Weird read input or bad printf output?

Hi,

I have been struggling with this now for a couple weeks. I am writing a program that looks for headers of files. Upon finding one, it looks in the header for how large the program is. The code below is a subset of the program I am writing. I already know where the header is, but when I try to read in the bytes I get some weird output.

The output I get is (Notice the Hex:FFFFFF80):
Starting File Read -- findenddatorg
Hex:00 Hex:FFFFFF80 Hex:00 Hex:00 Filename: (null) Startpos: 26215452 Endpos: 0 Size: 0 -- Filelength: 140736547508496

It should be:
Starting File Read -- findenddatorg
Hex:00 Hex:80 Hex:00 Hex:00 Filename: (null) Startpos: 26215452 Endpos: 0 Size: 0 -- Filelength: 140736547508496

Why in the world do I have a FFFFFF80? If I adjust this line:
startpos = startpos+28;
to
startpos = startpos+29;

I get:
Starting File Read -- findenddatorg
Hex:FFFFFF80 Hex:00 Hex:00 Hex:00 Filename: (null) Startpos: 26215453 Endpos: 0 Size: 0 -- Filelength: 140736975497536

If I change to: startpos = startpos+30;
Starting File Read -- findenddatorg
Hex:00 Hex:00 Hex:00 Hex:40 Filename: (null) Startpos: 26215454 Endpos: 0 Size: 0 -- Filelength: 140734021634096

Any ideas??

Below is my code:

Code:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <inttypes.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>

// My headers
#include "main.h"
     

char *filename = NULL;
char *programname = NULL;
int fd; //File
FILE *logfile;
FILE *foundfile;
int row,col; // Curses row and col
char *configfilename = NULL;
char *logfilename = NULL;



off_t findenddatorg(off_t startpos, off_t endpos, unsigned long long size) {
    //off_t getsize,getsizefinal = 0;
    off_t getsizefinal = 0;
    char getsize[] = "AAAA";
    char getsize2[] ="AAAA";
    char blowme[]="AAAA";
    int *getsize_ptr;
    char out[12];
    int fileend = 0;
    long fileend2,testlong = 0;
    int out_file = 0;
    int read_size = 0;
    int dat_length = 0;
    off_t currpos;
    int hexcnt = 0;
    unsigned long long filelength = 0;
    unsigned long long fileleft = 0;
    char holda,holdb;

    startpos = startpos+28;
    currpos = lseek(fd, startpos, SEEK_SET);
    getsize_ptr = &getsize;

    if (currpos == -1)
           fprintf(stderr, "Could not seek ending position of --  Startpos: %lld -- Endpos: %lld -- Size: %lld -- Filename: %s\n", startpos,endpos,size,filename);
        else {
                printf("Starting File Read -- findenddatorg\n");

                read_size = read(fd, getsize, sizeof(getsize));
		if ( read_size < 0 ) {
			exit(8);
		}
		for (hexcnt = 0; hexcnt < 4; hexcnt++) 
	    		printf("Hex:%02X ", getsize[hexcnt]);

                printf("Filename: %s \t Startpos: %lld \t Endpos: %lld \t Size: %lld -- Filelength: %lld \n\n",filename, startpos,endpos,size, getsize);
                return(getsizefinal);
    }
}








int main (int argc, char **argv) {


 off_t currpos;
 long saveline;

    fd = open("test_small.dd", O_RDONLY|O_LARGEFILE);
    //fd = open(filename, O_RDONLY|O_BINARY|O_LARGEFILE);
    if (fd == -1) {
	fprintf(stderr, "Error opening file: %s\n", argv[optind]);
	exit(1);
    }
    
    currpos = lseek(fd, 0, SEEK_CUR);


    saveline = findenddatorg(26215424, 0, 0);


       return 0;
}

Thanks,
CM

make your value - you are trying to print with %x format - unsigned char

Declare getsize[] as an array of unsigned char as suggested in the previous post.
The unwanted F come from the propagation of the sign bit when converting to
an 4 bytes value.

Thank you for helping out a C newbie. That fixed it.

CM