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#! /usr/bin/env perl
# Copyright (c) 2003 The Regents of The University of Michigan
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met: redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer;
# redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution;
# neither the name of the copyright holders nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
# Diff two streams.
#
# Unlike regular diff, this script does not read in the entire input
# before doing a diff, so it can be used on lengthy outputs piped from
# other programs (e.g., M5 traces). The best way to do this is to
# take advantage of the power of Perl's open function, which will
# automatically fork a subprocess if the last character in the
# "filename" is a pipe (|). Thus to compare the instruction traces
# from two versions of m5 (m5a and m5b), you can do this:
#
# rundiff 'm5a --traceflags=InstExec |' 'm5b --traceflags=InstExec |'
#
use strict;
use FileHandle;
use Getopt::Std;
#
# Options:
# -c <n> : print n lines of context before & after changes
# -l <n> : use n lines of lookahead
# -x : use "complex" diff from Algorithm::Diff (see below)
#
our ($opt_c, $opt_l, $opt_x);
getopts('c:l:x');
#
# For the highest-quality (minimal) diffs, we can use the
# Algorithm::Diff package. By default, a built-in, simple, and
# generally quite adequate algorithm will be used. If you have
# Algorithm::Diff installed on your system, and don't mind having the
# script go slower (like 3-4x slower, based on informal observation),
# then specify '-x' on the command line to use it.
my $use_complexdiff = defined($opt_x);
if ($use_complexdiff) {
# Don't use 'use', as that's a compile-time option and will fail
# on systems that don't have Algorithm::Diff installed even if
# $use_complexdiff is false. 'require' is evaluated at runtime,
# so it's OK.
require Algorithm::Diff;
import Algorithm::Diff qw(traverse_sequences);
};
my $lookahead_lines = $opt_l || 200;
# in theory you could have different amounts of context before and
# after a diff, but until someone needs that there's only one arg to
# set both.
my $precontext_lines = $opt_c || 3;
my $postcontext_lines = $precontext_lines;
my $file1 = $ARGV[0];
my $file2 = $ARGV[1];
die "Need two args." if (!(defined($file1) && defined($file2)));
my ($fh1, $fh2);
open($fh1, $file1) or die "Can't open $file1";
open($fh2, $file2) or die "Can't open $file2";
# print files to output so we know which is which
print "-$file1\n";
print "+$file2\n";
# buffer of matching lines for pre-diff context
my @precontext = ();
# number of post-diff matching lines remaining to print
my $postcontext = 0;
# lookahead buffers for $file1 and $file2 respectively
my @lines1 = ();
my @lines2 = ();
# Next line number available to print from each file. Generally this
# corresponds to the oldest line in @precontext, or the oldest line in
# @lines1 and @lines2 if @precontext is empty.
my $lineno1 = 1;
my $lineno2 = 1;
# Fill a lookahead buffer to $lookahead_lines lines (or until EOF).
sub fill
{
my ($fh, $array) = @_;
while (@$array < $lookahead_lines) {
my $line = <$fh>;
last if (!defined($line));
push @$array, $line;
}
}
# Print and delete n lines from front of given array with given prefix.
sub printlines
{
my ($array, $n, $prefix) = @_;
while ($n--) {
my $line = shift @$array;
last if (!defined($line));
print $prefix, $line;
}
}
# Print a difference region where n1 lines of file1 were replaced by
# n2 lines of file2 (where either n1 or n2 could be zero).
sub printdiff
{
my ($n1, $n2)= @_;
# If the precontext buffer is full or we're at the beginning of a
# file, then this is a new diff region, so we should print a
# header indicating the current line numbers. If we're past the
# beginning and the precontext buffer isn't full, then whatever
# we're about to print is contiguous with the end of the last
# region we printed, so we just concatenate them on the output.
if (@precontext == $precontext_lines || ($lineno1 == 0 && $lineno2 == 0)) {
print "@@ -$lineno1 +$lineno2 @@\n";
}
# Print and clear the precontext buffer.
if (@precontext) {
print ' ', join(' ', @precontext);
$lineno1 += scalar(@precontext);
$lineno2 += scalar(@precontext);
@precontext = ();
}
# Print the differing lines.
printlines(\@lines1, $n1, '-');
printlines(\@lines2, $n2, '+');
$lineno1 += $n1;
$lineno2 += $n2;
