grow and shrink factor is 2, 1.5 might give different results i guess
+// but i'm basing myself in that Rust implementation of array does use
+// 2 as the factor so i guess is good :)
+static ArrayListErr arraylist_grow(ArrayList *arr);
+static ArrayListErr arraylist_shrink(ArrayList *arr);
+
+ArrayList *arraylist_init(size_t capacity, size_t elem_size) {
     if (capacity == 0) {
-        return (ArrayListResult) {
-            .is_valid = false,
-            .err = ARRLIST_INVALID_CAPACITY};
+        return NULL;
     }
 
     if (elem_size == 0) {
-        return (ArrayListResult) {
-            .is_valid = false,
-            .err = ARRLIST_INVALID_ELEM_SIZE,
-        };
+        return NULL;
     }
 
-    ArrayList arr = {
-        .data = malloc(capacity * elem_size),
-        .capacity = capacity,
-        .elem_size = elem_size,
-        .len = 0
-    };
-
-    if (arr.data == NULL) {
-        return (ArrayListResult) {
-            .is_valid = false,
-            .err = ARRLIST_BAD_ALLOC,
-        };
+    ArrayList *arr = malloc(sizeof(ArrayList));
+    if (arr == NULL) {
+        return NULL;
+    }
+    arr->capacity = capacity;
+    arr->elem_size = elem_size;
+    arr->len = 0;
+    arr->data = malloc(capacity * elem_size);
+    if (arr->data == NULL) {
+        free(arr);
+        return NULL;
     }
 
-    return (ArrayListResult) {.is_valid = true, .array = arr};
+    return arr;
 }
 
 ArrayListErr arraylist_destroy(ArrayList *arr) {
@@ -44,6 +52,7 @@ ArrayListErr arraylist_destroy(ArrayList *arr) {
     arr->len = 0;
     free(arr->data);
     arr->data = NULL;
+    free(arr);
     return ARRLIST_OK;
 }
 
@@ -59,23 +68,48 @@ ArrayListErr arraylist_clear(ArrayList *arr) {
     return ARRLIST_OK;
 }
 
-size_t arraylist_size(ArrayList *arr) {
+size_t arraylist_size(const ArrayList *arr) {
     if (arr == NULL) {
         return 0;
     }
     return arr->len;
 }
 
-size_t arraylist_capacity(ArrayList *arr) {
+size_t arraylist_capacity(const ArrayList *arr) {
     if (arr == NULL) {
         return 0;
     }
     return arr->capacity;
 }
 
-bool arraylist_is_empty(ArrayList *arr) {
+bool arraylist_is_empty(const ArrayList *arr) {
     if (arr == NULL) {
         return true;
     }
     return arr->capacity == 0;
 }
+
+static ArrayListErr arraylist_grow(ArrayList *arr) {
+    // We can asume is not null because is internal
+    // and only used by funtions that already verified
+    // arr is not null, same with shrink.
+    size_t new_capacity = arr->capacity * 2;
+    void *tmp = realloc(arr->data, new_capacity * arr->elem_size);
+    if (tmp == NULL) {
+        return ARRLIST_BAD_ALLOC;
+    }
+    arr->capacity = new_capacity;
+    arr->data = tmp;
+    return ARRLIST_OK;
+}
+
+static ArrayListErr arraylist_shrink(ArrayList *arr) {
+    size_t new_capacity = arr->capacity / 2;
+    void *tmp = realloc(arr->data, new_capacity *arr->elem_size);
+    if (tmp == NULL) {
+        return ARRLIST_BAD_ALLOC;
+    }
+    arr->capacity = new_capacity;
+    arr->data = tmp;
+    return ARRLIST_OK;
+}