c++ - 内存超出范围 C++

Question

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。当我尝试发送超过 10 MB 的文件时出现问题，堆栈内存超出范围。我尽可能地释放分配的内存，但错误仍然存​​在。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 的头文件声明如下。

#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处理给我的内存，我将不胜感激。

Answer 1

我认为这是你的内存泄漏的地方:

        Byte *newright=new Byte[4];
        newright=function_des(right,key48[i]);
        /*...*/
        delete[] newright;

您分配内存，将其分配给一个指针，然后将另一个值分配给指针，因此 delete[] 释放新引用的内存，而先前分配的内存将丢失。

也在这里:

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 - 不要像那样覆盖你的指针变量，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 ... */

而且我不确定您是否需要动态分配这些临时数组，但是您转储了很多代码所以我不确定(也许您递归调用您的方法，如果您在堆栈上分配数组，您将遇到堆栈溢出).