This file is indexed.

/usr/bin/enc2xs is in perl 5.14.2-21+deb7u3.

This file is owned by root:root, with mode 0o755.

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
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
#!/usr/bin/perl
    eval 'exec /usr/bin/perl -S $0 ${1+"$@"}'
	if $running_under_some_shell;
#!./perl
BEGIN {
    # @INC poking  no longer needed w/ new MakeMaker and Makefile.PL's
    # with $ENV{PERL_CORE} set
    # In case we need it in future...
    require Config; import Config;
}
use strict;
use warnings;
use Getopt::Std;
use Config;
my @orig_ARGV = @ARGV;
our $VERSION  = do { my @r = (q$Revision: 2.7 $ =~ /\d+/g); sprintf "%d."."%02d" x $#r, @r };

# These may get re-ordered.
# RAW is a do_now as inserted by &enter
# AGG is an aggreagated do_now, as built up by &process

use constant {
  RAW_NEXT => 0,
  RAW_IN_LEN => 1,
  RAW_OUT_BYTES => 2,
  RAW_FALLBACK => 3,

  AGG_MIN_IN => 0,
  AGG_MAX_IN => 1,
  AGG_OUT_BYTES => 2,
  AGG_NEXT => 3,
  AGG_IN_LEN => 4,
  AGG_OUT_LEN => 5,
  AGG_FALLBACK => 6,
};

# (See the algorithm in encengine.c - we're building structures for it)

# There are two sorts of structures.
# "do_now" (an array, two variants of what needs storing) is whatever we need
# to do now we've read an input byte.
# It's housed in a "do_next" (which is how we got to it), and in turn points
# to a "do_next" which contains all the "do_now"s for the next input byte.

# There will be a "do_next" which is the start state.
# For a single byte encoding it's the only "do_next" - each "do_now" points
# back to it, and each "do_now" will cause bytes. There is no state.

# For a multi-byte encoding where all characters in the input are the same
# length, then there will be a tree of "do_now"->"do_next"->"do_now"
# branching out from the start state, one step for each input byte.
# The leaf "do_now"s will all be at the same distance from the start state,
# only the leaf "do_now"s cause output bytes, and they in turn point back to
# the start state.

# For an encoding where there are varaible length input byte sequences, you
# will encounter a leaf "do_now" sooner for the shorter input sequences, but
# as before the leaves will point back to the start state.

# The system will cope with escape encodings (imagine them as a mostly
# self-contained tree for each escape state, and cross links between trees
# at the state-switching characters) but so far no input format defines these.

# The system will also cope with having output "leaves" in the middle of
# the bifurcating branches, not just at the extremities, but again no
# input format does this yet.

# There are two variants of the "do_now" structure. The first, smaller variant
# is generated by &enter as the input file is read. There is one structure
# for each input byte. Say we are mapping a single byte encoding to a
# single byte encoding, with  "ABCD" going "abcd". There will be
# 4 "do_now"s, {"A" => [...,"a",...], "B" => [...,"b",...], "C"=>..., "D"=>...}

# &process then walks the tree, building aggregate "do_now" structres for
# adjacent bytes where possible. The aggregate is for a contiguous range of
# bytes which each produce the same length of output, each move to the
# same next state, and each have the same fallback flag.
# So our 4 RAW "do_now"s above become replaced by a single structure
# containing:
# ["A", "D", "abcd", 1, ...]
# ie, for an input byte $_ in "A".."D", output 1 byte, found as
# substr ("abcd", (ord $_ - ord "A") * 1, 1)
# which maps very nicely into pointer arithmetic in C for encengine.c

sub encode_U
{
 # UTF-8 encode long hand - only covers part of perl's range
 ## my $uv = shift;
 # chr() works in native space so convert value from table
 # into that space before using chr().
 my $ch = chr(utf8::unicode_to_native($_[0]));
 # Now get core perl to encode that the way it likes.
 utf8::encode($ch);
 return $ch;
}

sub encode_S
{
 # encode single byte
 ## my ($ch,$page) = @_; return chr($ch);
 return chr $_[0];
}

sub encode_D
{
 # encode double byte MS byte first
 ## my ($ch,$page) = @_; return chr($page).chr($ch);
 return chr ($_[1]) . chr $_[0];
}

sub encode_M
{
 # encode Multi-byte - single for 0..255 otherwise double
 ## my ($ch,$page) = @_;
 ## return &encode_D if $page;
 ## return &encode_S;
 return chr ($_[1]) . chr $_[0] if $_[1];
 return chr $_[0];
}

my %encode_types = (U => \&encode_U,
                    S => \&encode_S,
                    D => \&encode_D,
                    M => \&encode_M,
                   );

# Win32 does not expand globs on command line
eval "\@ARGV = map(glob(\$_),\@ARGV)" if ($^O eq 'MSWin32');

my %opt;
# I think these are:
# -Q to disable the duplicate codepoint test
# -S make mapping errors fatal
# -q to remove comments written to output files
# -O to enable the (brute force) substring optimiser
# -o <output> to specify the output file name (else it's the first arg)
# -f <inlist> to give a file with a list of input files (else use the args)
# -n <name> to name the encoding (else use the basename of the input file.
getopts('CM:SQqOo:f:n:',\%opt);

$opt{M} and make_makefile_pl($opt{M}, @ARGV);
$opt{C} and make_configlocal_pm($opt{C}, @ARGV);

