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/*
* A simple temp malloc for Sysliux project from fstk. For now, just used
* in fsc branch, which it's would be easy to remove it when we have a
* powerful one, as hpa said this would happen when elflink branch do the
* work.
*
* Copyright (C) 2009 Liu Aleaxander -- All rights reserved. This file
* may be redistributed under the terms of the GNU Public License.
*/
#include <stdio.h>
#include <stdint.h>
#include <string.h>
/* The memory managemant structure */
struct mem_struct {
struct mem_struct *prev;
int size;
int free;
};
/* First, assume we just need 64K memory */
static char memory[0x10000];
/* Next free memory address */
static struct mem_struct *next_start = (struct mem_struct *)memory;
static uint32_t mem_end = (uint32_t)(memory + 0x10000);
static inline struct mem_struct *get_next(struct mem_struct *mm)
{
uint32_t next = (uint32_t)mm + mm->size;
if (next >= mem_end)
return NULL;
else
return (struct mem_struct *)next;
}
/*
* Here are the _merge_ functions, that merges a adjacent memory region,
* from front, or from back, or even merges both. It returns the headest
* region mem_struct.
*
*/
static struct mem_struct * merge_front(struct mem_struct *mm,
struct mem_struct *prev)
{
struct mem_struct *next = get_next(mm);
prev->size += mm->size;
if (next)
next->prev = prev;
return prev;
}
static struct mem_struct * merge_back(struct mem_struct *mm,
struct mem_struct *next)
{
mm->free = 1; /* Mark it free first */
mm->size += next->size;
next = get_next(next);
if (next)
next->prev = mm;
return mm;
}
static struct mem_struct * merge_both(struct mem_struct *mm,
struct mem_struct *prev,
struct mem_struct *next)
{
prev->size += mm->size + next->size;
next = get_next(next);
if (next)
next->prev = prev;
return prev;
}
static inline struct mem_struct * try_merge_front(struct mem_struct *mm)
{
mm->free = 1;
if (mm->prev->free)
mm = merge_front(mm, mm->prev);
return mm;
}
static inline struct mem_struct * try_merge_back(struct mem_struct *mm)
{
struct mem_struct *next = get_next(mm);
mm->free = 1;
if (next->free)
merge_back(mm, next);
return mm;
}
/*
* Here's the main function, malloc, which allocates a memory rigon
* of size _size_. Returns NULL if failed, or the address newly allocated.
*
*/
void *malloc(size_t size)
{
struct mem_struct *next = next_start;
struct mem_struct *good = next, *prev;
int size_needed = (size + sizeof(struct mem_struct) + 3) & ~3;
while(next) {
if (next->free && next->size >= size_needed) {
good = next;
break;
}
next = get_next(next);
}
if (good->size < size_needed) {
printf("Out of memory, maybe we need append it\n");
return NULL;
} else if (good->size == size_needed) {
/*
* We just found a right memory that with the exact
* size we want. So we just Mark it _not_free_ here,
* and move on the _next_start_ pointer, even though
* the next may not be a right next start.
*/
good->free = 0;
next_start = get_next(good);
goto out;
} else
size = good->size; /* save the total size */
/*
* Note: allocate a new memory region will not change
* it's prev memory, so we don't need change it here.
*/
good->free = 0; /* Mark it not free any more */
good->size = size_needed;
next = get_next(good);
if (next) {
next->size = size - size_needed;
/* check if it can contain 1 byte allocation at least */
if (next->size <= (int)sizeof(struct mem_struct)) {
good->size = size; /* restore the original size */
next_start = get_next(good);
goto out;
}
next->prev = good;
next->free = 1;
next_start = next; /* Update next_start */
prev = next;
next = get_next(next);
if (next)
next->prev = prev;
} else
next_start = (struct mem_struct *)memory;
out:
return (void *)((uint32_t)good + sizeof(struct mem_struct));
}
void *zalloc(size_t size)
{
void *p = malloc(size);
if (p)
memset(p, 0, size);
return p;
}
void free(void *ptr)
{
struct mem_struct *mm = ptr - sizeof(*mm);
struct mem_struct *prev = mm->prev;
struct mem_struct *next = get_next(mm);
if (!prev)
mm = try_merge_back(mm);
else if (!next)
mm = try_merge_front(mm);
else if (prev->free && !next->free)
merge_front(mm, prev);
else if (!prev->free && next->free)
merge_back(mm, next);
else if (prev->free && next->free)
merge_both(mm, prev, next);
else
mm->free = 1;
if (mm < next_start)
next_start = mm;
}
/*
* The debug function
*/
void check_mem(void)
{
struct mem_struct *next = (struct mem_struct *)memory;
printf("____________\n");
while (next) {
printf("%-6d %s\n", next->size, next->free ? "Free" : "Notf");
next = get_next(next);
}
printf("\n");
}
void mem_init(void)
{
struct mem_struct *first = (struct mem_struct *)memory;
first->prev = NULL;
first->size = 0x10000;
first->free = 1;
next_start = first;
}
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