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|
------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- S C A N S --
-- --
-- S p e c --
-- --
-- --
-- Copyright (C) 1992-2001 Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 2, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING. If not, write --
-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
-- MA 02111-1307, USA. --
-- --
-- As a special exception, if other files instantiate generics from this --
-- unit, or you link this unit with other files to produce an executable, --
-- this unit does not by itself cause the resulting executable to be --
-- covered by the GNU General Public License. This exception does not --
-- 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 Types; use Types;
package Scans is
-- The scanner maintains a current state in the global variables defined
-- in this package. The call to the Scan routine advances this state to
-- the next token. The state is initialized by the call to one of the
-- initialization routines in Sinput.
-- The following type is used to identify token types returned by Scan.
-- The class column in this table indicates the token classes which
-- apply to the token, as defined by subsquent subtype declarations.
-- Note: the coding in SCN depends on the fact that the first entry in
-- this type declaration is *not* for a reserved word. For details on
-- why there is this requirement, see Scn.Initialize_Scanner.
type Token_Type is (
-- Token name Token type Class(es)
Tok_Integer_Literal, -- numeric lit Literal, Lit_Or_Name
Tok_Real_Literal, -- numeric lit Literal, Lit_Or_Name
Tok_String_Literal, -- string lit Literal. Lit_Or_Name
Tok_Char_Literal, -- char lit Name, Literal. Lit_Or_Name
Tok_Operator_Symbol, -- op symbol Name, Literal, Lit_Or_Name, Desig
Tok_Identifier, -- identifier Name, Lit_Or_Name, Desig
Tok_Double_Asterisk, -- **
Tok_Ampersand, -- & Binary_Addop
Tok_Minus, -- - Binary_Addop, Unary_Addop
Tok_Plus, -- + Binary_Addop, Unary_Addop
Tok_Asterisk, -- * Mulop
Tok_Mod, -- MOD Mulop
Tok_Rem, -- REM Mulop
Tok_Slash, -- / Mulop
Tok_New, -- NEW
Tok_Abs, -- ABS
Tok_Others, -- OTHERS
Tok_Null, -- NULL
Tok_Dot, -- . Namext
Tok_Apostrophe, -- ' Namext
Tok_Left_Paren, -- ( Namext, Consk
Tok_Delta, -- DELTA Atkwd, Sterm, Consk
Tok_Digits, -- DIGITS Atkwd, Sterm, Consk
Tok_Range, -- RANGE Atkwd, Sterm, Consk
Tok_Right_Paren, -- ) Sterm
Tok_Comma, -- , Sterm
Tok_And, -- AND Logop, Sterm
Tok_Or, -- OR Logop, Sterm
Tok_Xor, -- XOR Logop, Sterm
Tok_Less, -- < Relop, Sterm
Tok_Equal, -- = Relop, Sterm
Tok_Greater, -- > Relop, Sterm
Tok_Not_Equal, -- /= Relop, Sterm
Tok_Greater_Equal, -- >= Relop, Sterm
Tok_Less_Equal, -- <= Relop, Sterm
Tok_In, -- IN Relop, Sterm
Tok_Not, -- NOT Relop, Sterm
Tok_Box, -- <> Relop, Eterm, Sterm
Tok_Colon_Equal, -- := Eterm, Sterm
Tok_Colon, -- : Eterm, Sterm
Tok_Greater_Greater, -- >> Eterm, Sterm
Tok_Abstract, -- ABSTRACT Eterm, Sterm