# This really should go first, else the die here causes empty (non-erroneous)
# output files to be written.
my @encfiles;
if (exists $opt{'f'}) {
    # -F is followed by name of file containing list of filenames
    my $flist = $opt{'f'};
    open(FLIST,$flist) || die "Cannot open $flist:$!";
    chomp(@encfiles = <FLIST>);
    close(FLIST);
} else {
    @encfiles = @ARGV;
}

my $cname = (exists $opt{'o'}) ? $opt{'o'} : shift(@ARGV);
chmod(0666,$cname) if -f $cname && !-w $cname;
open(C,">$cname") || die "Cannot open $cname:$!";

my $dname = $cname;
my $hname = $cname;

my ($doC,$doEnc,$doUcm,$doPet);

if ($cname =~ /\.(c|xs)$/i) # VMS may have upcased filenames with DECC$ARGV_PARSE_STYLE defined
 {
  $doC = 1;
  $dname =~ s/(\.[^\.]*)?$/.exh/;
  chmod(0666,$dname) if -f $cname && !-w $dname;
  open(D,">$dname") || die "Cannot open $dname:$!";
  $hname =~ s/(\.[^\.]*)?$/.h/;
  chmod(0666,$hname) if -f $cname && !-w $hname;
  open(H,">$hname") || die "Cannot open $hname:$!";

  foreach my $fh (\*C,\*D,\*H)
  {
   print $fh <<"END" unless $opt{'q'};
/*
 !!!!!!!   DO NOT EDIT THIS FILE   !!!!!!!
 This file was autogenerated by:
 $^X $0 @orig_ARGV
 enc2xs VERSION $VERSION
*/
END
  }

  if ($cname =~ /(\w+)\.xs$/)
   {
    print C "#include <EXTERN.h>\n";
    print C "#include <perl.h>\n";
    print C "#include <XSUB.h>\n";
    print C "#define U8 U8\n";
   }
  print C "#include \"encode.h\"\n\n";

 }
elsif ($cname =~ /\.enc$/)
 {
  $doEnc = 1;
 }
elsif ($cname =~ /\.ucm$/)
 {
  $doUcm = 1;
 }
elsif ($cname =~ /\.pet$/)
 {
  $doPet = 1;
 }

my %encoding;
my %strings;
my $string_acc;
my %strings_in_acc;

my $saved = 0;
my $subsave = 0;
my $strings = 0;

sub cmp_name
{
 if ($a =~ /^.*-(\d+)/)
  {
   my $an = $1;
   if ($b =~ /^.*-(\d+)/)
    {
     my $r = $an <=> $1;
     return $r if $r;
    }
  }
 return $a cmp $b;
}


foreach my $enc (sort cmp_name @encfiles)
 {
  my ($name,$sfx) = $enc =~ /^.*?([\w-]+)\.(enc|ucm)$/;
  $name = $opt{'n'} if exists $opt{'n'};
  if (open(E,$enc))
   {
    if ($sfx eq 'enc')
     {
      compile_enc(\*E,lc($name));
     }
    else
     {
      compile_ucm(\*E,lc($name));
     }
   }
  else
   {
    warn "Cannot open $enc for $name:$!";
   }
 }

if ($doC)
 {
  print STDERR "Writing compiled form\n";
  foreach my $name (sort cmp_name keys %encoding)
   {
    my ($e2u,$u2e,$erep,$min_el,$max_el) = @{$encoding{$name}};
    process($name.'_utf8',$e2u);
    addstrings(\*C,$e2u);

    process('utf8_'.$name,$u2e);
    addstrings(\*C,$u2e);
   }
  outbigstring(\*C,"enctable");
  foreach my $name (sort cmp_name keys %encoding)
   {
    my ($e2u,$u2e,$erep,$min_el,$max_el) = @{$encoding{$name}};
    outtable(\*C,$e2u, "enctable");
    outtable(\*C,$u2e, "enctable");

    # push(@{$encoding{$name}},outstring(\*C,$e2u->{Cname}.'_def',$erep));
   }
  my $cpp = ($Config{d_cplusplus} || '') eq 'define';
  my $exta = $cpp ? 'extern "C" ' : "static";
  my $extb = $cpp ? 'extern "C" ' : "";
  foreach my $enc (sort cmp_name keys %encoding)
   {
    # my ($e2u,$u2e,$rep,$min_el,$max_el,$rsym) = @{$encoding{$enc}};
    my ($e2u,$u2e,$rep,$min_el,$max_el) = @{$encoding{$enc}};
    #my @info = ($e2u->{Cname},$u2e->{Cname},$rsym,length($rep),$min_el,$max_el);
    my $replen = 0; 
    $replen++ while($rep =~ /\G\\x[0-9A-Fa-f]/g);
    my $sym = "${enc}_encoding";
    $sym =~ s/\W+/_/g;
    my @info = ($e2u->{Cname},$u2e->{Cname},"${sym}_rep_character",$replen,
        $min_el,$max_el);
    print C "${exta} const U8 ${sym}_rep_character[] = \"$rep\";\n";
    print C "${exta} const char ${sym}_enc_name[] = \"$enc\";\n\n";
    print C "${extb} const encode_t $sym = \n";
    # This is to make null encoding work -- dankogai
    for (my $i = (scalar @info) - 1;  $i >= 0; --$i){
    $info[$i] ||= 1;
    }
    # end of null tweak -- dankogai
    print C " {",join(',',@info,"{${sym}_enc_name,(const char *)0}"),"};\n\n";
   }

  foreach my $enc (sort cmp_name keys %encoding)
   {
    my $sym = "${enc}_encoding";
    $sym =~ s/\W+/_/g;
    print H "extern encode_t $sym;\n";
    print D " Encode_XSEncoding(aTHX_ &$sym);\n";
   }

  if ($cname =~ /(\w+)\.xs$/)
   {
    my $mod = $1;
    print C <<'END';

static void
Encode_XSEncoding(pTHX_ encode_t *enc)
{
 dSP;
 HV *stash = gv_stashpv("Encode::XS", TRUE);
 SV *sv    = sv_bless(newRV_noinc(newSViv(PTR2IV(enc))),stash);
 int i = 0;
 PUSHMARK(sp);
 XPUSHs(sv);
 while (enc->name[i])
  {
   const char *name = enc->name[i++];
   XPUSHs(sv_2mortal(newSVpvn(name,strlen(name))));
  }
 PUTBACK;
 call_pv("Encode::define_encoding",G_DISCARD);
 SvREFCNT_dec(sv);
}

