113 lines
2.4 KiB
C
113 lines
2.4 KiB
C
/*
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* memlib.c - a module that simulates the memory system. Needed because it
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* allows us to interleave calls from the student's malloc package
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* with the system's malloc package in libc.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <assert.h>
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#ifndef _WIN32
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#include <unistd.h>
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#endif
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#include <string.h>
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#include <errno.h>
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#include "memlib.h"
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#include "config.h"
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/* private variables */
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static char* mem_start_brk; /* points to first byte of heap */
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static char* mem_brk; /* points to last byte of heap */
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static char* mem_max_addr; /* largest legal heap address */
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#ifdef _WIN32
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#include <windows.h>
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int getpagesize(void)
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{
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SYSTEM_INFO system_info;
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GetSystemInfo(&system_info);
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return system_info.dwPageSize;
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}
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#endif
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/*
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* mem_init - initialize the memory system model
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*/
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void mem_init(void)
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{
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/* allocate the storage we will use to model the available VM */
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if ((mem_start_brk = (char*)malloc(MAX_HEAP)) == NULL) {
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printf("[%s]malloc失败\n", __func__);
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exit(1);
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}
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mem_max_addr = mem_start_brk + MAX_HEAP; /* max legal heap address */
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mem_brk = mem_start_brk; /* heap is empty initially */
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}
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/*
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* mem_deinit - free the storage used by the memory system model
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*/
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void mem_deinit(void)
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{
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free(mem_start_brk);
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}
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/*
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* mem_reset_brk - reset the simulated brk pointer to make an empty heap
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*/
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void mem_reset_brk()
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{
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mem_brk = mem_start_brk;
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}
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/*
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* mem_sbrk - simple model of the sbrk function. Extends the heap
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* by incr bytes and returns the start address of the new area. In
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* this model, the heap cannot be shrunk.
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*/
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void* mem_sbrk(int incr)
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{
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char* old_brk = mem_brk;
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if ((incr < 0) || ((mem_brk + incr) > mem_max_addr)) {
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errno = ENOMEM;
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printf("[%s]失败: 内存已被耗光...\n", __func__);
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return (void*)-1;
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}
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mem_brk += incr;
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return (void*)old_brk;
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}
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/*
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* mem_heap_lo - return address of the first heap byte
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*/
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void* mem_heap_lo()
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{
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return (void*)mem_start_brk;
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}
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/*
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* mem_heap_hi - return address of last heap byte
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*/
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void* mem_heap_hi()
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{
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return (void*)(mem_brk - 1);
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}
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/*
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* mem_heapsize() - returns the heap size in bytes
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*/
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size_t mem_heapsize()
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{
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return (size_t)(mem_brk - mem_start_brk);
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}
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/*
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* mem_pagesize() - returns the page size of the system
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*/
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size_t mem_pagesize()
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{
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return (size_t)getpagesize();
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}
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