/usr/share/perl5/Algorithm/Merge.pm is in libalgorithm-merge-perl 0.08-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 | package Algorithm::Merge;
use Algorithm::Diff ();
use Carp;
use strict;
use Data::Dumper;
use vars qw(@EXPORT_OK @ISA $VERSION $REVISION);
$VERSION = '0.08';
$REVISION = (qw$Revision: 1.11 $)[-1];
@EXPORT_OK = qw(diff3 merge traverse_sequences3);
@ISA = qw(Exporter);
sub diag {
main::diag(@_) if($Algorithm::Merge::DEBUG);
}
sub diff3 {
my $pivot = shift; # array ref
my $doca = shift; # array ref
my $docb = shift; # array ref
my $keyGen = shift;
my @ret;
if(@$doca == 0 && @$docb == 0 && @$pivot == 0) {
return [ [ ] ];
}
my $no_change;
# if($keyGen) {
# $no_change = sub {
# if($keyGen->($pivot -> [$_[0]]) ne $keyGen->($doca -> [$_[1]])
# || $keyGen->($pivot -> [$_[0]]) ne $keyGen->($docb -> [$_[2]])
# || $keyGen->($doca -> [$_[1]]) ne $keyGen->($docb -> [$_[2]]))
# {
# croak "No change detected, but elements differ between sequences. Please submit a bug report to jsmith\@cpan.org with a description of the set of sequences which lead to this error.\n";
# }
# push @ret, [ 'u', $pivot -> [$_[0]], $doca -> [$_[1]], $docb -> [$_[2]] ];
# };
# }
# else {
$no_change = sub {
# if($pivot -> [$_[0]] ne $doca -> [$_[1]]
# || $pivot -> [$_[0]] ne $docb -> [$_[2]]
# || $doca -> [$_[1]] ne $docb -> [$_[2]])
# {
# croak "No change detected, but elements differ between sequences. Please submit a bug report to jsmith\@cpan.org with a description of the set of sequences which lead to this error.\n";
# }
push @ret, [ 'u', $pivot -> [$_[0]], $doca -> [$_[1]], $docb -> [$_[2]] ];
};
# }
my $conflict = sub {
my($a, $b, $c);
$a = $pivot -> [$_[0]] if defined $_[0];
$b = $doca -> [$_[1]] if defined $_[1];
$c = $docb -> [$_[2]] if defined $_[2];
push @ret, [ 'c', $a, $b, $c ];
};
my $diff_a = sub {
if(@_ == 1) {
push @ret, [ 'o', $pivot -> [$_[0]], undef, undef ];
}
elsif(@_ == 2) {
push @ret, [ 'o', undef, $doca -> [$_[0]], $docb -> [$_[1]] ];
}
elsif(@_ == 3) {
push @ret, [ 'o', $pivot -> [$_[0]], $doca -> [$_[1]], $docb -> [$_[2]] ];
}
};
my $diff_b = sub {
if(@_ == 1) {
push @ret, [ 'l', undef, $doca -> [$_[0]], undef ];
}
elsif(@_ == 2) {
push @ret, [ 'l', $pivot -> [$_[0]], undef, $docb -> [$_[1]] ];
}
elsif(@_ == 3) {
push @ret, [ 'l', $pivot -> [$_[0]], $doca -> [$_[1]], $docb -> [$_[2]] ];
}
};
my $diff_c = sub {
if(@_ == 1) {
push @ret, [ 'r', undef, undef, (defined($_[0]) ? $docb -> [$_[0]] : undef) ];
}
elsif(@_ == 2) {
push @ret, [ 'r', (defined($_[0]) ? $pivot -> [$_[0]] : undef), (defined($_[1]) ? $doca -> [$_[1]] : undef), undef ];
}
elsif(@_ == 3) {
push @ret, [ 'r', (defined($_[0]) ? $pivot -> [$_[0]] : undef), (defined($_[1]) ? $doca -> [$_[1]] : undef), (defined($_[0]) ? $docb -> [$_[2]] : undef)];
}
};
traverse_sequences3(
$pivot, $doca, $docb,
{
NO_CHANGE => $no_change,
A_DIFF => $diff_a,
B_DIFF => $diff_b,
C_DIFF => $diff_c,
CONFLICT => $conflict,
},
$keyGen, @_
);
if(wantarray) {
return @ret;
}
else {
return \@ret;
}
}
use constant A => 4;
