Hex to ascii string conversion

Question

i have an hex string and want it to be converted to ascii string in C  How can i accomplish this

User · Answer

strtol   is your friend here  The third parameter is the numerical base that you are converting   Example    include  lt stdio h gt          printf     include  lt stdlib h gt         strtol     int main int argc  char   argv        long int num    0      long int num2  0      char   str     f00d       char   str2    0xf00d        num   strtol  str  0  16      converts hexadecimal string to long      num2   strtol  str2  0  0     conversion depends on the string passed in  0x    Is hex  0    Is octal and everything else is decimal       printf    ld n   num       printf    ld n   num

User · Answer

If I understand correctly  you want to know how to convert bytes encoded as a hex string to its form as an ASCII text  like  quot 537461636B quot  would be converted to  quot Stack quot   in such case then the following code should solve your problem  Have not run any benchmarks but I assume it is not the peak of efficiency  static char ByteToAscii const char  input      char singleChar  out    memcpy  amp singleChar  input  2     sprintf  amp out   quot  c quot    int strtol  amp singleChar  NULL  16      return out     int HexStringToAscii const char  input  unsigned int length                              char   output      int mIndex  sIndex   0    char buffer length     for  mIndex   0  mIndex  lt  length  mIndex          sIndex   mIndex   2      char b   ByteToAscii  amp input sIndex        memcpy  amp buffer mIndex    amp b  1          output   strdup buffer     return 0

User · Answer

you need to take 2  hex  chars at the same time    then calculate the int value  and after that make the char conversion like     char d    char intValue    do this for every 2chars in the hex string   this works if the string chars are only 0-9A-F    include  lt stdio h gt   include  lt string h gt   int hex to int char c           int first   c   16 - 3          int second   c   16          int result   first 10   second          if result  gt  9  result--          return result     int hex to ascii char c  char d           int high   hex to int c    16          int low   hex to int d           return high low     int main            const char  st    48656C6C6F3B           int length   strlen st           int i          char buf   0          for i   0  i  lt  length  i                     if i   2    0                           printf   c   hex to ascii buf  st i                      else                          buf   st i

User · Answer

Few characters like alphabets i-o couldn t be  converted into respective ASCII chars   like in string  6631653064316f30723161  corresponds to fedora   but it gives fedra   Just modify hex to int   function a little  and it will work for all characters  modified function is   int hex to int char c        if  c  gt   97          c   c - 32      int first   c   16 - 3      int second   c   16      int result   first   10   second      if  result  gt  9  result--      return result      Now try it will work for all characters

[c] Hex to ascii string conversion

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