END

    print C "\nMODULE = Encode::$mod\tPACKAGE = Encode::$mod\n\n";
    print C "BOOT:\n{\n";
    print C "#include \"$dname\"\n";
    print C "}\n";
   }
  # Close in void context is bad, m'kay
  close(D) or warn "Error closing '$dname': $!";
  close(H) or warn "Error closing '$hname': $!";

  my $perc_saved    = $saved/($strings + $saved) * 100;
  my $perc_subsaved = $subsave/($strings + $subsave) * 100;
  printf STDERR "%d bytes in string tables\n",$strings;
  printf STDERR "%d bytes (%.3g%%) saved spotting duplicates\n",
    $saved, $perc_saved              if $saved;
  printf STDERR "%d bytes (%.3g%%) saved using substrings\n",
    $subsave, $perc_subsaved         if $subsave;
 }
elsif ($doEnc)
 {
  foreach my $name (sort cmp_name keys %encoding)
   {
    my ($e2u,$u2e,$erep,$min_el,$max_el) = @{$encoding{$name}};
    output_enc(\*C,$name,$e2u);
   }
 }
elsif ($doUcm)
 {
  foreach my $name (sort cmp_name keys %encoding)
   {
    my ($e2u,$u2e,$erep,$min_el,$max_el) = @{$encoding{$name}};
    output_ucm(\*C,$name,$u2e,$erep,$min_el,$max_el);
   }
 }

# writing half meg files and then not checking to see if you just filled the
# disk is bad, m'kay
close(C) or die "Error closing '$cname': $!";

# End of the main program.

sub compile_ucm
{
 my ($fh,$name) = @_;
 my $e2u = {};
 my $u2e = {};
 my $cs;
 my %attr;
 while (<$fh>)
  {
   s/#.*$//;
   last if /^\s*CHARMAP\s*$/i;
   if (/^\s*<(\w+)>\s+"?([^"]*)"?\s*$/i) # " # Grrr
    {
     $attr{$1} = $2;
    }
  }
 if (!defined($cs =  $attr{'code_set_name'}))
  {
   warn "No <code_set_name> in $name\n";
  }
 else
  {
   $name = $cs unless exists $opt{'n'};
  }
 my $erep;
 my $urep;
 my $max_el;
 my $min_el;
 if (exists $attr{'subchar'})
  {
   #my @byte;
   #$attr{'subchar'} =~ /^\s*/cg;
   #push(@byte,$1) while $attr{'subchar'} =~ /\G\\x([0-9a-f]+)/icg;
   #$erep = join('',map(chr(hex($_)),@byte));
   $erep = $attr{'subchar'}; 
   $erep =~ s/^\s+//; $erep =~ s/\s+$//;
  }
 print "Reading $name ($cs)\n";
 my $nfb = 0;
 my $hfb = 0;
 while (<$fh>)
  {
   s/#.*$//;
   last if /^\s*END\s+CHARMAP\s*$/i;
   next if /^\s*$/;
   my (@uni, @byte) = ();
   my ($uni, $byte, $fb) = m/^(\S+)\s+(\S+)\s+(\S+)\s+/o
       or die "Bad line: $_";
   while ($uni =~  m/\G<([U0-9a-fA-F\+]+)>/g){
       push @uni, map { substr($_, 1) } split(/\+/, $1);
   }
   while ($byte =~ m/\G\\x([0-9a-fA-F]+)/g){
       push @byte, $1;
   }
   if (@uni)
    {
     my $uch =  join('', map { encode_U(hex($_)) } @uni );
     my $ech = join('',map(chr(hex($_)),@byte));
     my $el  = length($ech);
     $max_el = $el if (!defined($max_el) || $el > $max_el);
     $min_el = $el if (!defined($min_el) || $el < $min_el);
     if (length($fb))
      {
       $fb = substr($fb,1);
       $hfb++;
      }
     else
      {
       $nfb++;
       $fb = '0';
      }
     # $fb is fallback flag
     # 0 - round trip safe
     # 1 - fallback for unicode -> enc
     # 2 - skip sub-char mapping
     # 3 - fallback enc -> unicode
     enter($u2e,$uch,$ech,$u2e,$fb+0) if ($fb =~ /[01]/);
     enter($e2u,$ech,$uch,$e2u,$fb+0) if ($fb =~ /[03]/);
    }
   else
    {
     warn $_;
    }
  }
 if ($nfb && $hfb)
  {
   die "$nfb entries without fallback, $hfb entries with\n";
  }
 $encoding{$name} = [$e2u,$u2e,$erep,$min_el,$max_el];
}



sub compile_enc
{
 my ($fh,$name) = @_;
 my $e2u = {};
 my $u2e = {};

