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Text File | 1996-09-28 | 18KB | 395 lines

------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- S C A N S -- -- -- -- S p e c -- -- -- -- $Revision: 1.27 $ -- -- -- -- Copyright (c) 1992,1993,1994 NYU, All Rights Reserved -- -- -- -- 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, 675 Mass Ave, Cambridge, MA 02139, USA. -- -- -- ------------------------------------------------------------------------------ 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, -- identifer 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 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. 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_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;