/*
  This is the hex dump format I prefer.
  David Anderson
  This code is put into the Public Domain: you may
  copy/modify/use it in any form or manner you wish
  without restriction.

*/

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>

#define OPTSTR  "ds:e:l:"

static int errflag;

char *Usage = 
{
	"Usage: hxdump [-d] [-s startaddr] [-e endaddr] [-l length] file ...\n"
	" -s supply a starting offset to use, for example, -s 0x1000\n"
	" -e supply an end address for the dump.\n"
	" -l supply a length for the dump\n"
	" -d display data only, not file offsets"
	"    (If both -e and -l supplied, take the shortest dump implied)\n"
	"    (dump length etc are not reset between files)\n"
	"    (use the usual C number conventions for numeric values)\n"
};

FILE *fin;
static void dumpfile(FILE *f,long offset,long endoffset);

int shownooffsets;

int
main(int argc, char **argv)
{
	long startoffset = 0;
	long endoffset = 0;
	long length = 0;
	long finalendoffset;
	int c;

	if(argc == 1) {
		printf("%s",Usage);
		exit(1);
	}

	while ((c = getopt(argc, argv, OPTSTR)) != EOF)
	{
	        switch(c) {
		case 'e':
			  {
			    char *istr = optarg;
			    char *ostr = 0;
			    endoffset = strtoul(istr,&ostr,0);
			    if(endoffset == 0 && ostr == istr) {
				printf("Error understanding -e value %s\n",
					istr);
				return 1;
			    }
			
			  }
			  break;
		case 'd':
			shownooffsets = 1;
			break;
		case 'l':
			  {
			    char *istr = optarg;
			    char *ostr = 0;
			    length = strtoul(istr,&ostr,0);
			    if(length == 0 && ostr == istr) {
				printf("Error understanding -l value %s\n",
					istr);
				return 1;
			    }
			
			  }
			  break;
		case 's':
		        {
			 char *istr = optarg;
			 char *ostr = 0;
			 startoffset = strtoul(istr,&ostr,0);
			 if(startoffset == 0 && ostr == istr) {
				printf("Error understanding offset %s\n",
					istr);
				return 1;
			 }
			}         
			break;
		case '?':
			return 1;
		}
	}
	for(; optind < argc;optind++)
	{
		struct stat statbuf;
		int res;
		if( (fin = fopen(argv[optind],"r")) == NULL)
		{
			printf("Open of %s failed!\n",argv[optind]);
		        ++errflag;
			continue;
		}
		res = fstat(fileno(fin), &statbuf);
		if(res != 0) {
		  printf("fstat of %s failed!\n",argv[0]);
		  fclose(fin);	
		  ++errflag;
		  continue;
		}
		if(statbuf.st_size <= startoffset) {
		  printf("Only %lu bytes in the file. "
			"Starting at %lu (decimal) impossible!\n",
			(unsigned long)statbuf.st_size,
			(unsigned long)startoffset);
		  fclose(fin);
		  ++errflag;
		  continue;
		}
		res =fseek(fin,startoffset,SEEK_SET);
		if(res) {
			printf("fseek to %ld failed!\n",(long)startoffset);
			fclose(fin);
		        ++errflag;
			continue;
		}
		finalendoffset = statbuf.st_size;
		if(endoffset != 0 && endoffset < finalendoffset){
			finalendoffset = endoffset;
		}
		if(length != 0 && (startoffset + length) < finalendoffset) {
			finalendoffset = startoffset + length;
		}
		dumpfile(fin,startoffset,finalendoffset);
		fclose(fin);
	}
	return(0);
} 


static void
dumpfile(FILE *f,long offset,long endoffset)
{
	char buf[100];
	int c;
	int i;
	int j;
	char *bp;
	int stop = 0;

	while(stop == 0 && feof(f) ==0)
	{
		if(shownooffsets) {
		   printf("       ");
		} else {
		   printf("%7lx",offset);
		}
		bp = buf;
		*bp = 0;
		for( i = 0; i < 4 && stop == 0; i++)
		{
			printf(" ");
			for(j = 0; j < 4; j++,offset++)
			{
				if(feof(f)) {
					printf("  ");
					stop = 1;
					break;
				} else if (offset > endoffset) {
					printf("  ");
					stop = 1;
					break;
				} else {
				  c = getc(f);
				  if(c  != EOF) {
					printf("%02x",c);
					if( c < ' ' || c > '~')
						*bp = '.';
					else
						*bp = c;
					bp++;
					*bp = 0;
				  } else {
					printf("  ");
				  }
				}
			}
		}
		printf("  %s\n",buf);
	}
}