------------------------------------------------------------------------------
--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
--                                                                          --
--                                N A M E T                                 --
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--                                                                          --
--                            $Revision$
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--          Copyright (C) 1992-2002 Free Software Foundation, Inc.          --
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-- GNAT is free software;  you can  redistribute it  and/or modify it under --
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-- unit, or you link  this unit with other files  to produce an executable, --
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-- however invalidate  any other reasons why  the executable file  might be --
-- covered by the  GNU Public License.                                      --
--                                                                          --
-- GNAT was originally developed  by the GNAT team at  New York University. --
-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
--                                                                          --
------------------------------------------------------------------------------

with Alloc;
with Table;
with System;   use System;
with Types;    use Types;

package Namet is

--  WARNING: There is a C version of this package. Any changes to this
--  source file must be properly reflected in the C header file namet.h
--  which is created manually from namet.ads and namet.adb.

--  This package contains routines for handling the names table. The table
--  is used to store character strings for identifiers and operator symbols,
--  as well as other string values such as unit names and file names.

--  The forms of the entries are as follows:

--    Identifiers        Stored with upper case letters folded to lower case.
--                       Upper half (16#80# bit set) and wide characters are
--                       stored in an encoded form (Uhh for upper half and
--                       Whhhh for wide characters, as provided by the routine
--                       Store_Encoded_Character, where hh are hex digits for
--                       the character code using lower case a-f). Other
--                       internally generated names use upper case letters
--                       (other than O,Q,U,W) to ensure that they do not clash
--                       with identifier names in the source program.

--    Operator symbols   Stored with an initial letter O, and the remainder
--                       of the name is the lower case characters XXX where
--                       the name is Name_Op_XXX, see Snames spec for a full
--                       list of the operator names.

--    Character literals Character literals have names that are used only for
--                       debugging and error message purposes. The form is a
--                       upper case Q followed by a single letter, or by a Uxx
--                       or Wxxxx encoding as described for identifiers. The
--                       Set_Character_Literal_Name procedure should be used
--                       to construct these encodings.

--    Unit names         Stored with upper case letters folded to lower case,
--                       using Uhh/Whhhh encoding as described for identifiers,
--                       and a %s or %b suffix for specs/bodies. See package
--                       Uname for further details.

--    File names         Are stored in the form provided by Osint. Typically
--                       they may include wide character escape sequences and
--                       upper case characters (in non-encoded form). Casing
--                       is also derived from the external environment. Note
--                       that file names provided by Osint must generally be
--                       consistent with the names from Fname.Get_File_Name.

--    Other strings      The names table is also used as a convenient storage
--                       location for other variable length strings such as
--                       error messages etc. There are no restrictions on what
--                       characters may appear for such entries.

--  Note: the encodings Uhh (upper half characters), Whhhh (wide characters),
--  and Qx (character literal names) are described in the spec, since they
--  are visible throughout the system (e.g. in debugging output). However,
--  no code should depend on these particular encodings, so it should be
--  possible to change the encodings by making changes only to the Namet
--  specification (to change these comments) and the body (which actually
--  implements the encodings).

--  The names are hashed so that a given name appears only once in the table,
--  except that names entered with Name_Enter as opposed to Name_Find are
--  omitted from the hash table.

--  The first 26 entries in the names table (with Name_Id values in the range
--  First_Name_Id .. First_Name_Id + 25) represent names which are the one
--  character lower case letters in the range a-z, and these names are created
--  and initialized by the Initialize procedure.

--  Two values, one of type Int and one of type Byte, are stored with each
--  names table entry and subprograms are provided for setting and retrieving
--  these associated values. The usage of these values is up to the client.
--  In the compiler, the Int field is used to point to a chain of potentially
--  visible entities (see Sem.Ch8 for details), and the Byte field is used
--  to hold the Token_Type value for reserved words (see Sem for details).
--  In the binder, the Byte field is unused, and the Int field is used in
--  various ways depending on the name involved (see binder documentation).

