gcc/ada/a-stwiun-shared.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --           A D A . S T R I N G S . W I D E _ U N B O U N D E D            --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2012, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 with Ada.Strings.Wide_Search;
  33 with Ada.Unchecked_Deallocation;
  34
  35 package body Ada.Strings.Wide_Unbounded is
  36
  37    use Ada.Strings.Wide_Maps;
  38
  39    Growth_Factor : constant := 32;
  40    --  The growth factor controls how much extra space is allocated when
  41    --  we have to increase the size of an allocated unbounded string. By
  42    --  allocating extra space, we avoid the need to reallocate on every
  43    --  append, particularly important when a string is built up by repeated
  44    --  append operations of small pieces. This is expressed as a factor so
  45    --  32 means add 1/32 of the length of the string as growth space.
  46
  47    Min_Mul_Alloc : constant := Standard'Maximum_Alignment;
  48    --  Allocation will be done by a multiple of Min_Mul_Alloc. This causes
  49    --  no memory loss as most (all?) malloc implementations are obliged to
  50    --  align the returned memory on the maximum alignment as malloc does not
  51    --  know the target alignment.
  52
  53    function Aligned_Max_Length (Max_Length : Natural) return Natural;
  54    --  Returns recommended length of the shared string which is greater or
  55    --  equal to specified length. Calculation take in sense alignment of
  56    --  the allocated memory segments to use memory effectively by
  57    --  Append/Insert/etc operations.
  58
  59    ---------
  60    -- "&" --
  61    ---------
  62
  63    function "&"
  64      (Left  : Unbounded_Wide_String;
  65       Right : Unbounded_Wide_String) return Unbounded_Wide_String
  66    is
  67       LR : constant Shared_Wide_String_Access := Left.Reference;
  68       RR : constant Shared_Wide_String_Access := Right.Reference;
  69       DL : constant Natural := LR.Last + RR.Last;
  70       DR : Shared_Wide_String_Access;
  71
  72    begin
  73       --  Result is an empty string, reuse shared empty string
  74
  75       if DL = 0 then
  76          Reference (Empty_Shared_Wide_String'Access);
  77          DR := Empty_Shared_Wide_String'Access;
  78
  79       --  Left string is empty, return Rigth string
  80
  81       elsif LR.Last = 0 then
  82          Reference (RR);
  83          DR := RR;
  84
  85       --  Right string is empty, return Left string
  86
  87       elsif RR.Last = 0 then
  88          Reference (LR);
  89          DR := LR;
  90
  91       --  Overwise, allocate new shared string and fill data
  92
  93       else
  94          DR := Allocate (LR.Last + RR.Last);
  95          DR.Data (1 .. LR.Last) := LR.Data (1 .. LR.Last);
  96          DR.Data (LR.Last + 1 .. DL) := RR.Data (1 .. RR.Last);
  97          DR.Last := DL;
  98       end if;
  99
 100       return (AF.Controlled with Reference => DR);
 101    end "&";
 102
 103    function "&"
 104      (Left  : Unbounded_Wide_String;
 105       Right : Wide_String) return Unbounded_Wide_String
 106    is
 107       LR : constant Shared_Wide_String_Access := Left.Reference;
 108       DL : constant Natural := LR.Last + Right'Length;
 109       DR : Shared_Wide_String_Access;
 110
 111    begin
 112       --  Result is an empty string, reuse shared empty string
 113
 114       if DL = 0 then
 115          Reference (Empty_Shared_Wide_String'Access);
 116          DR := Empty_Shared_Wide_String'Access;
 117
 118       --  Right is an empty string, return Left string
 119
 120       elsif Right'Length = 0 then
 121          Reference (LR);
 122          DR := LR;
 123
 124       --  Otherwise, allocate new shared string and fill it
 125
 126       else
 127          DR := Allocate (DL);
 128          DR.Data (1 .. LR.Last) := LR.Data (1 .. LR.Last);
 129          DR.Data (LR.Last + 1 .. DL) := Right;
 130          DR.Last := DL;
 131       end if;
 132
 133       return (AF.Controlled with Reference => DR);
 134    end "&";
 135
 136    function "&"
 137      (Left  : Wide_String;
 138       Right : Unbounded_Wide_String) return Unbounded_Wide_String
 139    is
 140       RR : constant Shared_Wide_String_Access := Right.Reference;
 141       DL : constant Natural := Left'Length + RR.Last;
 142       DR : Shared_Wide_String_Access;
 143
 144    begin
 145       --  Result is an empty string, reuse shared one
 146
 147       if DL = 0 then
 148          Reference (Empty_Shared_Wide_String'Access);
 149          DR := Empty_Shared_Wide_String'Access;
 150
 151       --  Left is empty string, return Right string
 152
 153       elsif Left'Length = 0 then
 154          Reference (RR);
 155          DR := RR;
 156
 157       --  Otherwise, allocate new shared string and fill it
 158
 159       else
 160          DR := Allocate (DL);
 161          DR.Data (1 .. Left'Length) := Left;
 162          DR.Data (Left'Length + 1 .. DL) := RR.Data (1 .. RR.Last);
 163          DR.Last := DL;
 164       end if;
 165
 166       return (AF.Controlled with Reference => DR);
 167    end "&";
 168
 169    function "&"
 170      (Left  : Unbounded_Wide_String;
 171       Right : Wide_Character) return Unbounded_Wide_String
 172    is
 173       LR : constant Shared_Wide_String_Access := Left.Reference;
 174       DL : constant Natural := LR.Last + 1;
 175       DR : Shared_Wide_String_Access;
 176
 177    begin
 178       DR := Allocate (DL);
 179       DR.Data (1 .. LR.Last) := LR.Data (1 .. LR.Last);
 180       DR.Data (DL) := Right;
 181       DR.Last := DL;
 182
 183       return (AF.Controlled with Reference => DR);
 184    end "&";
 185
 186    function "&"
 187      (Left  : Wide_Character;
 188       Right : Unbounded_Wide_String) return Unbounded_Wide_String
 189    is
 190       RR : constant Shared_Wide_String_Access := Right.Reference;
 191       DL : constant Natural := 1 + RR.Last;
 192       DR : Shared_Wide_String_Access;
 193
 194    begin
 195       DR := Allocate (DL);
 196       DR.Data (1) := Left;
 197       DR.Data (2 .. DL) := RR.Data (1 .. RR.Last);
 198       DR.Last := DL;
 199
 200       return (AF.Controlled with Reference => DR);
 201    end "&";
 202
 203    ---------
 204    -- "*" --
 205    ---------
 206
 207    function "*"
 208      (Left  : Natural;
 209       Right : Wide_Character) return Unbounded_Wide_String
 210    is
 211       DR : Shared_Wide_String_Access;
 212
 213    begin
 214       --  Result is an empty string, reuse shared empty string
 215
 216       if Left = 0 then
 217          Reference (Empty_Shared_Wide_String'Access);
 218          DR := Empty_Shared_Wide_String'Access;
 219
 220       --  Otherwise, allocate new shared string and fill it
 221
 222       else
 223          DR := Allocate (Left);
 224
 225          for J in 1 .. Left loop
 226             DR.Data (J) := Right;
 227          end loop;
 228
 229          DR.Last := Left;
 230       end if;
 231
 232       return (AF.Controlled with Reference => DR);
 233    end "*";
 234
 235    function "*"
 236      (Left  : Natural;
 237       Right : Wide_String) return Unbounded_Wide_String
 238    is
 239       DL : constant Natural := Left * Right'Length;
 240       DR : Shared_Wide_String_Access;
 241       K  : Positive;
 242
 243    begin
 244       --  Result is an empty string, reuse shared empty string
 245
 246       if DL = 0 then
 247          Reference (Empty_Shared_Wide_String'Access);
 248          DR := Empty_Shared_Wide_String'Access;
 249
 250       --  Otherwise, allocate new shared string and fill it
 251
 252       else
 253          DR := Allocate (DL);
 254          K := 1;
 255
 256          for J in 1 .. Left loop
 257             DR.Data (K .. K + Right'Length - 1) := Right;
 258             K := K + Right'Length;
 259          end loop;
 260
 261          DR.Last := DL;
 262       end if;
 263
 264       return (AF.Controlled with Reference => DR);
 265    end "*";
 266
 267    function "*"
 268      (Left  : Natural;
 269       Right : Unbounded_Wide_String) return Unbounded_Wide_String
 270    is
 271       RR : constant Shared_Wide_String_Access := Right.Reference;
 272       DL : constant Natural := Left * RR.Last;
 273       DR : Shared_Wide_String_Access;
 274       K  : Positive;
