add resizeing functions

src/util/gen/dynarr.h

@@ -2,11 +2,15 @@
 #define DYNARR_H
 #include <stddef.h>
 #include <stdint.h>
+
 #define DYNARR_COMB2(a, b) a##b
 #define DYNARR_COMB1(a, b) DYNARR_COMB2(a, b)
 #endif // DYNARR_H
 
+#define DYNARR_TYPE float
+
 #ifdef DYNARR_TYPE
+#include <math.h>
 #include <stdlib.h>
 
 // customising the linkage
@@ -19,14 +23,9 @@
 #define DYNARR_NAME DYNARR_COMB1(dynarr_, DYNARR_TYPE)
 #endif // DYNARR_NAME
 
-#define DYNARR_init   DYNARR_COMB1(DYNARR_NAME, _init)   // name of the initialization funcition
-#define DYNARR_add    DYNARR_COMB1(DYNARR_NAME, _add)    // name of the addition function
-#define DYNARR_remove DYNARR_COMB1(DYNARR_NAME, _remove) // name of the removal function
-#define DYNARR_free   DYNARR_COMB1(DYNARR_NAME, _free)   // name of the freeing function
+#define DYNARR_FUNC(name) DYNARR_COMB1(DYNARR_NAME, _##name) // name of the initialization funcition
 // TODO: add shrink function (call when count < cap / 4)
-// TODO: add resize function
 // TODO: add bulk addition function
-// TODO: add bulk addition function (doesn't respec growth factor)
 // TODO: add bulk deletion function
 
 
@@ -37,31 +36,50 @@ typedef struct {
     size_t cap;       // contains the capacity of the dynamic array
 } DYNARR_NAME;
 
-// initializes the dynamic array with a specific capacity (dat may be null if malloc fails)
-DYNARR_LINKAGE DYNARR_NAME DYNARR_init(const size_t cap) {
-    return (DYNARR_NAME){
-        malloc(cap * sizeof(DYNARR_TYPE)),
-        0,
-        cap,
-    };
+// adds an exact number of items to the capacity, does not respect scaling
+// returns 0 upon success, 1 upon failure
+DYNARR_LINKAGE uint8_t DYNARR_FUNC(resize_exact)(DYNARR_NAME* arr, size_t ncap) {
+    if (ncap < arr->count) return 1; // the new capacity is smaller than the count, this is very likely unintentional
+    if (ncap == arr->cap) return 0;  // the capacity is already the new capacity; no work needs to be done
+
+    // (re)allocate the memory for the array
+    DYNARR_TYPE* nptr = (arr->dat == NULL)
+                            ? malloc(ncap * sizeof(DYNARR_TYPE))
+                            : realloc(arr->dat, ncap * sizeof(DYNARR_TYPE));
+
+    // if memory (re)allocation failed; return
+    if (nptr == NULL)
+        return 1;
+
+    arr->dat = nptr;
+    arr->cap = ncap;
+    return 0;
+}
+
+// resizes the array by adding `nitems` to the count, respects capacity scaling
+// returns 0 upon success, 1 upon failure
+DYNARR_LINKAGE uint8_t DYNARR_FUNC(resize)(DYNARR_NAME* arr, size_t ncount) {
+    if (ncount < arr->count) return 1; // the new count is less than the current count, this is very likely unintentional
+    if (ncount == arr->cap) return 0;  // the current capacity has already been set to this
+
+    // calculates what the new size should be by adding the amount of items to the count
+    // assumes scaling factor is 2
+    return DYNARR_FUNC(resize_exact)(arr, 1 << (size_t)ceil(log2(ncount)));
 }
 
 // adds an item to the dynamic array, doubles the capacity if the new count exceeds the maximum
 // returns 0 upon success, 1 upon failure
-DYNARR_LINKAGE uint8_t DYNARR_add(DYNARR_NAME* arr, DYNARR_TYPE item) {
+DYNARR_LINKAGE uint8_t DYNARR_FUNC(add)(DYNARR_NAME* arr, DYNARR_TYPE item) {
     size_t idx = arr->count;
     arr->count++;
 
     // resize the dynamic array if the new count has hit the max capacity
     if (arr->cap == arr->count) {
-        if (!arr->cap) arr->cap = 1; // set the capacity to 1 if it's 0
-        else arr->cap *= 2;          // otherwise, multiply the capacity by 2
-        DYNARR_TYPE* nptr = realloc(arr->dat, arr->cap * sizeof(DYNARR_TYPE));
-
-        if (nptr == NULL)
-            return 1;
-
-        arr->dat = nptr;
+        uint8_t const s = !arr->cap                                           // if zero
+                              ? DYNARR_FUNC(resize_exact)(arr, 1)             // set the capacity to 1 if it's 0
+                              : DYNARR_FUNC(resize_exact)(arr, arr->cap * 2); // otherwise, multiply the capacity by 2
+        // return 1 upon non-zero
+        if (s) return 1;
     }
 
     arr->dat[idx] = item;
@@ -70,7 +88,7 @@ DYNARR_LINKAGE uint8_t DYNARR_add(DYNARR_NAME* arr, DYNARR_TYPE item) {
 
 // removes an item from the dynamic array from a certain index
 // returns 0 upon success, 1 upon failure
-DYNARR_LINKAGE uint8_t DYNARR_remove(DYNARR_NAME* arr, size_t idx) {
+DYNARR_LINKAGE uint8_t DYNARR_FUNC(remove)(DYNARR_NAME* arr, size_t idx) {
     if (arr->count == 0 || idx >= arr->count) return 1;
 
     // remove one from the count
@@ -85,17 +103,21 @@ DYNARR_LINKAGE uint8_t DYNARR_remove(DYNARR_NAME* arr, size_t idx) {
     return 0;
 }
 
+// trims the parts of the dynamic array that isn't in use
+DYNARR_LINKAGE uint8_t DYNARR_FUNC(trim)(DYNARR_NAME* arr) {
+    if (arr->cap == arr->count) return 0; // return success if no work needs to be done
+    return DYNARR_FUNC(resize_exact)(arr, arr->count);
+}
+
 // cleans up the resources associated with the array, do not use after this step. This is undefined behaviour
-DYNARR_LINKAGE void DYNARR_free(DYNARR_NAME* arr) {
+DYNARR_LINKAGE void DYNARR_FUNC(free)(DYNARR_NAME* arr) {
+    if (arr->dat == NULL) return;
     free(arr->dat);
-    arr->dat = NULL;
+    *arr = (DYNARR_NAME){0}; // zero out all fields to re-initialize
 }
 
 // clean up all defined definitions so they can be used again later
-#undef DYNARR_init
-#undef DYNARR_add
-#undef DYNARR_remove
-#undef DYNARR_free
+#undef DYNARR_FUNC
 #undef DYNARR_NAME
 #undef DYNARR_LINKAGE
 #undef DYNARR_TYPE