   Name_Buffer : String (1 .. 16*1024);
   --  This buffer is used to set the name to be stored in the table for the
   --  Name_Find call, and to retrieve the name for the Get_Name_String call.
   --  The plus 1 in the length allows for cases of adding ASCII.NUL. The
   --  16K here is intended to be an infinite value that ensures that we
   --  never overflow the buffer (names this long are too absurd to worry!)

   Name_Len : Natural;
   --  Length of name stored in Name_Buffer. Used as an input parameter for
   --  Name_Find, and as an output value by Get_Name_String, or Write_Name.

   -----------------
   -- Subprograms --
   -----------------

   procedure Finalize;
   --  Called at the end of a use of the Namet package (before a subsequent
   --  call to Initialize). Currently this routine is only used to generate
   --  debugging output.

   procedure Get_Name_String (Id : Name_Id);
   --  Get_Name_String is used to retrieve the string associated with an entry
   --  in the names table. The resulting string is stored in Name_Buffer
   --  and Name_Len is set. It is an error to call Get_Name_String with one
   --  of the special name Id values (No_Name or Error_Name).

   function Get_Name_String (Id : Name_Id) return String;
   --  This functional form returns the result as a string without affecting
   --  the contents of either Name_Buffer or Name_Len.

   procedure Get_Unqualified_Name_String (Id : Name_Id);
   --  Similar to the above except that qualification (as defined in unit
   --  Exp_Dbug) is removed (including both preceding __ delimited names,
   --  and also the suffixes used to indicate package body entities and to
   --  distinguish between overloaded entities). Note that names are not
   --  qualified until just before the call to gigi, so this routine is
   --  only needed by processing that occurs after gigi has been called.
   --  This includes all ASIS processing, since ASIS works on the tree
   --  written after gigi has been called.

   procedure Get_Name_String_And_Append (Id : Name_Id);
   --  Like Get_Name_String but the resulting characters are appended to
   --  the current contents of the entry stored in Name_Buffer, and Name_Len
   --  is incremented to include the added characters.

   procedure Get_Decoded_Name_String (Id : Name_Id);
   --  Same calling sequence an interface as Get_Name_String, except that the
   --  result is decoded, so that upper half characters and wide characters
   --  appear as originally found in the source program text, operators have
   --  their source forms (special characters and enclosed in quotes), and
   --  character literals appear surrounded by apostrophes.

   procedure Get_Unqualified_Decoded_Name_String (Id : Name_Id);
   --  Similar to the above except that qualification (as defined in unit
   --  Exp_Dbug) is removed (including both preceding __ delimited names,
   --  and also the suffix used to indicate package body entities). Note
   --  that names are not qualified until just before the call to gigi, so
   --  this routine is only needed by processing that occurs after gigi has
   --  been called. This includes all ASIS processing, since ASIS works on
   --  the tree written after gigi has been called.

   procedure Get_Decoded_Name_String_With_Brackets (Id : Name_Id);
   --  This routine is similar to Decoded_Name, except that the brackets
   --  notation (Uhh replaced by ["hh"], Whhhh replaced by ["hhhh"]) is
   --  used for all non-lower half characters, regardless of the setting
   --  of Opt.Wide_Character_Encoding_Method, and also in that characters
   --  in the range 16#80# .. 16#FF# are converted to brackets notation
   --  in all cases. This routine can be used when there is a requirement
   --  for a canonical representation not affected by the character set
   --  options (e.g. in the binder generation of symbols).

   function Get_Name_Table_Byte (Id : Name_Id) return Byte;
   pragma Inline (Get_Name_Table_Byte);
   --  Fetches the Byte value associated with the given name

   function Get_Name_Table_Info (Id : Name_Id) return Int;
   pragma Inline (Get_Name_Table_Info);
   --  Fetches the Int value associated with the given name

   procedure Initialize;
   --  Initializes the names table, including initializing the first 26
   --  entries in the table (for the 1-character lower case names a-z)
   --  Note that Initialize must not be called if Tree_Read is used.

   procedure Lock;
   --  Lock name table before calling back end. Space for up to 10 extra
   --  names and 1000 extra characters is reserved before the table is locked.

   procedure Unlock;
   --  Unlocks the name table to allow use of the 10 extra names and 1000
   --  extra characters reserved by the Lock call. See gnat1drv for details
   --  of the need for this.

