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具有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 类，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();
有没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？或者你能推荐一个类似简单的免费（非 GPL）替代品（效率无关紧要）吗？
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。您可以随意使用它。
你可以像这样使用它：
const BaseConverter& hex2dec = BaseConverter::HexToDecimalConverter();
std::cout << hex2dec.Convert("07AA17C660F3DD1D2A1B48F1B746C148");
输出将是：
10187768649047767717933300899576725832
该类不仅限于十六进制数字，还可以使用任何基数编码在任何基数之间进行转换。
BaseConverter::BaseConverter(const std::string& sourceBaseSet, const std::string& targetBaseSet);
构造一个新的 BaseConverter 实例。该类在源数字基数中表示的数字之间转换为目标数字基数。
构造函数采用两个字符串参数来指定要用于源数字基数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，依此类推。示例：八进制数基数的符号通常是"01234567", 和十六进制"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，因此这些符号"0123456789abcdef"不会使用大写字符解码十六进制数字。
std::string BaseConverter::Convert(std::string value) const;
std::string BaseConverter::Convert(const std::string& value, size_t minDigits) const;
将value源数字基数中的数字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值为0的符号来填充。
std::string BaseConverter::FromDecimal(unsigned int value) const;
std::string BaseConverter::FromDecimal(unsigned int value, size_t minDigits) const;
将unsigned int十进制数转换为目标数字基数。
unsigned int BaseConverter::ToDecimal(std::string value) const;
将源数字系统中的数字转换为十进制unsigned int。注意：如果源基础系统中数字的十进制值超过 UINT_MAX，结果将是错误的。
static const BaseConverter& BaseConverter::DecimalToBinaryConverter();
static const BaseConverter& BaseConverter::BinaryToDecimalConverter();
static const BaseConverter& BaseConverter::DecimalToHexConverter();
static const BaseConverter& BaseConverter::HexToDecimalConverter();
BaseConverter便利函数返回适合在常用数字基数之间转换的实例。注意：大写字符 A - F 用于十六进制数基数。
// 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_;
};
// 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;
}
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;
}
}
比您可以使用它来转换字符串：
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;
}
}
std::istringstream (sHex ) >> std::hex >> sDec;