 275
 276    begin
 277       --  Result is an empty string, reuse shared empty string
 278
 279       if DL = 0 then
 280          Reference (Empty_Shared_Wide_String'Access);
 281          DR := Empty_Shared_Wide_String'Access;
 282
 283       --  Coefficient is one, just return string itself
 284
 285       elsif Left = 1 then
 286          Reference (RR);
 287          DR := RR;
 288
 289       --  Otherwise, allocate new shared string and fill it
 290
 291       else
 292          DR := Allocate (DL);
 293          K := 1;
 294
 295          for J in 1 .. Left loop
 296             DR.Data (K .. K + RR.Last - 1) := RR.Data (1 .. RR.Last);
 297             K := K + RR.Last;
 298          end loop;
 299
 300          DR.Last := DL;
 301       end if;
 302
 303       return (AF.Controlled with Reference => DR);
 304    end "*";
 305
 306    ---------
 307    -- "<" --
 308    ---------
 309
 310    function "<"
 311      (Left  : Unbounded_Wide_String;
 312       Right : Unbounded_Wide_String) return Boolean
 313    is
 314       LR : constant Shared_Wide_String_Access := Left.Reference;
 315       RR : constant Shared_Wide_String_Access := Right.Reference;
 316    begin
 317       return LR.Data (1 .. LR.Last) < RR.Data (1 .. RR.Last);
 318    end "<";
 319
 320    function "<"
 321      (Left  : Unbounded_Wide_String;
 322       Right : Wide_String) return Boolean
 323    is
 324       LR : constant Shared_Wide_String_Access := Left.Reference;
 325    begin
 326       return LR.Data (1 .. LR.Last) < Right;
 327    end "<";
 328
 329    function "<"
 330      (Left  : Wide_String;
 331       Right : Unbounded_Wide_String) return Boolean
 332    is
 333       RR : constant Shared_Wide_String_Access := Right.Reference;
 334    begin
 335       return Left < RR.Data (1 .. RR.Last);
 336    end "<";
 337
 338    ----------
 339    -- "<=" --
 340    ----------
 341
 342    function "<="
 343      (Left  : Unbounded_Wide_String;
 344       Right : Unbounded_Wide_String) return Boolean
 345    is
 346       LR : constant Shared_Wide_String_Access := Left.Reference;
 347       RR : constant Shared_Wide_String_Access := Right.Reference;
 348
 349    begin
 350       --  LR = RR means two strings shares shared string, thus they are equal
 351
 352       return LR = RR or else LR.Data (1 .. LR.Last) <= RR.Data (1 .. RR.Last);
 353    end "<=";
 354
 355    function "<="
 356      (Left  : Unbounded_Wide_String;
 357       Right : Wide_String) return Boolean
 358    is
 359       LR : constant Shared_Wide_String_Access := Left.Reference;
 360    begin
 361       return LR.Data (1 .. LR.Last) <= Right;
 362    end "<=";
 363
 364    function "<="
 365      (Left  : Wide_String;
 366       Right : Unbounded_Wide_String) return Boolean
 367    is
 368       RR : constant Shared_Wide_String_Access := Right.Reference;
 369    begin
 370       return Left <= RR.Data (1 .. RR.Last);
 371    end "<=";
 372
 373    ---------
 374    -- "=" --
 375    ---------
 376
 377    function "="
 378      (Left  : Unbounded_Wide_String;
 379       Right : Unbounded_Wide_String) return Boolean
 380    is
 381       LR : constant Shared_Wide_String_Access := Left.Reference;
 382       RR : constant Shared_Wide_String_Access := Right.Reference;
 383
 384    begin
 385       return LR = RR or else LR.Data (1 .. LR.Last) = RR.Data (1 .. RR.Last);
 386       --  LR = RR means two strings shares shared string, thus they are equal
 387    end "=";
 388
 389    function "="
 390      (Left  : Unbounded_Wide_String;
 391       Right : Wide_String) return Boolean
 392    is
 393       LR : constant Shared_Wide_String_Access := Left.Reference;
 394    begin
 395       return LR.Data (1 .. LR.Last) = Right;
 396    end "=";
 397
 398    function "="
 399      (Left  : Wide_String;
 400       Right : Unbounded_Wide_String) return Boolean
 401    is
 402       RR : constant Shared_Wide_String_Access := Right.Reference;
 403    begin
 404       return Left = RR.Data (1 .. RR.Last);
 405    end "=";
 406
 407    ---------
 408    -- ">" --
 409    ---------
 410
 411    function ">"
 412      (Left  : Unbounded_Wide_String;
 413       Right : Unbounded_Wide_String) return Boolean
 414    is
 415       LR : constant Shared_Wide_String_Access := Left.Reference;
 416       RR : constant Shared_Wide_String_Access := Right.Reference;
 417    begin
 418       return LR.Data (1 .. LR.Last) > RR.Data (1 .. RR.Last);
 419    end ">";
 420
 421    function ">"
 422      (Left  : Unbounded_Wide_String;
 423       Right : Wide_String) return Boolean
 424    is
 425       LR : constant Shared_Wide_String_Access := Left.Reference;
 426    begin
 427       return LR.Data (1 .. LR.Last) > Right;
 428    end ">";
 429
 430    function ">"
 431      (Left  : Wide_String;
 432       Right : Unbounded_Wide_String) return Boolean
 433    is
 434       RR : constant Shared_Wide_String_Access := Right.Reference;
 435    begin
 436       return Left > RR.Data (1 .. RR.Last);
 437    end ">";
 438
 439    ----------
 440    -- ">=" --
 441    ----------
 442
 443    function ">="
 444      (Left  : Unbounded_Wide_String;
 445       Right : Unbounded_Wide_String) return Boolean
 446    is
 447       LR : constant Shared_Wide_String_Access := Left.Reference;
 448       RR : constant Shared_Wide_String_Access := Right.Reference;
 449
 450    begin
 451       --  LR = RR means two strings shares shared string, thus they are equal
 452
 453       return LR = RR or else LR.Data (1 .. LR.Last) >= RR.Data (1 .. RR.Last);
 454    end ">=";
 455
 456    function ">="
 457      (Left  : Unbounded_Wide_String;
 458       Right : Wide_String) return Boolean
 459    is
 460       LR : constant Shared_Wide_String_Access := Left.Reference;
 461    begin
 462       return LR.Data (1 .. LR.Last) >= Right;
 463    end ">=";
 464
 465    function ">="
 466      (Left  : Wide_String;
 467       Right : Unbounded_Wide_String) return Boolean
 468    is
 469       RR : constant Shared_Wide_String_Access := Right.Reference;
 470    begin
 471       return Left >= RR.Data (1 .. RR.Last);
 472    end ">=";
 473
 474    ------------
 475    -- Adjust --
 476    ------------
 477
 478    procedure Adjust (Object : in out Unbounded_Wide_String) is
 479    begin
 480       Reference (Object.Reference);
 481    end Adjust;
 482
 483    ------------------------
 484    -- Aligned_Max_Length --
 485    ------------------------
 486
 487    function Aligned_Max_Length (Max_Length : Natural) return Natural is
 488       Static_Size  : constant Natural :=
 489                        Empty_Shared_Wide_String'Size / Standard'Storage_Unit;
 490       --  Total size of all static components
 491
 492       Element_Size : constant Natural :=
 493                        Wide_Character'Size / Standard'Storage_Unit;
 494
 495    begin
 496       return
 497         (((Static_Size + Max_Length * Element_Size - 1) / Min_Mul_Alloc + 2)
 498           * Min_Mul_Alloc - Static_Size) / Element_Size;
 499    end Aligned_Max_Length;
 500
 501    --------------
 502    -- Allocate --
 503    --------------
 504
 505    function Allocate (Max_Length : Natural) return Shared_Wide_String_Access is
 506    begin
 507       --  Empty string requested, return shared empty string
 508
 509       if Max_Length = 0 then
 510          Reference (Empty_Shared_Wide_String'Access);
 511          return Empty_Shared_Wide_String'Access;
 512
 513       --  Otherwise, allocate requested space (and probably some more room)
 514
 515       else
 516          return new Shared_Wide_String (Aligned_Max_Length (Max_Length));
 517       end if;
 518    end Allocate;
 519
 520    ------------
 521    -- Append --
 522    ------------
 523
 524    procedure Append
 525      (Source   : in out Unbounded_Wide_String;
 526       New_Item : Unbounded_Wide_String)
 527    is
 528       SR  : constant Shared_Wide_String_Access := Source.Reference;
 529       NR  : constant Shared_Wide_String_Access := New_Item.Reference;
 530       DL  : constant Natural                   := SR.Last + NR.Last;
 531       DR  : Shared_Wide_String_Access;
 532
 533    begin
 534       --  Source is an empty string, reuse New_Item data
 535
 536       if SR.Last = 0 then
 537          Reference (NR);
 538          Source.Reference := NR;
 539          Unreference (SR);
