Mercurial > hg > ucx / file diff

--- a/docs/Writerside/topics/array_list.h.md	Wed Mar 12 18:32:57 2025 +0100
+++ b/docs/Writerside/topics/array_list.h.md	Thu Mar 13 11:07:00 2025 +0100
@@ -33,9 +33,59 @@
 #define cx_array_initialize_a(allocator, ARRAY, capacity)
 ```
 
-<warning>
-TODO: document
-</warning>
+The purpose of the UCX array functions is to keep track of the size and capacity of a plain C array.
+
+The raw functions do not need this information packed into a structure, but working with independent variables is quite cumbersome.
+Therefore, UCX defines several macros that call the raw functions assuming certain variable names.
+
+This is what the `CX_ARRAY_DECLARE_SIZED()` and `CX_ARRAY_DECLARE()` macros are for.
+They take a `type` for the array members, a `name` for the array variable, and a `size_type` for the type of the size and capacity variables (`size_t` by default when you use `CX_ARRAY_DECLARE()`),
+and generate three variables named `name`, `name_size`, and `name_capacity`.
+
+For example, you can abbreviate the following code
+```C
+struct my_data {
+    int other_int;
+    float other_float;
+    int *my_array;
+    size_t my_array_size;
+    size_t my_array_capacity;
+}
+```
+by substituting the three members for the array with `CX_ARRAY_DECLARE()`.
+```C
+struct my_data {
+    int other_int;
+    float other_float;
+    CX_ARRAY_DECLARE(int, my_array);
+}
+```
+
+> Using `CX_ARRAY_DECLARE_SIZED()` can save some space when you are using a size type that is _half_ as wide as `sizeof(void*)`.
+> On 64-bit architectures, having the possibility to store more than four billion items is rarely necessary, hence using 32-bit integers for size and capacity
+> saves eight bytes (assuming proper alignment in your struct).
+
+Once the array is declared, you can use one of the macros `cx_array_initialize()` or `cx_array_initialize_a()` to allocate memory.
+The former uses a stdlib default allocator and the latter allows you to use a specific allocator.
+Important to note is, that the `ARRAY` argument expects the variable's _name_.
+The macros set `ARRAY_size` to zero, `ARRAY_capacity` to the specified initial capacity, and invoke the allocator's `malloc()` function to allocate the memory.
+
+Using the example from above, and the UCX [memory pool](mempool.h.md), this could look like this:
+
+```C
+CxMempool *mpool = cxMempoolCreateSimple(128);
+
+struct my_data data;
+cx_array_initialize_a(mpool->allocator, data.my_array, 16);
+```
+
+> The aforementioned macros make your life simpler, but keep in mind that using them is not mandatory.
+> All other macros continue to work perfectly, if you declare and initialize your array manually, as long as you use
+> the naming convention to suffix the size variable with `_size` and the capacity variable with `_capacity`.
+> Also you can freely decide in which order you want to declare the variables.
+> 
+> For example, when you have multiple arrays in your struct with 8-bit `size_type` (because in your use case you don't expect more than 255 elements),
+> it is favorable to group all pointers and then declare the size and capacity variables to avoid padding between the array declarations. 
 
 ## Array Reallocator
 
@@ -66,7 +116,9 @@
 ```C
 #include <cx/array_list.h>
 
-cx_array_add(target, size, capacity, elem_size, elem, reallocator)
+int cx_array_add(void **target, void *size, void *capacity,
+        size_t elem_size, const void *elem,
+        CxArrayReallocator *reallocator);
 
 #define cx_array_simple_add(ARRAY, elem)