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% $Id: pdf_base.ps,v 1.10 2000/09/19 18:29:11 lpd Exp $
% pdf_base.ps
% Basic parser for PDF reader.
% This handles basic parsing of the file (including the trailer
% and cross-reference table), as well as objects, object references,
% streams, and name/number trees; it doesn't include any facilities for
% making marks on the page.
/.setlanguagelevel where { pop 2 .setlanguagelevel } if
.currentglobal true .setglobal
/pdfdict where { pop } { /pdfdict 100 dict def } ifelse
pdfdict begin
% Define the name interpretation dictionary for reading values.
/valueopdict mark
(<<) cvn { mark } bind % don't push an actual mark!
(>>) cvn /.dicttomark load
([) cvn { mark } bind % ditto
(]) cvn dup load
/true true
/false false
/null null
/F dup cvx % see Objects section below
/R dup cvx % see Objects section below
/stream dup cvx % see Streams section below
.dicttomark readonly def
% ------ Utilities ------ %
% Define a scratch string. The PDF language definition says that
% no line in a PDF file can exceed 255 characters.
/pdfstring 255 string def
% Read the previous line of a file. If we aren't at a line boundary,
% read the line containing the current position.
% Skip any blank lines.
/prevline % - prevline <startpos> <substring>
{ PDFfile fileposition dup () pdfstring
2 index 257 sub 0 .max PDFfile exch setfileposition
{ % Stack: initpos linepos line string
PDFfile fileposition
PDFfile 2 index readline pop
dup length 0 gt
{ 3 2 roll 5 -2 roll pop pop 2 index }
{ pop }
ifelse
% Stack: initpos linepos line string startpos
PDFfile fileposition 5 index ge { exit } if
pop
}
loop pop pop 3 -1 roll pop
} bind def
% Handle the PDF 1.2 #nn escape convention when reading from a file.
% This should eventually be done in C.
/.pdffixname { % <execname> .pdffixname <execname'>
PDFversion 1.2 ge {
dup .namestring (#) search {
name#escape cvn exch pop
} {
pop
} ifelse
} if
} bind def
/name#escape % <post> <(#)> <pre> name#escape <string>
{ exch pop
1 index 2 () /SubFileDecode filter dup (x) readhexstring
% Stack: post pre stream char t/f
not { /.pdftoken cvx /syntaxerror signalerror } if
exch closefile concatstrings
exch 2 1 index length 2 sub getinterval
(#) search { name#escape } if concatstrings
} bind def
% Execute a file, interpreting its executable names in a given
% dictionary. The name procedures may do whatever they want
% to the operand stack.
/.pdfexectoken { % <count> <opdict> <exectoken> .pdfexectoken ?
DEBUG { dup == flush } if
2 copy .knownget {
exch pop exch pop exch pop exec
} {
BXlevel 0 le {
(%stderr) (w) file
dup (****************Unknown operator: ) writestring
dup 2 index .writecvs dup (\n) writestring flushfile
} if pop pop
count exch sub { pop } repeat % pop all the operands
} ifelse
} bind def
/.pdfrun { % <file> <opdict> .pdfrun -
% Construct a procedure with the stack depth, file and opdict
% bound into it.
1 index cvlit count 2 sub 3 1 roll mark mark 5 2 roll
{ % Stack: ..operands.. count opdict file
token {
dup type /nametype eq {
dup xcheck {
.pdfexectoken
} {
.pdffixname
exch pop exch pop DEBUG { dup ==only ( ) print flush } if
} ifelse
} {
exch pop exch pop DEBUG { dup ==only ( ) print flush } if
} ifelse
} {
(%%EOF) cvn cvx .pdfexectoken
} ifelse
}
aload pop .packtomark cvx
/loop cvx 2 packedarray cvx
{ stopped /PDFsource } aload pop
PDFsource
{ store { stop } if } aload pop .packtomark cvx
/PDFsource 3 -1 roll store exec
} bind def
% Execute a file, like .pdfrun, for a marking context.
