C++ Source code to encrypt and decrypt the Ceasar cipher

The following code accepts one line from the standard input and uses the functions encrypt and decrypt to break the Ceasar cipher when the key is known. In this example, the key was the number 12, the day of birth of Julius Ceasar.

[download id=”11738″]

#include <iostream>
#include <string> 

using namespace std;

#define OFFSET_SMALL (97)
#define OFFSET_BIG (65)

// Text and offset for the shift are sent into this function, which returns the text's encrypted version.
string encrypt(string text, int offset)
    string result = "";

    for (long unsigned int i = 0; i < text.length(); i++)
        if (std::isalpha(text[i]))
            if (std::islower(text[i]))
                result += char (int(text[i] + offset - OFFSET_SMALL) % LATIN_CHARACTERS + OFFSET_SMALL);
                result += char (int(text[i] + offset - OFFSET_BIG) % LATIN_CHARACTERS + OFFSET_BIG);

            result += text[i];

    return result;

// Text and offset for the shift are sent into this function, which returns the text's decrypted version.
string decrypt(string text, int offset)
    return encrypt(text, LATIN_CHARACTERS - offset);

int main() {
    string encrypted;
    getline(cin, encrypted);

    // Sample execution showing how to decrypt an already encrypted message.
    // Julius Ceasar was born on July 12, 100BC
    cout << decrypt(encrypted, 12);

    return 0;

[download id=”11738″]


Side note:

While authoring this post, we found a peculiar bug in the plugin named “SyntaxHlighlighter Evolved.”

Specifically, when we added the string char( in our C++ source code, we would get the following error back:

Updating failed. The response is not a valid JSON response.

To mitigate the problem, we added a space character between the word char and the open parenthesis as follows char (.

Compiling DJI Onboard-SDK: error: ‘fd_set’ does not name a type

While compiling the DJI Onboard SDK on a Fedora GNU/Linux we got the following error:

[ 41%] Building CXX object osdk-core/CMakeFiles/djiosdk-core.dir/platform/linux/src/linux_serial_device.cpp.o
In file included from Onboard-SDK/osdk-core/platform/linux/src/linux_serial_device.cpp:33:0:
Onboard-SDK/osdk-core/platform/linux/inc/linux_serial_device.hpp:97:3: error: ‘fd_set’ does not name a type; did you mean ‘tzset’?
 fd_set m_serial_fd_set;
In file included from /usr/include/sys/types.h:197:0,
 from /usr/include/stdlib.h:279,
 from /usr/include/c++/7/cstdlib:75,
 from /usr/include/c++/7/bits/stl_algo.h:59,
 from /usr/include/c++/7/algorithm:62,
 from Onboard-SDK/osdk-core/platform/linux/src/linux_serial_device.cpp:34:
Onboard-SDK/osdk-core/platform/linux/src/linux_serial_device.cpp: In member function ‘int DJI::OSDK::LinuxSerialDevice::_serialStart(const char*, int)’:
Onboard-SDK/osdk-core/platform/linux/src/linux_serial_device.cpp:330:14: error: ‘m_serial_fd_set’ was not declared in this scope
Onboard-SDK/osdk-core/platform/linux/src/linux_serial_device.cpp:330:14: note: suggested alternative: ‘m_serial_fd’
Onboard-SDK/osdk-core/platform/linux/src/linux_serial_device.cpp:331:26: error: ‘m_serial_fd_set’ was not declared in this scope
 FD_SET(m_serial_fd, &m_serial_fd_set);
Onboard-SDK/osdk-core/platform/linux/src/linux_serial_device.cpp:331:26: note: suggested alternative: ‘m_serial_fd’
make[2]: *** [osdk-core/CMakeFiles/djiosdk-core.dir/build.make:735: osdk-core/CMakeFiles/djiosdk-core.dir/platform/linux/src/linux_serial_device.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:86: osdk-core/CMakeFiles/djiosdk-core.dir/all] Error 2
make: *** [Makefile:130: all] Error 2

To resolve this, we added to the file Onboard-SDK/osdk-core/platform/linux/inc/linux_serial_device.hpp the following include directive right after line 37 (which contained #define LINUXSERIALDEVICE_H):

#include <sys/select.h>

Then, we issued make again which terminated successfully.

Source: https://github.com/dji-sdk/Onboard-SDK

Compilation Commands:

git clone https://github.com/dji-sdk/Onboard-SDK;

cd Onboard-SDK;

mkdir build;

cd build;

cmake ..;

#Modify the file Onboard-SDK/osdk-core/platform/linux/inc/linux_serial_device.hpp and add #include <sys/select.h> at the top

make all;

# Something

# Make profit

Converting a (void*) buffer to a std::vector

On a project we were recently working on, some legacy C code was producing a (void*) voidBuffer accompanied by its size.
The rest of the project was in C++ and we needed to convert the (void*) voidBuffer to a std::vector<unsigned char> vector.

To do so, we used the following code:

//First cast the (void *) voidBuffer to an (unsigned char *) to implicitly get the element size (1 Byte each)
const unsigned char *charBuffer = (unsigned char *) voidBuffer;
//Then we create the vector (named vectorBuffer) by copying the contents of charBuffer to the vector
std::vector<unsigned char> vectorBuffer(charBuffer, charBuffer + length);

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