 540
 541       --  New_Item is empty string, nothing to do
 542
 543       elsif NR.Last = 0 then
 544          null;
 545
 546       --  Try to reuse existent shared string
 547
 548       elsif Can_Be_Reused (SR, DL) then
 549          SR.Data (SR.Last + 1 .. DL) := NR.Data (1 .. NR.Last);
 550          SR.Last := DL;
 551
 552       --  Otherwise, allocate new one and fill it
 553
 554       else
 555          DR := Allocate (DL + DL / Growth_Factor);
 556          DR.Data (1 .. SR.Last) := SR.Data (1 .. SR.Last);
 557          DR.Data (SR.Last + 1 .. DL) := NR.Data (1 .. NR.Last);
 558          DR.Last := DL;
 559          Source.Reference := DR;
 560          Unreference (SR);
 561       end if;
 562    end Append;
 563
 564    procedure Append
 565      (Source   : in out Unbounded_Wide_String;
 566       New_Item : Wide_String)
 567    is
 568       SR : constant Shared_Wide_String_Access := Source.Reference;
 569       DL : constant Natural                   := SR.Last + New_Item'Length;
 570       DR : Shared_Wide_String_Access;
 571
 572    begin
 573       --  New_Item is an empty string, nothing to do
 574
 575       if New_Item'Length = 0 then
 576          null;
 577
 578       --  Try to reuse existing shared string
 579
 580       elsif Can_Be_Reused (SR, DL) then
 581          SR.Data (SR.Last + 1 .. DL) := New_Item;
 582          SR.Last := DL;
 583
 584       --  Otherwise, allocate new one and fill it
 585
 586       else
 587          DR := Allocate (DL + DL / Growth_Factor);
 588          DR.Data (1 .. SR.Last) := SR.Data (1 .. SR.Last);
 589          DR.Data (SR.Last + 1 .. DL) := New_Item;
 590          DR.Last := DL;
 591          Source.Reference := DR;
 592          Unreference (SR);
 593       end if;
 594    end Append;
 595
 596    procedure Append
 597      (Source   : in out Unbounded_Wide_String;
 598       New_Item : Wide_Character)
 599    is
 600       SR : constant Shared_Wide_String_Access := Source.Reference;
 601       DL : constant Natural := SR.Last + 1;
 602       DR : Shared_Wide_String_Access;
 603
 604    begin
 605       --  Try to reuse existing shared string
 606
 607       if Can_Be_Reused (SR, SR.Last + 1) then
 608          SR.Data (SR.Last + 1) := New_Item;
 609          SR.Last := SR.Last + 1;
 610
 611       --  Otherwise, allocate new one and fill it
 612
 613       else
 614          DR := Allocate (DL + DL / Growth_Factor);
 615          DR.Data (1 .. SR.Last) := SR.Data (1 .. SR.Last);
 616          DR.Data (DL) := New_Item;
 617          DR.Last := DL;
 618          Source.Reference := DR;
 619          Unreference (SR);
 620       end if;
 621    end Append;
 622
 623    -------------------
 624    -- Can_Be_Reused --
 625    -------------------
 626
 627    function Can_Be_Reused
 628      (Item   : Shared_Wide_String_Access;
 629       Length : Natural) return Boolean is
 630    begin
 631       return
 632         System.Atomic_Counters.Is_One (Item.Counter)
 633           and then Item.Max_Length >= Length
 634           and then Item.Max_Length <=
 635                      Aligned_Max_Length (Length + Length / Growth_Factor);
 636    end Can_Be_Reused;
 637
 638    -----------
 639    -- Count --
 640    -----------
 641
 642    function Count
 643      (Source  : Unbounded_Wide_String;
 644       Pattern : Wide_String;
 645       Mapping : Wide_Maps.Wide_Character_Mapping := Wide_Maps.Identity)
 646       return Natural
 647    is
 648       SR : constant Shared_Wide_String_Access := Source.Reference;
 649    begin
 650       return Wide_Search.Count (SR.Data (1 .. SR.Last), Pattern, Mapping);
 651    end Count;
 652
 653    function Count
 654      (Source  : Unbounded_Wide_String;
 655       Pattern : Wide_String;
 656       Mapping : Wide_Maps.Wide_Character_Mapping_Function) return Natural
 657    is
 658       SR : constant Shared_Wide_String_Access := Source.Reference;
 659    begin
 660       return Wide_Search.Count (SR.Data (1 .. SR.Last), Pattern, Mapping);
 661    end Count;
 662
 663    function Count
 664      (Source : Unbounded_Wide_String;
 665       Set    : Wide_Maps.Wide_Character_Set) return Natural
 666    is
 667       SR : constant Shared_Wide_String_Access := Source.Reference;
 668    begin
 669       return Wide_Search.Count (SR.Data (1 .. SR.Last), Set);
 670    end Count;
 671
 672    ------------
 673    -- Delete --
 674    ------------
 675
 676    function Delete
 677      (Source  : Unbounded_Wide_String;
 678       From    : Positive;
 679       Through : Natural) return Unbounded_Wide_String
 680    is
 681       SR : constant Shared_Wide_String_Access := Source.Reference;
 682       DL : Natural;
 683       DR : Shared_Wide_String_Access;
 684
 685    begin
 686       --  Empty slice is deleted, use the same shared string
 687
 688       if From > Through then
 689          Reference (SR);
 690          DR := SR;
 691
 692       --  Index is out of range
 693
 694       elsif Through > SR.Last then
 695          raise Index_Error;
 696
 697       --  Compute size of the result
 698
 699       else
 700          DL := SR.Last - (Through - From + 1);
 701
 702          --  Result is an empty string, reuse shared empty string
 703
 704          if DL = 0 then
 705             Reference (Empty_Shared_Wide_String'Access);
 706             DR := Empty_Shared_Wide_String'Access;
 707
 708          --  Otherwise, allocate new shared string and fill it
 709
 710          else
 711             DR := Allocate (DL);
 712             DR.Data (1 .. From - 1) := SR.Data (1 .. From - 1);
 713             DR.Data (From .. DL) := SR.Data (Through + 1 .. SR.Last);
 714             DR.Last := DL;
 715          end if;
 716       end if;
 717
 718       return (AF.Controlled with Reference => DR);
 719    end Delete;
 720
 721    procedure Delete
 722      (Source  : in out Unbounded_Wide_String;
 723       From    : Positive;
 724       Through : Natural)
 725    is
 726       SR : constant Shared_Wide_String_Access := Source.Reference;
 727       DL : Natural;
 728       DR : Shared_Wide_String_Access;
 729
 730    begin
 731       --  Nothing changed, return
 732
 733       if From > Through then
 734          null;
 735
 736       --  Through is outside of the range
 737
 738       elsif Through > SR.Last then
 739          raise Index_Error;
 740
 741       else
 742          DL := SR.Last - (Through - From + 1);
 743
 744          --  Result is empty, reuse shared empty string
 745
 746          if DL = 0 then
 747             Reference (Empty_Shared_Wide_String'Access);
 748             Source.Reference := Empty_Shared_Wide_String'Access;
 749             Unreference (SR);
 750
 751          --  Try to reuse existent shared string
 752
 753          elsif Can_Be_Reused (SR, DL) then
 754             SR.Data (From .. DL) := SR.Data (Through + 1 .. SR.Last);
 755             SR.Last := DL;
 756
 757          --  Otherwise, allocate new shared string
 758
 759          else
 760             DR := Allocate (DL);
 761             DR.Data (1 .. From - 1) := SR.Data (1 .. From - 1);
 762             DR.Data (From .. DL) := SR.Data (Through + 1 .. SR.Last);
 763             DR.Last := DL;
 764             Source.Reference := DR;
 765             Unreference (SR);
 766          end if;
 767       end if;
 768    end Delete;
 769
 770    -------------
 771    -- Element --
 772    -------------
 773
 774    function Element
 775      (Source : Unbounded_Wide_String;
 776       Index  : Positive) return Wide_Character
 777    is
 778       SR : constant Shared_Wide_String_Access := Source.Reference;
 779    begin
 780       if Index <= SR.Last then
 781          return SR.Data (Index);
 782       else
 783          raise Index_Error;
 784       end if;
 785    end Element;
 786
 787    --------------
 788    -- Finalize --
 789    --------------
 790
 791    procedure Finalize (Object : in out Unbounded_Wide_String) is
 792       SR : constant Shared_Wide_String_Access := Object.Reference;
 793
 794    begin
 795       if SR /= null then
 796
 797          --  The same controlled object can be finalized several times for
 798          --  some reason. As per 7.6.1(24) this should have no ill effect,
 799          --  so we need to add a guard for the case of finalizing the same
 800          --  object twice.
