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/*
A block array is an array of blocks of T.
They ensure that pointers to values in the array are not invalidated
when something is added to the array.
*/
/*
Note: the block size must be a power of 2, to use right shifting instead of division
(for optimization)!
*/
static void block_arr_create(BlockArr *arr, int lg_block_sz, size_t item_sz) {
arr->blocks = NULL;
arr->item_sz = item_sz;
arr->lg_block_sz = lg_block_sz;
}
static void *block_arr_add(BlockArr *arr) {
ArrBlock *last_block;
last_block = arr_last(arr->blocks);
if (arr->blocks == NULL ||
(unsigned long)last_block->n >= (1UL << arr->lg_block_sz)) {
ArrBlock *block;
/* no blocks yet / ran out of blocks*/
block = arr_add(&arr->blocks);
block->n = 1;
size_t bytes = arr->item_sz << arr->lg_block_sz;
block->data = err_malloc(bytes);
block->last = block->data;
return block->data;
} else {
last_block->last = (char*)last_block->last + arr->item_sz;
last_block->n++;
return last_block->last;
}
}
static inline void *block_arr_get(BlockArr *arr, size_t index) {
size_t block_index = index >> arr->lg_block_sz;
ArrBlock *block = &arr->blocks[block_index];
return (char*)block->data + arr->item_sz * index;
}
static void block_arr_free(BlockArr *arr) {
arr_foreach(arr->blocks, ArrBlock, block) {
free(block->data);
}
arr_clear(&arr->blocks);
}
static void block_arr_test(void) {
BlockArr a;
int *ps[100];
block_arr_create(&a, 3, sizeof(int));
for (int i = 0; i < 100; i++) {
int *p = block_arr_add(&a);
*p = i;
ps[i] = p;
}
for (int i = 0; i < 100; i++) {
assert(*ps[i] == i);
}
block_arr_free(&a);
}
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