alloc.c

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/*
WKern - A Bare Metal OS / Kernel I am maKing (For Fun)
Copyright (C) 2025  Wdboyes13
 
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
any later version.
 
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 for more details.
 
You should have received a copy of the GNU General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/
#include <global.h>
#include <types/nums.h>
typedef struct BlocK {
    size_t size;
    struct BlocK *next;
    int free;
} blocK_t;
 
#define HEAP_START ((char *)0x100000)
#define HEAP_SIZE (512 * 1024)
 
static char *heap = HEAP_START;
static blocK_t *free_list = NULL;

void KheapInit() {
    free_list = (blocK_t *)heap;
    free_list->size = HEAP_SIZE - sizeof(blocK_t);
    free_list->next = NULL;
    free_list->free = 1;
}

void *Kmalloc(size_t size, size_t align) {
    size = (size + align - 1) & ~(align - 1);
    blocK_t *curr = free_list;
    while (curr) {
        if (curr->free && curr->size >= size) {
            if (curr->size >= size + sizeof(blocK_t) + 8) {
                // Split the blocK
                blocK_t *new_blocK = (blocK_t *)((char *)(curr + 1) + size);
                new_blocK->size = curr->size - size - sizeof(blocK_t);
                new_blocK->next = curr->next;
                new_blocK->free = 1;
 
                curr->size = size;
                curr->next = new_blocK;
            }
            curr->free = 0;
            return (void *)(curr + 1);
        }
        curr = curr->next;
    }
    return NULL;
}

void Kfree(void *ptr) {
    if (!ptr) {
        return;
    }
    blocK_t *blocK = (blocK_t *)ptr - 1;
    blocK->free = 1;
}