I am trying to learn VC.NET and convert some Borland C++ applications. The
syntax differences are killing me...
Is there an easy way to convert a hex string, entered by the user, to a
binary string and back? This is the actual code I am trying to convert.
HexToBin(KeyEdit->Text.c_str(), BinKey, sizeof(BinKey));
HexToBin is a generic function that converts a string like "1b34c38d" to
it's binary equivalent. There is also a BinToHex which reverses the
process.
I know I could write a function to do it, but I threw all those routines
away 10 years ago when I started using Borland.
I am hoping that someone can help, because I really don't want to have to
go back to writing all of those little conversion routines.
Binary value or binary string?
To convert a value <= ULONG_MAX to an unsigned long binary value:
val = strtoul(strval, NULL, 0); // If strval as 0x1234abcd
val = strtoul(strval, NULL, 16); // if strval as 12341bcd
I'm sure there are STL and MFC classes that can do this too.
If you need to convert a hex string to a binary strings, I would use a
table For efficiency (sample below), though some languages may provide
built-in functions or extra formatting specifications.
Converting from hex to a binary value then to binary text might be
faster, but this will handle arbitrarily-long hex and binary values.
Sample ANSI C code:
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>
#include <stdio.h>
#define TESTING
#undef TRUE
#define TRUE 1
#undef FALSE
#define FALSE 0
/* Error codes */
#define eDIGIT 1
#define eTRUNC 2
#define eSEPAR 4
static int setdigit(int c, char *binval, int pos);
/* SevStrHexToBin()
Parameters:
hexval - Hex value to convert. May be prefixed with h, H,
x, X, 0x or 0X.
May be suffixed with h, H, x, or X.
groupchar - Group digits by this char (0 for no sep)
groupchar is also ignored in the input string
(groupchar cannot be any hex digit)
binval - Where to place the binary string
binmaxlen - Size of binval (with room for terminating \0)
Return values:
0 - Success
eTRUNC - binval not large enough
eDIGIT - invalid hex character in input string
eSEPAR - invalid groupchar
*/
int SevStrHexToBin(const char *hexval, int groupchar,
char *binval, int binmaxlen)
{
static const char hexdig[] = "0123456789abcdef";
int e = 0, pos, c, diglen = groupchar ? 5 : 4;
size_t hexlen = strlen(hexval);
memset(binval, 0, binmaxlen); /* In case of error */
if (!hexval || hexlen < 1)
return eDIGIT;
if (groupchar && strchr(hexdig, tolower((unsigned char)groupchar)))
return eSEPAR;
if (hexlen >= 2 && hexval[0] == '0' && tolower(hexval[1]) == 'x')
hexval += 2; /* Skip 0x if prepended */
else if ( (c = tolower(hexval[0])) == 'x' || c == 'h')
hexval++; /* Skip x or h if prepended */
hexlen = strlen(hexval);
if (hexlen &&
(((c = tolower(hexval[hexlen-1])) == 'x') || c == 'h'))
hexlen--; /* Ignore trailing "hHxX" */
for (pos = 0; hexlen-- && ((c =*hexval++) != 0); pos += diglen) {
if (pos + diglen - (groupchar && (hexlen == 0)) > binmaxlen)
return e | eTRUNC;
e |= setdigit(c, binval, pos);
if (groupchar && hexlen != 0)
binval[pos+4] = (char)groupchar;
}
return e;
}
static int setdigit(int c, char *binval, int pos)
{
static const char errdig[] = "****";
static const char bindig[] =
"0000 0001 0010 0011 " /* Spaces for readability */
"0100 0101 0110 0111 "
"1000 1001 1010 1011 "
"1100 1101 1110 1111 ";
int e = 0;
if (c >='0' && c <= '9')
memcpy(binval+pos, bindig + 5*(c-'0'), 4); /* Decimal */
else {
c = tolower((unsigned char)c);
if (c >= 'a' && c <= 'f')
memcpy(binval+pos, bindig + 5*(c-'a'+10), 4); /* Alpha */
else {
memcpy(binval+pos, errdig, 4);
e = eDIGIT; /* Invalid digit */
}
}
return e;
}
#ifdef TESTING
static char *hexbinerrmsg(int e)
{
switch (e) {
case eDIGIT: return " (invalid)";
case eTRUNC: return " (truncated)";
case eDIGIT|eTRUNC: return " (invalid & truncated)";
case eSEPAR: return " (invalid separator)";
default: return "";
}
}
int main(int argc, char *argv[])
{
char binval[82] = "";
int e = 0;
if (argc < 2) {
printf("%s\n", hexbinerrmsg(eDIGIT));
return EXIT_FAILURE;
}
/* Simple conversion */
e = SevStrHexToBin(argv[1], 0, binval, sizeof binval);
printf("%s: %s%s\n", argv[1], binval, hexbinerrmsg(e));
/* Space separators */
e = SevStrHexToBin(argv[1], ' ', binval, sizeof binval);
printf("%s: %s%s\n", argv[1], binval, hexbinerrmsg(e));
/* Colon separators */
e = SevStrHexToBin(argv[1], ':', binval, sizeof binval);
printf("%s: %s%s\n", argv[1], binval, hexbinerrmsg(e));
/* Invalid separators */
e = SevStrHexToBin(argv[1], '0', binval, sizeof binval);
printf("%s: %s%s\n", argv[1], binval, hexbinerrmsg(e));
return EXIT_SUCCESS;
}
#endif
((c)<='F')?((c)-'A')