 801
 802          Object.Reference := null;
 803          Unreference (SR);
 804       end if;
 805    end Finalize;
 806
 807    ----------------
 808    -- Find_Token --
 809    ----------------
 810
 811    procedure Find_Token
 812      (Source : Unbounded_Wide_String;
 813       Set    : Wide_Maps.Wide_Character_Set;
 814       From   : Positive;
 815       Test   : Strings.Membership;
 816       First  : out Positive;
 817       Last   : out Natural)
 818    is
 819       SR : constant Shared_Wide_String_Access := Source.Reference;
 820    begin
 821       Wide_Search.Find_Token
 822         (SR.Data (From .. SR.Last), Set, Test, First, Last);
 823    end Find_Token;
 824
 825    procedure Find_Token
 826      (Source : Unbounded_Wide_String;
 827       Set    : Wide_Maps.Wide_Character_Set;
 828       Test   : Strings.Membership;
 829       First  : out Positive;
 830       Last   : out Natural)
 831    is
 832       SR : constant Shared_Wide_String_Access := Source.Reference;
 833    begin
 834       Wide_Search.Find_Token
 835         (SR.Data (1 .. SR.Last), Set, Test, First, Last);
 836    end Find_Token;
 837
 838    ----------
 839    -- Free --
 840    ----------
 841
 842    procedure Free (X : in out Wide_String_Access) is
 843       procedure Deallocate is
 844          new Ada.Unchecked_Deallocation (Wide_String, Wide_String_Access);
 845    begin
 846       Deallocate (X);
 847    end Free;
 848
 849    ----------
 850    -- Head --
 851    ----------
 852
 853    function Head
 854      (Source : Unbounded_Wide_String;
 855       Count  : Natural;
 856       Pad    : Wide_Character := Wide_Space) return Unbounded_Wide_String
 857    is
 858       SR : constant Shared_Wide_String_Access := Source.Reference;
 859       DR : Shared_Wide_String_Access;
 860
 861    begin
 862       --  Result is empty, reuse shared empty string
 863
 864       if Count = 0 then
 865          Reference (Empty_Shared_Wide_String'Access);
 866          DR := Empty_Shared_Wide_String'Access;
 867
 868       --  Length of the string is the same as requested, reuse source shared
 869       --  string.
 870
 871       elsif Count = SR.Last then
 872          Reference (SR);
 873          DR := SR;
 874
 875       --  Otherwise, allocate new shared string and fill it
 876
 877       else
 878          DR := Allocate (Count);
 879
 880          --  Length of the source string is more than requested, copy
 881          --  corresponding slice.
 882
 883          if Count < SR.Last then
 884             DR.Data (1 .. Count) := SR.Data (1 .. Count);
 885
 886          --  Length of the source string is less than requested, copy all
 887          --  contents and fill others by Pad character.
 888
 889          else
 890             DR.Data (1 .. SR.Last) := SR.Data (1 .. SR.Last);
 891
 892             for J in SR.Last + 1 .. Count loop
 893                DR.Data (J) := Pad;
 894             end loop;
 895          end if;
 896
 897          DR.Last := Count;
 898       end if;
 899
 900       return (AF.Controlled with Reference => DR);
 901    end Head;
 902
 903    procedure Head
 904      (Source : in out Unbounded_Wide_String;
 905       Count  : Natural;
 906       Pad    : Wide_Character := Wide_Space)
 907    is
 908       SR : constant Shared_Wide_String_Access := Source.Reference;
 909       DR : Shared_Wide_String_Access;
 910
 911    begin
 912       --  Result is empty, reuse empty shared string
 913
 914       if Count = 0 then
 915          Reference (Empty_Shared_Wide_String'Access);
 916          Source.Reference := Empty_Shared_Wide_String'Access;
 917          Unreference (SR);
 918
 919       --  Result is same with source string, reuse source shared string
 920
 921       elsif Count = SR.Last then
 922          null;
 923
 924       --  Try to reuse existent shared string
 925
 926       elsif Can_Be_Reused (SR, Count) then
 927          if Count > SR.Last then
 928             for J in SR.Last + 1 .. Count loop
 929                SR.Data (J) := Pad;
 930             end loop;
 931          end if;
 932
 933          SR.Last := Count;
 934
 935       --  Otherwise, allocate new shared string and fill it
 936
 937       else
 938          DR := Allocate (Count);
 939
 940          --  Length of the source string is greater than requested, copy
 941          --  corresponding slice.
 942
 943          if Count < SR.Last then
 944             DR.Data (1 .. Count) := SR.Data (1 .. Count);
 945
 946          --  Length of the source string is less than requested, copy all
 947          --  exists data and fill others by Pad character.
 948
 949          else
 950             DR.Data (1 .. SR.Last) := SR.Data (1 .. SR.Last);
 951
 952             for J in SR.Last + 1 .. Count loop
 953                DR.Data (J) := Pad;
 954             end loop;
 955          end if;
 956
 957          DR.Last := Count;
 958          Source.Reference := DR;
 959          Unreference (SR);
 960       end if;
 961    end Head;
 962
 963    -----------
 964    -- Index --
 965    -----------
 966
 967    function Index
 968      (Source  : Unbounded_Wide_String;
 969       Pattern : Wide_String;
 970       Going   : Strings.Direction := Strings.Forward;
 971       Mapping : Wide_Maps.Wide_Character_Mapping := Wide_Maps.Identity)
 972       return Natural
 973    is
 974       SR : constant Shared_Wide_String_Access := Source.Reference;
 975    begin
 976       return Wide_Search.Index
 977         (SR.Data (1 .. SR.Last), Pattern, Going, Mapping);
 978    end Index;
 979
 980    function Index
 981      (Source  : Unbounded_Wide_String;
 982       Pattern : Wide_String;
 983       Going   : Direction := Forward;
 984       Mapping : Wide_Maps.Wide_Character_Mapping_Function) return Natural
 985    is
 986       SR : constant Shared_Wide_String_Access := Source.Reference;
 987    begin
 988       return Wide_Search.Index
 989         (SR.Data (1 .. SR.Last), Pattern, Going, Mapping);
 990    end Index;
 991
 992    function Index
 993      (Source : Unbounded_Wide_String;
 994       Set    : Wide_Maps.Wide_Character_Set;
 995       Test   : Strings.Membership := Strings.Inside;
 996       Going  : Strings.Direction  := Strings.Forward) return Natural
 997    is
 998       SR : constant Shared_Wide_String_Access := Source.Reference;
 999    begin
1000       return Wide_Search.Index (SR.Data (1 .. SR.Last), Set, Test, Going);
1001    end Index;
1002
1003    function Index
1004      (Source  : Unbounded_Wide_String;
1005       Pattern : Wide_String;
1006       From    : Positive;
1007       Going   : Direction := Forward;
1008       Mapping : Wide_Maps.Wide_Character_Mapping := Wide_Maps.Identity)
1009       return Natural
1010    is
1011       SR : constant Shared_Wide_String_Access := Source.Reference;
1012    begin
1013       return Wide_Search.Index
1014         (SR.Data (1 .. SR.Last), Pattern, From, Going, Mapping);
1015    end Index;
1016
1017    function Index
1018      (Source  : Unbounded_Wide_String;
1019       Pattern : Wide_String;
1020       From    : Positive;
1021       Going   : Direction := Forward;
1022       Mapping : Wide_Maps.Wide_Character_Mapping_Function) return Natural
1023    is
1024       SR : constant Shared_Wide_String_Access := Source.Reference;
1025    begin
1026       return Wide_Search.Index
1027         (SR.Data (1 .. SR.Last), Pattern, From, Going, Mapping);
1028    end Index;
1029
1030    function Index
1031      (Source  : Unbounded_Wide_String;
1032       Set     : Wide_Maps.Wide_Character_Set;
1033       From    : Positive;
1034       Test    : Membership := Inside;
1035       Going   : Direction := Forward) return Natural
1036    is
1037       SR : constant Shared_Wide_String_Access := Source.Reference;
1038    begin
1039       return Wide_Search.Index
1040         (SR.Data (1 .. SR.Last), Set, From, Test, Going);
1041    end Index;
1042
1043    ---------------------
1044    -- Index_Non_Blank --
1045    ---------------------
1046
1047    function Index_Non_Blank
1048      (Source : Unbounded_Wide_String;
1049       Going  : Strings.Direction := Strings.Forward) return Natural
1050    is
1051       SR : constant Shared_Wide_String_Access := Source.Reference;
1052    begin
1053       return Wide_Search.Index_Non_Blank (SR.Data (1 .. SR.Last), Going);
1054    end Index_Non_Blank;
1055
1056    function Index_Non_Blank
1057      (Source : Unbounded_Wide_String;
1058       From   : Positive;
1059       Going  : Direction := Forward) return Natural
1060    is
1061       SR : constant Shared_Wide_String_Access := Source.Reference;
1062    begin
1063       return Wide_Search.Index_Non_Blank
1064         (SR.Data (1 .. SR.Last), From, Going);
1065    end Index_Non_Blank;
1066
1067    ----------------
1068    -- Initialize --
1069    ----------------
1070
1071    procedure Initialize (Object : in out Unbounded_Wide_String) is
1072    begin
1073       Reference (Object.Reference);
