我正在为DES实现代码。它接收8个字节的数据并返回8个字节的编码数据。当我尝试发送大小超过10 MB的文件时出现问题， 堆栈内存超出范围。我尽可能释放分配的内存但仍然存在错误。 这是我的代码。
// DES.cpp : Defines the entry point for the console application.
//
#include<iostream>
#include "stdafx.h"
#include "des.h"
using namespace std;
//loads of const array declarations here
des::des(const char Key[17]){
// constructor work
}
void des::tokey_56(){
//works on the keys and converts it to 56 bits.
tokey_48(); //called to convert to 48 bit keys.
}
void leftshift(int a[],int shift){
//leftshifts a by shif number of bits
}
void des::tokey_48(){
/* */
//makes 16 subkeys of 48bits each.
}
//This function calculates permutation using the const arrays decalared above.
Byte* des::permute(Byte bytes[],const int permutatn[],int permlen,int bytelen){
Byte *newbytes=new Byte[permlen/8];
//init
for(int i=0;i<permlen/8;i++)
newbytes[i]=0;
//initclose
/*for(int i=0;i<bytelen;i++){
printf("%d - ",bytes[i]);
}*/
for(int i=0;i<permlen;i++){
int temp=permutatn[i];
int index1=(permutatn[i]-1)/8;
int index2=(permutatn[i]-1)%8;
int tempvar=bytes[index1]&masks[index2];
int tempvar_1;
tempvar_1=(tempvar>0)?masks[i%8]:0;
newbytes[i/8]= newbytes[i/8] | tempvar_1;
/*if(i==13){
printf(" %d-%d ",bytes[index1],newbytes[i/8]);
}*/
}
/*for(int i=0;i<permlen/8;i++){
printf("%d - ",newbytes[i]);
}*/
return newbytes;
}
void des::create_sub_array(Byte array[], Byte subarray[],int start,int end){
// creates 2 subarrays from start to end
}
void des::swap(Byte a[],Byte b[]){
// Swaps array a and b
}
//This is the main DES function (Key,Right)
Byte* des::function_des(Byte right[],Byte k[]){
Byte *right_p=new Byte[6];
Byte *B=new Byte[8];
right_p=permute(right,E,48,4);
for(int i=0;i<6;i++){
right_p[i]=right_p[i]^k[i];
//printf(" %d ",right_p[i]);
}
B[0]=(right_p[0]&0xFC)>>2;
B[1]=( ((right_p[0]&0x3 )<<4)|0x0F ) & ( ((right_p[1]&0xF0)>>4)|0xF0 );
B[2]=( ((right_p[1]&0x0F)<<2)|0x03 ) & ( ((right_p[2]&0xC0)>>6)|0xFC );
B[3]=(right_p[2]&0x3F);
B[4]=(right_p[3]&0xFC)>>2;
B[5]=( ((right_p[3]&0x3 )<<4)|0x0F ) & ( ((right_p[4]&0xF0)>>4)|0xF0 );
B[6]=( ((right_p[4]&0x0F)<<2)|0x03 ) & ( ((right_p[5]&0xC0)>>6)|0xFC );
B[7]= (right_p[5]&0x3F);
for(int i=0;i<8;i++){
int row=( ((B[i]&0x20)>>4)|0x01) & ( (B[i]&0x01)|0x3E);
int column= (B[i]&0x1E)>>1;
//using SBoxes
switch(i){
case 0: B[0]=S1[row][column];
break;
case 1: B[1]=S2[row][column];
break;
case 2: B[2]=S3[row][column];
break;
case 3: B[3]=S4[row][column];
break;
case 4: B[4]=S5[row][column];
break;
case 5: B[5]=S6[row][column];
break;
case 6: B[6]=S7[row][column];
break;
case 7: B[7]=S8[row][column];
break;
}
}
for(int i=0,j=0; i<4; i++,j+=2){
B[i]=(B[j]<<4)|(B[j+1]);
}
B=permute(B,P,32,4);
delete[] right_p;
return B;
}
void des::XOR(Byte a[],Byte b[],int len){
//XOR Function bit by bit.
