Hex: Difference between revisions

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Many examples come from [http://www.cplusplus.com/ cplusplus.com] and [http://stackoverflow.com stackoverflow.com].
Many examples come from [http://www.cplusplus.com/ cplusplus.com] and [http://stackoverflow.com stackoverflow.com].


= Shell =
== Shell ==
See also [[Linux Commands]].
See also [[Linux Commands]].


== Convert 66 6f 6f → "foo" ==
=== Convert 66 6f 6f → "foo" ===
<source lang="bash">
<source lang="bash">
hexdump -e '"%2x"' <myfile> # Convert myfile into a long hexadecimal string - ! See DOUBLE-QUOTED parameter
hexdump -e '"%2x"' <myfile> # Convert myfile into a long hexadecimal string - ! See DOUBLE-QUOTED parameter
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</source>
</source>


== Convert "foo" &rarr; 66 6f 6f ==
=== Convert "foo" &rarr; 66 6f 6f ===
<source lang="bash">
<source lang="bash">
xxd -g8 -c32 <file> # Output 32 bytes, grouped in 8-byte columns
xxd -g8 -c32 <file> # Output 32 bytes, grouped in 8-byte columns
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</source>
</source>


== hex editors ==
=== hex editors ===
* [http://sourceforge.net/projects/hexered/ hexer]
* [http://sourceforge.net/projects/hexered/ hexer]
* [http://www.physics.ohio-state.edu/~prewett/hexedit/ hexedit] (adapts to width of the terminal!).
* [http://www.physics.ohio-state.edu/~prewett/hexedit/ hexedit] (adapts to width of the terminal!).
* See [[Vim]]
* See [[Vim]]


== hex diffs ==
=== hex diffs ===
<source lang=bash>
<source lang=bash>
diff -u <(hexdump -v -C file1) <(hexdump -v -C file2)
diff -u <(hexdump -v -C file1) <(hexdump -v -C file2)
</source>
</source>


= C / C ++ =
== C / C ++ ==
== Read an integer from an hex string ==
=== Convert an integer to hex string ===
==== C++ ====
This looks simple but is in fact extremelly '''treacherous''' because of persistent iomanip flags:
<source lang="c++">
#include <iostream>
#include <iomanip>

unsigned value = 10;

# 'internal' to make sure we use correct alignment (because 'left' is persistent)
cout << "0x" << setfill('0') << setw(2) << internal << hex << 10 << endl;
</source>

==== C char2hex====
A complete C solution, <code>char2hex</code>:
<source lang="c">
// ############################################################################################################
static uint32_t _char2hex(char *s, const uint8_t data[], size_t data_n, size_t n)
{
uint32_t o = 0;

#define out(f, a ...) { \
o += (uint32_t)snprintf(s + o, n - (uint32_t)o, f, ## a); \
o = o <= n ? o : n; \
}
if (n > 0) {
s[0] = 0;
}
for (size_t i = 0; i < data_n; i++) {
out("%.2x", data[i]);
}

return o;
#undef out
}

/**
* Convert an array of char into a list of hexadecimal values.
* For instance, "\xca\xfe" is converted into "cafe".
*/
char * char2hex(char *s, const uint8_t data[], size_t data_n, size_t n)
{
uint32_t o = _char2hex(s, data, data_n, n);

assert(o < n); // Check if given buffer was big enough

return s;
}
</source>

=== Read an integer from an hex string ===
(See [http://stackoverflow.com/questions/1070497/c-convert-hex-string-to-signed-integer], [http://stackoverflow.com/questions/10324/how-can-i-convert-a-hexadecimal-number-to-base-10-efficiently-in-c]).
(See [http://stackoverflow.com/questions/1070497/c-convert-hex-string-to-signed-integer], [http://stackoverflow.com/questions/10324/how-can-i-convert-a-hexadecimal-number-to-base-10-efficiently-in-c]).
=== Homebrew ===
==== Homebrew ====
<div style="column-width:36em">
<div style="column-width:36em">
<source lang="c">
<source lang="c">
Line 130: Line 180:
</div>
</div>


=== Using atol ===
==== Using atol ====
<source lang="c">
<source lang="c">
/* atol example */
/* atol example */
Line 148: Line 198:
</source>
</source>


=== Using strtol, strtoll ===
==== Using strtol, strtoll ====
<code>strtol</code> (resp. <code>strtoll</code>) returns <tt>LONG_MIN</tt>, <tt>LONG_MAX</tt> (resp. <tt>LLONG_MIN</tt>, <tt>LLONGMAX</tt>) in case of under/overflow.
<code>strtol</code> (resp. <code>strtoll</code>) returns <tt>LONG_MIN</tt>, <tt>LONG_MAX</tt> (resp. <tt>LLONG_MIN</tt>, <tt>LLONGMAX</tt>) in case of under/overflow.


