Курсовая работа1 / Tokenizer / UCcBuffer

{
C-like language compiler v0.1.0.485

12 november 2007

Copyright (C) 2006, 2007 Igor Krooshch
rheo.ikro@gmail.com

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
}

unit UCcBuffer;

interface

uses
SysUtils, Classes;

type
TCcPosition = record
Line: integer;
Offset: integer;
end;


ECcBufferException = class(Exception)
private
FPosition: TCcPosition;
public
constructor Create(const AMsg: string; APos: TCcPosition); reintroduce;
function Position: TCcPosition;
end;

ECcBufferExceptionClass = class of ECcBufferException;


TCcBuffer = class
private
FLastChar: char;
FLastPosition: TCcPosition;
FPosition: TCcPosition;
FStream: TStream;
FBuffer: string;
FBufferSize: integer;
FBufferPos: integer;
public
constructor Create(AStream: TStream; const ABufferSize: byte = 2);

procedure CheckEof(A: char);

procedure Error(const AMsg: string); overload;
procedure Error(
const AMsg: string; AErrClass: ECcBufferExceptionClass); overload;

function GetChar: char;
procedure UngetChar;

property Position: TCcPosition read FPosition;
end;


function CcPosition(ALine, APos: integer): TCcPosition;

implementation

uses
UCcTokenizerConsts;


function CcPosition(ALine, APos: integer): TCcPosition;
begin
Result.Line := ALine;
Result.Offset := APos;
end;


{ ECcBufferException }

constructor ECcBufferException.Create(
const AMsg: string; APos: TCcPosition);
begin
FPosition := APos;
inherited CreateFmt(SCcErrorPrefix + AMsg, [APos.Line, APos.Offset]);
end;


function ECcBufferException.Position: TCcPosition;
begin
Result := FPosition;
end;


{ TCcBuffer }

procedure TCcBuffer.CheckEof(A: char);
begin
if A = #0 then
Error(SCcTokenUnexpectedEOFError);
end;


constructor TCcBuffer.Create(AStream: TStream; const ABufferSize: byte);
var
pc: PChar;
sz: integer;
begin
FBuffer := '';
FBufferPos := 0;
FBufferSize := ABufferSize;
FStream := AStream;
FLastChar := #0;

FPosition.Line := 1;
FPosition.Offset := 0;

FLastPosition := FPosition;

pc := nil;
try
sz := ABufferSize * sizeof(char);
GetMem(pc, sz);
sz := FStream.Read(pc^, sz) div sizeof(char);
if sz > 0 then
FBuffer := FBuffer + Copy(pc, 1, sz);
finally
FreeMem(pc);
end;
end;


procedure TCcBuffer.Error(const AMsg: string);
begin
Error(AMsg, ECcBufferException);
end;


procedure TCcBuffer.Error(
const AMsg: string; AErrClass: ECcBufferExceptionClass);
begin
raise AErrClass.Create(AMsg, FPosition);
end;


function TCcBuffer.GetChar: char;
var
c: char;
begin
Result := #0;
try
FLastPosition := FPosition;
Inc(FBufferPos);
if (FBufferPos > Length(FBuffer)) then begin
Delete(FBuffer, 1, 1);
if (FStream.Read(c, 1) = 0) then
Exit
else
FBuffer := FBuffer + c;
Dec(FBufferPos);
end;
Result := FBuffer[FBufferPos];
if (FLastChar in [#13]) then begin
Inc(FPosition.Line);
FPosition.Offset := 1;
end
else
Inc(FPosition.Offset);
finally
FLastChar := Result;
end;
end;


procedure TCcBuffer.UngetChar;
begin
if (FLastChar <> #0) and (FBufferPos > 0) then begin
Dec(FBufferPos);
Dec(FPosition.Offset);
end;
end;


end.