 my $type;
 while ($type = <$fh>)
  {
   last if $type !~ /^\s*#/;
  }
 chomp($type);
 return if $type eq 'E';
 # Do the hash lookup once, rather than once per function call. 4% speedup.
 my $type_func = $encode_types{$type};
 my ($def,$sym,$pages) = split(/\s+/,scalar(<$fh>));
 warn "$type encoded $name\n";
 my $rep = '';
 # Save a defined test by setting these to defined values.
 my $min_el = ~0; # A very big integer
 my $max_el = 0;  # Anything must be longer than 0
 {
  my $v = hex($def);
  $rep = &$type_func($v & 0xFF, ($v >> 8) & 0xffe);
 }
 my $errors;
 my $seen;
 # use -Q to silence the seen test. Makefile.PL uses this by default.
 $seen = {} unless $opt{Q};
 do
  {
   my $line = <$fh>;
   chomp($line);
   my $page = hex($line);
   my $ch = 0;
   my $i = 16;
   do
    {
     # So why is it 1% faster to leave the my here?
     my $line = <$fh>;
     $line =~ s/\r\n$/\n/;
     die "$.:${line}Line should be exactly 65 characters long including
     newline (".length($line).")" unless length ($line) == 65;
     # Split line into groups of 4 hex digits, convert groups to ints
     # This takes 65.35		
     # map {hex $_} $line =~ /(....)/g
     # This takes 63.75 (2.5% less time)
     # unpack "n*", pack "H*", $line
     # There's an implicit loop in map. Loops are bad, m'kay. Ops are bad, m'kay
     # Doing it as while ($line =~ /(....)/g) took 74.63
     foreach my $val (unpack "n*", pack "H*", $line)
      {
       next if $val == 0xFFFD;
       my $ech = &$type_func($ch,$page);
       if ($val || (!$ch && !$page))
        {
         my $el  = length($ech);
         $max_el = $el if $el > $max_el;
         $min_el = $el if $el < $min_el;
         my $uch = encode_U($val);
         if ($seen) {
           # We're doing the test.
           # We don't need to read this quickly, so storing it as a scalar,
           # rather than 3 (anon array, plus the 2 scalars it holds) saves
           # RAM and may make us faster on low RAM systems. [see __END__]
           if (exists $seen->{$uch})
             {
               warn sprintf("U%04X is %02X%02X and %04X\n",
                            $val,$page,$ch,$seen->{$uch});
               $errors++;
             }
           else
             {
               $seen->{$uch} = $page << 8 | $ch;
             }
         }
         # Passing 2 extra args each time is 3.6% slower!
         # Even with having to add $fallback ||= 0 later
         enter_fb0($e2u,$ech,$uch);
         enter_fb0($u2e,$uch,$ech);
        }
       else
        {
         # No character at this position
         # enter($e2u,$ech,undef,$e2u);
        }
       $ch++;
      }
    } while --$i;
  } while --$pages;
 die "\$min_el=$min_el, \$max_el=$max_el - seems we read no lines"
   if $min_el > $max_el;
 die "$errors mapping conflicts\n" if ($errors && $opt{'S'});
 $encoding{$name} = [$e2u,$u2e,$rep,$min_el,$max_el];
}

# my ($a,$s,$d,$t,$fb) = @_;
sub enter {
  my ($current,$inbytes,$outbytes,$next,$fallback) = @_;
  # state we shift to after this (multibyte) input character defaults to same
  # as current state.
  $next ||= $current;
  # Making sure it is defined seems to be faster than {no warnings;} in
  # &process, or passing it in as 0 explicity.
  # XXX $fallback ||= 0;

  # Start at the beginning and work forwards through the string to zero.
  # effectively we are removing 1 character from the front each time
  # but we don't actually edit the string. [this alone seems to be 14% speedup]
  # Hence -$pos is the length of the remaining string.
  my $pos = -length $inbytes;
  while (1) {
    my $byte = substr $inbytes, $pos, 1;
    #  RAW_NEXT => 0,
    #  RAW_IN_LEN => 1,
    #  RAW_OUT_BYTES => 2,
    #  RAW_FALLBACK => 3,
    # to unicode an array would seem to be better, because the pages are dense.
    # from unicode can be very sparse, favouring a hash.
    # hash using the bytes (all length 1) as keys rather than ord value,
    # as it's easier to sort these in &process.

    # It's faster to always add $fallback even if it's undef, rather than
    # choosing between 3 and 4 element array. (hence why we set it defined
    # above)
    my $do_now = $current->{Raw}{$byte} ||= [{},-$pos,'',$fallback];
    # When $pos was -1 we were at the last input character.
    unless (++$pos) {
      $do_now->[RAW_OUT_BYTES] = $outbytes;
      $do_now->[RAW_NEXT] = $next;
      return;
    }
    # Tail recursion. The intermdiate state may not have a name yet.
    $current = $do_now->[RAW_NEXT];
  }
}

# This is purely for optimistation. It's just &enter hard coded for $fallback
# of 0, using only a 3 entry array ref to save memory for every entry.
sub enter_fb0 {
  my ($current,$inbytes,$outbytes,$next) = @_;
  $next ||= $current;

  my $pos = -length $inbytes;
  while (1) {
    my $byte = substr $inbytes, $pos, 1;
    my $do_now = $current->{Raw}{$byte} ||= [{},-$pos,''];
    unless (++$pos) {
      $do_now->[RAW_OUT_BYTES] = $outbytes;
      $do_now->[RAW_NEXT] = $next;
      return;
    }
    $current = $do_now->[RAW_NEXT];
  }
}

sub process
{
  my ($name,$a) = @_;
  $name =~ s/\W+/_/g;
  $a->{Cname} = $name;
  my $raw = $a->{Raw};
  my ($l, $agg_max_in, $agg_next, $agg_in_len, $agg_out_len, $agg_fallback);
  my @ent;
  $agg_max_in = 0;
  foreach my $key (sort keys %$raw) {
    #  RAW_NEXT => 0,
    #  RAW_IN_LEN => 1,
    #  RAW_OUT_BYTES => 2,
    #  RAW_FALLBACK => 3,
    my ($next, $in_len, $out_bytes, $fallback) = @{$raw->{$key}};
    # Now we are converting from raw to aggregate, switch from 1 byte strings
    # to numbers
    my $b = ord $key;
    $fallback ||= 0;
    if ($l &&
        # If this == fails, we're going to reset $agg_max_in below anyway.
        $b == ++$agg_max_in &&
        # References in numeric context give the pointer as an int.
        $agg_next == $next &&
        $agg_in_len == $in_len &&
        $agg_out_len == length $out_bytes &&
        $agg_fallback == $fallback
        # && length($l->[AGG_OUT_BYTES]) < 16
       ) {
      #     my $i = ord($b)-ord($l->[AGG_MIN_IN]);
      # we can aggregate this byte onto the end.
      $l->[AGG_MAX_IN] = $b;
      $l->[AGG_OUT_BYTES] .= $out_bytes;
    } else {
      # AGG_MIN_IN => 0,
      # AGG_MAX_IN => 1,
      # AGG_OUT_BYTES => 2,
      # AGG_NEXT => 3,
      # AGG_IN_LEN => 4,
      # AGG_OUT_LEN => 5,
      # AGG_FALLBACK => 6,
      # Reset the last thing we saw, plus set 5 lexicals to save some derefs.
      # (only gains .6% on euc-jp  -- is it worth it?)
      push @ent, $l = [$b, $agg_max_in = $b, $out_bytes, $agg_next = $next,
                       $agg_in_len = $in_len, $agg_out_len = length $out_bytes,
                       $agg_fallback = $fallback];
    }
    if (exists $next->{Cname}) {
      $next->{'Forward'} = 1 if $next != $a;
    } else {
      process(sprintf("%s_%02x",$name,$b),$next);
    }
  }
  # encengine.c rules say that last entry must be for 255
  if ($agg_max_in < 255) {
    push @ent, [1+$agg_max_in, 255,undef,$a,0,0];
  }
  $a->{'Entries'} = \@ent;
}