Tok_Access, -- ACCESS Eterm, Sterm
Tok_Aliased, -- ALIASED Eterm, Sterm
Tok_All, -- ALL Eterm, Sterm
Tok_Array, -- ARRAY Eterm, Sterm
Tok_At, -- AT Eterm, Sterm
Tok_Body, -- BODY Eterm, Sterm
Tok_Constant, -- CONSTANT Eterm, Sterm
Tok_Do, -- DO Eterm, Sterm
Tok_Is, -- IS Eterm, Sterm
Tok_Limited, -- LIMITED Eterm, Sterm
Tok_Of, -- OF Eterm, Sterm
Tok_Out, -- OUT Eterm, Sterm
Tok_Record, -- RECORD Eterm, Sterm
Tok_Renames, -- RENAMES Eterm, Sterm
Tok_Reverse, -- REVERSE Eterm, Sterm
Tok_Tagged, -- TAGGED Eterm, Sterm
Tok_Then, -- THEN Eterm, Sterm
Tok_Less_Less, -- << Eterm, Sterm, After_SM
Tok_Abort, -- ABORT Eterm, Sterm, After_SM
Tok_Accept, -- ACCEPT Eterm, Sterm, After_SM
Tok_Case, -- CASE Eterm, Sterm, After_SM
Tok_Delay, -- DELAY Eterm, Sterm, After_SM
Tok_Else, -- ELSE Eterm, Sterm, After_SM
Tok_Elsif, -- ELSIF Eterm, Sterm, After_SM
Tok_End, -- END Eterm, Sterm, After_SM
Tok_Exception, -- EXCEPTION Eterm, Sterm, After_SM
Tok_Exit, -- EXIT Eterm, Sterm, After_SM
Tok_Goto, -- GOTO Eterm, Sterm, After_SM
Tok_If, -- IF Eterm, Sterm, After_SM
Tok_Pragma, -- PRAGMA Eterm, Sterm, After_SM
Tok_Raise, -- RAISE Eterm, Sterm, After_SM
Tok_Requeue, -- REQUEUE Eterm, Sterm, After_SM
Tok_Return, -- RETURN Eterm, Sterm, After_SM
Tok_Select, -- SELECT Eterm, Sterm, After_SM
Tok_Terminate, -- TERMINATE Eterm, Sterm, After_SM
Tok_Until, -- UNTIL Eterm, Sterm, After_SM
Tok_When, -- WHEN Eterm, Sterm, After_SM
Tok_Begin, -- BEGIN Eterm, Sterm, After_SM, Labeled_Stmt
Tok_Declare, -- DECLARE Eterm, Sterm, After_SM, Labeled_Stmt
Tok_For, -- FOR Eterm, Sterm, After_SM, Labeled_Stmt
Tok_Loop, -- LOOP Eterm, Sterm, After_SM, Labeled_Stmt
Tok_While, -- WHILE Eterm, Sterm, After_SM, Labeled_Stmt
Tok_Entry, -- ENTRY Eterm, Sterm, Declk, Deckn, After_SM
Tok_Protected, -- PROTECTED Eterm, Sterm, Declk, Deckn, After_SM
Tok_Task, -- TASK Eterm, Sterm, Declk, Deckn, After_SM
Tok_Type, -- TYPE Eterm, Sterm, Declk, Deckn, After_SM
Tok_Subtype, -- SUBTYPE Eterm, Sterm, Declk, Deckn, After_SM
Tok_Use, -- USE Eterm, Sterm, Declk, Deckn, After_SM
Tok_Function, -- FUNCTION Eterm, Sterm, Cunit, Declk, After_SM
Tok_Generic, -- GENERIC Eterm, Sterm, Cunit, Declk, After_SM
Tok_Package, -- PACKAGE Eterm, Sterm, Cunit, Declk, After_SM
Tok_Procedure, -- PROCEDURE Eterm, Sterm, Cunit, Declk, After_SM
Tok_Private, -- PRIVATE Eterm, Sterm, Cunit, After_SM
Tok_With, -- WITH Eterm, Sterm, Cunit, After_SM
Tok_Separate, -- SEPARATE Eterm, Sterm, Cunit, After_SM
Tok_EOF, -- End of file Eterm, Sterm, Cterm, After_SM
Tok_Semicolon, -- ; Eterm, Sterm, Cterm
Tok_Arrow, -- => Sterm, Cterm, Chtok
Tok_Vertical_Bar, -- | Cterm, Sterm, Chtok
Tok_Dot_Dot, -- .. Sterm, Chtok
-- The following three entries are used only when scanning
-- project files.
Tok_Project,
Tok_Extends,
Tok_External,
No_Token);
-- No_Token is used for initializing Token values to indicate that
-- no value has been set yet.
-- Note: in the RM, operator symbol is a special case of string literal.