% This temporarily rebinds LocalResources and DefaultMatrix.
/.pdfruncontext { % <resdict> <file> <opdict> .pdfruncontext -
/.pdfrun load LocalResources DefaultMatrix
/LocalResources 7 -1 roll store
/DefaultMatrix matrix currentmatrix store
3 .execn
/DefaultMatrix exch store
/LocalResources exch store
} bind def
% Get the depth of the PDF operand stack. The main program (pdf_main.ps)
% sets pdfemptycount before calling .pdfrun.
/.pdfcount { % - .pdfcount <count>
count pdfemptycount sub
} bind def
% ------ File reading ------ %
% Read the cross-reference entry for an (unresolved) object.
% The caller must save and restore the PDFfile position if desired.
% For invalid (free) objects, we return 0.
/readxrefentry % <object#> readxrefentry <objpos>
{ dup Objects exch lget
PDFfile exch setfileposition
PDFfile token pop % object position
PDFfile token pop % generation #
PDFfile token pop % n or f
dup /n eq
{ pop 1 add dup 255 gt
{ Generations ltype /stringtype eq
{ % Convert Generations from a string to an array.
larray Generations llength lgrowto dup
0 1 2 index llength 1 sub
{ Generations 1 index lget lput dup
}
for pop /Generations exch store
}
if
}
if
}
{ /f eq
{ pop 0 }
{ /readxrefentry cvx /syntaxerror signalerror }
ifelse
}
ifelse
% Stack: obj# objpos 1+gen#
Generations 4 -1 roll 3 -1 roll lput
} bind def
% ================================ Objects ================================ %
% Since we may have more than 64K objects, we have to use a 2-D array to
% hold them (and the parallel Generations structure).
/lshift 9 def
/lnshift lshift neg def
/lsubmask 1 lshift bitshift 1 sub def
/lsublen lsubmask 1 add def
/larray { % - larray <larray>
[ [] ]
} bind def
/lstring { % - lstring <lstring>
[ () ]
} bind def
/ltype { % <lseq> type <type>
0 get type
} bind def
/lget { % <lseq> <index> lget <value>
dup //lsubmask and 3 1 roll //lnshift bitshift get exch get
} bind def
/lput { % <lseq> <index> <value> lput -
3 1 roll
dup //lsubmask and 4 1 roll //lnshift bitshift get
3 1 roll put
} bind def
/llength { % <lseq> llength <length>
dup length 1 sub dup //lshift bitshift
3 1 roll get length add
} bind def
% lgrowto assumes newlength > llength(lseq)
/growto { % <string/array> <length> growto <string'/array'>
1 index type /stringtype eq { string } { array } ifelse
2 copy copy pop exch pop
} bind def
/lgrowto { % <lseq> <newlength> lgrowto <lseq'>
dup //lsubmask add //lnshift bitshift dup 3 index length gt {
% Add more sub-arrays. Start by completing the last existing one.
% Stack: lseq newlen newtoplen
3 -1 roll dup llength 1 sub //lsubmask or 1 add lgrowto
% Stack: newlen newtoplen lseq
[ exch aload pop
counttomark 2 add -1 roll % newtoplen
counttomark sub { dup 0 0 getinterval lsublen growto } repeat
dup 0 0 getinterval ] exch
} {
pop
} ifelse
% Expand the last sub-array.
1 sub //lsubmask and 1 add
exch dup dup length 1 sub 2 copy
% Stack: newsublen lseq lseq len-1 lseq len-1
get 5 -1 roll growto put
} bind def
/lforall { % <lseq> <proc> lforall -
/forall cvx 2 packedarray cvx forall
} bind def
% We keep track of PDF objects using the following PostScript variables:
%
% Generations (lstring): Generations[N] holds 1+ the current
% generation number for object number N. (As far as we can tell,
% this is needed only for error checking.) For free objects,
% Generations[N] is 0.
