Add -e and -E flags to od(1) and properly handle endianness

The -e and -E flags allow the user to override the host endianness
and force od(1) to handle input according to a little (-e) or big (-E)
endian environment.
The previous handling was broken as bitshifts alone are already
endian-independent.

od.1

@@ -1,4 +1,4 @@
-.Dd 2015-10-09
+.Dd 2015-10-25
 .Dt OD 1
 .Os sbase
 .Sh NAME
@@ -7,6 +7,7 @@
 .Sh SYNOPSIS
 .Nm
 .Op Fl A Ar addrformat
+.Op Fl E | e
 .Op Fl t Ar outputformat...
 .Op Fl v
 .Op Ar file ...
@@ -26,6 +27,12 @@ reads from stdin.
 is one of d|o|x|n and sets the address to be
 either in \fId\fRecimal, \fIo\fRctal, he\fIx\fRadecimal or \fIn\fRot
 printed at all.  The default is octal.
+.It Fl E | e
+Force Little Endian
+.Fl ( e )
+or Big Endian
+.Fl ( E )
+system-independently.
 .It Fl t Ar outputformat
 .Ar outputformat
 is a list of a|c|d|o|u|x followed by a digit or C|S|I|L and sets
@@ -49,3 +56,7 @@ The
 flag is enabled by default and the 'd' parameter for the
 .Op Fl t
 flag is interpreted as 'u'.
+.Pp
+The
+.Op Ee
+flags are an extension to that specification.

od.c

@@ -1,5 +1,4 @@
 /* See LICENSE file for copyright and license details. */
-#include <endian.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -8,6 +7,8 @@
 #include "queue.h"
 #include "util.h"
 
+#define HOST_BIG_ENDIAN (*(uint16_t *)"\0\xff" == 0xff)
+
 struct type {
 	unsigned char     format;
 	unsigned int      len;
@@ -19,6 +20,7 @@ static unsigned char addr_format = 'o';
 static off_t skip = 0;
 static off_t max = -1;
 static size_t linelen = 1;
+static int big_endian;
 
 static void
 printaddress(off_t addr)
@@ -37,7 +39,7 @@ static void
 printchunk(unsigned char *s, unsigned char format, size_t len) {
 	long long res, basefac;
 	size_t i;
-	char fmt[] = " %0*ll#";
+	char fmt[] = " %#*ll#";
 
 	const char *namedict[] = {
 		"nul", "soh", "stx", "etx", "eot", "enq", "ack",
@@ -70,17 +72,18 @@ printchunk(unsigned char *s, unsigned char format, size_t len) {
 		}
 		break;
 	default:
-		res = 0;
+		if (big_endian == HOST_BIG_ENDIAN) {
-		basefac = 1;
+			for (res = 0, basefac = 1, i = 0; i < len; i++) {
-#if __BYTE_ORDER == __BIG_ENDIAN
-		for (i = len; i; i--) {
-			res += s[i - 1] * basefac;
-#else
-		for (i = 0; i < len; i++) {
 				res += s[i] * basefac;
-#endif
 				basefac <<= 8;
 			}
+		} else {
+			for (res = 0, basefac = 1, i = len; i; i--) {
+				res += s[i - 1] * basefac;
+				basefac <<= 8;
+			}
+		}
+		fmt[2] = big_endian ? '-' : '+';
 		fmt[6] = format;
 		printf(fmt, (int)(3 * len + len - 1), res);
 	}
@@ -165,7 +168,7 @@ lcm(unsigned int a, unsigned int b)
 static void
 usage(void)
 {
-	eprintf("usage: %s [-A addressformat] [-t outputformat] "
+	eprintf("usage: %s [-A addressformat] [-E | -e] [-t outputformat] "
 	        "[-v] [file ...]\n", argv0);
 }
 
@@ -177,6 +180,8 @@ main(int argc, char *argv[])
 	int ret = 0;
 	char *s;
 
+	big_endian = HOST_BIG_ENDIAN;
+
 	ARGBEGIN {
 	case 'A':
 		s = EARGF(usage());
@@ -184,6 +189,10 @@ main(int argc, char *argv[])
 			usage();
 		addr_format = s[0];
 		break;
+	case 'E':
+	case 'e':
+		big_endian = (ARGC() == 'E');
+		break;
 	case 'j':
 		if ((skip = parseoffset(EARGF(usage()))) < 0)
 			usage();