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</div>
</div>


=== Using strtoul, strtoull ===
==== Using strtoul, strtoull ====
Use <code>strtoul</code> (resp. <code>strtoull</code>) when value to read is greater than <code>numeric_limits<long>::max()</code> (resp. <code>numeric_limits<long long>::max()</code>).
Use <code>strtoul</code> (resp. <code>strtoull</code>) when value to read is greater than <code>numeric_limits<long>::max()</code> (resp. <code>numeric_limits<long long>::max()</code>).


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</div>
</div>


=== Using sscanf ===
==== Using sscanf ====
<source lang="c">
<source lang="c">
#include <stdio.h>
#include <stdio.h>
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</source>
</source>


=== Using stringstream ===
==== Using stringstream ====


<source lang="cpp">
<source lang="cpp">
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</source>
</source>


=== The fastest solution ===
==== C - hex2char ====
<source lang="c">
From [https://stackoverflow.com/questions/10324/convert-a-hexadecimal-string-to-an-integer-efficiently-in-c SO]:
// ############################################################################################################
static uint8_t _htoi(char hex)
{
return ((uint8_t)hex >> 6) + (((uint8_t)hex >> 6) << 3) + ((uint8_t)hex & 0x0F);
}

// ############################################################################################################

/** Convert an hex null-terminated string ("cafe") into a byte array ({0xca, 0xfe}).
*
* Convert at most `n` bytes from an hexadecimal null-terminated string into a byte array.
* For instance, it converts "cafe" to {0xca, 0xfe}.
*
* @param[out] dst pointer to destination buffer (at least #n-byte long).
* @param[in] src pointer to source string.
* @param[in] n maximum number of bytes to write in #dst.
*
* @return Number of bytes converted.
*/
uint32_t hex2char(void *dst, const char *src, uint32_t n)
{
uint8_t * p;
uint8_t * _dst = dst;
const char *_src = src;

for (p = _dst; (p < _dst + n) && _src[0] && _src[1]; p++, _src += 2) {
*p = (_htoi(_src[0]) << 4) + _htoi(_src[1]);
}

return p - _dst;
}
</source>

==== C - hex2char - fastest and lowercase/uppercase ====
Inspired from [https://stackoverflow.com/questions/10324/convert-a-hexadecimal-string-to-an-integer-efficiently-in-c SO]:


<source lang="c">
<source lang="c">
// ############################################################################################################
static const long hextable[] = {
// 74ns on i686 (32-bit), vs 150ns for version above
[0 ... 255] = -1, // bit aligned access into this table is considerably
uint32_t hex2char(void *dst, const char *src, uint32_t n)
['0'] = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, // faster for most modern processors,
{
['A'] = 10, 11, 12, 13, 14, 15, // for the space conscious, reduce to
uint8_t * p;
['a'] = 10, 11, 12, 13, 14, 15 // signed char.
uint8_t * _dst = dst;
const char *_src = src;

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Winitializer-overrides"
static const long hextable[] = { // Reduce to signed char for space saving
[0 ... 255] = -1,
['0'] = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
['A'] = 10, 11, 12, 13, 14, 15,
['a'] = 10, 11, 12, 13, 14, 15,
};
};
#pragma clang diagnostic pop


for (p = _dst; (p < _dst + n) && _src[0] && _src[1]; p++) {
/**
*p = hextable[*_src++];
* @brief convert a hexidecimal string to a signed long
*p = (*p << 4) | hextable[*_src++];
* will not produce or process negative numbers except
}
* to signal error.