1074    end Initialize;
1075
1076    ------------
1077    -- Insert --
1078    ------------
1079
1080    function Insert
1081      (Source   : Unbounded_Wide_String;
1082       Before   : Positive;
1083       New_Item : Wide_String) return Unbounded_Wide_String
1084    is
1085       SR : constant Shared_Wide_String_Access := Source.Reference;
1086       DL : constant Natural := SR.Last + New_Item'Length;
1087       DR : Shared_Wide_String_Access;
1088
1089    begin
1090       --  Check index first
1091
1092       if Before > SR.Last + 1 then
1093          raise Index_Error;
1094       end if;
1095
1096       --  Result is empty, reuse empty shared string
1097
1098       if DL = 0 then
1099          Reference (Empty_Shared_Wide_String'Access);
1100          DR := Empty_Shared_Wide_String'Access;
1101
1102       --  Inserted string is empty, reuse source shared string
1103
1104       elsif New_Item'Length = 0 then
1105          Reference (SR);
1106          DR := SR;
1107
1108       --  Otherwise, allocate new shared string and fill it
1109
1110       else
1111          DR := Allocate (DL + DL / Growth_Factor);
1112          DR.Data (1 .. Before - 1) := SR.Data (1 .. Before - 1);
1113          DR.Data (Before .. Before + New_Item'Length - 1) := New_Item;
1114          DR.Data (Before + New_Item'Length .. DL) :=
1115            SR.Data (Before .. SR.Last);
1116          DR.Last := DL;
1117       end if;
1118
1119       return (AF.Controlled with Reference => DR);
1120    end Insert;
1121
1122    procedure Insert
1123      (Source   : in out Unbounded_Wide_String;
1124       Before   : Positive;
1125       New_Item : Wide_String)
1126    is
1127       SR : constant Shared_Wide_String_Access := Source.Reference;
1128       DL : constant Natural                   := SR.Last + New_Item'Length;
1129       DR : Shared_Wide_String_Access;
1130
1131    begin
1132       --  Check bounds
1133
1134       if Before > SR.Last + 1 then
1135          raise Index_Error;
1136       end if;
1137
1138       --  Result is empty string, reuse empty shared string
1139
1140       if DL = 0 then
1141          Reference (Empty_Shared_Wide_String'Access);
1142          Source.Reference := Empty_Shared_Wide_String'Access;
1143          Unreference (SR);
1144
1145       --  Inserted string is empty, nothing to do
1146
1147       elsif New_Item'Length = 0 then
1148          null;
1149
1150       --  Try to reuse existent shared string first
1151
1152       elsif Can_Be_Reused (SR, DL) then
1153          SR.Data (Before + New_Item'Length .. DL) :=
1154            SR.Data (Before .. SR.Last);
1155          SR.Data (Before .. Before + New_Item'Length - 1) := New_Item;
1156          SR.Last := DL;
1157
1158       --  Otherwise, allocate new shared string and fill it
1159
1160       else
1161          DR := Allocate (DL + DL / Growth_Factor);
1162          DR.Data (1 .. Before - 1) := SR.Data (1 .. Before - 1);
1163          DR.Data (Before .. Before + New_Item'Length - 1) := New_Item;
1164          DR.Data (Before + New_Item'Length .. DL) :=
1165            SR.Data (Before .. SR.Last);
1166          DR.Last := DL;
1167          Source.Reference := DR;
1168          Unreference (SR);
1169       end if;
1170    end Insert;
1171
1172    ------------
1173    -- Length --
1174    ------------
1175
1176    function Length (Source : Unbounded_Wide_String) return Natural is
1177    begin
1178       return Source.Reference.Last;
1179    end Length;
1180
1181    ---------------
1182    -- Overwrite --
1183    ---------------
1184
1185    function Overwrite
1186      (Source   : Unbounded_Wide_String;
1187       Position : Positive;
1188       New_Item : Wide_String) return Unbounded_Wide_String
1189    is
1190       SR : constant Shared_Wide_String_Access := Source.Reference;
1191       DL : Natural;
1192       DR : Shared_Wide_String_Access;
1193
1194    begin
1195       --  Check bounds
1196
1197       if Position > SR.Last + 1 then
1198          raise Index_Error;
1199       end if;
1200
1201       DL := Integer'Max (SR.Last, Position + New_Item'Length - 1);
1202
1203       --  Result is empty string, reuse empty shared string
1204
1205       if DL = 0 then
1206          Reference (Empty_Shared_Wide_String'Access);
1207          DR := Empty_Shared_Wide_String'Access;
1208
1209       --  Result is same with source string, reuse source shared string
1210
1211       elsif New_Item'Length = 0 then
1212          Reference (SR);
1213          DR := SR;
1214
1215       --  Otherwise, allocate new shared string and fill it
1216
1217       else
1218          DR := Allocate (DL);
1219          DR.Data (1 .. Position - 1) := SR.Data (1 .. Position - 1);
1220          DR.Data (Position .. Position + New_Item'Length - 1) := New_Item;
1221          DR.Data (Position + New_Item'Length .. DL) :=
1222            SR.Data (Position + New_Item'Length .. SR.Last);
1223          DR.Last := DL;
1224       end if;
1225
1226       return (AF.Controlled with Reference => DR);
1227    end Overwrite;
1228
1229    procedure Overwrite
1230      (Source    : in out Unbounded_Wide_String;
1231       Position  : Positive;
1232       New_Item  : Wide_String)
1233    is
1234       SR : constant Shared_Wide_String_Access := Source.Reference;
1235       DL : Natural;
1236       DR : Shared_Wide_String_Access;
1237
1238    begin
1239       --  Bounds check
1240
1241       if Position > SR.Last + 1 then
1242          raise Index_Error;
1243       end if;
1244
1245       DL := Integer'Max (SR.Last, Position + New_Item'Length - 1);
1246
1247       --  Result is empty string, reuse empty shared string
1248
1249       if DL = 0 then
1250          Reference (Empty_Shared_Wide_String'Access);
1251          Source.Reference := Empty_Shared_Wide_String'Access;
1252          Unreference (SR);
1253
1254       --  String unchanged, nothing to do
1255
1256       elsif New_Item'Length = 0 then
1257          null;
1258
1259       --  Try to reuse existent shared string
1260
1261       elsif Can_Be_Reused (SR, DL) then
1262          SR.Data (Position .. Position + New_Item'Length - 1) := New_Item;
1263          SR.Last := DL;
1264
1265       --  Otherwise allocate new shared string and fill it
1266
1267       else
1268          DR := Allocate (DL);
1269          DR.Data (1 .. Position - 1) := SR.Data (1 .. Position - 1);
1270          DR.Data (Position .. Position + New_Item'Length - 1) := New_Item;
1271          DR.Data (Position + New_Item'Length .. DL) :=
1272            SR.Data (Position + New_Item'Length .. SR.Last);
1273          DR.Last := DL;
1274          Source.Reference := DR;
1275          Unreference (SR);
1276       end if;
1277    end Overwrite;
1278
1279    ---------------
1280    -- Reference --
1281    ---------------
1282
1283    procedure Reference (Item : not null Shared_Wide_String_Access) is
1284    begin
1285       System.Atomic_Counters.Increment (Item.Counter);
1286    end Reference;
1287
1288    ---------------------
1289    -- Replace_Element --
1290    ---------------------
1291
1292    procedure Replace_Element
1293      (Source : in out Unbounded_Wide_String;
1294       Index  : Positive;
1295       By     : Wide_Character)
1296    is
1297       SR : constant Shared_Wide_String_Access := Source.Reference;
1298       DR : Shared_Wide_String_Access;
1299
1300    begin
1301       --  Bounds check
1302
1303       if Index <= SR.Last then
1304
1305          --  Try to reuse existent shared string
1306
1307          if Can_Be_Reused (SR, SR.Last) then
1308             SR.Data (Index) := By;
1309
1310          --  Otherwise allocate new shared string and fill it
1311
1312          else
1313             DR := Allocate (SR.Last);
1314             DR.Data (1 .. SR.Last) := SR.Data (1 .. SR.Last);
1315             DR.Data (Index) := By;
1316             DR.Last := SR.Last;
1317             Source.Reference := DR;
1318             Unreference (SR);
1319          end if;
1320
1321       else
1322          raise Index_Error;
1323       end if;
1324    end Replace_Element;
1325
1326    -------------------
1327    -- Replace_Slice --
1328    -------------------
1329
1330    function Replace_Slice
1331      (Source : Unbounded_Wide_String;
1332       Low    : Positive;
1333       High   : Natural;
1334       By     : Wide_String) return Unbounded_Wide_String
1335    is
1336       SR : constant Shared_Wide_String_Access := Source.Reference;
1337       DL : Natural;
1338       DR : Shared_Wide_String_Access;
1339
1340    begin
1341       --  Check bounds
1342
1343       if Low > SR.Last + 1 then
1344          raise Index_Error;
1345       end if;
1346
1347       --  Do replace operation when removed slice is not empty
1348
1349       if High >= Low then
1350          DL := By'Length + SR.Last + Low - Integer'Min (High, SR.Last) - 1;
1351          --  This is the number of characters remaining in the string after
1352          --  replacing the slice.
