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C ++が文字列を16進数に、またはその逆に変換します

C++で文字列を16進数に、またはその逆に変換する最良の方法は何ですか？

例：

  • "Hello World"から16進形式への変換のような文字列：48656C6C6F20576F726C64
  • 16進数48656C6C6F20576F726C64から文字列："Hello World"
c++stringhex
56
Sebtm

「Hello World」のような16進形式の文字列：48656C6C6F20576F726C64。

ああ、ここに行きます：

#include <string>

std::string string_to_hex(const std::string& input)
{
    static const char* const lut = "0123456789ABCDEF";
    size_t len = input.length();

    std::string output;
    output.reserve(2 * len);
    for (size_t i = 0; i < len; ++i)
    {
        const unsigned char c = input[i];
        output.Push_back(lut[c >> 4]);
        output.Push_back(lut[c & 15]);
    }
    return output;
}

#include <algorithm>
#include <stdexcept>

std::string hex_to_string(const std::string& input)
{
    static const char* const lut = "0123456789ABCDEF";
    size_t len = input.length();
    if (len & 1) throw std::invalid_argument("odd length");

    std::string output;
    output.reserve(len / 2);
    for (size_t i = 0; i < len; i += 2)
    {
        char a = input[i];
        const char* p = std::lower_bound(lut, lut + 16, a);
        if (*p != a) throw std::invalid_argument("not a hex digit");

        char b = input[i + 1];
        const char* q = std::lower_bound(lut, lut + 16, b);
        if (*q != b) throw std::invalid_argument("not a hex digit");

        output.Push_back(((p - lut) << 4) | (q - lut));
    }
    return output;
}

（これは、charが8ビットであると想定しているため、あまり移植性がありませんが、ここから取得できます。）

74
fredoverflow
string ToHex(const string& s, bool upper_case /* = true */)
{
    ostringstream ret;

    for (string::size_type i = 0; i < s.length(); ++i)
        ret << std::hex << std::setfill('0') << std::setw(2) << (upper_case ? std::uppercase : std::nouppercase) << (int)s[i];

    return ret.str();
}

int FromHex(const string &s) { return strtoul(s.c_str(), NULL, 16); }
27
Krevan

これを試すことができます。それは働いています...

#include <algorithm>
#include <sstream>
#include <iostream>
#include <iterator>
#include <iomanip>

namespace {
   const std::string test="hello world";
}

int main() {
   std::ostringstream result;
   result << std::setw(2) << std::setfill('0') << std::hex << std::uppercase;
   std::copy(test.begin(), test.end(), std::ostream_iterator<unsigned int>(result, " "));
   std::cout << test << ":" << result.str() << std::endl;
}
10
Mahmut EFE

ルックアップテーブルなどを使用しても機能しますが、やり過ぎです。文字列を16進数に、16進数を文字列に戻す非常に簡単な方法を次に示します。

#include <stdexcept>
#include <sstream>
#include <iomanip>
#include <string>
#include <cstdint>

std::string string_to_hex(const std::string& in) {
    std::stringstream ss;

    ss << std::hex << std::setfill('0');
    for (size_t i = 0; in.length() > i; ++i) {
        ss << std::setw(2) << static_cast<unsigned int>(static_cast<unsigned char>(in[i]));
    }

    return ss.str(); 
}

std::string hex_to_string(const std::string& in) {
    std::string output;

    if ((in.length() % 2) != 0) {
        throw std::runtime_error("String is not valid length ...");
    }

    size_t cnt = in.length() / 2;

    for (size_t i = 0; cnt > i; ++i) {
        uint32_t s = 0;
        std::stringstream ss;
        ss << std::hex << in.substr(i * 2, 2);
        ss >> s;

        output.Push_back(static_cast<unsigned char>(s));
    }

    return output;
}
9
X-Istence

標準ライブラリを使用した最も簡単な例。

#include <iostream>
using namespace std;

int main()
{
  char c = 'n';
  cout << "HEX " << hex << (int)c << endl;  // output in hexadecimal
  cout << "ASC" << c << endl; // output in ascii
  return 0;
}