sub addstrings
{
 my ($fh,$a) = @_;
 my $name = $a->{'Cname'};
 # String tables
 foreach my $b (@{$a->{'Entries'}})
  {
   next unless $b->[AGG_OUT_LEN];
   $strings{$b->[AGG_OUT_BYTES]} = undef;
  }
 if ($a->{'Forward'})
  {
   my $cpp = ($Config{d_cplusplus} || '') eq 'define';
   my $var = $^O eq 'MacOS' || $cpp ? 'extern' : 'static';
   my $const = $cpp ? '' : 'const';
   print $fh "$var $const encpage_t $name\[",scalar(@{$a->{'Entries'}}),"];\n";
  }
 $a->{'DoneStrings'} = 1;
 foreach my $b (@{$a->{'Entries'}})
  {
   my ($s,$e,$out,$t,$end,$l) = @$b;
   addstrings($fh,$t) unless $t->{'DoneStrings'};
  }
}

sub outbigstring
{
  my ($fh,$name) = @_;

  $string_acc = '';

  # Make the big string in the string accumulator. Longest first, on the hope
  # that this makes it more likely that we find the short strings later on.
  # Not sure if it helps sorting strings of the same length lexcically.
  foreach my $s (sort {length $b <=> length $a || $a cmp $b} keys %strings) {
    my $index = index $string_acc, $s;
    if ($index >= 0) {
      $saved += length($s);
      $strings_in_acc{$s} = $index;
    } else {
    OPTIMISER: {
    if ($opt{'O'}) {
      my $sublength = length $s;
      while (--$sublength > 0) {
        # progressively lop characters off the end, to see if the start of
        # the new string overlaps the end of the accumulator.
        if (substr ($string_acc, -$sublength)
        eq substr ($s, 0, $sublength)) {
          $subsave += $sublength;
          $strings_in_acc{$s} = length ($string_acc) - $sublength;
          # append the last bit on the end.
          $string_acc .= substr ($s, $sublength);
          last OPTIMISER;
        }
        # or if the end of the new string overlaps the start of the
        # accumulator
        next unless substr ($string_acc, 0, $sublength)
          eq substr ($s, -$sublength);
        # well, the last $sublength characters of the accumulator match.
        # so as we're prepending to the accumulator, need to shift all our
        # existing offsets forwards
        $_ += $sublength foreach values %strings_in_acc;
        $subsave += $sublength;
        $strings_in_acc{$s} = 0;
        # append the first bit on the start.
        $string_acc = substr ($s, 0, -$sublength) . $string_acc;
        last OPTIMISER;
      }
    }
    # Optimiser (if it ran) found nothing, so just going have to tack the
    # whole thing on the end.
    $strings_in_acc{$s} = length $string_acc;
    $string_acc .= $s;
      };
    }
  }

  $strings = length $string_acc;
  my $cpp = ($Config{d_cplusplus} || '') eq 'define';
  my $var = $cpp ? '' : 'static';
  my $definition = "\n$var const U8 $name\[$strings] = { " .
    join(',',unpack "C*",$string_acc);
  # We have a single long line. Split it at convenient commas.
  print $fh $1, "\n" while $definition =~ /\G(.{74,77},)/gcs;
  print $fh substr ($definition, pos $definition), " };\n";
}

sub findstring {
  my ($name,$s) = @_;
  my $offset = $strings_in_acc{$s};
  die "Can't find string " . join (',',unpack "C*",$s) . " in accumulator"
    unless defined $offset;
  "$name + $offset";
}

sub outtable
{
 my ($fh,$a,$bigname) = @_;
 my $name = $a->{'Cname'};
 $a->{'Done'} = 1;
 foreach my $b (@{$a->{'Entries'}})
  {
   my ($s,$e,$out,$t,$end,$l) = @$b;
   outtable($fh,$t,$bigname) unless $t->{'Done'};
  }
 my $cpp = ($Config{d_cplusplus} || '') eq 'define';
 my $var = $cpp ? '' : 'static';
 my $const = $cpp ? '' : 'const';
 print $fh "\n$var $const encpage_t $name\[",
   scalar(@{$a->{'Entries'}}), "] = {\n";
 foreach my $b (@{$a->{'Entries'}})
  {
   my ($sc,$ec,$out,$t,$end,$l,$fb) = @$b;
   # $end |= 0x80 if $fb; # what the heck was on your mind, Nick?  -- Dan
   print  $fh "{";
   if ($l)
    {
     printf $fh findstring($bigname,$out);
    }
   else
    {
     print  $fh "0";
    }
   print  $fh ",",$t->{Cname};
   printf $fh ",0x%02x,0x%02x,$l,$end},\n",$sc,$ec;
  }
 print $fh "};\n";
}