}
//This Function is called from outside the class DES with a 8 byte packet
Byte* des::encode(Byte bytes[8]){
Byte *encoded=new Byte[8];
tokey_56();
bytes=permute(bytes,IP,64,8);
Byte left[4],right[4];
create_sub_array(bytes,left,0,4);
create_sub_array(bytes,right,4,8);
//printf("\n\n");
for(int i=0;i<16;i++){
Byte *newright=new Byte[4];
newright=function_des(right,key48[i]);
XOR(left,newright,4);
swap(left,right);
delete[] newright;
}
swap(left,right);
for(int i=0;i<4;i++){
encoded[i]=left[i];
encoded[i+4]=right[i];
}
encoded=permute(encoded,IPi,64,8);
//print final coded message
/*(for(int i=0;i<8;i++){
printf("%2X",encoded[i]);
}*/
return encoded;
}
Byte* des::decode(Byte bytes[8]){
Byte *decoded=new Byte[8];
tokey_56();
bytes=permute(bytes,IP,64,8);
Byte left[4],right[4];
create_sub_array(bytes,left,0,4);
create_sub_array(bytes,right,4,8);
//printf("\n\n");
for(int i=0;i<16;i++){
Byte *newright=new Byte[4];
newright=function_des(right,key48[15-i]);
XOR(left,newright,4);
swap(left,right);
delete[] newright;
}
swap(left,right);
for(int i=0;i<4;i++){
decoded[i]=left[i];
decoded[i+4]=right[i];
}
decoded=permute(decoded,IPi,64,8);
/*for(int i=0;i<8;i++){
printf("%2X",decoded[i]);
}*/
return decoded;
}
类DES的头文件在下面声明。
#pragma once
#include<ctype.h>
#include<string.h>
#include<stdio.h>
#include<conio.h>
#include"stdafx.h"
using namespace std;
typedef unsigned char Byte;
class des
{
private:
static const int PC_1[56];
static const int PC_2[];
static const int IP[];
static const int E[];
static const int S1[4][16];
static const int S2[4][16];
static const int S3[4][16];
static const int S4[4][16];
static const int S5[4][16];
static const int S6[4][16];
static const int S7[4][16];
static const int S8[4][16];
static const int P[];
static const int IPi[];
static const char binary[16][5];
static const Byte masks[8];
//static const Byte masks_1[8];
char key[16][5];
int key_56[56];
//int key_48[16][48];
Byte key48[16][6];
public:
char toBinary();
des(const char Key[17]);
void tokey_56();
void tokey_48();
Byte* encode(Byte bytes[]);
Byte* des::decode(Byte bytes[8]);
Byte* permute(Byte byte[],const int permutatn[],int permlen,int bytelen);
void create_sub_array(Byte array[],Byte subarray[],int start,int end);
void swap(Byte a[],Byte b[]);
void XOR(Byte a[],Byte b[],int len);
Byte* function_des(Byte right[],Byte k[]);
~des(void){}
};
如果有人告诉我如何有效地处理给予我的记忆，我会感激一些帮助。
答案 0 :(得分：6)
我认为这是你的记忆泄漏的地方：
Byte *newright=new Byte[4];
newright=function_des(right,key48[i]);
/*...*/
delete[] newright;
您分配内存，将其分配给指针，然后为指针分配另一个值，因此delete []释放新引用的内存，之前分配的内存将丢失。
同样在这里：
Byte* des::function_des(Byte right[],Byte k[]){
Byte *right_p=new Byte[6];
Byte *B=new Byte[8];
/*...*/
B=permute(B,P,32,4);
delete[] right_p;
}
如何修复它 - 不要像这样覆盖指针变量，声明新指针：
Byte *newright=new Byte[4];
Byte *really_newright=function_des(right,key48[i]);
/* use really_newright instead of newright */
delete[] newright;
/* ... delete[] really_newright; delete it when appropriate ... */
我不确定你是否需要动态分配这些临时数组，但你抛弃了很多代码，所以我不确定（也许你递归地调用你的方法，如果在堆栈上分配数组，你会遇到堆栈溢出）。