出力を確認するには、 codepad が返されます：6e

また、オンラインの ascii-to-hexadecimal変換ツール でも6eが生成されます。それで動作します。

これも行うことができます：

template<class T> std::string toHexString(const T& value, int width) {
    std::ostringstream oss;
    oss << hex;
    if (width > 0) {
        oss << setw(width) << setfill('0');
    }
    oss << value;
    return oss.str();
}
8
user195488

もっとシンプルでエレガントなソリューションがあると思います。上記のメソッドの中には、場合によっては未処理の例外をスローするものもあります。絶対に間違いないように、非常に高速なコードをご紹介します。試してみて、速度とコンパクトさの点で結果を比較してください。

#include <string>

// Convert string of chars to its representative string of hex numbers
void stream2hex(const std::string str, std::string& hexstr, bool capital = false)
{
    hexstr.resize(str.size() * 2);
    const size_t a = capital ? 'A' - 1 : 'a' - 1;

    for (size_t i = 0, c = str[0] & 0xFF; i < hexstr.size(); c = str[i / 2] & 0xFF)
    {
        hexstr[i++] = c > 0x9F ? (c / 16 - 9) | a : c / 16 | '0';
        hexstr[i++] = (c & 0xF) > 9 ? (c % 16 - 9) | a : c % 16 | '0';
    }
}

// Convert string of hex numbers to its equivalent char-stream
void hex2stream(const std::string hexstr, std::string& str)
{
    str.resize((hexstr.size() + 1) / 2);

    for (size_t i = 0, j = 0; i < str.size(); i++, j++)
    {
        str[i] = (hexstr[j] & '@' ? hexstr[j] + 9 : hexstr[j]) << 4, j++;
        str[i] |= (hexstr[j] & '@' ? hexstr[j] + 9 : hexstr[j]) & 0xF;
    }
}

コードをテストする ：

#include <iostream>
int main()
{
    std::string s = "Hello World!";
    std::cout << "original string: " << s << '\n';
    stream2hex(s, s);
    std::cout << "hex format: " << s << '\n';
    hex2stream(s, s);
    std::cout << "original one: " << s << '\n';
}

結果は次のとおりです。

original string: Hello World!
hex format: 48656C6C6F20576F726C6421
original one: Hello World!
7
polfosol ఠ_ఠ

これは少し高速です：

static const char* s_hexTable[256] = 
{
    "00", "01", "02", "03", "04", "05", "06", "07", "08", "09", "0a", "0b", "0c", "0d", "0e", "0f", "10", "11",
    "12", "13", "14", "15", "16", "17", "18", "19", "1a", "1b", "1c", "1d", "1e", "1f", "20", "21", "22", "23",
    "24", "25", "26", "27", "28", "29", "2a", "2b", "2c", "2d", "2e", "2f", "30", "31", "32", "33", "34", "35",
    "36", "37", "38", "39", "3a", "3b", "3c", "3d", "3e", "3f", "40", "41", "42", "43", "44", "45", "46", "47",
    "48", "49", "4a", "4b", "4c", "4d", "4e", "4f", "50", "51", "52", "53", "54", "55", "56", "57", "58", "59",
    "5a", "5b", "5c", "5d", "5e", "5f", "60", "61", "62", "63", "64", "65", "66", "67", "68", "69", "6a", "6b",
    "6c", "6d", "6e", "6f", "70", "71", "72", "73", "74", "75", "76", "77", "78", "79", "7a", "7b", "7c", "7d",
    "7e", "7f", "80", "81", "82", "83", "84", "85", "86", "87", "88", "89", "8a", "8b", "8c", "8d", "8e", "8f",
    "90", "91", "92", "93", "94", "95", "96", "97", "98", "99", "9a", "9b", "9c", "9d", "9e", "9f", "a0", "a1",
    "a2", "a3", "a4", "a5", "a6", "a7", "a8", "a9", "aa", "ab", "ac", "ad", "ae", "af", "b0", "b1", "b2", "b3",
    "b4", "b5", "b6", "b7", "b8", "b9", "ba", "bb", "bc", "bd", "be", "bf", "c0", "c1", "c2", "c3", "c4", "c5",
    "c6", "c7", "c8", "c9", "ca", "cb", "cc", "cd", "ce", "cf", "d0", "d1", "d2", "d3", "d4", "d5", "d6", "d7",
    "d8", "d9", "da", "db", "dc", "dd", "de", "df", "e0", "e1", "e2", "e3", "e4", "e5", "e6", "e7", "e8", "e9",
    "ea", "eb", "ec", "ed", "ee", "ef", "f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7", "f8", "f9", "fa", "fb",
    "fc", "fd", "fe", "ff"
};