1353
1354          --  Result is empty string, reuse empty shared string
1355
1356          if DL = 0 then
1357             Reference (Empty_Shared_Wide_String'Access);
1358             DR := Empty_Shared_Wide_String'Access;
1359
1360          --  Otherwise allocate new shared string and fill it
1361
1362          else
1363             DR := Allocate (DL);
1364             DR.Data (1 .. Low - 1) := SR.Data (1 .. Low - 1);
1365             DR.Data (Low .. Low + By'Length - 1) := By;
1366             DR.Data (Low + By'Length .. DL) := SR.Data (High + 1 .. SR.Last);
1367             DR.Last := DL;
1368          end if;
1369
1370          return (AF.Controlled with Reference => DR);
1371
1372       --  Otherwise just insert string
1373
1374       else
1375          return Insert (Source, Low, By);
1376       end if;
1377    end Replace_Slice;
1378
1379    procedure Replace_Slice
1380      (Source : in out Unbounded_Wide_String;
1381       Low    : Positive;
1382       High   : Natural;
1383       By     : Wide_String)
1384    is
1385       SR : constant Shared_Wide_String_Access := Source.Reference;
1386       DL : Natural;
1387       DR : Shared_Wide_String_Access;
1388
1389    begin
1390       --  Bounds check
1391
1392       if Low > SR.Last + 1 then
1393          raise Index_Error;
1394       end if;
1395
1396       --  Do replace operation only when replaced slice is not empty
1397
1398       if High >= Low then
1399          DL := By'Length + SR.Last + Low - Integer'Min (High, SR.Last) - 1;
1400          --  This is the number of characters remaining in the string after
1401          --  replacing the slice.
1402
1403          --  Result is empty string, reuse empty shared string
1404
1405          if DL = 0 then
1406             Reference (Empty_Shared_Wide_String'Access);
1407             Source.Reference := Empty_Shared_Wide_String'Access;
1408             Unreference (SR);
1409
1410          --  Try to reuse existent shared string
1411
1412          elsif Can_Be_Reused (SR, DL) then
1413             SR.Data (Low + By'Length .. DL) := SR.Data (High + 1 .. SR.Last);
1414             SR.Data (Low .. Low + By'Length - 1) := By;
1415             SR.Last := DL;
1416
1417          --  Otherwise allocate new shared string and fill it
1418
1419          else
1420             DR := Allocate (DL);
1421             DR.Data (1 .. Low - 1) := SR.Data (1 .. Low - 1);
1422             DR.Data (Low .. Low + By'Length - 1) := By;
1423             DR.Data (Low + By'Length .. DL) := SR.Data (High + 1 .. SR.Last);
1424             DR.Last := DL;
1425             Source.Reference := DR;
1426             Unreference (SR);
1427          end if;
1428
1429       --  Otherwise just insert item
1430
1431       else
1432          Insert (Source, Low, By);
1433       end if;
1434    end Replace_Slice;
1435
1436    -------------------------------
1437    -- Set_Unbounded_Wide_String --
1438    -------------------------------
1439
1440    procedure Set_Unbounded_Wide_String
1441      (Target : out Unbounded_Wide_String;
1442       Source : Wide_String)
1443    is
1444       TR : constant Shared_Wide_String_Access := Target.Reference;
1445       DR : Shared_Wide_String_Access;
1446
1447    begin
1448       --  In case of empty string, reuse empty shared string
1449
1450       if Source'Length = 0 then
1451          Reference (Empty_Shared_Wide_String'Access);
1452          Target.Reference := Empty_Shared_Wide_String'Access;
1453
1454       else
1455          --  Try to reuse existent shared string
1456
1457          if Can_Be_Reused (TR, Source'Length) then
1458             Reference (TR);
1459             DR := TR;
1460
1461          --  Otherwise allocate new shared string
1462
1463          else
1464             DR := Allocate (Source'Length);
1465             Target.Reference := DR;
1466          end if;
1467
1468          DR.Data (1 .. Source'Length) := Source;
1469          DR.Last := Source'Length;
1470       end if;
1471
1472       Unreference (TR);
1473    end Set_Unbounded_Wide_String;
1474
1475    -----------
1476    -- Slice --
1477    -----------
1478
1479    function Slice
1480      (Source : Unbounded_Wide_String;
1481       Low    : Positive;
1482       High   : Natural) return Wide_String
1483    is
1484       SR : constant Shared_Wide_String_Access := Source.Reference;
1485
1486    begin
1487       --  Note: test of High > Length is in accordance with AI95-00128
1488
1489       if Low > SR.Last + 1 or else High > SR.Last then
1490          raise Index_Error;
1491
1492       else
1493          return SR.Data (Low .. High);
1494       end if;
1495    end Slice;
1496
1497    ----------
1498    -- Tail --
1499    ----------
1500
1501    function Tail
1502      (Source : Unbounded_Wide_String;
1503       Count  : Natural;
1504       Pad    : Wide_Character := Wide_Space) return Unbounded_Wide_String
1505    is
1506       SR : constant Shared_Wide_String_Access := Source.Reference;
1507       DR : Shared_Wide_String_Access;
1508
1509    begin
1510       --  For empty result reuse empty shared string
1511
1512       if Count = 0 then
1513          Reference (Empty_Shared_Wide_String'Access);
1514          DR := Empty_Shared_Wide_String'Access;
1515
1516       --  Result is hole source string, reuse source shared string
1517
1518       elsif Count = SR.Last then
1519          Reference (SR);
1520          DR := SR;
1521
1522       --  Otherwise allocate new shared string and fill it
1523
1524       else
1525          DR := Allocate (Count);
1526
1527          if Count < SR.Last then
1528             DR.Data (1 .. Count) := SR.Data (SR.Last - Count + 1 .. SR.Last);
1529
1530          else
1531             for J in 1 .. Count - SR.Last loop
1532                DR.Data (J) := Pad;
1533             end loop;
1534
1535             DR.Data (Count - SR.Last + 1 .. Count) := SR.Data (1 .. SR.Last);
1536          end if;
1537
1538          DR.Last := Count;
1539       end if;
1540
1541       return (AF.Controlled with Reference => DR);
1542    end Tail;
1543
1544    procedure Tail
1545      (Source : in out Unbounded_Wide_String;
1546       Count  : Natural;
1547       Pad    : Wide_Character := Wide_Space)
1548    is
1549       SR : constant Shared_Wide_String_Access := Source.Reference;
1550       DR : Shared_Wide_String_Access;
1551
1552       procedure Common
1553         (SR    : Shared_Wide_String_Access;
1554          DR    : Shared_Wide_String_Access;
1555          Count : Natural);
1556       --  Common code of tail computation. SR/DR can point to the same object
1557
1558       ------------
1559       -- Common --
1560       ------------
1561
1562       procedure Common
1563         (SR    : Shared_Wide_String_Access;
1564          DR    : Shared_Wide_String_Access;
1565          Count : Natural) is
1566       begin
1567          if Count < SR.Last then
1568             DR.Data (1 .. Count) := SR.Data (SR.Last - Count + 1 .. SR.Last);
1569
1570          else
1571             DR.Data (Count - SR.Last + 1 .. Count) := SR.Data (1 .. SR.Last);
1572
1573             for J in 1 .. Count - SR.Last loop
1574                DR.Data (J) := Pad;
1575             end loop;
1576          end if;
1577
1578          DR.Last := Count;
1579       end Common;
1580
1581    begin
1582       --  Result is empty string, reuse empty shared string
1583
1584       if Count = 0 then
1585          Reference (Empty_Shared_Wide_String'Access);
1586          Source.Reference := Empty_Shared_Wide_String'Access;
1587          Unreference (SR);
1588
1589       --  Length of the result is the same with length of the source string,
1590       --  reuse source shared string.