# Set $postcontext to print the next $postcontext_lines matching lines.
$postcontext = $postcontext_lines;
# Normally we flush after the postcontext lines are printed, but if
# the user has decreed that there aren't any we need to flush now
if ($postcontext == 0) {
STDOUT->flush();
}
}
########################
#
# Complex diff algorithm
#
########################
{
my $match_found;
my $discard_lines1;
my $discard_lines2;
sub match { $match_found = 1; }
sub discard1 { $discard_lines1++ unless $match_found; }
sub discard2 { $discard_lines2++ unless $match_found; }
sub complex_diff
{
$match_found = 0;
$discard_lines1 = 0;
$discard_lines2 = 0;
# See Diff.pm. Note that even though this call generates a
# complete diff of both lookahead buffers, all we use it for
# is to figure out how many lines to discard off the front of
# each buffer to resync the streams.
traverse_sequences( \@lines1, \@lines2,
{ MATCH => \&match,
DISCARD_A => \&discard1,
DISCARD_B => \&discard2 });
if (!$match_found) {
printdiff(scalar(@lines1), scalar(@lines2));
die "Lost sync!";
}
# Since we shouldn't get here unless the first lines of the
# buffers are different, then we must discard some lines off
# at least one of the buffers.
die if ($discard_lines1 == 0 && $discard_lines2 == 0);
printdiff($discard_lines1, $discard_lines2);
}
}
#######################
#
# Simple diff algorithm
#
#######################
# Check for a pair of matching lines; if found, generate appropriate
# diff output.
sub checkmatch
{
my ($n1, $n2) = @_;
# Check if two adjacent lines match, to reduce false resyncs
# (particularly on unrelated blank lines). This generates
# larger-than-necessary diffs when a single line really should be
# treated as common; if that bugs you, use Algorithm::Diff.
if ($lines1[$n1] eq $lines2[$n2] && $lines1[$n1+1] eq $lines2[$n2+1]) {
printdiff($n1, $n2);
return 1;
}
return 0;
}
sub simple_diff
{
# Look for differences of $cnt lines to resync,
# increasing $cnt from 1 to $lookahead_lines until we find
# something.
for (my $cnt = 1; $cnt < $lookahead_lines-1; ++$cnt) {
# Check for n lines in one file being replaced by
# n lines in the other.
return if checkmatch($cnt, $cnt);
# Find differences where n lines in one file were
# replaced by m lines in the other. We let m = $cnt
# and iterate for n = 0 to $cnt-1.
for (my $n = 0; $n < $cnt; ++$n) {
return if checkmatch($n, $cnt);
return if checkmatch($cnt, $n);
}
}
printdiff(scalar(@lines1), scalar(@lines2));
die "Lost sync!";
}
# Set the pointer to the appropriate diff function.
#
# Note that in either case the function determines how many lines to
# discard from the front of each lookahead buffer to resync the
# streams, then prints the appropriate diff output and discards them.
# After the function returns, it should always be the case that
# $lines1[0] eq $lines2[0].
my $find_diff = $use_complexdiff ? \&complex_diff : \&simple_diff;
# The main loop.
while (1) {
# keep lookahead buffers topped up
fill($fh1, \@lines1);
fill($fh2, \@lines2);
# peek at first line in each buffer
my $l1 = $lines1[0];
my $l2 = $lines2[0];
if (!defined($l1) && !defined($l2)) {
# reached EOF on both streams: exit
exit(1);
}
if ($l1 eq $l2) {
# matching lines: delete from lookahead buffer
shift @lines1;
shift @lines2;
# figure out what to do with this line
if ($postcontext > 0) {
# we're in the post-context of a diff: print it
print ' ', $l1;
$lineno1++;
$lineno2++;
if (--$postcontext == 0) {
STDOUT->flush();
}
}
else {
# we're in the middle of a matching region... save this
# line for precontext in case we run into a difference.
push @precontext, $l1;
# don't let precontext buffer get bigger than needed
while (@precontext > $precontext_lines) {
shift @precontext;
$lineno1++;
$lineno2++;
}
}
}
else {
# Mismatch. Deal with it.
&$find_diff();
}
}