*
return p - _dst;
* @param hex without decoration, case insensitive.
*
* @return -1 on error, or result (max (sizeof(long)*8)-1 bits)
*/
long hexdec(unsigned const char *hex) {
long ret = 0;
while (*hex && ret >= 0) {
ret = (ret << 4) | hextable[*hex++];
}
return ret;
}
}
</source>
</source>
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;Integer
;Integer
* References [https://stackoverflow.com/questions/21017698/converting-int-to-bytes-in-python-3]


<source lang=python>
<source lang=python>
'4d2' == '%x' % 1234 # to hex
'4d2' == '%x' % 1234 # to hex
'0x4d2' == hex(1234) # to hex (with '0x' prefix)
'0x4d2' == hex(1234) # to hex (with '0x' prefix)
'0x4d2' == '0x%x' % 1234
'0x4d2' == '0x%x' % 1234
'000004d2' == '%08x' % 1234 # to hex (padded)
'000004d2' == '%08x' % 1234 # to hex (padded)
'000004D2' == '%08X' % 1234 # to hex (padded,caps)
'000004D2' == '%08X' % 1234 # to hex (padded,caps)
'\x41' == chr(0x41) # to hex char
'\x41' == chr(0x41) # to hex char
1234 == int('04d2',16) # from hex
b'\x04\xd2'== (1234).to_bytes(2,'big') # to bytes
1234 == int('0x04d2',0) # from hex - base 0, autodetect
b'\xd2\x04'== (1234).to_bytes(2,'little') # to bytes (little endian)
1234 == 0x04d2 # from hex
'04d2' == (1234).to_bytes(2,'big').hex() # to hex
'1234' == '%d' % 0x04d2 # from hex
'd204' == (1234).to_bytes(2,'little').hex() # to hex (little endian)
# Use ((1234).bit_length() + 7)//8 to get length
'0x1234' == '0x%d' % 0x04d2 # from hex (with '0x' prefix)
'0000010011010010' == f"{1234:016b}" # to bin
'10011010010' == f"{1234:11b}" # to bin
'10011010010' == bin(1234)[2:] # to bin
'10011010010' == bin(1234).removeprefix('0b) # to bin
'0b10011010010' == bin(1234) # to bin

1234 == int('04d2',16) # from hex
1234 == int('0x04d2',0) # from hex - base 0, autodetect
1234 == 0x04d2 # from hex
1234 == int.from_bytes(b'\x04\xd2','big') # from hex
1234 == int.from_bytes(b'\xd2\x04','little') # from hex (little endian)
22 == int('10110',2) # from binary

'1234' == '%d' % 0x04d2 # from hex
'0x1234' == '0x%d' % 0x04d2 # from hex (with '0x' prefix)

# Some functions
def int_to_bytes(x: int) -> bytes:
return x.to_bytes((x.bit_length() + 7) // 8, 'big')
def int_from_bytes(xbytes: bytes) -> int:
return int.from_bytes(xbytes, 'big')
</source>
</source>


;Strings
;Strings, arrays or lists - Python 2


<source lang=python>
<source lang=python>
'68656c6c6f' == 'hello'.encode("hex") # Python 2.x -- binary string to hex string -- built-in

import binascii
import binascii
'68656c6c6f' == binascii.b2a_hex('hello') # binary string to hex string -- binascii module
'68656c6c6f' == binascii.hexlify('hello')


'\xde\xad\xbe\xef' == 'deadbeef'.decode("hex") # Python 2.x -- hex string to binary string -- built-in
'deadbeef' == '\xde\xad\xbe\xef'.encode("hex")
'deadbeef' == binascii.b2a_hex('\xde\xad\xbe\xef')
'deadbeef' == binascii.hexlify('\xde\xad\xbe\xef')
'deadbeef' == str(bytearray([0xde,0xad,0xbe,0xef])).encode('hex')
'deadbeef' == ''.join(map(chr,[0xde,0xad,0xbe,0xef])).encode('hex') # Likely slow, but need benchmarks on 2.x / 3.x
'deadbeef' == str(bytearray([222, 173, 190, 239])).encode('hex')


