将大的十六进制字符串转换为十进制字符串

Question

我需要将一个大的（对于内置数据类型来说太大）十六进制字符串转换为十进制表示的字符串。例如：

std::string sHex = "07AA17C660F3DD1D2A1B48F1B746C148";
std::string sDec; // should end up with: "10187768649047767717933300899576725832"

我目前正在使用c++ BigInt Class，它提供了一种非常简单的方法来实现这一点（但仅限 GPL）：

BigInt::Vin vbiTemp(sHex, 16);
sDec = vbiTemp.toStrDec();

是否有简单的方法可以在没有 3rd 方算术库的情况下进行这种转换？或者您能推荐一个具有类似简单性（效率无关紧要）的免费（非 GPL）替代方案吗？

Answer 1

好的，这是一个通用的基本转换器类。我用 C# 编写了原始实现，现在将其转换为 C++。它的 .NET 起源可能仍然闪耀。随意使用它。

你可以这样使用它：

const BaseConverter& hex2dec = BaseConverter::HexToDecimalConverter();
std::cout << hex2dec.Convert("07AA17C660F3DD1D2A1B48F1B746C148");

输出将是：

10187768649047767717933300899576725832

该类不限于十六进制数字，而是可以使用任何基数编码在任何基数之间进行转换。

API

• <strong>BaseConverter::BaseConverter</strong>(const std::string&amp; sourceBaseSet, const std::string&amp; targetBaseSet);

  构造一个新的 BaseConverter 实例。该类在 source 数字基数中表示的数字之间转换为 target 数字基数。

  构造函数采用两个 string 参数来指定用于源和目标数字基数的符号。字符串中的第一个字符的值为 0，第二个字符的值为 1，以此类推。示例：八进制数字基数的符号通常为 "01234567"，十六进制符号为 "0123456789ABCDEF"。任何可打印的 ASCII 字符都可以用作符号，因此您可以例如。对二进制系统使用"OI"（而不是"01"）。

  注意：基本符号区分大小写，因此符号"0123456789abcdef" 将不解码使用大写字符的十六进制数字。

• std::string <strong>BaseConverter::Convert</strong>(std::string value) const;
std::string <strong>BaseConverter::Convert</strong>(const std::string&amp; value, size_t minDigits) const;

  将源数字基数中的数字value 转换为目标数字基数并返回结果。第二个重载需要一个附加参数minDigits 来指定结果中的最小位数。返回的值将通过在目标数字基数中添加零个或多个具有值 0 的符号来填充。

• std::string <strong>BaseConverter::FromDecimal</strong>(unsigned int value) const;
std::string <strong>BaseConverter::FromDecimal</strong>(unsigned int value, size_t minDigits) const;
  

  将 unsigned int 十进制数转换为目标数基数。

• unsigned int <strong>BaseConverter::ToDecimal</strong>(std::string value) const;

  将源数字系统中的数字转换为十进制无符号整数。 注意：如果源基系统中数字的十进制值超过UINT_MAX，结果会出错。

• static const BaseConverter&amp; <strong>BaseConverter::DecimalToBinaryConverter</strong>();
static const BaseConverter&amp; <strong>BaseConverter::BinaryToDecimalConverter</strong>();
static const BaseConverter&amp; <strong>BaseConverter::DecimalToHexConverter</strong>();
static const BaseConverter&amp; <strong>BaseConverter::HexToDecimalConverter</strong>();
  

  返回BaseConverter 实例的便利函数适合在常用数字基数之间进行转换。 注意：大写字符 A - F 用于十六进制数基数。

BaseConverter.h：

// Arbitrary precision base conversion by Daniel Gehriger <gehriger@linkcad.com>   

#include <string>

class BaseConverter
{
public:
    std::string GetSourceBaseSet() const { return sourceBaseSet_; }
    std::string GetTargetBaseSet() const { return targetBaseSet_; }
    unsigned int GetSourceBase() const { return (unsigned int)sourceBaseSet_.length(); }
    unsigned int GetTargetBase() const { return (unsigned int)targetBaseSet_.length(); }

