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/* Copyright (C) 2023 Aryadev Chavali
* You may distribute and modify this code under the terms of the
* GPLv2 license. You should have received a copy of the GPLv2
* license with this file. If not, please write to:
* aryadev@aryadevchavali.com.
* Created: 2023-11-01
* Author: Aryadev Chavali
* Description: Arena allocator
*/
#include "./heap.h"
page_t *page_create(size_t max, page_t *next)
{
page_t *page = calloc(1, sizeof(*page) + max);
page->used = 0;
page->available = max;
page->next = next;
return page;
}
size_t page_space_left(page_t *page)
{
return WORD_SAFE_SUB(page->available, page->used);
}
void page_delete(page_t *page)
{
free(page);
}
void heap_create(heap_t *heap)
{
heap->beg = page_create(PAGE_DEFAULT_SIZE, NULL);
heap->end = heap->beg;
heap->pages = 1;
}
byte *heap_allocate(heap_t *heap, size_t requested)
{
page_t *ptr = heap->beg;
while (page_space_left(ptr) < requested)
ptr = ptr->next;
if (ptr)
{
byte *data = ptr->used + ptr->data;
ptr->used += requested;
return data;
}
// Otherwise we are at the end of the heap, and we need to allocate
// a new page
// Create new page and get the pointer to the start of requested data
page_t *new_page = page_create(MAX(PAGE_DEFAULT_SIZE, requested), NULL);
byte *data = new_page->used + new_page->data;
// Set the end of the heap to the new page (update linked list)
heap->end->next = new_page;
heap->end = new_page;
new_page->used += requested;
++heap->pages;
return data;
}
void heap_stop(heap_t *heap)
{
page_t *ptr = heap->beg;
for (size_t i = 0; i < heap->pages; ++i)
{
page_t *cur = ptr;
page_t *next = ptr->next;
page_delete(cur);
ptr = next;
}
heap->beg = NULL;
heap->end = NULL;
heap->pages = 0;
}
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