'\xde\xad\xbe\xef' == 'deadbeef'.decode("hex")
import binascii
'\xde\xad\xbe\xef' == binascii.a2b_hex('deadbeef') # hex string to binary string -- binascii module
'\xde\xad\xbe\xef' == binascii.a2b_hex('deadbeef')
'\xde\xad\xbe\xef' == binascii.unhexlify('deadbeef')
'\xde\xad\xbe\xef' == binascii.unhexlify('deadbeef')
'\xde\xad\xbe\xef' == bytearray.fromhex('deadbeef') # IGNORE SPACES, IF ANY
'\xde\xad\xbe\xef' == bytearray('\xde\xad\xbe\xef')
'\xde\xad\xbe\xef' == bytearray([0xde,0xad,0xbe,0xef])
'\xde\xad\xbe\xef' == str(bytearray([0xde,0xad,0xbe,0xef]))


[0xde,0xad,0xbe,0xef] == map(ord,'\xde\xad\xbe\xef')
'\xde\xad\xbe\xef' == bytes.fromhex('deadbeef') # Python 3.x -- hex string to binary string - IGNORE SPACES, IF ANY
[0xde,0xad,0xbe,0xef] == list(bytearray.fromhex('deadbeef')) # IGNORE SPACES, IF ANY
</source>
</source>


;Strings, arrays or lists - Python 3
;Array


<source lang=python>
<source lang=python>
import binascii
[0xde,0xad,0xbe,0xef] == map(ord,'\xde\xad\xbe\xef') # binary string to array


'deadbeef' == (b'\xde\xad\xbe\xef').hex()
bytearray(b'\xde\xad\xbe\xef') == bytearray.fromhex('deadbeef') # Python 2.x or 3.x - IGNORE SPACES, IF ANY
'deadbeef' == binascii.b2a_hex(b'\xde\xad\xbe\xef').decode()
'\xde\xad\xbe\xef' == bytearray.fromhex('deadbeef') # Python 2.x or 3.x - IGNORE SPACES, IF ANY
'deadbeef' == binascii.hexlify(b'\xde\xad\xbe\xef').decode()
bytearray([0xde,0xad,0xbe,0xef]) == bytearray.fromhex('deadbeef') # Python 2.x or 3.x - IGNORE SPACES, IF ANY
'deadbeef' == binascii.b2a_hex(bytes([0xde,0xad,0xbe,0xef])).decode()
'deadbeef' == binascii.hexlify(bytes([0xde,0xad,0xbe,0xef])).decode()
'10110' == bytes([x + 48 for x in [1?0,1,1,0]]).decode()


# These are not recommended, since they produces bytes(), which could be seen as array of actual bytes
'deadbeef' == str(bytearray([0xde,0xad,0xbe,0xef])).encode('hex') # array to hex string
b'deadbeef' == binascii.b2a_hex(b'\xde\xad\xbe\xef')
'deadbeef' == ''.join(map(chr,[0xde,0xad,0xbe,0xef])).encode('hex') # Likely slow, but need benchmarks on 2.x / 3.x
b'deadbeef' == binascii.hexlify(b'\xde\xad\xbe\xef')
</source>
b'deadbeef' == binascii.b2a_hex(bytes([0xde,0xad,0xbe,0xef]))
b'deadbeef' == binascii.hexlify(bytes([0xde,0xad,0xbe,0xef]))
b'10110' == bytes([x + 48 for x in [1?0,1,1,0]])


b'\xde\xad\xbe\xef' == bytes.fromhex('deadbeef') # IGNORE SPACES, IF ANY
;List
b'\xde\xad\xbe\xef' == binascii.a2b_hex('deadbeef')
b'\xde\xad\xbe\xef' == binascii.unhexlify('deadbeef')
b'\xde\xad\xbe\xef' == binascii.a2b_hex(b'deadbeef')
b'\xde\xad\xbe\xef' == binascii.unhexlify(b'deadbeef')
b'\xde\xad\xbe\xef' == bytes([0xde,0xad,0xbe,0xef])
b'\x01\x00\x01\x01\x00' == bytes([1,0,1,1,0])


from bitstring import BitArray
<source lang=python>
# BitArray is an army swisknife for bytes <-> bin <-> hex <-> (u)int conversion
[222, 173, 190, 239] == list(bytearray.fromhex('deadbeef')) # Python 2.x or 3.x - IGNORE SPACES, IF ANY
# Conversion to any format:
'deadbeef' == str(bytearray([222, 173, 190, 239])).encode('hex')
'aaaa' == BitArray(hex="aaaa").hex
</source>
b'\xaa\xaa' == BitArray(hex="aaaa").bytes
-21846 == BitArray(hex="aaaa").int
43690 == BitArray(hex="aaaa").uint
'1010101010101010' == BitArray(hex="aaaa").bin
# Conversion from any format:
'aaaa' == BitArray(hex="aaaa").hex
'aaaa' == BitArray(bytes=b'\xaa\xaa').hex
'aaaa' == BitArray(int=-21846,length=16).hex
'aaaa' == BitArray(uint=43690,length=16).hex
'aaaa' == BitArray(bin='1010101010101010').hex


