You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
101 lines
2.2 KiB
101 lines
2.2 KiB
/*
|
|
* memlib.c - a module that simulates the memory system. Needed because it
|
|
* allows us to interleave calls from the student's malloc package
|
|
* with the system's malloc package in libc.
|
|
*/
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <assert.h>
|
|
#include <unistd.h>
|
|
#include <sys/mman.h>
|
|
#include <string.h>
|
|
#include <errno.h>
|
|
|
|
#include "memlib.h"
|
|
#include "config.h"
|
|
|
|
/* private variables */
|
|
static char *mem_start_brk; /* points to first byte of heap */
|
|
static char *mem_brk; /* points to last byte of heap */
|
|
static char *mem_max_addr; /* largest legal heap address */
|
|
|
|
/*
|
|
* mem_init - initialize the memory system model
|
|
*/
|
|
void mem_init(void)
|
|
{
|
|
/* allocate the storage we will use to model the available VM */
|
|
if ((mem_start_brk = (char *)malloc(MAX_HEAP)) == NULL) {
|
|
fprintf(stderr, "mem_init_vm: malloc error\n");
|
|
exit(1);
|
|
}
|
|
|
|
mem_max_addr = mem_start_brk + MAX_HEAP; /* max legal heap address */
|
|
mem_brk = mem_start_brk; /* heap is empty initially */
|
|
}
|
|
|
|
/*
|
|
* mem_deinit - free the storage used by the memory system model
|
|
*/
|
|
void mem_deinit(void)
|
|
{
|
|
free(mem_start_brk);
|
|
}
|
|
|
|
/*
|
|
* mem_reset_brk - reset the simulated brk pointer to make an empty heap
|
|
*/
|
|
void mem_reset_brk()
|
|
{
|
|
mem_brk = mem_start_brk;
|
|
}
|
|
|
|
/*
|
|
* mem_sbrk - simple model of the sbrk function. Extends the heap
|
|
* by incr bytes and returns the start address of the new area. In
|
|
* this model, the heap cannot be shrunk.
|
|
*/
|
|
void *mem_sbrk(int incr)
|
|
{
|
|
char *old_brk = mem_brk;
|
|
|
|
if ( (incr < 0) || ((mem_brk + incr) > mem_max_addr)) {
|
|
errno = ENOMEM;
|
|
fprintf(stderr, "ERROR: mem_sbrk failed. Ran out of memory...\n");
|
|
return (void *)-1;
|
|
}
|
|
mem_brk += incr;
|
|
return (void *)old_brk;
|
|
}
|
|
|
|
/*
|
|
* mem_heap_lo - return address of the first heap byte
|
|
*/
|
|
void *mem_heap_lo()
|
|
{
|
|
return (void *)mem_start_brk;
|
|
}
|
|
|
|
/*
|
|
* mem_heap_hi - return address of last heap byte
|
|
*/
|
|
void *mem_heap_hi()
|
|
{
|
|
return (void *)(mem_brk - 1);
|
|
}
|
|
|
|
/*
|
|
* mem_heapsize() - returns the heap size in bytes
|
|
*/
|
|
size_t mem_heapsize()
|
|
{
|
|
return (size_t)(mem_brk - mem_start_brk);
|
|
}
|
|
|
|
/*
|
|
* mem_pagesize() - returns the page size of the system
|
|
*/
|
|
size_t mem_pagesize()
|
|
{
|
|
return (size_t)getpagesize();
|
|
}
|