sub output_enc
{
 my ($fh,$name,$a) = @_;
 die "Changed - fix me for new structure";
 foreach my $b (sort keys %$a)
  {
   my ($s,$e,$out,$t,$end,$l,$fb) = @{$a->{$b}};
  }
}

sub decode_U
{
 my $s = shift;
}

my @uname;
sub char_names
{
 my $s = do "unicore/Name.pl";
 die "char_names: unicore/Name.pl: $!\n" unless defined $s;
 pos($s) = 0;
 while ($s =~ /\G([0-9a-f]+)\t([0-9a-f]*)\t(.*?)\s*\n/igc)
  {
   my $name = $3;
   my $s = hex($1);
   last if $s >= 0x10000;
   my $e = length($2) ? hex($2) : $s;
   for (my $i = $s; $i <= $e; $i++)
    {
     $uname[$i] = $name;
#    print sprintf("U%04X $name\n",$i);
    }
  }
}

sub output_ucm_page
{
  my ($cmap,$a,$t,$pre) = @_;
  # warn sprintf("Page %x\n",$pre);
  my $raw = $t->{Raw};
  foreach my $key (sort keys %$raw) {
    #  RAW_NEXT => 0,
    #  RAW_IN_LEN => 1,
    #  RAW_OUT_BYTES => 2,
    #  RAW_FALLBACK => 3,
    my ($next, $in_len, $out_bytes, $fallback) = @{$raw->{$key}};
    my $u = ord $key;
    $fallback ||= 0;

    if ($next != $a && $next != $t) {
      output_ucm_page($cmap,$a,$next,(($pre|($u &0x3F)) << 6)&0xFFFF);
    } elsif (length $out_bytes) {
      if ($pre) {
        $u = $pre|($u &0x3f);
      }
      my $s = sprintf "<U%04X> ",$u;
      #foreach my $c (split(//,$out_bytes)) {
      #  $s .= sprintf "\\x%02X",ord($c);
      #}
      # 9.5% faster changing that loop to this:
      $s .= sprintf +("\\x%02X" x length $out_bytes), unpack "C*", $out_bytes;
      $s .= sprintf " |%d # %s\n",($fallback ? 1 : 0),$uname[$u];
      push(@$cmap,$s);
    } else {
      warn join(',',$u, @{$raw->{$key}},$a,$t);
    }
  }
}

sub output_ucm
{
 my ($fh,$name,$h,$rep,$min_el,$max_el) = @_;
 print $fh "# $0 @orig_ARGV\n" unless $opt{'q'};
 print $fh "<code_set_name> \"$name\"\n";
 char_names();
 if (defined $min_el)
  {
   print $fh "<mb_cur_min> $min_el\n";
  }
 if (defined $max_el)
  {
   print $fh "<mb_cur_max> $max_el\n";
  }
 if (defined $rep)
  {
   print $fh "<subchar> ";
   foreach my $c (split(//,$rep))
    {
     printf $fh "\\x%02X",ord($c);
    }
   print $fh "\n";
  }
 my @cmap;
 output_ucm_page(\@cmap,$h,$h,0);
 print $fh "#\nCHARMAP\n";
 foreach my $line (sort { substr($a,8) cmp substr($b,8) } @cmap)
  {
   print $fh $line;
  }
 print $fh "END CHARMAP\n";
}

use vars qw(
    $_Enc2xs
    $_Version
    $_Inc
    $_E2X 
    $_Name
    $_TableFiles
    $_Now
);

sub find_e2x{
    eval { require File::Find; };
    my (@inc, %e2x_dir);
    for my $inc (grep -d, @INC){
    push @inc, $inc unless $inc eq '.'; #skip current dir
    }
    File::Find::find(
         { wanted => sub {
         my ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,
             $atime,$mtime,$ctime,$blksize,$blocks)
             = lstat($_) or return;
         -f _ or return;
         if (/^.*\.e2x$/o){
             no warnings 'once';
             $e2x_dir{$File::Find::dir} ||= $mtime;
         }
         return;
         }, follow => 1}, @inc);
    warn join("\n", keys %e2x_dir), "\n";
    for my $d (sort {$e2x_dir{$a} <=> $e2x_dir{$b}} keys %e2x_dir){
    $_E2X = $d;
    # warn "$_E2X => ", scalar localtime($e2x_dir{$d});
    return $_E2X;
    }
}

sub make_makefile_pl
{
    eval { require Encode; };
    $@ and die "You need to install Encode to use enc2xs -M\nerror: $@\n";
    # our used for variable expanstion
    $_Enc2xs = $0;
    $_Version = $VERSION;
    $_E2X = find_e2x();
    $_Name = shift;
    $_TableFiles = join(",", map {qq('$_')} @_);
    $_Now = scalar localtime();

    eval { require File::Spec; };
    _print_expand(File::Spec->catfile($_E2X,"Makefile_PL.e2x"),"Makefile.PL");
    _print_expand(File::Spec->catfile($_E2X,"_PM.e2x"),        "$_Name.pm");
    _print_expand(File::Spec->catfile($_E2X,"_T.e2x"),         "t/$_Name.t");
    _print_expand(File::Spec->catfile($_E2X,"README.e2x"),     "README");
    _print_expand(File::Spec->catfile($_E2X,"Changes.e2x"),    "Changes");
    exit;
}

use vars qw(
        $_ModLines
        $_LocalVer
        );

sub make_configlocal_pm {
    eval { require Encode; };
    $@ and die "Unable to require Encode: $@\n";
    eval { require File::Spec; };