%
% Objects (larray): If object N is loaded, Objects[N] is the actual
% object; otherwise, Objects[N] is an executable integer giving
% the file offset of the object's entry in the cross-reference
% table.
%
% GlobalObjects (dictionary): If object N has been resolved in
% global VM, GlobalObjects[N] is the same as Objects[N]
% (except that GlobalObjects itself is stored in global VM,
% so the entry will not be deleted at the end of the page).
%
% IsGlobal (lstring): IsGlobal[N] = 1 iff object N was resolved in
% global VM. This is an accelerator to avoid having to do a
% dictionary lookup in GlobalObjects when resolving every object.
% Initialize the PDF object tables.
/initPDFobjects { % - initPDFobjects -
/Objects larray def
/Generations lstring def
.currentglobal true .setglobal
/GlobalObjects 20 dict def
.setglobal
/IsGlobal lstring def
} bind def
% Grow the tables to a specified size.
/growPDFobjects { % <minsize> growPDFobjects -
dup Objects llength gt {
dup Objects exch lgrowto /Objects exch def
} if
dup Generations llength gt {
dup Generations exch lgrowto /Generations exch def
} if
dup IsGlobal llength gt {
dup IsGlobal exch lgrowto /IsGlobal exch def
} if
pop
} bind def
% We represent an unresolved object reference by a procedure of the form
% {obj# gen# resolveR}. This is not a possible PDF object, because PDF has
% no way to represent procedures. Since PDF in fact has no way to represent
% any PostScript object that doesn't evaluate to itself, we can 'force'
% a possibly indirect object painlessly with 'exec'.
% Note that since we represent streams by executable dictionaries
% (see below), we need both an xcheck and a type check to determine
% whether an object has been resolved.
/resolved? { % <object#> resolved? <value> true
% <object#> resolved? false
Objects 1 index lget dup xcheck {
dup type /integertype eq {
% Check whether the object is in GlobalObjects.
pop IsGlobal 1 index lget 0 eq {
pop false
} {
% Update Objects from GlobalObjects
DEBUG { (%Global=>local: ) print dup == } if
GlobalObjects 1 index get dup Objects 4 1 roll lput true
} ifelse
} {
exch pop true
} ifelse
} {
exch pop true
} ifelse
} bind def
/oforce /exec load def
/oget { % <array> <index> oget <object>
% <dict> <key> oget <object>
% Before release 6.20, this procedure stored the resolved
% object back into the referring slot. In order to support
% PDF linearization, we no longer do this.
get oforce
} bind def
% A null value in a dictionary is equivalent to an omitted key;
% we must check for this specially.
/knownoget { % <dict> <key> knownoget <value> true
% <dict> <key> knownoget false
% See oget above regarding this procedure.
.knownget {
oforce dup null eq { pop false } { true } ifelse
} {
false
} ifelse
} bind def
% PDF 1.1 defines a 'foreign file reference', but not its meaning.
% Per the specification, we convert these to nulls.
/F { % <file#> <object#> <generation#> F <object>
% Some PDF 1.1 files use F as a synonym for f!
.pdfcount 3 lt { f } { pop pop pop null } ifelse
} bind def
/checkgeneration { % <object#> <generation#> checkgeneration <object#> <OK>
Generations 2 index lget 1 sub 1 index eq {
pop true
} {
QUIET not {
Generations 2 index lget 0 eq {
(Warning: reference to free object: )
} {
(Warning: wrong generation: )
} ifelse print 1 index =only ( ) print =only ( R) =
} {
pop
} ifelse false
} ifelse
} bind def
/R { % <object#> <generation#> R <object>
/resolveR cvx 3 packedarray cvx
} bind def
% If we encounter an object definition while reading sequentially,
% we just store it away and keep going.
/objopdict mark
valueopdict { } forall
/endobj dup cvx
.dicttomark readonly def
/obj { % <object#> <generation#> obj <object>
PDFfile objopdict .pdfrun
} bind def
/endobj { % <object#> <generation#> <object> endobj <object>
3 1 roll
% Read the xref entry if we haven't yet done so.