1591
1592       elsif Count = SR.Last then
1593          null;
1594
1595       --  Try to reuse existent shared string
1596
1597       elsif Can_Be_Reused (SR, Count) then
1598          Common (SR, SR, Count);
1599
1600       --  Otherwise allocate new shared string and fill it
1601
1602       else
1603          DR := Allocate (Count);
1604          Common (SR, DR, Count);
1605          Source.Reference := DR;
1606          Unreference (SR);
1607       end if;
1608    end Tail;
1609
1610    --------------------
1611    -- To_Wide_String --
1612    --------------------
1613
1614    function To_Wide_String
1615      (Source : Unbounded_Wide_String) return Wide_String is
1616    begin
1617       return Source.Reference.Data (1 .. Source.Reference.Last);
1618    end To_Wide_String;
1619
1620    ------------------------------
1621    -- To_Unbounded_Wide_String --
1622    ------------------------------
1623
1624    function To_Unbounded_Wide_String
1625      (Source : Wide_String) return Unbounded_Wide_String
1626    is
1627       DR : constant Shared_Wide_String_Access := Allocate (Source'Length);
1628    begin
1629       DR.Data (1 .. Source'Length) := Source;
1630       DR.Last := Source'Length;
1631       return (AF.Controlled with Reference => DR);
1632    end To_Unbounded_Wide_String;
1633
1634    function To_Unbounded_Wide_String
1635      (Length : Natural) return Unbounded_Wide_String
1636    is
1637       DR : constant Shared_Wide_String_Access := Allocate (Length);
1638    begin
1639       DR.Last := Length;
1640       return (AF.Controlled with Reference => DR);
1641    end To_Unbounded_Wide_String;
1642
1643    ---------------
1644    -- Translate --
1645    ---------------
1646
1647    function Translate
1648      (Source  : Unbounded_Wide_String;
1649       Mapping : Wide_Maps.Wide_Character_Mapping) return Unbounded_Wide_String
1650    is
1651       SR : constant Shared_Wide_String_Access := Source.Reference;
1652       DR : Shared_Wide_String_Access;
1653
1654    begin
1655       --  Nothing to translate, reuse empty shared string
1656
1657       if SR.Last = 0 then
1658          Reference (Empty_Shared_Wide_String'Access);
1659          DR := Empty_Shared_Wide_String'Access;
1660
1661       --  Otherwise, allocate new shared string and fill it
1662
1663       else
1664          DR := Allocate (SR.Last);
1665
1666          for J in 1 .. SR.Last loop
1667             DR.Data (J) := Value (Mapping, SR.Data (J));
1668          end loop;
1669
1670          DR.Last := SR.Last;
1671       end if;
1672
1673       return (AF.Controlled with Reference => DR);
1674    end Translate;
1675
1676    procedure Translate
1677      (Source  : in out Unbounded_Wide_String;
1678       Mapping : Wide_Maps.Wide_Character_Mapping)
1679    is
1680       SR : constant Shared_Wide_String_Access := Source.Reference;
1681       DR : Shared_Wide_String_Access;
1682
1683    begin
1684       --  Nothing to translate
1685
1686       if SR.Last = 0 then
1687          null;
1688
1689       --  Try to reuse shared string
1690
1691       elsif Can_Be_Reused (SR, SR.Last) then
1692          for J in 1 .. SR.Last loop
1693             SR.Data (J) := Value (Mapping, SR.Data (J));
1694          end loop;
1695
1696       --  Otherwise, allocate new shared string
1697
1698       else
1699          DR := Allocate (SR.Last);
1700
1701          for J in 1 .. SR.Last loop
1702             DR.Data (J) := Value (Mapping, SR.Data (J));
1703          end loop;
1704
1705          DR.Last := SR.Last;
1706          Source.Reference := DR;
1707          Unreference (SR);
1708       end if;
1709    end Translate;
1710
1711    function Translate
1712      (Source  : Unbounded_Wide_String;
1713       Mapping : Wide_Maps.Wide_Character_Mapping_Function)
1714       return Unbounded_Wide_String
1715    is
1716       SR : constant Shared_Wide_String_Access := Source.Reference;
1717       DR : Shared_Wide_String_Access;
1718
1719    begin
1720       --  Nothing to translate, reuse empty shared string
1721
1722       if SR.Last = 0 then
1723          Reference (Empty_Shared_Wide_String'Access);
1724          DR := Empty_Shared_Wide_String'Access;
1725
1726       --  Otherwise, allocate new shared string and fill it
1727
1728       else
1729          DR := Allocate (SR.Last);
1730
1731          for J in 1 .. SR.Last loop
1732             DR.Data (J) := Mapping.all (SR.Data (J));
1733          end loop;
1734
1735          DR.Last := SR.Last;
1736       end if;
1737
1738       return (AF.Controlled with Reference => DR);
1739
1740    exception
1741       when others =>
1742          Unreference (DR);
1743
1744          raise;
1745    end Translate;
1746
1747    procedure Translate
1748      (Source  : in out Unbounded_Wide_String;
1749       Mapping : Wide_Maps.Wide_Character_Mapping_Function)
1750    is
1751       SR : constant Shared_Wide_String_Access := Source.Reference;
1752       DR : Shared_Wide_String_Access;
1753
1754    begin
1755       --  Nothing to translate
1756
1757       if SR.Last = 0 then
1758          null;
1759
1760       --  Try to reuse shared string
1761
1762       elsif Can_Be_Reused (SR, SR.Last) then
1763          for J in 1 .. SR.Last loop
1764             SR.Data (J) := Mapping.all (SR.Data (J));
1765          end loop;
1766
1767       --  Otherwise allocate new shared string and fill it
1768
1769       else
1770          DR := Allocate (SR.Last);
1771
1772          for J in 1 .. SR.Last loop
1773             DR.Data (J) := Mapping.all (SR.Data (J));
1774          end loop;
1775
1776          DR.Last := SR.Last;
1777          Source.Reference := DR;
1778          Unreference (SR);
1779       end if;
1780
1781    exception
1782       when others =>
1783          if DR /= null then
1784             Unreference (DR);
1785          end if;
1786
1787          raise;
1788    end Translate;
1789
1790    ----------
1791    -- Trim --
1792    ----------
1793
1794    function Trim
1795      (Source : Unbounded_Wide_String;
1796       Side   : Trim_End) return Unbounded_Wide_String
1797    is
1798       SR   : constant Shared_Wide_String_Access := Source.Reference;
1799       DL   : Natural;
1800       DR   : Shared_Wide_String_Access;
1801       Low  : Natural;
1802       High : Natural;
1803
1804    begin
1805       Low := Index_Non_Blank (Source, Forward);
1806
1807       --  All blanks, reuse empty shared string
1808
1809       if Low = 0 then
1810          Reference (Empty_Shared_Wide_String'Access);
1811          DR := Empty_Shared_Wide_String'Access;
1812
1813       else
1814          case Side is
1815             when Left =>
1816                High := SR.Last;
1817                DL   := SR.Last - Low + 1;
1818
1819             when Right =>
1820                Low  := 1;
1821                High := Index_Non_Blank (Source, Backward);
1822                DL   := High;
1823
1824             when Both =>
1825                High := Index_Non_Blank (Source, Backward);
1826                DL   := High - Low + 1;
1827          end case;
1828
1829          --  Length of the result is the same as length of the source string,
1830          --  reuse source shared string.