use constant B => 2;
use constant C => 1;
use constant D => 8; # should be an undef
use constant AB_A => 32;
use constant AB_B => 16;
use constant AC_A => 8;
use constant AC_C => 4;
use constant BC_B => 2;
use constant BC_C => 1;
use constant CB_C => 3; # not used in calculations
use constant CB_B => 5; # not used in calculations
my @abc_s;
$abc_s[(A|B)*8+A] = AB_A;
$abc_s[(A|B)*8+B] = AB_B;
$abc_s[(A|C)*8+A] = AC_A;
$abc_s[(A|C)*8+C] = AC_C;
$abc_s[(B|C)*8+B] = BC_B;
$abc_s[(B|C)*8+C] = BC_C;
sub traverse_sequences3 {
my $adoc = shift; # array ref
my $bdoc = shift; # array ref
my $cdoc = shift; # array ref
my $callbacks = shift || {};
my $keyGen = shift;
my $a_diff = $callbacks->{'A_DIFF'} || sub { };
my $b_diff = $callbacks->{'B_DIFF'} || sub { };
my $c_diff = $callbacks->{'C_DIFF'} || sub { };
my $no_change = $callbacks->{'NO_CHANGE'} || sub { };
my $conflict = $callbacks->{'CONFLICT'} || sub { };
my $b_len = scalar(@{$bdoc});
my $c_len = scalar(@{$cdoc});
my $target_len = $b_len < $c_len ? $b_len : $c_len;
my $bc_different_lengths = $b_len != $c_len;
my(@bdoc_save, @cdoc_save);
# make these into traverse_sequences calls
my($left, $right);
my %diffs;
my $ts_callbacks = {
DISCARD_A => sub { # discard left
push @{$diffs{$left}}, $_[0];
},
DISCARD_B => sub { # discard right
push @{$diffs{$right}}, $_[1];
},
};
@diffs{(AB_A, AB_B)} = ([], []);
$left = AB_A; $right = AB_B;
Algorithm::Diff::traverse_sequences( $adoc, $bdoc, $ts_callbacks, $keyGen, @_);
@diffs{(AC_A, AC_C)} = ([], []);
$left = AC_A; $right = AC_C;
Algorithm::Diff::traverse_sequences( $adoc, $cdoc, $ts_callbacks, $keyGen, @_);
if($bc_different_lengths) {
@diffs{(CB_C, CB_B)} = ([], []);
$left = CB_C; $right = CB_B;
Algorithm::Diff::traverse_sequences( $cdoc, $bdoc, $ts_callbacks, $keyGen, @_);
@diffs{(BC_B, BC_C)} = ([], []);
$left = BC_B; $right = BC_C;
Algorithm::Diff::traverse_sequences( $bdoc, $cdoc, $ts_callbacks, $keyGen, @_);
if(join(",", @{$diffs{&CB_B}}) ne join(",", @{$diffs{&BC_B}}) ||
join(",", @{$diffs{&CB_C}}) ne join(",", @{$diffs{&BC_C}}))
{
@bdoc_save = splice @{$bdoc}, $target_len;
@cdoc_save = splice @{$cdoc}, $target_len;
carp "Algorithm::Diff::diff is not symmetric for second and third sequences - results might not be correct";
}
@diffs{(BC_B, BC_C)} = ([], []);
$left = BC_B; $right = BC_C;
Algorithm::Diff::traverse_sequences( $bdoc, $cdoc, $ts_callbacks, $keyGen, @_);
if(scalar(@bdoc_save) || scalar(@cdoc_save)) {
push @{$diffs{&BC_B}}, ($target_len .. $b_len) if $target_len < $b_len;
push @{$diffs{&BC_C}}, ($target_len .. $c_len) if $target_len < $c_len;
push @{$bdoc}, @bdoc_save; undef @bdoc_save;
push @{$cdoc}, @cdoc_save; undef @cdoc_save;
}
}
else {
@diffs{(BC_B, BC_C)} = ([], []);
$left = BC_B; $right = BC_C;
Algorithm::Diff::traverse_sequences( $bdoc, $cdoc, $ts_callbacks, $keyGen, @_);
}
my @pos;
@pos[A, B, C] = (0, 0, 0);
my @sizes;
@sizes[A, B, C] = ( scalar(@{$adoc}), scalar(@{$bdoc}), scalar(@{$cdoc}) );
my @matches;
$#matches = 32;
my $callback = 0;
my $noop = sub { };