    # our used for variable expanstion
    my %in_core = map { $_ => 1 } (
        'ascii',      'iso-8859-1', 'utf8',
        'ascii-ctrl', 'null',       'utf-8-strict'
    );
    my %LocalMod = ();
    # check @enc;
    use File::Find ();
    my $wanted = sub{
	-f $_ or return;
	$File::Find::name =~ /\A\./        and return;
	$File::Find::name =~ /\.pm\z/      or  return;
	$File::Find::name =~ m/\bEncode\b/ or  return;
	my $mod = $File::Find::name;
	$mod =~ s/.*\bEncode\b/Encode/o;
	$mod =~ s/\.pm\z//o;
	$mod =~ s,/,::,og;
	warn qq{ require $mod;\n};
	eval qq{ require $mod; };
	$@ and die "Can't require $mod: $@\n";
	for my $enc ( Encode->encodings() ) {
	    no warnings;
	    $in_core{$enc}                   and next;
	    $Encode::Config::ExtModule{$enc} and next;
	    $LocalMod{$enc} ||= $mod;
	}
    };
    File::Find::find({wanted => $wanted, follow => 1}, grep -d && !/^\./, @INC);
    $_ModLines = "";
    for my $enc ( sort keys %LocalMod ) {
        $_ModLines .=
          qq(\$Encode::ExtModule{'$enc'} = "$LocalMod{$enc}";\n);
    }
    warn $_ModLines;
    $_LocalVer = _mkversion();
    $_E2X      = find_e2x();
    $_Inc      = $INC{"Encode.pm"};
    $_Inc =~ s/\.pm$//o;
    _print_expand( File::Spec->catfile( $_E2X, "ConfigLocal_PM.e2x" ),
        File::Spec->catfile( $_Inc, "ConfigLocal.pm" ), 1 );
    exit;
}

sub _mkversion{
    # v-string is now depreciated; use time() instead;
    #my ($ss,$mm,$hh,$dd,$mo,$yyyy) = localtime();
    #$yyyy += 1900, $mo +=1;
    #return sprintf("v%04d.%04d.%04d", $yyyy, $mo*100+$dd, $hh*100+$mm);
    return time();
}

sub _print_expand{
    eval { require File::Basename; };
    $@ and die "File::Basename needed.  Are you on miniperl?;\nerror: $@\n";
    File::Basename->import();
    my ($src, $dst, $clobber) = @_;
    if (!$clobber and -e $dst){
    warn "$dst exists. skipping\n";
    return;
    }
    warn "Generating $dst...\n";
    open my $in, $src or die "$src : $!";
    if ((my $d = dirname($dst)) ne '.'){
    -d $d or mkdir $d, 0755 or die  "mkdir $d : $!";
    }	   
    open my $out, ">$dst" or die "$!";
    my $asis = 0;
    while (<$in>){ 
    if (/^#### END_OF_HEADER/){
        $asis = 1; next;
    }	  
    s/(\$_[A-Z][A-Za-z0-9]+)_/$1/gee unless $asis;
    print $out $_;
    }
}
__END__

=head1 NAME

enc2xs -- Perl Encode Module Generator

=head1 SYNOPSIS

  enc2xs -[options]
  enc2xs -M ModName mapfiles...
  enc2xs -C

=head1 DESCRIPTION

F<enc2xs> builds a Perl extension for use by Encode from either
Unicode Character Mapping files (.ucm) or Tcl Encoding Files (.enc).
Besides being used internally during the build process of the Encode
module, you can use F<enc2xs> to add your own encoding to perl.
No knowledge of XS is necessary.

=head1 Quick Guide

If you want to know as little about Perl as possible but need to
add a new encoding, just read this chapter and forget the rest.

=over 4

=item 0.

Have a .ucm file ready.  You can get it from somewhere or you can write
your own from scratch or you can grab one from the Encode distribution
and customize it.  For the UCM format, see the next Chapter.  In the
example below, I'll call my theoretical encoding myascii, defined
in I<my.ucm>.  C<$> is a shell prompt.

  $ ls -F
  my.ucm

=item 1.

Issue a command as follows;

  $ enc2xs -M My my.ucm
  generating Makefile.PL
  generating My.pm
  generating README
  generating Changes

Now take a look at your current directory.  It should look like this.

  $ ls -F
  Makefile.PL   My.pm         my.ucm        t/

The following files were created.

  Makefile.PL - MakeMaker script
  My.pm       - Encode submodule
  t/My.t      - test file

=over 4

=item 1.1.

If you want *.ucm installed together with the modules, do as follows;

  $ mkdir Encode
  $ mv *.ucm Encode
  $ enc2xs -M My Encode/*ucm

=back

=item 2.

Edit the files generated.  You don't have to if you have no time AND no
intention to give it to someone else.  But it is a good idea to edit
the pod and to add more tests.

=item 3.

Now issue a command all Perl Mongers love:

  $ perl Makefile.PL
  Writing Makefile for Encode::My

=item 4.

Now all you have to do is make.

  $ make
  cp My.pm blib/lib/Encode/My.pm
  /usr/local/bin/perl /usr/local/bin/enc2xs -Q -O \
    -o encode_t.c -f encode_t.fnm
  Reading myascii (myascii)
  Writing compiled form
  128 bytes in string tables
  384 bytes (75%) saved spotting duplicates
  1 bytes (0.775%) saved using substrings
  ....
  chmod 644 blib/arch/auto/Encode/My/My.bs
  $

The time it takes varies depending on how fast your machine is and
how large your encoding is.  Unless you are working on something big
like euc-tw, it won't take too long.

=item 5.

You can "make install" already but you should test first.

  $ make test
  PERL_DL_NONLAZY=1 /usr/local/bin/perl -Iblib/arch -Iblib/lib \
    -e 'use Test::Harness  qw(&runtests $verbose); \
    $verbose=0; runtests @ARGV;' t/*.t
  t/My....ok
  All tests successful.
  Files=1, Tests=2,  0 wallclock secs
   ( 0.09 cusr + 0.01 csys = 0.09 CPU)

=item 6.

If you are content with the test result, just "make install"

=item 7.

If you want to add your encoding to Encode's demand-loading list
(so you don't have to "use Encode::YourEncoding"), run

  enc2xs -C

to update Encode::ConfigLocal, a module that controls local settings.
After that, "use Encode;" is enough to load your encodings on demand.

