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#include <lib.h>
#include <comus/memory.h>
#define MAGIC 0xBEEFCAFE
struct page_header {
size_t len;
uint64_t magic;
};
static struct page_header *get_header(void *ptr)
{
struct page_header *header =
(struct page_header *)((uintptr_t)ptr - PAGE_SIZE);
if (header->magic != MAGIC)
return NULL; // invalid pointer
return header;
}
void *kalloc(size_t size)
{
struct page_header *header;
size_t pages;
pages = (size + PAGE_SIZE - 1) / PAGE_SIZE;
header = kalloc_pages(pages + 1);
if (header == NULL)
return NULL;
header->magic = MAGIC;
header->len = size;
return (char *)header + PAGE_SIZE;
}
void *krealloc(void *src, size_t dst_len)
{
struct page_header *header;
size_t src_len;
void *dst;
// realloc of 0 means free pointer
if (dst_len == 0) {
kfree(src);
return NULL;
}
// NULL src means allocate ptr
if (src == NULL) {
dst = kalloc(dst_len);
return dst;
}
header = get_header(src);
if (header == NULL)
return NULL;
src_len = header->len;
if (src_len == 0)
return NULL;
dst = kalloc(dst_len);
if (dst == NULL)
return NULL; // allocation failed
if (dst_len < src_len)
src_len = dst_len;
memcpy(dst, src, src_len);
kfree(src);
return dst;
}
void kfree(void *ptr)
{
struct page_header *header;
if (ptr == NULL)
return;
header = get_header(ptr);
if (header == NULL)
return;
kfree_pages(header);
}
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