# Callback_Map is indexed by the sum of AB_A, AB_B, ..., as indicated by @matches
# this isn't the most efficient, but it's a bit easier to maintain and
# read than if it were broken up into separate arrays
# half the entries are not $noop - it would seem then that no
# entries should be $noop. I need patterns to figure out what the
# other entries are.
my @Callback_Map = (
[ $no_change, A, B, C ], # 0 - no matches
#[ $noop, ], # 1 - BC_C
[ $b_diff, A, C ], # 1 - BC_C
[ $b_diff, B ], #*2 - BC_B
[ $noop, ], # 3 - BC_B BC_C
[ $noop, ], # 4 - AC_C
[ $c_diff, C ], # 5 - AC_C BC_C
[ $noop, ], # 6 - AC_C BC_B
[ $noop, ], # 7 - AC_C BC_B BC_C
[ $a_diff, A ], # 8 - AC_A
[ $noop, ], # 9 - AC_A BC_C
[ $c_diff, A, B ], # 10 - AC_A BC_B
[ $c_diff, A, B, ], # 11 - AC_A BC_B BC_C
[ $noop, ], # 12 - AC_A AC_C
[ $noop, ], # 13 - AC_A AC_C BC_C
[ $c_diff, A, B, ], # 14 - AC_A AC_C BC_B
[ $c_diff, A, B, C ], # 15 - AC_A AC_C BC_B BC_C
[ $noop, ], # 16 - AB_B
[ $no_change, ], # 17 - AB_B BC_C
[ $b_diff, B ], # 18 - AB_B BC_B
[ $noop, ], # 19 - AB_B BC_B BC_C
[ $a_diff, B, C ], # 20 - AB_B AC_C
[ $noop, ], # 21 - AB_B AC_C BC_C
[ $noop, ], # 22 - AB_B AC_C BC_B
[ $conflict, D, B, C ], # 23 - AB_B AC_C BC_B BC_C
[ $b_diff, B ], # 24 - AB_B AC_A
[ $noop, ], # 25 - AB_B AC_A BC_C
[ $c_diff, D, B, C ], # 26 - AB_B AC_A BC_B
[ $noop, ], # 27 - AB_B AC_A BC_B BC_C
[ $a_diff, B, C ], # 28 - AB_B AC_A AC_C
[ $noop, ], # 29 - AB_B AC_A AC_C BC_C
[ $noop, ], # 30 - AB_B AC_A AC_C BC_B
[ $b_diff, B ], # 31 - AB_B AC_A AC_C BC_B BC_C
[ $no_change, A, B, C ], # 32 - AB_A
[ $b_diff, A, C ], # 33 - AB_A BC_C
[ $noop, ], # 34 - AB_A BC_B
[ $b_diff, A, C ], # 35 - AB_A BC_B BC_C
[ $noop, ], # 36 - AB_A AC_C
[ $noop, ], # 37 - AB_A AC_C BC_C
[ $noop, ], # 38 - AB_A AC_C BC_B
[ $noop, ], # 39 - AB_A AC_C BC_B BC_C
[ $a_diff, A, ], # 40 - AB_A AC_A
[ $noop, ], # 41 - AB_A AC_A BC_C
[ $a_diff, A ], # 42 - AB_A AC_A BC_B
[ $noop, ], # 43 - AB_A AC_A BC_B BC_C
[ $noop, ], # 44 - AB_A AC_A AC_C
[ $c_diff, A, D, C ], # 45 - AB_A AC_A AC_C BC_C
[ $noop, ], # 46 - AB_A AC_A AC_C BC_B
[ $noop, ], # 47 - AB_A AC_A AC_C BC_B BC_C
[ $noop, ], # 48 - AB_A AB_B
[ $b_diff, A, C ], # 49 - AB_A AB_B BC_C
[ $noop, ], # 50 - AB_A AB_B BC_B
[ $b_diff, A, B, C ], # 51 - AB_A AB_B BC_B BC_C
[ $a_diff, B, C ], # 52 - AB_A AB_B AC_C
[ $noop, ], # 53 - AB_A AB_B AC_C BC_C
[ $noop, ], # 54 - AB_A AB_B AC_C BC_B
[ $c_diff, C ], # 55 - AB_A AB_B AC_C BC_B BC_C
[ $b_diff, A, C ], # 56 - AB_A AB_B AC_A
[ $noop, ], # 57 - AB_A AB_B AC_A BC_C
[ $b_diff, A, B, D ], # 58 - AB_A AB_B AC_A BC_B
[ $noop, ], # 59 - AB_A AB_B AC_A BC_B BC_C
[ $a_diff, A, B, C ], # 60 - AB_A AB_B AC_A AC_C
[ $conflict, A, D, C ], # 61 - AB_A AB_B AC_A AC_C BC_C
[ $conflict, A, B, D ], # 62 - AB_A AB_B AC_A AC_C BC_B
[ $conflict, A, B, C ], # 63 - AB_A AB_B AC_A AC_C BC_B BC_C
);