[0xde,0xad,0xbe,0xef] == list(b'\xde\xad\xbe\xef')
;
[0xde,0xad,0xbe,0xef] == list(bytes.fromhex('deadbeef')) # IGNORE SPACES, IF ANY
[0xde,0xad,0xbe,0xef] == list(bytearray.fromhex('deadbeef')) # IGNORE SPACES, IF ANY

# Note that in Python3, bytearray is a different from bytes, but both are equivalent
bytearray(b'\xde\xad\xbe\xef') == bytearray([0xde,0xad,0xbe,0xef])
</source>

Latest revision as of 22:51, 15 July 2024

References

Many examples come from cplusplus.com and stackoverflow.com.

Shell

See also Linux Commands.

Convert 66 6f 6f → "foo"

hexdump -e '"%2x"' <myfile>             # Convert myfile into a long hexadecimal string - ! See DOUBLE-QUOTED parameter
hexdump -C <myfile>                     # Canonical hex + ascii display (16 bytes)
hd <myfile>                             # (idem)

echo 202122 | xxd -r -p                 # Convert hexdump to a binary string
echo -e '\x66\x6f\x6f'                  # 'foo'

or to convert hex to decimal [1]

echo $((0x15a))
printf '%d\n' 0x15a
perl -e 'printf ("%d\n", 0x15a)'
echo 'ibase=16;obase=A;15A' | bc

Convert "foo" → 66 6f 6f

xxd -g8 -c32 <file>                     # Output 32 bytes, grouped in 8-byte columns
xxd -p -c64 <file>                      # Output 64 bytes per line, plain (postscript) mode
echo -n ' !"' | xxd -p                  # Convert binary string to hexdump - DON'T FORGET -n

Or to convert decimal to hex

printf '%x\n' 346
perl -e 'printf ("%x\n", 346)'
echo 'ibase=10;obase=16;346' | bc

hex editors

hex diffs

diff -u <(hexdump -v -C file1) <(hexdump -v -C file2)

C / C ++

Convert an integer to hex string

C++

This looks simple but is in fact extremelly treacherous because of persistent iomanip flags:

#include <iostream>
#include <iomanip>

unsigned value = 10;

# 'internal' to make sure we use correct alignment (because 'left' is persistent)
cout << "0x" << setfill('0') << setw(2) << internal << hex << 10 << endl;

C char2hex

A complete C solution, char2hex:

// ############################################################################################################
static uint32_t _char2hex(char *s, const uint8_t data[], size_t data_n, size_t n)
{
    uint32_t  o = 0;

#define out(f, a ...)  {                                          \
        o += (uint32_t)snprintf(s + o, n - (uint32_t)o, f, ## a); \
        o  = o <= n ? o : n;                                      \
}
    if (n > 0) {
        s[0] = 0;
    }
    for (size_t i = 0; i < data_n; i++) {
        out("%.2x", data[i]);
    }

    return o;
#undef out
}

/**
 * Convert an array of char into a list of hexadecimal values.
 * For instance, "\xca\xfe" is converted into "cafe".
 */
char * char2hex(char *s, const uint8_t data[], size_t data_n, size_t n)
{
    uint32_t  o = _char2hex(s, data, data_n, n);

    assert(o < n);                                                   // Check if given buffer was big enough

    return s;
}

Read an integer from an hex string

(See [2], [3]).