-- We distinguish at the lexical level in this compiler, since there are
-- many syntactic situations in which only an operator symbol is allowed.
-- The following subtype declarations group the token types into classes.
-- These are used for class tests in the parser.
subtype Token_Class_Numeric_Literal is
Token_Type range Tok_Integer_Literal .. Tok_Real_Literal;
-- Numeric literal
subtype Token_Class_Literal is
Token_Type range Tok_Integer_Literal .. Tok_Operator_Symbol;
-- Literal
subtype Token_Class_Lit_Or_Name is
Token_Type range Tok_Integer_Literal .. Tok_Identifier;
subtype Token_Class_Binary_Addop is
Token_Type range Tok_Ampersand .. Tok_Plus;
-- Binary adding operator (& + -)
subtype Token_Class_Unary_Addop is
Token_Type range Tok_Minus .. Tok_Plus;
-- Unary adding operator (+ -)
subtype Token_Class_Mulop is
Token_Type range Tok_Asterisk .. Tok_Slash;
-- Multiplying operator
subtype Token_Class_Logop is
Token_Type range Tok_And .. Tok_Xor;
-- Logical operator (and, or, xor)
subtype Token_Class_Relop is
Token_Type range Tok_Less .. Tok_Box;
-- Relational operator (= /= < <= > >= not, in plus <> to catch misuse
-- of Pascal style not equal operator).
subtype Token_Class_Name is
Token_Type range Tok_Char_Literal .. Tok_Identifier;
-- First token of name (4.1),
-- (identifier, char literal, operator symbol)
subtype Token_Class_Desig is
Token_Type range Tok_Operator_Symbol .. Tok_Identifier;
-- Token which can be a Designator (identifier, operator symbol)
subtype Token_Class_Namext is
Token_Type range Tok_Dot .. Tok_Left_Paren;
-- Name extension tokens. These are tokens which can appear immediately
-- after a name to extend it recursively (period, quote, left paren)
subtype Token_Class_Consk is
Token_Type range Tok_Left_Paren .. Tok_Range;
-- Keywords which can start constraint
-- (left paren, delta, digits, range)
subtype Token_Class_Eterm is
Token_Type range Tok_Colon_Equal .. Tok_Semicolon;
-- Expression terminators. These tokens can never appear within a simple
-- expression. This is used for error recovery purposes (if we encounter
-- an error in an expression, we simply scan to the next Eterm token).
subtype Token_Class_Sterm is
Token_Type range Tok_Delta .. Tok_Dot_Dot;
-- Simple_Expression terminators. A Simple_Expression must be followed
-- by a token in this class, or an error message is issued complaining
-- about a missing binary operator.
subtype Token_Class_Atkwd is
Token_Type range Tok_Delta .. Tok_Range;
-- Attribute keywords. This class includes keywords which can be used
-- as an Attribute_Designator, namely DELTA, DIGITS and RANGE
subtype Token_Class_Cterm is
Token_Type range Tok_EOF .. Tok_Vertical_Bar;
-- Choice terminators. These tokens terminate a choice. This is used for
-- error recovery purposes (if we encounter an error in a Choice, we
-- simply scan to the next Cterm token).
subtype Token_Class_Chtok is
Token_Type range Tok_Arrow .. Tok_Dot_Dot;
-- Choice tokens. These tokens signal a choice when used in an Aggregate
subtype Token_Class_Cunit is
Token_Type range Tok_Function .. Tok_Separate;
-- Tokens which can begin a compilation unit
subtype Token_Class_Declk is
Token_Type range Tok_Entry .. Tok_Procedure;
-- Keywords which start a declaration
subtype Token_Class_Deckn is
Token_Type range Tok_Entry .. Tok_Use;
-- Keywords which start a declaration but can't start a compilation unit
subtype Token_Class_After_SM is
Token_Type range Tok_Less_Less .. Tok_EOF;
-- Tokens which always, or almost always, appear after a semicolon. Used
-- in the Resync_Past_Semicolon routine to avoid gobbling up stuff when
-- a semicolon is missing. Of significance only for error recovery.