% This is only needed for generation # checking.
1 index resolved? {
pop
} {
PDFfile fileposition
2 index readxrefentry pop
PDFoffset add PDFfile exch setfileposition
} ifelse
checkgeneration {
% The only global objects we bother to save are
% (resource) dictionaries.
1 index dup gcheck exch type /dicttype eq and {
DEBUG { (%Local=>global: ) print dup == } if
GlobalObjects 1 index 3 index put
IsGlobal 1 index 1 put
} if
Objects exch 2 index lput
} {
pop pop null
} ifelse
} bind def
% When resolving an object reference, we stop at the endobj.
/resolveopdict mark
valueopdict { } forall
/endobj { endobj exit } bind
.dicttomark readonly def
/resolveR { % <object#> <generation#> resolveR <object>
DEBUG { (%Resolving: ) print 2 copy 2 array astore == } if
1 index resolved? {
exch pop exch pop
} {
PDFfile fileposition 3 1 roll
1 index readxrefentry
3 1 roll checkgeneration {
% Stack: savepos objpos obj#
exch PDFoffset add PDFfile exch setfileposition
PDFfile token pop 2 copy ne
{ (xref error!) = /resolveR cvx /rangecheck signalerror
}
if pop PDFfile token pop
PDFfile token pop /obj ne
{ (xref error!) = /resolveR cvx /rangecheck signalerror
}
if
pdf_run_resolve % PDFfile resolveopdict .pdfrun
}
{ % Don't cache if the generation # is wrong.
pop pop null
} ifelse
exch PDFfile exch setfileposition
} ifelse
} bind def
% ================================ Streams ================================ %
% We represent a stream by an executable dictionary that contains,
% in addition to the contents of the original stream dictionary:
% /File - the file or string where the stream contents are stored,
% if the stream is not an external one.
% /FilePosition - iff File is a file, the position in the file
% where the contents start.
% /StreamKey - the key used to decrypt this stream, if any.
% We do the real work of constructing the data stream only when the
% contents are needed.
% Construct a stream. The length is not reliable in the face of
% different end-of-line conventions, but it's all we've got.
%
% PDF files are inconsistent about what may fall between the 'stream' keyword
% and the actual stream data, and it appears that no one algorithm can
% detect this reliably. We used to try to guess whether the file included
% extraneous \r and/or \n characters, but we no longer attempt to do so,
% especially since the PDF 1.2 specification states flatly that the only
% legal terminators following the 'stream' keyword are \n or \r\n, both of
% which are properly skipped and discarded by the token operator.
/stream { % <dict> stream <modified_dict>
dup /F known dup PDFsource PDFfile eq or {
not {
dup /File PDFfile put
dup /FilePosition PDFfile fileposition put
DEBUG { (%FilePosition: ) print dup /FilePosition get == } if
} if
PDFfile fileposition 1 index /Length oget add
PDFfile exch setfileposition
} {
pop
% We're already reading from a stream, which we can't reposition.
% Capture the sub-stream contents in a string.
dup /Length oget string PDFsource exch readstring
not {
(Unexpected EOF in stream!) =
/stream cvx /rangecheck signalerror
} if
1 index exch /File exch put
} ifelse
PDFsource token pop
/endstream ne { /stream cvx /syntaxerror signalerror } if
cvx
} bind def
/endstream {
exit
} bind def
% Contrary to the published PDF (1.3) specification, Acrobat Reader
% accepts abbreviated filter names everywhere, not just for in-line images,
% and some applications (notably htmldoc) rely on this.
/unabbrevfilterdict mark
/AHx /ASCIIHexDecode /A85 /ASCII85Decode /CCF /CCITTFaxDecode
/DCT /DCTDecode /Fl /FlateDecode /LZW /LZWDecode /RL /RunLengthDecode
.dicttomark readonly def
% Extract and apply filters.
