Published by
Jan 26, 2012 (last update: Jan 4, 2013)

Hex viewer

Score: 4.1/5 (38 votes)
*****
Modification history:
  • 2012-01-26 - First version (in C).
  • 2013-01-04 - Complete rewrite (in C++).
  • 2013-01-04 - Fixed indentation.

This C++ program displays the contents of a file in hexadecimal in colour. It also displays the offset into the file of each line (on the left) and a conversion of the hex data into ASCII (on the right).

Note: Some terminal emulators don't support the ANSI escape codes used by the program for coloured output. If that is that is the case with your terminal emulator (e.g. cmd.exe and Console2 on Windows) then compile the code with the macro NO_COLOR defined to disable coloured output.

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// Copyright 2013 Chrisname. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
// 1. Redistributions of source code must retain the above copyright notice,
//    this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
// 
// THIS SOFTWARE IS PROVIDED BY CHRISNAME ``AS IS'' AND ANY EXPRESS OR IMPLIED
// WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
// EVENT SHALL CHRISNAME OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
// OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
// EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include <array>
#include <cctype>
#include <cstdint>
#include <cstdlib>
#include <exception>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <sstream>
#include <stdexcept>
#include <string>
#include <vector>

namespace ansi {
    std::string escape(const std::string& seq)
    {
#ifdef NO_COLOR
        return "";
#else
        return "\033[" + seq;
#endif
    }

    std::string reset()
    {
        return escape("0m");
    }

    namespace colors {
        enum t { black, red, green, yellow, blue, magenta, cyan, white };
    }

    typedef colors::t color_t;

    std::string color(color_t col, bool bright = true, bool is_fg = true)
    {
        std::stringstream sstream;
        if (bright)
            sstream << "1;";
        sstream << (unsigned(col) + ((is_fg) ? 30 : 40)) << "m";
        return escape(sstream.str());
    }
}

namespace hexview {
    static void print_offset(unsigned long offset)
    {
        static const std::array<std::string, 2> colors = {
            ansi::color(ansi::colors::white),
            ansi::color(ansi::colors::red, false, false)
        };
        std::cout << colors[0] << colors[1] << std::hex << std::setw(8)
                  << std::setfill('0') << offset << std::dec << std::setw(0)
                  << std::setfill(' ') << ansi::reset();
    }

    static void print_hex(const std::vector <uint8_t>& bytes)
    {
        static const std::array<std::string, 2> colors = {
            ansi::color(ansi::colors::white),
            ansi::color(ansi::colors::green, false, false)
        };
        size_t i = bytes.size();
        for (const auto& byte : bytes) {
            std::cout << colors[0] << colors[1] << std::hex << std::setw(2)
                      << std::setfill('0') << unsigned(byte) << ansi::reset();
            if (--i > 0)
                std::cout.put(' ');
        }
        std::cout << std::dec << std::setw(0) << std::setfill(' ');
    }

    static void print_ascii(const std::vector <uint8_t>& bytes)
    {
        static const std::array<std::string, 2> colors = {
            ansi::color(ansi::colors::white),
            ansi::color(ansi::colors::blue, false, false)
        };
        std::cout << colors[0] << colors[1];
        for (const auto& byte : bytes) {
            if (std::isprint(byte) && byte != '\n')
                std::cout.put(char(byte));
            else
                std::cout << '.';
        }
        std::cout << ansi::reset();
    }

    static const std::array<std::string, 2> error_colors = {
        ansi::color(ansi::colors::red),
        ansi::color(ansi::colors::black, false, false)
    };

    static unsigned long read_bytes(std::vector<uint8_t>& bytes,
              unsigned long count, std::ifstream& file, const std::string& path)
    {
        unsigned long i;
        uint8_t byte;
        for (i = 0; (i < count); ++i) {
            byte = (uint8_t)file.get();
            if (file.bad()) {
                std::stringstream sstream;
                sstream << error_colors[0] << error_colors[1]
                        << "Read error in file \"" << path << "\"";
                throw std::runtime_error(sstream.str().c_str());
            } else if (file.eof()) {
                break;
            } else {
                bytes[i] = byte;
            }
        }
        return i;
    }

    static int viewhex(std::ifstream& file, const std::string& path)
    {
        static const unsigned long bytes_per_line = 16;
        unsigned long offset = 0;
        while (true) {
            std::vector<uint8_t> bytes(bytes_per_line);
            print_offset(offset);
            std::cout << "  ";
            offset += read_bytes(bytes, bytes_per_line, file, path);
            print_hex(bytes);
            std::cout << "  ";
            print_ascii(bytes);
            std::cout.put('\n');
            if (file.eof())
                break;
        }
        std::cout << "Above file: " << path << std::endl;
        return 0;
    }

    static int viewhex(const std::string& path)
    {
        std::ifstream file(path.c_str());
        if (!(file.is_open())) {
            std::stringstream sstream;
            sstream << error_colors[0] << error_colors[1]
                    << "Error opening file \"" << path << "\"";
            throw std::runtime_error(sstream.str().c_str());
        }
        int ret = viewhex(file, path);
        file.close();
        return ret;
    }
}

int main (int argc, char* argv[])
{
    int i;
    if (argc < 2) {
        std::cerr << ansi::color(ansi::colors::red) << "Usage: " << argv[0]
                  << " [file [file 2 [... [file n]]]]" << ansi::reset()
                  << std::endl;
        std::exit(EXIT_FAILURE);
    }
    for (i = 1; i < argc; ++i)
        hexview::viewhex(argv[i]);
    return 0;
}