在C++中,将字符串转换为十六进制以及将十六进制转换为字符串的最佳方法是什么?
例如:
- 将类似于
"Hello World"
的字符串转换为十六进制格式:48656C6C6F20576F726C64
- 并将十六进制
48656C6C6F20576F726C64
转换为字符串:"Hello World"
在C++中,将字符串转换为十六进制以及将十六进制转换为字符串的最佳方法是什么?
例如:
"Hello World"
的字符串转换为十六进制格式:48656C6C6F20576F726C64
48656C6C6F20576F726C64
转换为字符串:"Hello World"
将类似于“Hello World”的字符串转换为十六进制格式:48656C6C6F20576F726C64。
好的,这里是:
#include <string>
std::string string_to_hex(const std::string& input)
{
static const char hex_digits[] = "0123456789ABCDEF";
std::string output;
output.reserve(input.length() * 2);
for (unsigned char c : input)
{
output.push_back(hex_digits[c >> 4]);
output.push_back(hex_digits[c & 15]);
}
return output;
}
#include <stdexcept>
int hex_value(unsigned char hex_digit)
{
static const signed char hex_values[256] = {
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1,
-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
};
int value = hex_values[hex_digit];
if (value == -1) throw std::invalid_argument("invalid hex digit");
return value;
}
std::string hex_to_string(const std::string& input)
{
const auto len = input.length();
if (len & 1) throw std::invalid_argument("odd length");
std::string output;
output.reserve(len / 2);
for (auto it = input.begin(); it != input.end(); )
{
int hi = hex_value(*it++);
int lo = hex_value(*it++);
output.push_back(hi << 4 | lo);
}
return output;
}
(这里假设一个char占8位,因此这种方法不太具有可移植性,但你可以从这里开始。)
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); }
istringstream
来实现第二个功能——因为strtoul
不是标准库函数。 - Billy ONeal(int)(unsigned char)
来代替特定平台的UINT8
。 - slawekwin使用查找表等方法虽然可行,但有些复杂。下面是一些非常简单的将字符串转换为十六进制和将十六进制转回字符串的方法:
#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;
}
uint32_t
- 必须添加 <cstdint>
。 - thomthom<< std::setw(2)
都会被重置,所以我必须在for
循环内部使用它。我查阅了文档,发现在许多情况下宽度都会被重置:http://en.cppreference.com/w/cpp/io/manip/setw - thomthomstd::string
构造函数版本(参见https://en.cppreference.com/w/cpp/string/basic_string/basic_string):std::string(const char* s, size_type count);
否则,你的测试字符串将在第一个空字节处被截断:string_to_hex(std::string("\x00\x01", 2)) == "0001" // 正确
,而string_to_hex("\x00\x01") == "" // 你实际上是在向函数输入一个空字符串
。 - muxator从C++17开始,还有std::from_chars。以下函数接受一个十六进制字符的字符串,并返回一个T类型的向量:
#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 (std::size_t 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;
}
我认为有一种更简单、更优雅的解决方案。一些上述方法甚至在某些情况下可能会抛出未处理的异常。这是一个百分之百可靠(永远不会出错)和非常快速的代码。只需尝试一下,比较其速度和紧凑性的结果:
#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;
}
}
测试代码:
#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';
}
结果是:
original string: Hello World!
hex format: 48656C6C6F20576F726C6421
original one: Hello World!
你可以尝试这个。它有效...
#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;
}
fffffff0
的原因了吗?编辑:在下面找到了解决方案:https://dev59.com/_XA75IYBdhLWcg3wSm24#16125797 需要进行双重静态转换。 - thomthom使用标准库的最简单示例。
#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;
}
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();
}
这个稍微快一些:
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];
}
}
#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;
}
/**
* 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();
}
在预期的使用中,长度是必需的参数。