    /// <summary>
    /// Constructor
    /// </summary>
    /// <param name="sourceBaseSet">Characters used for source base</param>
    /// <param name="targetBaseSet">Characters used for target base</param>
    BaseConverter(const std::string& sourceBaseSet, const std::string& targetBaseSet);

    /// <summary>
    /// Get a base converter for decimal to binary numbers
    /// </summary>
    static const BaseConverter& DecimalToBinaryConverter();

    /// <summary>
    /// Get a base converter for binary to decimal numbers
    /// </summary>
    static const BaseConverter& BinaryToDecimalConverter();

    /// <summary>
    /// Get a base converter for decimal to binary numbers
    /// </summary>
    static const BaseConverter& DecimalToHexConverter();

    /// <summary>
    /// Get a base converter for binary to decimal numbers
    /// </summary>
    static const BaseConverter& HexToDecimalConverter();

    /// <summary>
    /// Convert a value in the source number base to the target number base.
    /// </summary>
    /// <param name="value">Value in source number base.</param>
    /// <returns>Value in target number base.</returns>
    std::string  Convert(std::string value) const;


    /// <summary>
    /// Convert a value in the source number base to the target number base.
    /// </summary>
    /// <param name="value">Value in source number base.</param>
    /// <param name="minDigits">Minimum number of digits for returned value.</param>
    /// <returns>Value in target number base.</returns>
    std::string Convert(const std::string& value, size_t minDigits) const;

    /// <summary>
    /// Convert a decimal value to the target base.
    /// </summary>
    /// <param name="value">Decimal value.</param>
    /// <returns>Result in target base.</returns>
    std::string FromDecimal(unsigned int value) const;

    /// <summary>
    /// Convert a decimal value to the target base.
    /// </summary>
    /// <param name="value">Decimal value.</param>
    /// <param name="minDigits">Minimum number of digits for returned value.</param>
    /// <returns>Result in target base.</returns>
    std::string FromDecimal(unsigned int value, size_t minDigits) const;

    /// <summary>
    /// Convert value in source base to decimal.
    /// </summary>
    /// <param name="value">Value in source base.</param>
    /// <returns>Decimal value.</returns>
    unsigned int ToDecimal(std::string value) const;

private:
    /// <summary>
    /// Divides x by y, and returns the quotient and remainder.
    /// </summary>
    /// <param name="baseDigits">Base digits for x and quotient.</param>
    /// <param name="x">Numerator expressed in base digits; contains quotient, expressed in base digits, upon return.</param>
    /// <param name="y">Denominator</param>
    /// <returns>Remainder of x / y.</returns>
    static unsigned int divide(const std::string& baseDigits, 
                               std::string& x, 
                               unsigned int y);

    static unsigned int base2dec(const std::string& baseDigits,
                                 const std::string& value);

    static std::string dec2base(const std::string& baseDigits, unsigned int value);

private:
    static const char*  binarySet_;
    static const char*  decimalSet_;
    static const char*  hexSet_;
    std::string         sourceBaseSet_;
    std::string         targetBaseSet_;
};

BaseConverter.cpp:

// Arbitrary precision base conversion by Daniel Gehriger <gehriger@linkcad.com>   

#include "BaseConverter.h"
#include <stdexcept>
#include <algorithm>


const char* BaseConverter::binarySet_ = "01";
const char* BaseConverter::decimalSet_ = "0123456789";
const char* BaseConverter::hexSet_ = "0123456789ABCDEF";

BaseConverter::BaseConverter(const std::string& sourceBaseSet, const std::string& targetBaseSet) 
    : sourceBaseSet_(sourceBaseSet)
    , targetBaseSet_(targetBaseSet)
{
    if (sourceBaseSet.empty() || targetBaseSet.empty())
        throw std::invalid_argument("Invalid base character set");
}

const BaseConverter& BaseConverter::DecimalToBinaryConverter()
{
    static const BaseConverter dec2bin(decimalSet_, binarySet_);
    return dec2bin;
}

const BaseConverter& BaseConverter::BinaryToDecimalConverter()
{
    static const BaseConverter bin2dec(binarySet_, decimalSet_);
    return bin2dec;
}