my $t; # temporary values
# while we have something to work with...
while((grep { scalar(@{$_}) > 0 } values %diffs)
&& (grep { $pos[$_] < $sizes[$_] } (A, B, C)))
{
@matches[AB_A, AB_B, AC_A, AC_C, BC_B, BC_C] = undef;
foreach my $i (A, B, C) {
foreach my $j (A, B, C) {
next if $i == $j;
$t = $abc_s[($i|$j) * 8 | $i];
$matches[$t] = 1 if @{$diffs{$t}} && $pos[$i] == $diffs{$t} -> [0];
}
}
$callback = 0;
$callback |= $_ foreach grep { $matches[$_] } ( AB_A, AB_B, AC_A, AC_C, BC_B, BC_C );
my @args = @{$Callback_Map[$callback]};
diag(">>>>>> We hit a noop") if @args == 1;
my $f = shift @args;
diag(join "", "callback: $callback - \@pos: ", join(", ", @pos[A, B, C]), "\n");
diag(">>>>>> Callback is a no-op") unless @args;
diag(join "", " matches: ", join(", ", map { defined($_) ? $_ : 'undef' } @matches[AB_A, AB_B, AC_A, AC_C, BC_B, BC_C]), "\n");
diag(join "", " diffs: ", join(", ", map { defined($_) ? $_ : 'undef' } map { $diffs{$_}->[0] } (AB_A, AB_B, AC_A, AC_C, BC_B, BC_C)), "\n");
diag(join "", "args: ", join(", ", map { (qw(- C B - A - - - D))[$_] } @args), "(", join(", ", map { defined($_) ? $_ : 'undef' } @pos[@args]), ")\n");
diag('--------------------');
&{$f}(@pos[@args]);
foreach (@args) {
$pos[$_]++ unless $_ == D;
if($_ eq A) {
shift @{$diffs{&AB_A}} while @{$diffs{&AB_A}} && $diffs{&AB_A}[0] < $pos[$_];# if $matches[AB_A];
shift @{$diffs{&AC_A}} while @{$diffs{&AC_A}} && $diffs{&AC_A}[0] < $pos[$_];#if $matches[AC_A];
} elsif($_ eq B) {
shift @{$diffs{&AB_B}} while @{$diffs{&AB_B}} && $diffs{&AB_B}[0] < $pos[$_];#if $matches[AB_B];
shift @{$diffs{&BC_B}} while @{$diffs{&BC_B}} && $diffs{&BC_B}[0] < $pos[$_];#if $matches[BC_B];
} elsif($_ eq C) {
shift @{$diffs{&AC_C}} while @{$diffs{&AC_C}} && $diffs{&AC_C}[0] < $pos[$_];#if $matches[AC_C];
shift @{$diffs{&BC_C}} while @{$diffs{&BC_C}} && $diffs{&BC_C}[0] < $pos[$_];#if $matches[BC_C];
}
}
last unless @args;
}
my $switch;
my @args;
while(grep { $pos[$_] < $sizes[$_] } (A, B, C)) {
$switch = 0;
@args = ();
foreach my $i (A, B, C) {
if($pos[$i] < $sizes[$i]) {
#warn "$i: $pos[$i] < $sizes[$i]\n";
$switch |= $i;
#warn "switch: $switch\n";
push @args, $pos[$i]++;
}
}
my $match = $switch;
$switch = ( 0, 5, 24, 17, 34, 8, 10, 0 )[$switch];
#main::diag(join"", "callback: $switch - \@pos: ", join(", ", @pos[A, B, C]));
#main::diag(join"", " match: $match");
&{$Callback_Map[$switch][0]}(@args)
if $Callback_Map[$switch];
}
}
sub merge {
my $pivot = shift; # array ref
my $doca = shift; # array ref
my $docb = shift; # array ref
my $callbacks = shift || {};
my $keyGen = shift;
my $conflictCallback = $callbacks -> {'CONFLICT'} || sub ($$) { (
q{<!-- ------ START CONFLICT ------ -->},
(@{$_[0]}),
q{<!-- ---------------------------- -->},
(@{$_[1]}),
q{<!-- ------ END CONFLICT ------ -->},
) };
my $diff = diff3($pivot, $doca, $docb, $keyGen, @_);
# print Data::Dumper -> Dump([$diff]), "\n";
my @ret;
my @conflict = ( [], [] );
foreach my $h (@{$diff}) {
my $i = 0;
#print "op: ", $h -> [0];