=back

=head1 The Unicode Character Map

Encode uses the Unicode Character Map (UCM) format for source character
mappings.  This format is used by IBM's ICU package and was adopted
by Nick Ing-Simmons for use with the Encode module.  Since UCM is
more flexible than Tcl's Encoding Map and far more user-friendly,
this is the recommended format for Encode now.

A UCM file looks like this.

  #
  # Comments
  #
  <code_set_name> "US-ascii" # Required
  <code_set_alias> "ascii"   # Optional
  <mb_cur_min> 1             # Required; usually 1
  <mb_cur_max> 1             # Max. # of bytes/char
  <subchar> \x3F             # Substitution char
  #
  CHARMAP
  <U0000> \x00 |0 # <control>
  <U0001> \x01 |0 # <control>
  <U0002> \x02 |0 # <control>
  ....
  <U007C> \x7C |0 # VERTICAL LINE
  <U007D> \x7D |0 # RIGHT CURLY BRACKET
  <U007E> \x7E |0 # TILDE
  <U007F> \x7F |0 # <control>
  END CHARMAP

=over 4

=item *

Anything that follows C<#> is treated as a comment.

=item *

The header section continues until a line containing the word
CHARMAP. This section has a form of I<E<lt>keywordE<gt> value>, one
pair per line.  Strings used as values must be quoted. Barewords are
treated as numbers.  I<\xXX> represents a byte.

Most of the keywords are self-explanatory. I<subchar> means
substitution character, not subcharacter.  When you decode a Unicode
sequence to this encoding but no matching character is found, the byte
sequence defined here will be used.  For most cases, the value here is
\x3F; in ASCII, this is a question mark.

=item *

CHARMAP starts the character map section.  Each line has a form as
follows:

  <UXXXX> \xXX.. |0 # comment
    ^     ^      ^
    |     |      +- Fallback flag
    |     +-------- Encoded byte sequence
    +-------------- Unicode Character ID in hex

The format is roughly the same as a header section except for the
fallback flag: | followed by 0..3.   The meaning of the possible
values is as follows:

=over 4

=item |0 

Round trip safe.  A character decoded to Unicode encodes back to the
same byte sequence.  Most characters have this flag.

=item |1

Fallback for unicode -> encoding.  When seen, enc2xs adds this
character for the encode map only.

=item |2 

Skip sub-char mapping should there be no code point.

=item |3 

Fallback for encoding -> unicode.  When seen, enc2xs adds this
character for the decode map only.

=back

=item *

And finally, END OF CHARMAP ends the section.

=back

When you are manually creating a UCM file, you should copy ascii.ucm
or an existing encoding which is close to yours, rather than write
your own from scratch.

When you do so, make sure you leave at least B<U0000> to B<U0020> as
is, unless your environment is EBCDIC.

B<CAVEAT>: not all features in UCM are implemented.  For example,
icu:state is not used.  Because of that, you need to write a perl
module if you want to support algorithmical encodings, notably
the ISO-2022 series.  Such modules include L<Encode::JP::2022_JP>,
L<Encode::KR::2022_KR>, and L<Encode::TW::HZ>.

=head2 Coping with duplicate mappings

When you create a map, you SHOULD make your mappings round-trip safe.
That is, C<encode('your-encoding', decode('your-encoding', $data)) eq
$data> stands for all characters that are marked as C<|0>.  Here is
how to make sure:

=over 4

=item * 

Sort your map in Unicode order.

=item *

When you have a duplicate entry, mark either one with '|1' or '|3'.
  
=item * 

And make sure the '|1' or '|3' entry FOLLOWS the '|0' entry.

=back

Here is an example from big5-eten.

  <U2550> \xF9\xF9 |0
  <U2550> \xA2\xA4 |3

Internally Encoding -> Unicode and Unicode -> Encoding Map looks like
this;

  E to U               U to E
  --------------------------------------
  \xF9\xF9 => U2550    U2550 => \xF9\xF9
  \xA2\xA4 => U2550
 
So it is round-trip safe for \xF9\xF9.  But if the line above is upside
down, here is what happens.

  E to U               U to E
  --------------------------------------
  \xA2\xA4 => U2550    U2550 => \xF9\xF9
  (\xF9\xF9 => U2550 is now overwritten!)

The Encode package comes with F<ucmlint>, a crude but sufficient
utility to check the integrity of a UCM file.  Check under the
Encode/bin directory for this.

When in doubt, you can use F<ucmsort>, yet another utility under
Encode/bin directory.

=head1 Bookmarks

=over 4

=item *

ICU Home Page 
L<http://www.icu-project.org/>

=item *

ICU Character Mapping Tables
L<http://site.icu-project.org/charts/charset>

=item *

ICU:Conversion Data
L<http://www.icu-project.org/userguide/conversion-data.html>

=back

=head1 SEE ALSO

L<Encode>,
L<perlmod>,
L<perlpod>

=cut

# -Q to disable the duplicate codepoint test
# -S make mapping errors fatal
# -q to remove comments written to output files
# -O to enable the (brute force) substring optimiser
# -o <output> to specify the output file name (else it's the first arg)
# -f <inlist> to give a file with a list of input files (else use the args)
# -n <name> to name the encoding (else use the basename of the input file.

With %seen holding array refs:

      865.66 real        28.80 user         8.79 sys
      7904  maximum resident set size
      1356  average shared memory size
     18566  average unshared data size
       229  average unshared stack size
     46080  page reclaims
     33373  page faults

With %seen holding simple scalars:

      342.16 real        27.11 user         3.54 sys
      8388  maximum resident set size
      1394  average shared memory size
     14969  average unshared data size
       236  average unshared stack size
     28159  page reclaims
      9839  page faults

Yes, 5 minutes is faster than 15. Above is for CP936 in CN. Only difference is
how %seen is storing things its seen. So it is pathalogically bad on a 16M
RAM machine, but it's going to help even on modern machines.
Swapping is bad, m'kay :-)