const BaseConverter& BaseConverter::DecimalToHexConverter()
{
    static const BaseConverter dec2hex(decimalSet_, hexSet_);
    return dec2hex;
}

const BaseConverter& BaseConverter::HexToDecimalConverter()
{
    static const BaseConverter hex2dec(hexSet_, decimalSet_);
    return hex2dec;
}

std::string BaseConverter::Convert(std::string value) const
{
    unsigned int numberBase = GetTargetBase();
    std::string result;

    do
    {
        unsigned int remainder = divide(sourceBaseSet_, value, numberBase);
        result.push_back(targetBaseSet_[remainder]);
    }
    while (!value.empty() && !(value.length() == 1 && value[0] == sourceBaseSet_[0]));

    std::reverse(result.begin(), result.end());
    return result;
}

std::string BaseConverter::Convert(const std::string& value, size_t minDigits) const
{
    std::string result = Convert(value);
    if (result.length() < minDigits)
        return std::string(minDigits - result.length(), targetBaseSet_[0]) + result;
    else
        return result;
}

std::string BaseConverter::FromDecimal(unsigned int value) const
{
    return dec2base(targetBaseSet_, value);
}

std::string BaseConverter::FromDecimal(unsigned int value, size_t minDigits) const
{
    std::string result = FromDecimal(value);
    if (result.length() < minDigits)
        return std::string(minDigits - result.length(), targetBaseSet_[0]) + result;
    else
        return result;
}

unsigned int BaseConverter::ToDecimal(std::string value) const
{
    return base2dec(sourceBaseSet_, value);
}

unsigned int BaseConverter::divide(const std::string& baseDigits, std::string& x, unsigned int y)
{
    std::string quotient;

    size_t lenght = x.length();
    for (size_t i = 0; i < lenght; ++i)
    {
        size_t j = i + 1 + x.length() - lenght;
        if (x.length() < j)
            break;

        unsigned int value = base2dec(baseDigits, x.substr(0, j));

        quotient.push_back(baseDigits[value / y]);
        x = dec2base(baseDigits, value % y) + x.substr(j);
    }

    // calculate remainder
    unsigned int remainder = base2dec(baseDigits, x);

    // remove leading "zeros" from quotient and store in 'x'
    size_t n = quotient.find_first_not_of(baseDigits[0]);
    if (n != std::string::npos)
    {
        x = quotient.substr(n);
    }
    else
    {
        x.clear();
    }

    return remainder;
}

std::string BaseConverter::dec2base(const std::string& baseDigits, unsigned int value)
{
    unsigned int numberBase = (unsigned int)baseDigits.length();
    std::string result;
    do 
    {
        result.push_back(baseDigits[value % numberBase]);
        value /= numberBase;
    } 
    while (value > 0);

    std::reverse(result.begin(), result.end());
    return result;
}

unsigned int BaseConverter::base2dec(const std::string& baseDigits, const std::string& value)
{
    unsigned int numberBase = (unsigned int)baseDigits.length();
    unsigned int result = 0;
    for (size_t i = 0; i < value.length(); ++i)
    {
        result *= numberBase;
        int c = baseDigits.find(value[i]);
        if (c == std::string::npos)
            throw std::runtime_error("Invalid character");

        result += (unsigned int)c;
    }

    return result;
}

Answer 2

您可以使用此函数将十六进制字符转换为十进制字符：

void Hex2Char(const char* szHex, unsigned char& rch)
{
    rch = 0;
    for(int i=0; i<2; i++)
    {
        if(*(szHex + i) >='0' && *(szHex + i) <= '9')
            rch = (rch << 4) + (*(szHex + i) - '0');
        else if(*(szHex + i) >='A' && *(szHex + i) <= 'F')
            rch = (rch << 4) + (*(szHex + i) - 'A' + 10);
        else
            break;
    }
}    

你可以用它来转换字符串：

void HexStrToCharStr(const char* hexStr, unsigned char* decStr, int n)
{
    unsigned char d_ch;
    for(int i=0; i<n; i++)
    {
        Hex2Char(hexStr+2*i, d_ch);
        decStr[i] = d_ch;
    }
}

Answer 3

std::istringstream (sHex) >> std::hex >> sDec;