1831
1832          if DL = SR.Last then
1833             Reference (SR);
1834             DR := SR;
1835
1836          --  Otherwise, allocate new shared string
1837
1838          else
1839             DR := Allocate (DL);
1840             DR.Data (1 .. DL) := SR.Data (Low .. High);
1841             DR.Last := DL;
1842          end if;
1843       end if;
1844
1845       return (AF.Controlled with Reference => DR);
1846    end Trim;
1847
1848    procedure Trim
1849      (Source : in out Unbounded_Wide_String;
1850       Side   : Trim_End)
1851    is
1852       SR   : constant Shared_Wide_String_Access := Source.Reference;
1853       DL   : Natural;
1854       DR   : Shared_Wide_String_Access;
1855       Low  : Natural;
1856       High : Natural;
1857
1858    begin
1859       Low := Index_Non_Blank (Source, Forward);
1860
1861       --  All blanks, reuse empty shared string
1862
1863       if Low = 0 then
1864          Reference (Empty_Shared_Wide_String'Access);
1865          Source.Reference := Empty_Shared_Wide_String'Access;
1866          Unreference (SR);
1867
1868       else
1869          case Side is
1870             when Left =>
1871                High := SR.Last;
1872                DL   := SR.Last - Low + 1;
1873
1874             when Right =>
1875                Low  := 1;
1876                High := Index_Non_Blank (Source, Backward);
1877                DL   := High;
1878
1879             when Both =>
1880                High := Index_Non_Blank (Source, Backward);
1881                DL   := High - Low + 1;
1882          end case;
1883
1884          --  Length of the result is the same as length of the source string,
1885          --  nothing to do.
1886
1887          if DL = SR.Last then
1888             null;
1889
1890          --  Try to reuse existent shared string
1891
1892          elsif Can_Be_Reused (SR, DL) then
1893             SR.Data (1 .. DL) := SR.Data (Low .. High);
1894             SR.Last := DL;
1895
1896          --  Otherwise, allocate new shared string
1897
1898          else
1899             DR := Allocate (DL);
1900             DR.Data (1 .. DL) := SR.Data (Low .. High);
1901             DR.Last := DL;
1902             Source.Reference := DR;
1903             Unreference (SR);
1904          end if;
1905       end if;
1906    end Trim;
1907
1908    function Trim
1909      (Source : Unbounded_Wide_String;
1910       Left   : Wide_Maps.Wide_Character_Set;
1911       Right  : Wide_Maps.Wide_Character_Set) return Unbounded_Wide_String
1912    is
1913       SR   : constant Shared_Wide_String_Access := Source.Reference;
1914       DL   : Natural;
1915       DR   : Shared_Wide_String_Access;
1916       Low  : Natural;
1917       High : Natural;
1918
1919    begin
1920       Low := Index (Source, Left, Outside, Forward);
1921
1922       --  Source includes only characters from Left set, reuse empty shared
1923       --  string.
1924
1925       if Low = 0 then
1926          Reference (Empty_Shared_Wide_String'Access);
1927          DR := Empty_Shared_Wide_String'Access;
1928
1929       else
1930          High := Index (Source, Right, Outside, Backward);
1931          DL   := Integer'Max (0, High - Low + 1);
1932
1933          --  Source includes only characters from Right set or result string
1934          --  is empty, reuse empty shared string.
1935
1936          if High = 0 or else DL = 0 then
1937             Reference (Empty_Shared_Wide_String'Access);
1938             DR := Empty_Shared_Wide_String'Access;
1939
1940          --  Otherwise, allocate new shared string and fill it
1941
1942          else
1943             DR := Allocate (DL);
1944             DR.Data (1 .. DL) := SR.Data (Low .. High);
1945             DR.Last := DL;
1946          end if;
1947       end if;
1948
1949       return (AF.Controlled with Reference => DR);
1950    end Trim;
1951
1952    procedure Trim
1953      (Source : in out Unbounded_Wide_String;
1954       Left   : Wide_Maps.Wide_Character_Set;
1955       Right  : Wide_Maps.Wide_Character_Set)
1956    is
1957       SR   : constant Shared_Wide_String_Access := Source.Reference;
1958       DL   : Natural;
1959       DR   : Shared_Wide_String_Access;
1960       Low  : Natural;
1961       High : Natural;
1962
1963    begin
1964       Low := Index (Source, Left, Outside, Forward);
1965
1966       --  Source includes only characters from Left set, reuse empty shared
1967       --  string.
1968
1969       if Low = 0 then
1970          Reference (Empty_Shared_Wide_String'Access);
1971          Source.Reference := Empty_Shared_Wide_String'Access;
1972          Unreference (SR);
1973
1974       else
1975          High := Index (Source, Right, Outside, Backward);
1976          DL   := Integer'Max (0, High - Low + 1);
1977
1978          --  Source includes only characters from Right set or result string
1979          --  is empty, reuse empty shared string.
1980
1981          if High = 0 or else DL = 0 then
1982             Reference (Empty_Shared_Wide_String'Access);
1983             Source.Reference := Empty_Shared_Wide_String'Access;
1984             Unreference (SR);
1985
1986          --  Try to reuse existent shared string
1987
1988          elsif Can_Be_Reused (SR, DL) then
1989             SR.Data (1 .. DL) := SR.Data (Low .. High);
1990             SR.Last := DL;
1991
1992          --  Otherwise, allocate new shared string and fill it
1993
1994          else
1995             DR := Allocate (DL);
1996             DR.Data (1 .. DL) := SR.Data (Low .. High);
1997             DR.Last := DL;
1998             Source.Reference := DR;
1999             Unreference (SR);
2000          end if;
2001       end if;
2002    end Trim;
2003
2004    ---------------------
2005    -- Unbounded_Slice --
2006    ---------------------
2007
2008    function Unbounded_Slice
2009      (Source : Unbounded_Wide_String;
2010       Low    : Positive;
2011       High   : Natural) return Unbounded_Wide_String
2012    is
2013       SR : constant Shared_Wide_String_Access := Source.Reference;
2014       DL : Natural;
2015       DR : Shared_Wide_String_Access;
2016
2017    begin
2018       --  Check bounds
2019
2020       if Low > SR.Last + 1 or else High > SR.Last then
2021          raise Index_Error;
2022
2023       --  Result is empty slice, reuse empty shared string
2024
2025       elsif Low > High then
2026          Reference (Empty_Shared_Wide_String'Access);
2027          DR := Empty_Shared_Wide_String'Access;
2028
2029       --  Otherwise, allocate new shared string and fill it
2030
2031       else
2032          DL := High - Low + 1;
2033          DR := Allocate (DL);
2034          DR.Data (1 .. DL) := SR.Data (Low .. High);
2035          DR.Last := DL;
2036       end if;
2037
2038       return (AF.Controlled with Reference => DR);
2039    end Unbounded_Slice;
2040
2041    procedure Unbounded_Slice
2042      (Source : Unbounded_Wide_String;
2043       Target : out Unbounded_Wide_String;
2044       Low    : Positive;
2045       High   : Natural)
2046    is
2047       SR : constant Shared_Wide_String_Access := Source.Reference;
2048       TR : constant Shared_Wide_String_Access := Target.Reference;
2049       DL : Natural;
2050       DR : Shared_Wide_String_Access;
2051
2052    begin
2053       --  Check bounds
2054
2055       if Low > SR.Last + 1 or else High > SR.Last then
2056          raise Index_Error;
2057
2058       --  Result is empty slice, reuse empty shared string
2059
2060       elsif Low > High then
2061          Reference (Empty_Shared_Wide_String'Access);
2062          Target.Reference := Empty_Shared_Wide_String'Access;
2063          Unreference (TR);
2064
2065       else
2066          DL := High - Low + 1;
2067
2068          --  Try to reuse existent shared string
2069
2070          if Can_Be_Reused (TR, DL) then
2071             TR.Data (1 .. DL) := SR.Data (Low .. High);
2072             TR.Last := DL;
2073
2074          --  Otherwise, allocate new shared string and fill it
2075
2076          else
2077             DR := Allocate (DL);
2078             DR.Data (1 .. DL) := SR.Data (Low .. High);
2079             DR.Last := DL;
2080             Target.Reference := DR;
2081             Unreference (TR);
2082          end if;
2083       end if;
2084    end Unbounded_Slice;
2085
2086    -----------------
2087    -- Unreference --
2088    -----------------
2089
2090    procedure Unreference (Item : not null Shared_Wide_String_Access) is
2091
2092       procedure Free is
2093         new Ada.Unchecked_Deallocation
2094               (Shared_Wide_String, Shared_Wide_String_Access);
2095
2096       Aux : Shared_Wide_String_Access := Item;
2097
2098    begin
2099       if System.Atomic_Counters.Decrement (Aux.Counter) then
2100
2101          --  Reference counter of Empty_Shared_Wide_String must never reach
2102          --  zero.
2103
2104          pragma Assert (Aux /= Empty_Shared_Wide_String'Access);
2105
2106          Free (Aux);
2107       end if;
2108    end Unreference;
2109
2110 end Ada.Strings.Wide_Unbounded;