   function Length_Of_Name (Id : Name_Id) return Nat;
   pragma Inline (Length_Of_Name);
   --  Returns length of given name in characters. This is the length of the
   --  encoded name, as stored in the names table, the result is equivalent to
   --  calling Get_Name_String and reading Name_Len, except that a call to
   --  Length_Of_Name does not affect the contents of Name_Len and Name_Buffer.

   function Name_Chars_Address return System.Address;
   --  Return starting address of name characters table (used in Back_End
   --  call to Gigi).

   function Name_Find return Name_Id;
   --  Name_Find is called with a string stored in Name_Buffer whose length
   --  is in Name_Len (i.e. the characters of the name are in subscript
   --  positions 1 to Name_Len in Name_Buffer). It searches the names
   --  table to see if the string has already been stored. If so the Id of
   --  the existing entry is returned. Otherwise a new entry is created with
   --  its Name_Table_Info field set to zero. The contents of Name_Buffer
   --  and Name_Len are not modified by this call.

   function Name_Enter return Name_Id;
   --  Name_Enter has the same calling interface as Name_Find. The difference
   --  is that it does not search the table for an existing match, and also
   --  subsequent Name_Find calls using the same name will not locate the
   --  entry created by this call. Thus multiple calls to Name_Enter with the
   --  same name will create multiple entries in the name table with different
   --  Name_Id values. This is useful in the case of created names, which are
   --  never expected to be looked up. Note: Name_Enter should never be used
   --  for one character names, since these are efficiently located without
   --  hashing by Name_Find in any case.

   function Name_Entries_Address return System.Address;
   --  Return starting address of Names table. Used in Back_End call to Gigi.

   function Name_Entries_Count return Nat;
   --  Return current number of entries in the names table

   function Is_OK_Internal_Letter (C : Character) return Boolean;
   pragma Inline (Is_OK_Internal_Letter);
   --  Returns true if C is a suitable character for using as a prefix or a
   --  suffix of an internally generated name, i.e. it is an upper case letter
   --  other than one of the ones used for encoding source names (currently
   --  the set of reserved letters is O, Q, U, W) and also returns False for
   --  the letter X, which is reserved for debug output (see Exp_Dbug).

   function Is_Internal_Name (Id : Name_Id) return Boolean;
   --  Returns True if the name is an internal name (i.e. contains a character
   --  for which Is_OK_Internal_Letter is true, or if the name starts or ends
   --  with an underscore. This call destroys the value of Name_Len and
   --  Name_Buffer (it loads these as for Get_Name_String).
   --
   --  Note: if the name is qualified (has a double underscore), then
   --  only the final entity name is considered, not the qualifying
   --  names. Consider for example that the name:
   --
   --    pkg__B_1__xyz
   --
   --  is not an internal name, because the B comes from the internal
   --  name of a qualifying block, but the xyz means that this was
   --  indeed a declared identifier called "xyz" within this block
   --  and there is nothing internal about that name.

   function Is_Internal_Name return Boolean;
   --  Like the form with an Id argument, except that the name to be tested is
   --  passed in Name_Buffer and Name_Len (which are not affected by the call).
   --  Name_Buffer (it loads these as for Get_Name_String).

   procedure Reset_Name_Table;
   --  This procedure is used when there are multiple source files to reset
   --  the name table info entries associated with current entries in the
   --  names table. There is no harm in keeping the names entries themselves
   --  from one compilation to another, but we can't keep the entity info,
   --  since this refers to tree nodes, which are destroyed between each
   --  main source file.

   procedure Add_Char_To_Name_Buffer (C : Character);
   pragma Inline (Add_Char_To_Name_Buffer);
   --  Add given character to the end of the string currently stored in the
   --  Name_Buffer, incrementing Name_Len.

   procedure Add_Nat_To_Name_Buffer (V : Nat);
   --  Add decimal representation of given value to the end of the string
   --  currently stored in Name_Buffer, incrementing Name_Len as required.

   procedure Add_Str_To_Name_Buffer (S : String);
   --  Add characters of string S to the end of the string currently stored
   --  in the Name_Buffer, incrementing Name_Len by the length of the string.

