------------------------------------------------------------------------------
-- Copyright (c) 2013-2014, Natacha Porté --
-- --
-- Permission to use, copy, modify, and distribute this software for any --
-- purpose with or without fee is hereby granted, provided that the above --
-- copyright notice and this permission notice appear in all copies. --
-- --
-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES --
-- WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF --
-- MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR --
-- ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES --
-- WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN --
-- ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF --
-- OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. --
------------------------------------------------------------------------------
------------------------------------------------------------------------------
-- Natools.S_Expressions.Parsers implements an event-based S-expression --
-- parser that reads from an input stream. --
-- --
-- Subparser objects wrap together Parser and input Stream, exposing a --
-- Descriptor interface. A subparser is constrained to its initial nesting --
-- level, and reports end-of-input instead of reaching lower. --
------------------------------------------------------------------------------
with Ada.Streams;
with Natools.S_Expressions.Atom_Buffers;
package Natools.S_Expressions.Parsers is
pragma Preelaborate (Natools.S_Expressions.Parsers);
type Parser is tagged private;
function Current_Event (P : in Parser) return Events.Event;
function Current_Atom (P : in Parser) return Atom;
function Current_Level (P : in Parser) return Natural;
procedure Query_Atom
(P : in Parser;
Process : not null access procedure (Data : in Atom));
procedure Read_Atom
(P : in Parser;
Data : out Atom;
Length : out Count);
procedure Next_Event
(P : in out Parser;
Input : not null access Ada.Streams.Root_Stream_Type'Class);
type Subparser
(Backend : access Parser;
Input : access Ada.Streams.Root_Stream_Type'Class)
is new Descriptor with private;
overriding function Current_Event (P : in Subparser) return Events.Event;
overriding function Current_Atom (P : in Subparser) return Atom;
overriding function Current_Level (P : in Subparser) return Natural;
overriding procedure Query_Atom
(P : in Subparser;
Process : not null access procedure (Data : in Atom));
overriding procedure Read_Atom
(P : in Subparser;
Data : out Atom;
Length : out Count);
overriding procedure Next (P : in out Subparser; Event : out Events.Event);
procedure Finish (P : in out Subparser);
-- Read enough data to exhaust intial nesting level
private
type Internal_State is
(Waiting, -- waiting for a marker
Base64_Atom, -- reading an atom encoded in base 64
Base64_Expr, -- reading an expression encoded in base 64
Hex_Atom, -- reading an atom encoded in hexadecimal
Number, -- reading a number that can either be a verbatim
-- length prefix or an extended token
Quoted_Atom, -- reading an atom encoded in a C-like quoted string
Token, -- reading a token atom
Verbatim_Atom); -- reading a verbatim atom
subtype Read_Buffer_Count is Count range 0 .. 4;
type Read_Buffer is record
Data : Atom (0 .. 3);
Length : Read_Buffer_Count;
end record;
type State_Data (State : Internal_State := Waiting) is record
case State is
when Waiting | Number | Token =>
null;
when Base64_Atom | Base64_Expr =>
Chunk : Read_Buffer;
when Hex_Atom =>
Nibble_Buffer : Octet;
when Quoted_Atom =>
Escape : Read_Buffer;
when Verbatim_Atom =>
Size : Count;
end case;
end record;
type Parser is tagged record
Internal : State_Data;
Pending : Events.Event := Events.End_Of_Input;
Override : Atom_Buffers.Atom_Buffer;
Override_Pos : Count := 0;
Latest : Events.Event := Events.Error;
Buffer : Atom_Buffers.Atom_Buffer;
Level : Natural := 0;
end record;
type Subparser
(Backend : access Parser;
Input : access Ada.Streams.Root_Stream_Type'Class)
is new Descriptor with record
Base_Level : Natural := 0;
Initialized : Boolean := False;
Terminated : Boolean := False;
end record;
end Natools.S_Expressions.Parsers;