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#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
int
tohex(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 0;
}
int
isspace(int c)
{
if (c <= ' ')
return 1;
if (c == '\n')
return 1;
if (c == '\t')
return 1;
if (c == ':')
return 1;
if (c == ';')
return 1;
if (c == ',')
return 1;
return 0;
}
void
verify_nibble(int nibble, int current)
{
if (nibble != 0) {
fprintf(stderr, "count mismatch %d (nibbles=0x%x)\n", nibble, current);
fflush(stderr);
}
}
int
main(int argc, char **argv)
{
int c;
int current = 0;
int nibble = 0;
int skip = 0;
if (argv[1]) {
skip = atoi(argv[1]);
}
#define NIBBLE_COUNT 2
while ((c = getchar()) != EOF) {
if (isspace(c)) {
verify_nibble(nibble, current);
continue;
}
if (skip) {
skip--;
continue;
}
current = current << 4 | tohex(c);
nibble++;
if (nibble == NIBBLE_COUNT) {
putchar(current);
nibble = 0;
current = 0;
}
}
return 0;
}