Help writing C language to write hexadecimal to decimal?

1. Read strings using a function you write called getStr ().





2. Write a function named hextodecimal () that takes in (only) a string parameter representing a positive hexadecimal number and return its decimal equivalent (integer). This function returns -1 if the string provided connotes to a negative number and/or is comprised of invalid characters.





-note: you may not use any library functions in this function- you must write all code necessary to enact the coversion and return the appropriate result.


-this function must accept both upper and lower case versions of the hex character.


-You may want to write an additional function that vets any string for invalid hex character

Help writing C language to write hexadecimal to decimal?
This should do to get you started. The reading strings is simple.





#include %26lt;unistd.h%26gt;


#include %26lt;stdio.h%26gt;





unsigned int hex2dec( char *s )


{


unsigned int v = 0;


char *p;





for( p = s; *p; p++ )


{


if( isdigit( *p ) )


v = (v * 16) + (*p - '0');


else


{


*p = tolower( *p );


if( *p %26gt;= 'a' %26amp;%26amp; *p %26lt;= 'f' )


v = (v * 16) + 10 + (*p - 'a');


else


return -1; /* assume illegal hex char */


}


}





return v;


}





main( int argc, char **argv )


{


printf( "%s converts to %u\n", argv[1], hex2dec( argv[1] ) );


}