// Convert binary data sequence [beginIt, endIt) to hexadecimal string
void dataToHexString(const uint8_t*const beginIt, const uint8_t*const endIt, string& str)
{
    str.clear();
    str.reserve((endIt - beginIt) * 2);
    for(const uint8_t* it(beginIt); it != endIt; ++it)
    {
        str += s_hexTable[*it];
    }
}
6
Erik Hvatum

C++ 17以降、 std :: from_chars もあります。次の関数は、16進数の文字列を受け取り、Tのベクトルを返します。

#include <charconv>

template<typename T>
std::vector<T> hexstr_to_vec(const std::string& str, unsigned char chars_per_num = 2)
{
  std::vector<T> out(str.size() / chars_per_num, 0);

  T value;
  for (int i = 0; i < str.size() / chars_per_num; i++) {
    std::from_chars<T>(
      str.data() + (i * chars_per_num),
      str.data() + (i * chars_per_num) + chars_per_num,
      value,
      16
    );
    out[i] = value;
  }

  return out;
}
4
Nico

これにより、Hello Worldが48656c6c6f20576f726c64に変換され、print itになります。

#include <iostream>
#include <cstring>

using namespace std;

int main()
{
    char hello[20]="Hello World";

    for(unsigned int i=0; i<strlen(hello); i++)
        cout << hex << (int) hello[i];
    return 0;
}
2
Dilushan

これにより、「Hello World」が「48656c6c6f20576f726c64」に変換され、この16進値がstr1に格納され、「48656c6c6f20576f726c64」が「Hello World」に変換されます。

#include <iostream>
#include<sstream>

using namespace std;
int hexCharToInt(char);
string hexToString(string);
int main()
{
    std::string str;
    std::stringstream str1;

    str="Hello World";
    for(int i=0;i<str.length();i++){
        str1 << std::hex << (int)str.at(i);
    }
    std::cout << str1.str() <<"\n";
    string test = "48656c6c6f20576f726c64";
    std::cout << hexToString(test) <<"\n";
    return 0;
}
string hexToString(string str){
    std::stringstream HexString;
    for(int i=0;i<str.length();i++){
        char a = str.at(i++);
        char b = str.at(i);
        int x = hexCharToInt(a);
        int y = hexCharToInt(b);
        HexString << (char)((16*x)+y);
    }
    return HexString.str();
}

int hexCharToInt(char a){
    if(a>='0' && a<='9')
        return(a-48);
    else if(a>='A' && a<='Z')
        return(a-55);
    else
        return(a-87);
}
1
Anshul Jain

なぜ誰もsprintfを使用していないのですか？

#include <string>
#include <stdio.h>

static const std::string str = "hello world!";

int main()
{
  //copy the data from the string to a char array
  char *strarr = new char[str.size()+1];
  strarr[str.size()+1] = 0; //set the null terminator
  memcpy(strarr, str.c_str(),str.size()); //memory copy to the char array

  printf(strarr);
  printf("\n\nHEX: ");

  //now print the data
  for(int i = 0; i < str.size()+1; i++)
  {
    char x = strarr[i];
    sprintf("%x ", reinterpret_cast<const char*>(x));
  }

  //DO NOT FORGET TO DELETE
  delete(strarr);

  return 0;
}
0
Alexander Frankland

主に@fredoverflowによるものに触発された別のソリューションがあります。

/**
 * Return hexadecimal representation of the input binary sequence
 */
std::string hexitize(const std::vector<char>& input, const char* const digits = "0123456789ABCDEF")
{
    std::ostringstream output;

    for (unsigned char gap = 0, beg = input[gap]; gap < input.length(); beg = input[++gap])
        output << digits[beg >> 4] << digits[beg & 15];

    return output.str();
}

長さは目的の必須パラメーターでした

0
psychoslave