%    Copyright (C) 2002 artofcode LLC.  All rights reserved.% % This software is provided AS-IS with no warranty, either express or% implied.% % This software is distributed under license and may not be copied,% modified or distributed except as expressly authorized under the terms% of the license contained in the file LICENSE in this distribution.% % For more information about licensing, please refer to% http://www.ghostscript.com/licensing/. For information on% commercial licensing, go to http://www.artifex.com/licensing/ or% contact Artifex Software, Inc., 101 Lucas Valley Road #110,% San Rafael, CA  94903, U.S.A., +1(415)492-9861. % $Id: pdf_rbld.ps,v 1.8 2005/02/07 06:38:02 dan Exp $% pdf_rbld.ps - Rebuilding of broken PDF files (xref errors) % This module contains routines that are used if we detect an error% while reading the xref tables.  These routines will scan the file and% build an xref table by finding the objects.  We also need to find the% appropriate trailer dictionary.  Note:  One procedure is also used% even if we do not need to rebuild a PDF file.%% This module cannot rebuild a PDF file which has had errors created inside% of objects or binary data streams.  It often succeeds with files that% have had its end of lines converted between unix and dos versions. % if true --> we have an object with duplicate object and generation numbers./dup_obj_gen_num false def % Note:  This routine is also used by non-rebuild code.% Store a line in the xref array (Actually Objects and Generations arrays)% <obj num> (strm num> <obj loc> <gen num>  setxrefentry <obj num> strm num>% 						 	 <obj loc> <gen num>/setxrefentry{	% We store generation numbers as value + 1	% We reserve 0 to indicate an free xref entry  1 add			% increment generation number	% To save space, generations numbers are stored in a lstring unless we	% find a generation number greater than 255.  If so then transfer to 	% an larray.  dup 255 gt {    Generations ltype /stringtype eq {	% Convert Generations to an larray.      larray Generations llength lgrowto dup	% Create new larray      0 1 2 index llength 1 sub {	% Copy from old lstring to new larray	Generations 1 index lget lput dup      } for      pop      /Generations exch store		% Save new Generations larray    } if  } if	% Verify that the new values are for a new object.  If the current	% entry is null then we have a new entry.  Objects 4 index lget null eq {    ObjectStream 4 index 4 index cvx lput % Save ObjectStream object number    Objects 4 index 3 index cvx lput	% Save object location    Generations 4 index 2 index lput	% Save geenration number  } {	% Verify that the new entry has at least as high a generaton number	% We accept equal entry number because we have found PDF files in	% which there are multiple objects with the same object and entry	% numbers.  The normal xref logic only accepts the first such	% entry that it finds.  However the 'rebuild PDF' logic can find	% both such entries.  The correct one is usually the last one.    Generations 4 index lget 1 index le {      ObjectStream 4 index 4 index cvx lput % Save ObjectStream object number      Objects 4 index 3 index cvx lput	% Save object location      Generations 4 index 2 index lput	% Save geenration number    } if	% Set error flag if we have equal object and generation numbers    Generations 4 index lget 1 index eq { /dup_obj_gen_num true def } if  } ifelse} bind def % Print the contents of the xref array.  This actually consists of two% arrays (Objects and Generations).  Both are larrays.  larrays are a% special Ghostscript object which can be arrays with more than 64k% elements./print_xref				% - print_xref -{ 0 1 Objects llength 1 sub		% stack: 0 1 <number of objects - 1>  { dup =only				% print object number    (  ) print    dup Generations exch lget 1 sub =only % print Generation number    (  ) print    dup ObjectStream exch lget ==only	% print ObjectStream object number    (  ) print    Objects exch lget ===		% print object location  } for  flush} bind def % This is the same as the postscript token operator except that% errors are ignored./token_nofail{  { token } .internalstopped  { pop false } if} bind odef % Get token from string and check its type%   <string> <type> typed_token <false>		% no token or not match%   <string> <type> typed_token <obj> <last> <true>	% matching token type% Where last is the string remainder/typed_token{ exch  token_nofail			% get token  {    dup type			% stack:  type last token type    4 -1 roll eq {		% stack:  last token bool      exch true			% desired object found - set exit status    } {      pop pop false		% not type - clear stack, set exit status    } ifelse  } {    pop false			% no token - pop type, set exit status  } ifelse			% check if we got token} bind def % Allocate space for post_eof_count to be bound into procedures below./post_eof_count 0 def % We want the location of the trailer dictionary at the start of file.