if($h -> [0] eq 'c') { # conflict
push @{$conflict[0]}, $h -> [2] if defined $h -> [2];
push @{$conflict[1]}, $h -> [3] if defined $h -> [3];
}
else {
if(@{$conflict[0]} || @{$conflict[1]}) {
push @ret, &$conflictCallback(@conflict);
@conflict = ( [], [] );
}
if($h -> [0] eq 'u') { # unchanged
push @ret, $h -> [2] || $h -> [3];
}
elsif($h -> [0] eq 'o') { # added
push @ret, $h -> [2] if defined $h -> [2];
}
elsif($h -> [0] eq 'l') { # added by left
push @ret, $h -> [2] if defined $h -> [2];
}
elsif($h -> [0] eq 'r') { # added by right
push @ret, $h -> [3] if defined $h -> [3];
}
}
#print " : ", join(" ", @ret), " [$$h[1],$$h[2],$$h[3]]\n";
}
if(@{$conflict[0]} || @{$conflict[1]}) {
push @ret, &$conflictCallback(@conflict);
}
if(wantarray) {
return @ret;
}
return \@ret;
}
__END__
#
# For testing:
#
sub main::diag {
warn join("", @_) , "\n";
}
print join(" ", merge(
#print Data::Dumper -> Dump([
# merge(
# #[qw(a b c d h i j)], # ancestor
# #[qw(a b c d f h i j)], # left
# #[qw(a b c e g )], # right
[qw(0 1 2 3 4 7 9 b)],
[qw(0 6 8 a b)],
[qw(0 1 2 3 5 8 a b)],
##
{
CONFLICT => sub ($$) { (
q{<}, @{$_[0]}, q{|}, @{$_[1]}, q{>}
) },
},
)), "\n";
#)]), "\n";
#print join(" ", @{
# [qw(0 1 @ < 3 | # > 6)]
# }), "\n";
1;
__END__
1;
__END__
=head1 NAME
Algorithm::Merge - Three-way merge and diff
=head1 SYNOPSIS
use Algorithm::Merge qw(merge diff3 traverse_sequences3);
@merged = merge(\@ancestor, \@a, \@b, {
CONFLICT => sub { }
});
@merged = merge(\@ancestor, \@a, \@b, {
CONFLICT => sub { }
}, $key_generation_function);
$merged = merge(\@ancestor, \@a, \@b, {
CONFLICT => sub { }
});
$merged = merge(\@ancestor, \@a, \@b, {
CONFLICT => sub { }
}, $key_generation_function);
@diff = diff3(\@ancestor, \@a, \@b);
@diff = diff3(\@ancestor, \@a, \@b, $key_generation_function);
$diff = diff3(\@ancestor, \@a, \@b);
$diff = diff3(\@ancestor, \@a, \@b, $key_generation_function);
@trav = traverse_sequences3(\@ancestor, \@a, \@b, {
# callbacks
});
@trav = traverse_sequences3(\@ancestor, \@a, \@b, {
# callbacks
}, $key_generation_function);
$trav = traverse_sequences3(\@ancestor, \@a, \@b, {
# callbacks
});
$trav = traverse_sequences3(\@ancestor, \@a, \@b, {
# callbacks
}, $key_generation_function);
=head1 USAGE
This module complements L<Algorithm::Diff|Algorithm::Diff> by
providing three-way merge and diff functions.
In this documentation, the first list to C<diff3>, C<merge>, and
C<traverse_sequences3> is
called the `original' list. The second list is the `left' list. The
third list is the `right' list.
The optional key generation arguments are the same as in
L<Algorithm::Diff|Algorithm::Diff>. See L<Algorithm::Diff> for more
information.
=head2 diff3
Given references to three lists of items, C<diff3> performs a
three-way difference.
This function returns an array of operations describing how the
left and right lists differ from the original list. In scalar
context, this function returns a reference to such an array.
Perhaps an example would be useful.