subtype Token_Class_Labeled_Stmt is
Token_Type range Tok_Begin .. Tok_While;
-- Tokens which start labeled statements
type Token_Flag_Array is array (Token_Type) of Boolean;
Is_Reserved_Keyword : constant Token_Flag_Array := Token_Flag_Array'(
Tok_Mod .. Tok_Rem => True,
Tok_New .. Tok_Null => True,
Tok_Delta .. Tok_Range => True,
Tok_And .. Tok_Xor => True,
Tok_In .. Tok_Not => True,
Tok_Abstract .. Tok_Then => True,
Tok_Abort .. Tok_Separate => True,
others => False);
-- Flag array used to test for reserved word
--------------------------
-- Scan State Variables --
--------------------------
-- Note: these variables can only be referenced during the parsing of a
-- file. Reference to any of them from Sem or the expander is wrong.
Scan_Ptr : Source_Ptr;
-- Current scan pointer location. After a call to Scan, this points
-- just past the end of the token just scanned.
Token : Token_Type;
-- Type of current token
Token_Ptr : Source_Ptr;
-- Pointer to first character of current token
Current_Line_Start : Source_Ptr;
-- Pointer to first character of line containing current token
Start_Column : Column_Number;
-- Starting column number (zero origin) of the first non-blank character
-- on the line containing the current token. This is used for error
-- recovery circuits which depend on looking at the column line up.
Checksum : Word;
-- Used to accumulate a CRC representing the tokens in the source
-- file being compiled. This CRC includes only program tokens, and
-- excludes comments.
First_Non_Blank_Location : Source_Ptr;
-- Location of first non-blank character on the line containing the
-- current token (i.e. the location of the character whose column number
-- is stored in Start_Column).
Token_Node : Node_Id := Empty;
-- Node table Id for the current token. This is set only if the current
-- token is one for which the scanner constructs a node (i.e. it is an
-- identifier, operator symbol, or literal. For other token types,
-- Token_Node is undefined.
Token_Name : Name_Id := No_Name;
-- For identifiers, this is set to the Name_Id of the identifier scanned.
-- For all other tokens, Token_Name is set to Error_Name. Note that it
-- would be possible for the caller to extract this information from
-- Token_Node. We set Token_Name separately for two reasons. First it
-- allows a quicker test for a specific identifier. Second, it allows
-- a version of the parser to be built that does not build tree nodes,
-- usable as a syntax checker.
Prev_Token : Token_Type := No_Token;
-- Type of previous token
Prev_Token_Ptr : Source_Ptr;
-- Pointer to first character of previous token
Version_To_Be_Found : Boolean;
-- This flag is True if the scanner is still looking for an RCS version
-- number in a comment. Normally it is initialized to False so that this
-- circuit is not activated. If the -dv switch is set, then this flag is
-- initialized to True, and then reset when the version number is found.
-- We do things this way to minimize the impact on comment scanning.
--------------------------------------------------------
-- Procedures for Saving and Restoring the Scan State --
--------------------------------------------------------
-- The following procedures can be used to save and restore the entire
-- scan state. They are used in cases where it is necessary to backup
-- the scan during the parse.
type Saved_Scan_State is private;
-- Used for saving and restoring the scan state
procedure Save_Scan_State (Saved_State : out Saved_Scan_State);
pragma Inline (Save_Scan_State);
-- Saves the current scan state for possible later restoration. Note that
-- there is no harm in saving the state and then never restoring it.
procedure Restore_Scan_State (Saved_State : in Saved_Scan_State);
pragma Inline (Restore_Scan_State);
-- Restores a scan state saved by a call to Save_Scan_State.
-- The saved scan state must refer to the current source file.
private
type Saved_Scan_State is record
Save_Scan_Ptr : Source_Ptr;
Save_Token : Token_Type;
Save_Token_Ptr : Source_Ptr;
Save_Current_Line_Start : Source_Ptr;
Save_Start_Column : Column_Number;
Save_Checksum : Word;
Save_First_Non_Blank_Location : Source_Ptr;
Save_Token_Node : Node_Id;
Save_Token_Name : Name_Id;
Save_Prev_Token : Token_Type;
Save_Prev_Token_Ptr : Source_Ptr;
end record;
end Scans;
|
