hexstr.hpp

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//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012- OpenVPN Inc.
//
//    SPDX-License-Identifier: MPL-2.0 OR AGPL-3.0-only WITH openvpn3-openssl-exception
//
 
// A collection of functions for rendering and parsing hexadecimal strings
 
#ifndef OPENVPN_COMMON_HEXSTR_H
#define OPENVPN_COMMON_HEXSTR_H
 
#include <string>
#include <iomanip>
#include <sstream>
#include <algorithm>
 
#include <openvpn/common/clamp_typerange.hpp>
#include <openvpn/common/exception.hpp>
#include <openvpn/common/string.hpp>
 
using namespace openvpn::numeric_util;
 
namespace openvpn {
 
inline char render_hex_char(const int c, const bool caps = false)
{
    if (c < 0)
        return '?';
    if (c < 10)
        return '0' + static_cast<char>(c);
    if (c < 16)
        return static_cast<char>((caps ? 'A' : 'a') - 10 + c);
    return '?';
}
 
inline int parse_hex_char(const int c)
{
    if (c >= '0' && c <= '9')
        return c - '0';
    if (c >= 'a' && c <= 'f')
        return c - 'a' + 10;
    if (c >= 'A' && c <= 'F')
        return c - 'A' + 10;
    return -1;
}
 
 
class RenderHexByte
{
  public:
    RenderHexByte(const unsigned char byte, const bool caps = false)
    {
        c[0] = render_hex_char(byte >> 4, caps);
        c[1] = render_hex_char(byte & 0x0F, caps);
    }
 
    char char1() const
    {
        return c[0];
    }
    char char2() const
    {
        return c[1];
    }
 
    const char *str2() const
    {
        return c;
    } // Note: length=2, NOT null terminated
 
  private:
    char c[2];
};
 
 
inline std::string render_hex(const unsigned char *data, size_t size, const bool caps = false)
{
    if (!data)
        return "NULL";
    std::string ret;
    ret.reserve(size * 2 + 1);
    while (size--)
    {
        const RenderHexByte b(*data++, caps);
        ret += b.char1();
        ret += b.char2();
    }
    return ret;
}
 
 
inline std::string render_hex(const void *data, const size_t size, const bool caps = false)
{
    return render_hex((const unsigned char *)data, size, caps);
}
 
 
inline std::string render_hex_sep(const unsigned char *data, size_t size, const char sep, const bool caps = false)
{
    if (!data)
        return "NULL";
    std::string ret;
    ret.reserve(size * 3);
    bool prsep = false;
    while (size--)
    {
        if (prsep)
            ret += sep;
        const RenderHexByte b(*data++, caps);
        ret += b.char1();
        ret += b.char2();
        prsep = true;
    }
    return ret;
}
 
inline std::string render_hex_sep(const void *data, const size_t size, const char sep, const bool caps = false)
{
    return render_hex_sep((const unsigned char *)data, size, sep, caps);
}
 
 
template <typename V>
inline std::string render_hex_generic(const V &data, const bool caps = false)
{
    std::string ret;
    ret.reserve(data.size() * 2 + 1);
    for (size_t i = 0; i < data.size(); ++i)
    {
        const RenderHexByte b(data[i], caps);
        ret += b.char1();
        ret += b.char2();
    }
    return ret;
}
 
 
inline std::string dump_hex(const unsigned char *data, size_t size)
{
    if (!data)
        return "NULL\n";
    const unsigned int mask = 0x0F; // N bytes per line - 1
    std::ostringstream os;
    os << std::hex;
    std::string chars;
    size_t i;
    for (i = 0; i < size; ++i)
    {
        if (!(i & mask))
        {
            if (i)
            {
                os << "  " << chars << '\n';
                chars.clear();
            }
            os << std::setfill(' ') << std::setw(8) << i << ":";
        }
        const unsigned char c = data[i];
        os << ' ' << std::setfill('0') << std::setw(2) << (unsigned int)c;
        if (string::is_printable(c))
            chars += c;
        else
            chars += '.';
    }
    if (i)
        os << string::spaces(clamp_to_typerange<int>(2 + (((i - 1) & mask) ^ mask) * 3)) << chars << '\n';
    return os.str();
}
 
inline std::string dump_hex(void *data, size_t size)
{
    return dump_hex((const unsigned char *)data, size);
}
 
inline std::string dump_hex(const std::string &str)
{
    return dump_hex((const unsigned char *)str.c_str(), str.length());
}
 
 
template <typename V>
inline std::string dump_hex(const V &data)
{
    return dump_hex(data.c_data(), data.size());
}
 
OPENVPN_SIMPLE_EXCEPTION(parse_hex_error);
 
 
template <typename V>
inline void parse_hex(V &dest, const std::string &str)
{
    using vvalue_t = typename V::value_type;
    const int len = int(str.length());
    int i;
    for (i = 0; i <= len - 2; i += 2)
    {
        const int high = parse_hex_char(str[i]);
        const int low = parse_hex_char(str[i + 1]);
        if (high == -1 || low == -1)
            throw parse_hex_error();
        dest.push_back(static_cast<vvalue_t>((high << 4) + low));
    }
    if (i != len)
        throw parse_hex_error(); // straggler char
}
 
 
template <typename T>
inline bool parse_hex_number(const char *str, T &retval)
{
    if (!str[0])
        return false; // empty string
    size_t i = 0;
    T ret = T(0);
    while (true)
    {
        const char c = str[i++];
        const int hd = parse_hex_char(c);
        if (hd >= 0)
        {
            ret *= T(16);
            ret += T(hd);
        }
        else if (!c)
        {
            retval = ret;
            return true;
        }
        else
            return false; // non-hex-digit
    }
}
 
 
template <typename T>
inline bool parse_hex_number(const std::string &str, T &retval)
{
    return parse_hex_number(str.c_str(), retval);
}
 
 
template <typename T>
inline T parse_hex_number(const std::string &str)
{
    T ret;
    if (!parse_hex_number<T>(str.c_str(), ret))
        throw parse_hex_error();
    return ret;
}
 
template <typename T>
std::string render_hex_number(T value, const bool caps = false)
{
    unsigned char buf[sizeof(T)];
    for (size_t i = sizeof(T); i-- > 0;)
    {
        buf[i] = value & 0xFF;
        value >>= 8;
    }
    return render_hex(buf, sizeof(T), caps);
}
 
 
inline std::string render_hex_number(unsigned char uc, const bool caps = false)
{
    RenderHexByte b(uc, caps);
    return std::string(b.str2(), 2);
}
 
} // namespace openvpn
 
#endif // OPENVPN_COMMON_HEXSTR_H