Given the following three lists,
original: a b c e f h i k
left: a b d e f g i j k
right: a b c d e h i j k
merge: a b d e g i j k
we have the following result from diff3:
[ 'u', 'a', 'a', 'a' ],
[ 'u', 'b', 'b', 'b' ],
[ 'l', 'c', undef, 'c' ],
[ 'o', undef, 'd', 'd' ],
[ 'u', 'e', 'e', 'e' ],
[ 'r', 'f', 'f', undef ],
[ 'o', 'h', 'g', 'h' ],
[ 'u', 'i', 'i', 'i' ],
[ 'o', undef, 'j', 'j' ],
[ 'u', 'k', 'k', 'k' ]
The first element in each row is the array with the difference:
c - conflict (no two are the same)
l - left is different
o - original is different
r - right is different
u - unchanged
The next three elements are the lists from the original, left,
and right arrays respectively that the row refers to (in the synopsis,
these are C<@ancestor>, C<@a>, and C<@b>, respectively).
=head2 merge
Given references to three lists of items, C<merge> performs a three-way
merge. The C<merge> function uses the C<diff3> function to do most of
the work.
The only callback currently used is C<CONFLICT> which should be a
reference to a subroutine that accepts two array references. The
first array reference is to a list of elements from the left list.
The second array reference is to a list of elements from the right list.
This callback should return a list of elements to place in the merged
list in place of the conflict.
The default C<CONFLICT> callback returns the following:
q{<!-- ------ START CONFLICT ------ -->},
(@left),
q{<!-- ---------------------------- -->},
(@right),
q{<!-- ------ END CONFLICT ------ -->},
=head2 traverse_sequences3
This is the workhorse function that goes through the three sequences
and calls the callback functions.
The following callbacks are supported.
=over 4
=item NO_CHANGE
This is called if all three sequences have the same element at the
current position. The arguments are the current positions within each
sequence, the first argument being the current position within the
first sequence.
=item A_DIFF
This is called if the first sequence is different than the other two
sequences at the current position.
This callback will be called with one, two, or three arguments.
If one argument, then only the element at the given position from the
first sequence is not in either of the other two sequences.
If two arguments, then there is no element in the first sequence that
corresponds to the elements at the given positions in the second and
third sequences.
If three arguments, then the element at the given position in the first
sequence is different than the corresponding element in the other two
sequences, but the other two sequences have corresponding elements.
=item B_DIFF
This is called if the second sequence is different than the other two
sequences at the current position.
This callback will be called with one, two, or three arguments.
If one argument, then only the element at the given position from the
second sequence is not in either of the other two sequences.
If two arguments, then there is no element in the second sequence that
corresponds to the elements at the given positions in the first and
third sequences.
If three arguments, then the element at the given position in the second
sequence is different than the corresponding element in the other two
sequences, but the other two sequences have corresponding elements.
=item C_DIFF
This is called if the third sequence is different than the other two
sequences at the current position.
This callback will be called with one, two, or three arguments.
If one argument, then only the element at the given position from the
third sequence is not in either of the other two sequences.
If two arguments, then there is no element in the third sequence that
corresponds to the elements at the given positions in the first and
second sequences.
If three arguments, then the element at the given position in the third
sequence is different than the corresponding element in the other two
sequences, but the other two sequences have corresponding elements.
=item CONFLICT
This is called if all three sequences have different elements at the
current position. The three arguments are the current positions within
each sequence.
=back
=head1 BUGS
Most assuredly there are bugs. If a pattern similar to the above
example does not work, send it to <jsmith@cpan.org> or report it on
<http://rt.cpan.org/>, the CPAN bug tracker.
L<Algorithm::Diff|Algorithm::Diff>'s implementation of
C<traverse_sequences> may not be symmetric with respect to the input
sequences if the second and third sequence are of different lengths.
Because of this, C<traverse_sequences3> will calculate the diffs of
the second and third sequences as passed and swapped. If the differences
are not the same, it will issue an `Algorithm::Diff::diff is not symmetric
for second and third sequences...' warning. It will try to handle
this, but there may be some cases where it can't.
=head1 SEE ALSO
L<Algorithm::Diff>.
=head1 AUTHOR
James G. Smith, <jsmith@cpan.org>
=head1 COPYRIGHT
Copyright (C) 2003, 2007 Texas A&M University. All Rights Reserved.
This module is free software; you may redistribute it and/or
modify it under the same terms as Perl itself.
|