Homebrew

const char _hex[] = "0123456789ABCDEF";

// Change a 0x0A into 'A'
char itoh(int nibble)
{
    return _hex[nibble];
}

// Change a 'A' (or 'a') into 0x0A
int htoi(char hex)
{
    return ( hex >> 6 ) + (( hex >> 6 ) << 3 ) + ( hex & 0x0F );
}

// Change "A010" into 0xA010
template<class T>
T hextoint_BE(string h)
{
    T i=0;

    for(string::const_iterator it=h.begin(); it!=h.end(); ++it)
    {
        i=(i<<4)|htoi(*it);
    }

    return i;
}

// Change "A010" into "\xA0\x10"
string hextostring_BE(const string& h)
{
    string x;
    for(unsigned int i=0; (i+1)<h.length(); i+=2) {
        x += (htoi(h[i]) << 4)+ htoi(h[i+1]);
    }
    return x;
}

// Change 0xA010 into "A010"
template<class T> 
string inttohex_BE(T i, unsigned int size)
{
    string sh;
    while( i > 0 )
    {
        sh = itoh(i&0xF) + sh;
        i>>=4;
    }

    if(!size)
        return sh;
    if(size<sh.length())
        return string(sh,sh.length()-size,size);
    else
        return string(size-sh.length(),'0')+sh;
}

// Change "\xA0\x10" into "A010"
string stringtohex_BE(const string& s, unsigned int size)
{
    string h;
    for(string::const_iterator it=s.begin();it!=s.end();++it)
    {
        h += itoh((*it & 0xF0) >> 4);
        h += itoh((*it & 0x0F) >> 0);
    }

    if(!size)
        return h;
    if(size<h.length())
        return string(h,h.length()-size,size);
    else
        return string(size-h.length(),'0')+h;
}

Using atol

/* atol example */
#include <stdio.h>
#include <stdlib.h>

int main ()
{
  long int li;
  char szInput [256];
  printf ("Enter a long number: ");
  gets ( szInput );
  li = atol (szInput);
  printf ("The value entered is %d. The double is %d.\n",li,li*2);
  return 0;
}

Using strtol, strtoll

strtol (resp. strtoll) returns LONG_MIN, LONG_MAX (resp. LLONG_MIN, LLONGMAX) in case of under/overflow.

/* strtol example */
#include <stdio.h>
#include <stdlib.h>

int main ()
{
  char szNumbers[] = "2001 60c0c0 -1101110100110100100000 0x6fffff";
  char * pEnd;
  long int li1, li2, li3, li4;
  li1 = strtol (szNumbers,&pEnd,10);
  li2 = strtol (pEnd,&pEnd,16);
  li3 = strtol (pEnd,&pEnd,2);
  li4 = strtol (pEnd,NULL,0);
  printf ("The decimal equivalents are: %ld, %ld, %ld and %ld.\n", 
          li1, li2, li3, li4);
  return 0;
}
#include <cstdlib>
#include <iostream>
using namespace std;

int main() {
    string s = "abcd";
    char * p;
    long n = strtol( s.c_str(), & p, 16 );
    if ( * p != 0 ) {
        cout << "not a number" << endl;
    }
    else {
        cout << n << endl;
    }
}

Using strtoul, strtoull

Use strtoul (resp. strtoull) when value to read is greater than numeric_limits<long>::max() (resp. numeric_limits<long long>::max()).

/* strtoul example */
#include <stdio.h>
#include <stdlib.h>

int main ()
{
  char szInput [256];
  unsigned long ul;
  printf ("Enter an unsigned number: ");
  fgets (szInput,256,stdin);
  ul = strtoul (szInput,NULL,0);
  printf ("Value entered: %lu. Its double: %lu\n",ul,ul*2);
  return 0;
}
#include <cstdlib>
#include <iostream>
using namespace std;

int main() { 
    string s = "fffefffe";
    char * p;
    long n = strtoul( s.c_str(), & p, 16 ); 
    if ( * p != 0 ) {  
        cout << "not a number" << endl;
    }    else {  
        cout << n << endl;
    }
}

Using sscanf

#include <stdio.h>
main()
{
    char s[] = "fffffffe";
    int x;
    sscanf(s, "%x", &x);
    printf("%u\n", x);
}

Using stringstream

#include <sstream>
#include <iostream>

int main() {
    unsigned int x;   
    std::stringstream ss;
    ss << std::hex << "fffefffe";
    ss >> x;
    // output it as a signed type
    std::cout << static_cast<int>(x) << std::endl;
}

C - hex2char

// ############################################################################################################
static uint8_t _htoi(char hex)
{
    return ((uint8_t)hex >> 6) + (((uint8_t)hex >> 6) << 3) + ((uint8_t)hex & 0x0F);
}

