Stuck in while loop when change to c++ - c++

Question

i'm trying to rewrite this code in c++ which create a bitcoin mini private key
using System;
using System.Text;
using Org.BouncyCastle.Security;
public string CreateRandomMinikey(){
string keytotry = "S6c56bnXQiBjk9mqSYE7ykVQ7NzrQA";
char[] chars = keytotry.ToCharArray();
char[] charstest = (keytotry + "?").ToCharArray();
while (Util.ComputeSha256(utf8.GetBytes(charstest))[0] != 0) {// hash sha256 the key & check if the first character was '0'
// As long as key doesn't pass typo check, increment it.
for (int i = chars.Length - 1; i >= 0; i--) {
char c = chars[i];
if (c == '9') {
charstest[i] = chars[i] = 'A';
break;
} else if (c == 'H') {
charstest[i] = chars[i] = 'J';
break;
} else if (c == 'N') {
charstest[i] = chars[i] = 'P';
break;
} else if (c == 'Z') {
charstest[i] = chars[i] = 'a';
break;
} else if (c == 'k') {
charstest[i] = chars[i] = 'm';
break;
} else if (c == 'z') {
charstest[i] = chars[i] = '2';
// No break - let loop increment prior character.
} else {
charstest[i] = chars[i] = ++c;
break;
}
}
}
string result = new string(chars);//expect S6c56bnXQiBjk9mqSYE7ykVQ7NzrRy
return result;
}
Here my code when i transform into c++
#include "stdafx.h"
#include <string.h>
#include <iostream>
#include <cstring>
#include "sha256.h"
using namespace std;
int main()
{
string input = "S6c56bnXQiBjk9mqSYE7ykVQ7NzrQA";
string inputcharstest = input+"?";
char * chars = new char[input.size() + 1];
strcpy(chars, input.c_str());//convert input to char array
char * charstest = new char[inputcharstest.size() + 1];
strcpy(charstest, inputcharstest.c_str());// convert inputcharstest to char array
string output = sha256(inputcharstest); //hash sha256 inputcharstest to check typo
while (output[0] != '0') {
for (int i = strlen(chars) - 1; i >= 0; i--) {
char c = chars[i];
if (c == '9') {
charstest[i] = chars[i] = 'A';
break;
}
else if (c == 'H') {
charstest[i] = chars[i] = 'J';
break;
}
else if (c == 'N') {
charstest[i] = chars[i] = 'P';
break;
}
else if (c == 'Z') {
charstest[i] = chars[i] = 'a';
break;
}
else if (c == 'k') {
charstest[i] = chars[i] = 'm';
break;
}
else if (c == 'z') {
charstest[i] = chars[i] = '2';
}
else {
charstest[i] = chars[i] = ++c;
break;
}
}
}
string result = string(chars); //expect S6c56bnXQiBjk9mqSYE7ykVQ7NzrRy
cout << "input('" << input << "'):" << result << endl;
return 0;
}
This is the result i expected
The code was stuck & return blank when i run it on console application, i debug & find out it was stuck in while loop forever. May i ask if there're any problem with this & how do i fix it?

Answer 1

Here you are changing the content of the string every time:
char[] charstest = (keytotry + "?").ToCharArray();
while (Util.ComputeSha256(utf8.GetBytes(charstest))[0] != 0) {
charstest changes in every run through the loop, so the test in the while can terminate at some point. In the C++ code, however, you're not doing that:
string output = sha256(inputcharstest); //hash sha256 inputcharstest to check typo
while (output[0] != '0') {
Here, you're only doing the hash once before the loop, and then not again in the loop. The loop doesn't change output at all and neither does it break out of the while, so if output[0] != '0' is true the first time, it will always be true, thus the infinite loop.