加密功能的问题未链接到主机 [英] Issue With Encryption Function Not Linking To Main
问题描述
为了教育的目的，我正在编写一小堆功能，打开一个文件作为二进制文件，一次读取一个字符，更改所述字符的值并写入一个新的加密文件。 （注意，这不是真正的加密。）
由于某些原因，我在调试器中的while循环条件中收到此错误消息： / p>
线程1：EXC_BAD_ACCESS（code = 1，address = 0x0）
我怀疑问题是理解指针。这是我的程序的全部。提前感谢。
//此程序读取文件的内容，对其进行加密，并将内容写入单独的文件。
#include< iostream>
#include< fstream>
#include< cctype>
#include< cstring>
#include< cmath>
使用namespace std;
//全局常量
const int POSITIVE_INT_LIMIT = 10;
const int NEGATIVE_INT_LIMIT = -10;
const int SLOPE_NEGATIVE = -1;
const int SLOPE_POSITIVE = 1;
const int STEP = 1;
//函数原型
void encrypt（fstream * unEncryptedFile）;
fstream * fileOpener（）;
int main（）{
encrypt（fileOpener（））;
return 0;
}
/ ************************************ ****************
* fileOpener（）*
*打开具有错误检查的文件，并显示*
*消息，如果错误，然后正常退出。 *
************************************************* ******* /
fstream * fileOpener（）{
fstream inFile; //创建fstream对象
inFile.open（crypty.txt，ios :: in | ios :: binary）; //打开文件
if（！inFile）{
cout<<< 打开文件错误。 << ENDL;
返回NULL;
} else {
fstream * filePtr; //创建一个指向该文件的指针。
filePtr =& inFile; //将inFile的地址传递给指针。
return filePtr;
}
}
/ ******************* ********************************
* encrypt（）*
*加密文件一个simlpe算法。 *
************************************************* ****** /
void encrypt（fstream& unEncryptedFile）{
char ch，cy;
char * chPtr =& cy; //初始化并分配char指针。
fstream cryptFile;
cryptFile.open（decrypy.txt，ios :: out | ios :: binary）;
int幅度= 0，slope = SLOPE_NEGATIVE; //设置初始幅度和斜率。
int streamSize = 1;
/ * while循环内的加密模式。
limit> 10 *
9 * *
8 * *
7 * *
6 * *
5 * *
4 * *
3 * *
2 * *
1 * *
开始> 0 * 2345678901234567890 * 2345678901234567890 * - <一个赫兹（周期）
-1 * *
-2 * *（数字行：每个整数表示一个循环周期）
-3 * *
-4 * *
-5 * *
-6 * *
-7 * *
-8 * *
-9 * *
limit> -10 *
* /
/ ****************************** *****************************
上面的模式表示单个字符
被读取，然后增加幅度值。
****************************************** ******************* /
while（！unEncryptedFile.fail（））{//< - 代码报告此语句的错误。
ch = unEncryptedFile.get（）; //获取文件中的下一个字符。
if（amplitude> NEGATIVE_INT_LIMIT&& slope == SLOPE_NEGATIVE）{
amplitude - = STEP;
cy = ch +幅度;
cryptFile.write（chPtr，streamSize）; //调整后的字符值，cy被写入文件。
} else if（amplitude< = NEGATIVE_INT_LIMIT）{
slope = SLOPE_POSITIVE;
幅度= NEGATIVE_INT_LIMIT;
cy = ch +幅度;
cryptFile.write（chPtr，streamSize）; //调整后的字符值，cy被写入文件。
} else if（amplitude< POSITIVE_INT_LIMIT&& SLOPE_POSITIVE）{
幅度+ = STEP;
cy = ch +幅度;
cryptFile.write（chPtr，streamSize）; //调整后的字符值，cy被写入文件。
} else if（amplitude> = POSITIVE_INT_LIMIT）{
slope = SLOPE_NEGATIVE;
amplitude = POSITIVE_INT_LIMIT;
cy = ch +幅度;
cryptFile.write（chPtr，streamSize）; //调整后的字符值，cy被写入文件。
}
}
//文件关闭。
unEncryptedFile.close（）;
cryptFile.close（）;
}
我怀疑问题是理解指针。
可能，几乎你是对的，但理解指向本地的指针变量
当您定义本地变量时：
fstream INFILE; //创建fstream对象
inFile 在堆栈上。
具有以下内容：
filePtr =& inFile
...您将在
当您退出该功能时：
return filePtr;
...与函数调用相关联的堆栈部分将返回堆并且 filePtr 将指向未使用的内存地址，这将被下一个调用的函数/执行代码覆盖。
所以，为什么不只是返回 inFile 本身？
For the purpose of education, I'm writing a small pair of functions which open a file as a binary file, read each character one at a time, change the value of said character and write to a new, encrypted file. (Note, this isn't true encryption per se.)