// ############################################################################################################

/** Convert an hex null-terminated string ("cafe") into a byte array ({0xca, 0xfe}).
 *
 * Convert at most `n` bytes from an hexadecimal null-terminated string into a byte array.
 * For instance, it converts "cafe" to {0xca, 0xfe}.
 *
 * @param[out]  dst pointer to destination buffer (at least #n-byte long).
 * @param[in]   src pointer to source string.
 * @param[in]   n   maximum number of bytes to write in #dst.
 *
 * @return          Number of bytes converted.
 */
uint32_t hex2char(void *dst, const char *src, uint32_t n)
{
    uint8_t *   p;
    uint8_t *   _dst = dst;
    const char *_src = src;

    for (p = _dst; (p < _dst + n) && _src[0] && _src[1]; p++, _src += 2) {
        *p = (_htoi(_src[0]) << 4) + _htoi(_src[1]);
    }

    return p - _dst;
}

C - hex2char - fastest and lowercase/uppercase

Inspired from SO:

// ############################################################################################################
// 74ns on i686 (32-bit), vs 150ns for version above
uint32_t hex2char(void *dst, const char *src, uint32_t n)
{
    uint8_t *   p;
    uint8_t *   _dst = dst;
    const char *_src = src;

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Winitializer-overrides"
static const long  hextable[] = { // Reduce to signed char for space saving
    [0 ... 255] = -1,
    ['0']       =  0,  1,  2,  3,  4,  5,  6,  7,  8, 9,
    ['A']       = 10, 11, 12, 13, 14, 15,
    ['a']       = 10, 11, 12, 13, 14, 15,
};
#pragma clang diagnostic pop

    for (p = _dst; (p < _dst + n) && _src[0] && _src[1]; p++) {
        *p = hextable[*_src++];
        *p = (*p << 4) | hextable[*_src++];
    }

    return p - _dst;
}

Python

Integer
'4d2'      == '%x' % 1234                           # to hex
'0x4d2'    == hex(1234)                             # to hex (with '0x' prefix)
'0x4d2'    == '0x%x' % 1234
'000004d2' == '%08x' % 1234                         # to hex (padded)
'000004D2' == '%08X' % 1234                         # to hex (padded,caps)
'\x41'     == chr(0x41)                             # to hex char
b'\x04\xd2'== (1234).to_bytes(2,'big')              # to bytes
b'\xd2\x04'== (1234).to_bytes(2,'little')           # to bytes (little endian)
'04d2'     == (1234).to_bytes(2,'big').hex()        # to hex
'd204'     == (1234).to_bytes(2,'little').hex()     # to hex (little endian)
                                                    # Use ((1234).bit_length() + 7)//8 to get length
'0000010011010010' == f"{1234:016b}"                # to bin
'10011010010'   == f"{1234:11b}"                    # to bin
'10011010010'   == bin(1234)[2:]                    # to bin
'10011010010'   == bin(1234).removeprefix('0b)      # to bin
'0b10011010010' == bin(1234)                        # to bin

1234       == int('04d2',16)                        # from hex
1234       == int('0x04d2',0)                       # from hex - base 0, autodetect
1234       == 0x04d2                                # from hex
1234       == int.from_bytes(b'\x04\xd2','big')     # from hex
1234       == int.from_bytes(b'\xd2\x04','little')  # from hex (little endian)
22         == int('10110',2)                        # from binary

'1234'     == '%d' % 0x04d2                         # from hex
'0x1234'   == '0x%d' % 0x04d2                       # from hex (with '0x' prefix)

# Some functions
def int_to_bytes(x: int) -> bytes:
    return x.to_bytes((x.bit_length() + 7) // 8, 'big')
    
def int_from_bytes(xbytes: bytes) -> int:
    return int.from_bytes(xbytes, 'big')
Strings, arrays or lists - Python 2
import binascii

'deadbeef' == '\xde\xad\xbe\xef'.encode("hex")
'deadbeef' == binascii.b2a_hex('\xde\xad\xbe\xef')
'deadbeef' == binascii.hexlify('\xde\xad\xbe\xef')
'deadbeef' == str(bytearray([0xde,0xad,0xbe,0xef])).encode('hex')
'deadbeef' == ''.join(map(chr,[0xde,0xad,0xbe,0xef])).encode('hex')  # Likely slow, but need benchmarks on 2.x / 3.x
'deadbeef' == str(bytearray([222, 173, 190, 239])).encode('hex')