% First we will find the xref.  Then we will skip over the xref entries% to the trailer./search_start_trailer		% - search_start_trailer <trailer loc>{ % Read the first 300 bytes and check for xref  PDFfile 0 setfileposition  300 string 0 1 299 { 2 copy PDFfile read pop put pop } for  (xref) search {    % found 'xref'    exch pop exch pop length 4 add PDFfile exch setfileposition    PDFfile token pop		% get starting entry - or 'trailer'    (trailer) ne {		% if we do not already have 'trailer'      PDFfile token pop		% get number of entries      PDFfile token pop pop	% this moves us into the middle of the first entry      25 string exch		% define working string for readline      { PDFfile 1 index readline pop pop      } repeat			% skip entries      pop			% pop working string      PDFfile token pop pop	% get 'trailer'      PDFfile fileposition	% get file position    } if  } {    pop 0			% no xref - should not happen  } ifelse} bind def % We want the location of the trailer dictionary at the end of file.% We will read the last block of data and search for the final occurance% of the word 'trailer'/search_end_trailer		% - search_end_trailer <trailer loc>{ % Position to read block of data from the end of the file.  Note:  We ignore  % anything past the last %%EOF since this is not PDF data.  PDFfile 0 setfileposition  PDFfile bytesavailable post_eof_count sub	% location of end of data  dup 4096 .min			% block size to read				% stack: <file end pos> <block size>  % move file position to the start of the block  2 copy sub PDFfile exch setfileposition  % read block of data  dup string 0 1 4 -1 roll 1 sub { 2 copy PDFfile read pop put pop } for  % search for last occurance of 'trailer'  (trailer) { search not { exit } if pop } loop  % determine where the trailer is in the file  %   trailer loc = end loc - remaing string length  length sub } bind def % We want to find the trailer dictionary.  There is a trailer dictionary% for each xref object list.  We only want the trailer dictionary associated% with the first xref object list.  In theory this can be anywhere in the% file.  However since we are trying to repair a broken file, we cannot simply% follow the xref links.  So we are falling back to a simple strategy.  We% find the specified location of the first xref list.  If its location is in% the first half of the file then we search for the first trailer dictionary% at the start of the file.  Otherwise we search for the last trailer at the% end of the file./search_trailer			% - search_trailer -{ % Find the 'startxref' and associated position at the end of the file.  % Position to read block of data from the end of the file.  Note:  We  % actually end at the end of the last %%EOF since this is the end of the  % useful PDF data.  (Some files contain trailing garbage.)  PDFfile 0 setfileposition  PDFfile bytesavailable	% size of file  post_eof_count sub dup	% location of end of last %%EOF  dup 4096 .min			% block size to read  % stack: <useful file size> <useful file size file> <block size>  % move file position to the start of the block  2 copy sub PDFfile exch setfileposition  % read block of data  dup string 0 1 4 -1 roll 1 sub { 2 copy PDFfile read pop put pop } for  % search for last occurance of 'startxref'  (startxref) { search not { exit } if pop } loop  % determine where the trailer is in the file  %   trailer loc = end loc - remaing string length  length sub 9 sub  % move the file to this position and read startxref and position  PDFfile exch setfileposition  PDFfile token pop pop PDFfile token pop  % compare xref position to 1/2 the length of the file and search for trailer  exch 2 div lt { search_start_trailer } { search_end_trailer } ifelse  % get the trailer  PDFfile exch setfileposition		% set to the specified trailer location  PDFfile traileropdict .pdfrun		% read trailer info  /Trailer exch def} bind def % This routine will determine if there is stuff after the %%EOF.  There is% supposed to be only a line termination.  However many real life files% contain some garbage.  This routine checks how much.  We then ignore this% stuff when we are scanning for objects./determine_post_eof_count		% - determine_post_eof_count <count>{ % Position to read block of data from the end of the file.   