#!/usr/bin/perl -w

# ----------------------------------------------------------------
# John Kerl
# kerl.john.r@gmail.com
# 2000/05/23

# This script computes first differences of a sequence.

# Sample input:

# 08048254 ? _init
# 080482b0 T _start
# 080482d4 t call_gmon_start
# 08048300 t __do_global_dtors_aux
# 08048340 t frame_dummy
# 0804836c T calc_pnk
# 08048436 T main
# 08048530 t __do_global_ctors_aux
# 08048554 ? _fini
# 08048570 R _fp_hw
# 08048574 R _IO_stdin_used
# 080495a0 D __data_start
# 080495a0 W data_start
# 080495a4 d __dso_handle
# 080495a8 d p.0

# Sample output, after running through fdiff -x -r:

# 0x0000005c    08048254 ? _init
# 0x00000024    080482b0 T _start
# 0x0000002c    080482d4 t call_gmon_start
# 0x00000040    08048300 t __do_global_dtors_aux
# 0x0000002c    08048340 t frame_dummy
# 0x000000ca    0804836c T calc_pnk
# 0x000000fa    08048436 T main
# 0x00000024    08048530 t __do_global_ctors_aux
# 0x0000001c    08048554 ? _fini
# 0x00000004    08048570 R _fp_hw
# 0x0000102c    08048574 R _IO_stdin_used
# 0x00000000    080495a0 D __data_start
# 0x00000004    080495a0 W data_start
# 0x00000004    080495a4 d __dso_handle
#               080495a8 d p.0

# ----------------------------------------------------------------

$left    =  1;
$neither =  0;
$right   = -1;

# Defaults
$absdiff    = 0;
$hex_input  = 0;
$hex_output = 0;
$divide     = 0;
$negate     = 0;
$paste      = $neither;

# Parse options
while (@ARGV) {
	my $arg = $ARGV[0];
	last unless $arg =~ /^-/;

	if ($ARGV[0] eq "--help") {
		usage();
	}

	elsif ($ARGV[0] eq "-x") {
		$hex_input = 1;
		$hex_output = 1;
		shift @ARGV;
	}

	elsif ($ARGV[0] eq "-xi") {
		$hex_input = 1;
		shift @ARGV;
	}

	elsif ($ARGV[0] eq "-xo") {
		$hex_output = 1;
		shift @ARGV;
	}

	elsif ($ARGV[0] eq "-div") {
		$divide = 1;
		shift @ARGV;
	}

	elsif ($ARGV[0] eq "-n") {
		$negate = 1;
		shift @ARGV;
	}

	elsif ($ARGV[0] eq "-abs") {
		$absdiff = 1;
		shift @ARGV;
	}

	elsif ($ARGV[0] eq "-l") {
		$paste = $left;
		shift @ARGV;
	}

	elsif ($ARGV[0] eq "-r") {
		$paste = $right;
		shift @ARGV;
	}

	else {
		usage();
	}
}

# Process input
$i = 0;
$f1 = 0;
$line1 = "";
while ($line = <>) {
	chomp $line;

	# Strip leading whitespace from line.
	$line =~ s/^\s+//;
	$line2 = $line;

	# Get only the first word on the line.
	(@fields) = split /\s+/, $line;

	# Skip blank lines.
	next if (@fields == 0);
	$f2 = $fields[0];

	if ($hex_input) {
 		# Strip leading 0x, if any.
 		$f2 =~ s/^0x//;
 		$f2 =~ s/^0X//;
	 	$f2 = hex $f2;
	}

	# Calculate and print first differences, if at least two words have
	# been read.
	if ($i > 0) {
		my $diff;
		if ($divide) {
			$diff = $f1 / $f2;
		}
		elsif ($negate) {
			$diff = $f1 - $f2;
		}
		else {
			$diff = $f2 - $f1;
		}

		if ($absdiff) {
			if ($diff < 0) {
				$diff = -$diff;
			}
		}

		if ($paste == $left) {
			print "$line1\t";
		}
		
		if ($hex_output) {
 			printf "0x%08x", $diff;
		}
		else {
			print $diff;
		}

		if ($paste == $right) {
			print "\t$line1";
		}

		print "\n";
	}

	# Prepare for next pass.
	$line1 = $line2;
	$f1 = $f2;
	$i++;
}

if ($paste == $left) {
	print "$line1\n";
}
elsif ($paste == $right) {
	if ($hex_output) {
		print "\t";
	}
	print "\t$line1\n";
}

# ----------------------------------------------------------------
sub usage
{
	die
	"Usage: $0 [-x] [-l] [-n] [-t] {files ...}\n" .
	"  -x:  Use hexadecimal I/O (default is decimal).\n" .
	"  -n:  Compute negated differences.\n" .
	"  -l:  Paste input to the left  of first differences.\n" .
	"  -r:  Paste input to the right of first differences.\n";
	"  Input is taken from standard input if no file names are given.\n";
}

# Test input:
# 00000008 A _ssro_size
# 00000060 A _ssrw_size
# 00000100 A _STACK_SIZE
# 00000400 A _TEXT_START_ADDR
# 00000400 A _ftext
# 00000400 T _start
# 0000046c T exit
# 00000474 T my_get_line
# 00000474 t __gnu_compiled_c
# 00000474 t gcc2_compiled.