/filterparms { % <dict> <DPkey> <Fkey> filterparms
% <dict> <parms> <filternames>
2 index exch .knownget {
exch 2 index exch .knownget {
% Both filters and parameters.
exch dup type /nametype eq {
1 array astore exch 1 array astore exch
} if
} {
% Filters, but no parameters.
null exch
dup type /nametype eq { 1 array astore } if
} ifelse
} {
% No filters: ignore parameters, if any.
pop null { }
} ifelse
} bind def
/filtername { % <filtername> filtername <filtername'>
//unabbrevfilterdict 1 index .knownget { exch pop } if
} bind def
/applyfilters { % <parms> <source> <filternames> applyfilters <stream>
2 index null eq {
{ filtername filter }
} {
{ % Stack: parms stream filtername
2 index 0 oget dup null eq { pop } { exch } ifelse filtername filter
exch dup length 1 sub 1 exch getinterval exch
}
} ifelse forall exch pop
} bind def
% Resolve a stream dictionary to a PostScript stream.
% Streams with no filters require special handling:
% - If we are going to interpret their contents, we let endstream
% terminate the interpretation loop;
% - If we are just going to read data from them, we impose
% a SubFileDecode filter that reads just the requisite amount of data.
% Note that, in general, resolving a stream repositions PDFfile.
% Clients must save and restore the position of PDFfile themselves.
/resolvestream { % <streamdict> <readdata?> resolvestream <stream>
1 index /F .knownget {
% This stream is stored on an external file.
(r) file exch
/FDecodeParms /FFilter filterparms
% Stack: readdata? dict parms filternames
4 -1 roll exch
pdf_decrypt_stream
applyfilters
} {
exch dup /FilePosition .knownget {
1 index /File get exch setfileposition
} if
% Stack: readdata? dict
/DecodeParms /Filter filterparms
% Stack: readdata? dict parms filternames
2 index /File get exch
% Stack: readdata? dict parms file/string filternames
pdf_decrypt_stream % add decryption if needed
dup length 0 eq {
% All the PDF filters have EOD markers, but in this case
% there is no specified filter.
pop exch pop
% Stack: readdata? dict file/string
2 index {
% We're going to read data; use a SubFileDecode filter.
1 index /Length oget () /SubFileDecode filter
} {
dup type /filetype ne {
% Use a SubFileDecode filter to read from a string.
0 () /SubFileDecode filter
} if
} ifelse
} {
applyfilters
} ifelse
} ifelse
% Stack: readdata? dict file
exch pop exch pop
} bind def
% ============================ Name/number trees ============================ %
/nameoget { % <nametree> <key> nameoget <obj|null>
exch /Names exch .treeget
} bind def
/numoget { % <numtree> <key> numoget <obj|null>
exch /Nums exch .treeget
} bind def
/.treeget { % <key> <leafkey> <tree> .treeget <obj|null>
dup /Kids knownoget {
exch pop .branchget
} {
exch get .leafget
} ifelse
} bind def
/.branchget { % <key> <leafkey> <kids> .branchget <obj|null>
dup length 0 eq {
pop pop pop null
} {
dup length -1 bitshift 2 copy oget
% Stack: key leafkey kids mid kids[mid]
dup /Limits oget aload pop
% Stack: key leafkey kids mid kids[mid] min max
6 index lt {
pop pop
1 add 1 index length 1 index sub getinterval .branchget
} {
5 index gt {
pop
0 exch getinterval .branchget
} {
exch pop exch pop .treeget
} ifelse
} ifelse
} ifelse
} bind def
/.leafget { % <key> <pairs> .leafget <obj|null>
dup length 2 eq {
dup 0 get 2 index eq { 1 oget } { pop null } ifelse
exch pop
} {
dup length -1 bitshift -2 and 2 copy oget
% Stack: key pairs mid pairs[mid]
3 index gt { 0 exch } { 1 index length 1 index sub } ifelse
getinterval .leafget
} ifelse
} bind def
end % pdfdict
.setglobal
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