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/* Copyright (C) 2025 Aryadev Chavali
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License Version 2 for
* details.
* You may distribute and modify this code under the terms of the GNU General
* Public License Version 2, which you should have received a copy of along with
* this program. If not, please go to <https://www.gnu.org/licenses/>.
* Created: 2025-04-05
* Description: Implementations for memory models.
*/
#include <lib/arena.h>
#include <malloc.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
page_t *page_create(u64 size)
{
size = MAX(size, PAGE_DEFAULT_SIZE);
page_t *page = calloc(1, sizeof(*page) + size);
page->next = NULL;
page->size = 0;
page->capacity = size;
return page;
}
void page_resize(page_t **page, u64 size)
{
if (!page)
return;
else if (!(*page))
*page = page_create(size);
else if (page[0]->capacity < size)
{
page[0]->capacity = MAX(size, page[0]->capacity * 1.5);
page[0] = realloc(page[0], sizeof(*page[0]) + page[0]->capacity);
}
}
i64 page_append(page_t *page, void *data, u64 size)
{
if (!page || page->size + size >= page->capacity)
return -1;
if (data)
memcpy(page->data + page->size, data, size);
u64 ptr = page->size;
page->size += size;
return ptr;
}
u64 page_rappend(page_t **page, void *data, u64 size)
{
page_resize(page, page[0]->size + size);
if (data)
memcpy(page[0]->data + page[0]->size, data, size);
u64 ptr = page[0]->size;
page[0]->size += size;
return ptr;
}
void *arena_alloc(arena_t *arena, u64 size)
{
if (!arena)
return NULL;
else if (!arena->start)
{
arena->start = page_create(1);
arena->end = arena->start;
}
page_t *best_fit;
for (best_fit = arena->start; best_fit; best_fit = best_fit->next)
if (best_fit->size + size + MEMORY_ALIGNMENT < best_fit->capacity)
break;
if (!best_fit)
{
best_fit = page_create(size);
arena->end->next = best_fit;
arena->end = best_fit;
}
// NOTE: Fsanitize has a hissy fit if we don't align memory "correctly"
u64 offset = 0;
if (size % MEMORY_ALIGNMENT == 0)
{
u64 div = (((u64)(best_fit->data + best_fit->size)) % MEMORY_ALIGNMENT);
if (div != 0)
offset = MEMORY_ALIGNMENT - div;
}
void *start = best_fit->data + best_fit->size + offset;
best_fit->size += size + offset;
return start;
}
void *arena_realloc(arena_t *arena, void *ptr, u64 oldsize, u64 newsize)
{
if (!ptr)
return arena_alloc(arena, newsize);
else if (!arena || !arena->start)
return NULL;
else if (newsize <= oldsize)
// No need to change anything.
return ptr;
bool copy_into_new = true;
void *start = NULL;
page_t *old_page = NULL, *best_fit = NULL;
for (page_t *page = arena->start; page; page = page->next)
{
if (!best_fit && page->size + newsize < page->capacity)
best_fit = page;
if (page->data <= (u8 *)ptr &&
(u8 *)(ptr) + oldsize <= page->data + page->capacity)
old_page = page;
}
// If the old page exists, ptr is the latest allocation in it, and it has
// enough space to contain the new size, just resize and return.
if (old_page && old_page->data + old_page->size - oldsize == ptr &&
old_page->size - oldsize + newsize < old_page->capacity)
{
start = ptr;
old_page->size += newsize - oldsize;
copy_into_new = false;
}
else
{
if (!old_page)
copy_into_new = false;
if (!best_fit)
{
best_fit = page_create(newsize);
arena->end->next = best_fit;
arena->end = best_fit;
}
start = best_fit->data + best_fit->size;
best_fit->size += newsize;
}
if (copy_into_new)
{
memcpy(start, ptr, oldsize);
memset(start + oldsize, 0, newsize - oldsize);
}
return start;
}
void arena_attach(arena_t *arena, page_t *page)
{
if (!arena || !page)
return;
else if (!arena->start || !arena->end)
{
arena->start = page;
arena->end = page;
}
else
{
page->next = arena->start;
arena->start = page;
}
}
void arena_reset(arena_t *arena)
{
if (!arena || !arena->start)
return;
for (page_t *cur = arena->start; cur; cur = cur->next)
{
if (cur->size == 0)
continue;
cur->size = 0;
memset(cur->data, 0, cur->capacity);
}
}
void arena_cleanup(arena_t *arena)
{
if (!arena || !arena->start)
return;
for (page_t *cur = arena->start, *next = NULL; cur;
next = cur->next, free(cur), cur = next)
continue;
memset(arena, 0, sizeof(*arena));
}
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