[textmode]

    #include <unistd.h>
    #include <errno.h>
    #include <sys/types.h>
    int writeall(int fd,const void *xv,long long xlen)
    {
      const unsigned char *x = xv;
      long long w;
      while (xlen > 0) {
        w = xlen;
        if (w > 1048576) w = 1048576;
        w = write(fd,x,w);
        x += w;
        xlen -= w;
      }
      return 0;
    }
    static int hexdigit(char x)
    {
      if (x >= '0' && x <= '9') return x - '0';
      if (x >= 'a' && x <= 'f') return 10 + (x - 'a');
      if (x >= 'A' && x <= 'F') return 10 + (x - 'A');
      return -1;
    }
    int hexparse(unsigned char *y,long long len,const char *x)
    {
      if (!x) return 0;
      while (len > 0) {
        int digit0;
        int digit1;
        digit0 = hexdigit(x[0]); if (digit0 == -1) return 0;
        digit1 = hexdigit(x[1]); if (digit1 == -1) return 0;
        *y++ = digit1 + 16 * digit0;
        --len;
        x += 2;
      }
      if (x[0]) return 0;
      return 1;
    }