For some reason, I'm getting this error message in my debugger at the while-loop condition:
Thread 1: EXC_BAD_ACCESS (code=1, address=0x0)
I suspect the issue is with understanding pointer. Here is my program in it's entirety. Thanks ahead of time.
// This program reads the contents of a file, encrypts it, and write the contents into a separate file.
#include <iostream>
#include <fstream>
#include <cctype>
#include <cstring>
#include <cmath>
using namespace std;
// Global Constants
const int POSITIVE_INT_LIMIT = 10;
const int NEGATIVE_INT_LIMIT = -10;
const int SLOPE_NEGATIVE = -1;
const int SLOPE_POSITIVE = 1;
const int STEP = 1;
// Function Prototypes
void encrypt(fstream *unEncryptedFile);
fstream *fileOpener();
int main() {
encrypt(fileOpener());
return 0;
}
/****************************************************
* fileOpener() *
* Opens file with error checking and displays *
* message if error, then exiting gracefully. *
****************************************************/
fstream *fileOpener(){
fstream inFile; // Create fstream object
inFile.open("crypty.txt", ios::in | ios::binary); // Open file
if (!inFile) {
cout << "Error opening file." << endl;
return NULL;
} else {
fstream *filePtr; // create a pointer to the file.
filePtr = &inFile; // Pass the address of inFile to the pointer.
return filePtr;
}
}
/***************************************************
* encrypt() *
* Encrypts a file with a simlpe algorithm. *
***************************************************/
void encrypt(fstream &unEncryptedFile){
char ch, cy;
char *chPtr = &cy; // Initialize and assign char pointer.
fstream cryptFile;
cryptFile.open("decrypy.txt", ios::out | ios::binary);
int amplitude = 0, slope = SLOPE_NEGATIVE; //Set initial amplitude and slope.
int streamSize = 1;
/* Encryption pattern inside while-loop.
limit> 10 *
9 * *
8 * *
7 * *
6 * *
5 * *
4 * *
3 * *
2 * *
1 * *
start> 0*2345678901234567890*2345678901234567890* -- < one hertz (cycle)
-1 * *
-2 * * (Number line: each integer represents a single while loop cycle.)
-3 * *
-4 * *
-5 * *
-6 * *
-7 * *
-8 * *
-9 * *
limit> -10 *
*/
/*************************************************************
The pattern above depictes a single character
being read, and then the value of amplitude is added to it.
*************************************************************/
while (!unEncryptedFile.fail()) { // <--Code reports bug at this statement.
ch = unEncryptedFile.get(); // Get the next character in the file.
if (amplitude > NEGATIVE_INT_LIMIT && slope == SLOPE_NEGATIVE) {
amplitude -= STEP;
cy = ch + amplitude;
cryptFile.write(chPtr, streamSize); //Adjusted character value, cy, is written to file.
} else if (amplitude <= NEGATIVE_INT_LIMIT){
slope = SLOPE_POSITIVE;
amplitude = NEGATIVE_INT_LIMIT;
cy = ch + amplitude;
cryptFile.write(chPtr, streamSize); //Adjusted character value, cy, is written to file.
} else if (amplitude < POSITIVE_INT_LIMIT && SLOPE_POSITIVE){
amplitude += STEP;
cy = ch + amplitude;
cryptFile.write(chPtr, streamSize); //Adjusted character value, cy, is written to file.
} else if (amplitude >= POSITIVE_INT_LIMIT){
slope = SLOPE_NEGATIVE;
amplitude = POSITIVE_INT_LIMIT;
cy = ch + amplitude;
cryptFile.write(chPtr, streamSize); //Adjusted character value, cy, is written to file.
}
}
//Files are closed.
unEncryptedFile.close();
cryptFile.close();
}
I suspect the issue is with understanding pointer.
Probably, almost you right, but with understanding of pointers to local variables.
When you define local variables like this:
fstream inFile; // Create fstream object
inFile is allocated on the stack.
With following:
filePtr = &inFile
... you'll get pointer to some place on the stack in filePtr.
And when you exit that function:
return filePtr;
... stack portion, associated with function call will be returned to heap and filePtr will point to unused memory address, which will be overriden by next called function/executed code.
So, why not just return inFile itself?
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