PDFfile 0 setfileposition  PDFfile bytesavailable	% size of file  dup 4096 .min			% block size to read  % stack: <file size> <file size> <block size>  % move file position to the start of the block  2 copy sub PDFfile exch setfileposition  % read block of data  dup string 0 1 4 -1 roll 1 sub { 2 copy PDFfile read pop put pop } for  % search for last occurance of '%%EOF'  (%%EOF) { search not { exit } if pop } loop  % how much is left = remaining string length  length exch pop		% pop /%%EOF} bind def % This routine will scan a file searaching for object locations to build% an alternate version of the data in the xref tables.% Its purpose is to provide a basis for an xref fixing facility./search_objects				% - search_objects -{ % Initialize the Objects, Generations, etc. larrays  initPDFobjects  % reset duplicate object and generation numbers error flag  /dup_obj_gen_num false def  % Determine how many bytes are in the file after the final %%EOF  /post_eof_count determine_post_eof_count def  % Start at the beginning of the file  PDFfile 0 setfileposition  % Create a working string (and also store its length on stack).  We are  % using a maximum size string size the logic below wants a recovered object  % to fit into our working string.  65535 dup string  { % Now loop through the entire file lloking for objects    PDFfile fileposition		% save current file position    % When we get near the end of the file, we use a smaller interval of    % our working string to prevent reading past the end.  (See comments on    % EOF testing below.)    PDFfile bytesavailable post_eof_count sub 10 sub dup 4 index lt {      2 index 0 3 -1 roll getinterval	% near EOF, use interval of string    } { pop 1 index			% not near end, use full working string    }ifelse    % Read a line from file.  If the line does not fit into our working string,    % or any other error, then we will discard it.    PDFfile exch { readline } .internalstopped    { pop pop false } if		% indicate no string if we stopped    { % stack: <length> <working_str> <loc> <string>      % Now that we have line, get obj num, ref num, and 'obj'.  Verify that each      % of these is correct type.      /integertype typed_token {	% get obj number        /integertype typed_token {	% get ref number          /nametype typed_token {	% get 'obj' text	    pop				% pop remaining string	    /obj eq {			% verify name is 'obj'	      % make sure we have room in the arrays.  We work in increments	      % of 20 each time we increase the size.	      1 index 20 add 20 idiv 20 mul	      growPDFobjects	      % save xref parameters into ObjectStream, Objects and Generations	      1 index 0 4 index 3 index	% rearrange parms for setxrefentry	      setxrefentry		% save parameters	      pop pop pop pop		% clear parameters	    } if			% check if name is 'obj'          } if				% check if we got 'obj" string          pop				% remove ref number        } if				% check if we got ref number        pop				% remove obj number      } if				% check if we got object number    } if				% check if got a string from readline    pop					% remove location    % Check if we are approaching the end of the file.  We do not want to    % read past the end of the file since that closes it.  We actually stop    % 10-20 bytes early since there cannot be an object that close to the end.    % (There is a Trailer dictionary, etc. at the end of the file.)    PDFfile bytesavailable post_eof_count sub 20 lt { exit } if  } loop				% loop through the entire file  pop pop				% remove working string and its length  % Output warning if we have two objects with the same object and generation  % numbers.  dup_obj_gen_num {    (   **** Warning:  There are objects with matching object and generation\n)    pdfformaterror    (   **** numbers.  The accuracy of the resulting image is unknown.\n)    pdfformaterror  } if} bind def % Print warning message because we found a problem while reading the xref% tables/print_xref_warning{ (   **** Warning:  An error occurred while reading an XREF table.\n)  pdfformaterror  (   **** The file has been damaged.  This may have been caused\n)  pdfformaterror  (   **** by a problem while converting or transfering the file.\n)  pdfformaterror  (   **** Ghostscript will attempt to recover the data.\n)  pdfformaterror} bind def % Attempt to recover the XRef data.  This is called if we have a failure% while reading the normal XRef tables.  This routine usually works% only for pre PDF1.5 versions of PDF files./recover_xref_data		% - recover_xref_data -{ print_xref_warning		% Print warning message  count pdfemptycount sub { pop } repeat % remove anything left by readxref  search_objects		% Search for objects} bind def