   procedure Set_Character_Literal_Name (C : Char_Code);
   --  This procedure sets the proper encoded name for the character literal
   --  for the given character code. On return Name_Buffer and Name_Len are
   --  set to reflect the stored name.

   procedure Set_Name_Table_Info (Id : Name_Id; Val : Int);
   pragma Inline (Set_Name_Table_Info);
   --  Sets the Int value associated with the given name

   procedure Set_Name_Table_Byte (Id : Name_Id; Val : Byte);
   pragma Inline (Set_Name_Table_Byte);
   --  Sets the Byte value associated with the given name

   procedure Store_Encoded_Character (C : Char_Code);
   --  Stores given character code at the end of Name_Buffer, updating the
   --  value in Name_Len appropriately. Lower case letters and digits are
   --  stored unchanged. Other 8-bit characters are stored using the Uhh
   --  encoding (hh = hex code), and other 16-bit wide-character values
   --  are stored using the Whhhh (hhhh = hex code) encoding. Note that
   --  this procedure does not fold upper case letters (they are stored
   --  using the Uhh encoding). If folding is required, it must be done
   --  by the caller prior to the call.

   procedure Tree_Read;
   --  Initializes internal tables from current tree file using Tree_Read.
   --  Note that Initialize should not be called if Tree_Read is used.
   --  Tree_Read includes all necessary initialization.

   procedure Tree_Write;
   --  Writes out internal tables to current tree file using Tree_Write

   procedure Write_Name (Id : Name_Id);
   --  Write_Name writes the characters of the specified name using the
   --  standard output procedures in package Output. No end of line is
   --  written, just the characters of the name. On return Name_Buffer and
   --  Name_Len are set as for a call to Get_Name_String. The name is written
   --  in encoded form (i.e. including Uhh, Whhh, Qx, _op as they appear in
   --  the name table). If Id is Error_Name, or No_Name, no text is output.

   procedure wn (Id : Name_Id);
   pragma Export (Ada, wn);
   --  Like Write_Name, but includes new line at end. Intended for use
   --  from the debugger only.

   procedure Write_Name_Decoded (Id : Name_Id);
   --  Like Write_Name, except that the name written is the decoded name, as
   --  described for Get_Name_Decoded, and the resulting value stored in
   --  Name_Len and Name_Buffer is the decoded name.

   ---------------------------
   -- Table Data Structures --
   ---------------------------

   --  The following declarations define the data structures used to store
   --  names. The definitions are in the private part of the package spec,
   --  rather than the body, since they are referenced directly by gigi.

private

   --  This table stores the actual string names. Although logically there
   --  is no need for a terminating character (since the length is stored
   --  in the name entry table), we still store a NUL character at the end
   --  of every name (for convenience in interfacing to the C world).

   package Name_Chars is new Table.Table (
     Table_Component_Type => Character,
     Table_Index_Type     => Int,
     Table_Low_Bound      => 0,
     Table_Initial        => Alloc.Name_Chars_Initial,
     Table_Increment      => Alloc.Name_Chars_Increment,
     Table_Name           => "Name_Chars");

   type Name_Entry is record
      Name_Chars_Index : Int;
      --  Starting location of characters in the Name_Chars table minus
      --  one (i.e. pointer to character just before first character). The
      --  reason for the bias of one is that indexes in Name_Buffer are
      --  one's origin, so this avoids unnecessary adds and subtracts of 1.

      Name_Len : Short;
      --  Length of this name in characters

      Byte_Info : Byte;
      --  Byte value associated with this name

      Hash_Link : Name_Id;
      --  Link to next entry in names table for same hash code

      Int_Info : Int;
      --  Int Value associated with this name
   end record;

   --  This is the table that is referenced by Name_Id entries.
   --  It contains one entry for each unique name in the table.

   package Name_Entries is new Table.Table (
     Table_Component_Type => Name_Entry,
     Table_Index_Type     => Name_Id,
     Table_Low_Bound      => First_Name_Id,
     Table_Initial        => Alloc.Names_Initial,
     Table_Increment      => Alloc.Names_Increment,
     Table_Name           => "Name_Entries");

end Namet;