'\xde\xad\xbe\xef' == 'deadbeef'.decode("hex")
'\xde\xad\xbe\xef' == binascii.a2b_hex('deadbeef')
'\xde\xad\xbe\xef' == binascii.unhexlify('deadbeef')
'\xde\xad\xbe\xef' == bytearray.fromhex('deadbeef')          # IGNORE SPACES, IF ANY
'\xde\xad\xbe\xef' == bytearray('\xde\xad\xbe\xef')
'\xde\xad\xbe\xef' == bytearray([0xde,0xad,0xbe,0xef])
'\xde\xad\xbe\xef' == str(bytearray([0xde,0xad,0xbe,0xef]))

[0xde,0xad,0xbe,0xef] == map(ord,'\xde\xad\xbe\xef')
[0xde,0xad,0xbe,0xef] == list(bytearray.fromhex('deadbeef')) # IGNORE SPACES, IF ANY
Strings, arrays or lists - Python 3
import binascii

'deadbeef' == (b'\xde\xad\xbe\xef').hex()
'deadbeef' == binascii.b2a_hex(b'\xde\xad\xbe\xef').decode()
'deadbeef' == binascii.hexlify(b'\xde\xad\xbe\xef').decode()
'deadbeef' == binascii.b2a_hex(bytes([0xde,0xad,0xbe,0xef])).decode()
'deadbeef' == binascii.hexlify(bytes([0xde,0xad,0xbe,0xef])).decode()
'10110'    == bytes([x + 48 for x in [1?0,1,1,0]]).decode()

# These are not recommended, since they produces bytes(), which could be seen as array of actual bytes
b'deadbeef' == binascii.b2a_hex(b'\xde\xad\xbe\xef')
b'deadbeef' == binascii.hexlify(b'\xde\xad\xbe\xef')
b'deadbeef' == binascii.b2a_hex(bytes([0xde,0xad,0xbe,0xef]))
b'deadbeef' == binascii.hexlify(bytes([0xde,0xad,0xbe,0xef]))
b'10110'    == bytes([x + 48 for x in [1?0,1,1,0]])

b'\xde\xad\xbe\xef' == bytes.fromhex('deadbeef')             # IGNORE SPACES, IF ANY
b'\xde\xad\xbe\xef' == binascii.a2b_hex('deadbeef')
b'\xde\xad\xbe\xef' == binascii.unhexlify('deadbeef')
b'\xde\xad\xbe\xef' == binascii.a2b_hex(b'deadbeef')
b'\xde\xad\xbe\xef' == binascii.unhexlify(b'deadbeef')
b'\xde\xad\xbe\xef' == bytes([0xde,0xad,0xbe,0xef])
b'\x01\x00\x01\x01\x00' == bytes([1,0,1,1,0])

from bitstring import BitArray
# BitArray is an army swisknife for bytes <-> bin <-> hex <-> (u)int conversion
# Conversion to any format:
'aaaa'             == BitArray(hex="aaaa").hex
b'\xaa\xaa'        == BitArray(hex="aaaa").bytes
-21846             == BitArray(hex="aaaa").int
43690              == BitArray(hex="aaaa").uint
'1010101010101010' == BitArray(hex="aaaa").bin
# Conversion from any format:
'aaaa'             == BitArray(hex="aaaa").hex
'aaaa'             == BitArray(bytes=b'\xaa\xaa').hex
'aaaa'             == BitArray(int=-21846,length=16).hex
'aaaa'             == BitArray(uint=43690,length=16).hex
'aaaa'             == BitArray(bin='1010101010101010').hex

[0xde,0xad,0xbe,0xef] == list(b'\xde\xad\xbe\xef')
[0xde,0xad,0xbe,0xef] == list(bytes.fromhex('deadbeef'))     # IGNORE SPACES, IF ANY
[0xde,0xad,0xbe,0xef] == list(bytearray.fromhex('deadbeef')) # IGNORE SPACES, IF ANY

# Note that in Python3, bytearray is a different from bytes, but both are equivalent
bytearray(b'\xde\xad\xbe\xef') == bytearray([0xde,0xad,0xbe,0xef])