The idea is to massage the inline image data into something that
looks like a regular image, and then use the normal image drawing code:
We translate the inline image abbreviations to the expanded version at
rendering time, then unfilter (i.e. uncompress) the image data at
rendering time, and the go down the usual image drawing path.
Normal streams are unfiltered when they're first accessed, but
inline image streams live in a page's drawing operators, and this
fits the current approach of parsing a page's operators anew
every time the page is rendered.
(We also need to add some special-case handling for color spaces
of inline images: Inline images can use named color spaces, while
regular images always use direct color space objects.)
This commit un-deprecates DeprecatedString, and repurposes it as a byte
string.
As the null state has already been removed, there are no other
particularly hairy blockers in repurposing this type as a byte string
(what it _really_ is).
This commit is auto-generated:
$ xs=$(ack -l \bDeprecatedString\b\|deprecated_string AK Userland \
Meta Ports Ladybird Tests Kernel)
$ perl -pie 's/\bDeprecatedString\b/ByteString/g;
s/deprecated_string/byte_string/g' $xs
$ clang-format --style=file -i \
$(git diff --name-only | grep \.cpp\|\.h)
$ gn format $(git ls-files '*.gn' '*.gni')
Since all parents held a reference pointer to their children, and all
children held reference pointers to their parents, both objects would
never get free'd once the document was no longer being used.
Fixes ossfuzz-63833.
Per 1.7 spec 3.8.1, there are multiple logical text string types:
* text strings
* ASCII strings
* byte strings
Text strings can be in UTF-16BE, PDFDocEncoding, or (since PDF 2.0)
UTF-8.
But byte strings shouldn't be converted but treated as binary
data.
This makes us no longer convert strings used for drawing page text.
TABLE 5.6 "Text-showing operators" lists the operands for text-showing
operators as just "string", not "text string" (even though these strings
confusingly are called "text strings" in the body text), so not doing
this there is correct (and matches other viewers).
We also no longer incorrectly convert strings used for cypto data
(such as passwords), if they start with an UTF-16BE or UTF-8 marker.
No behavior change for outlines and info dict entries.
https://pdfa.org/understanding-utf-8-in-pdf-2-0/ has a good overview of
this.
(ASCII strings only contain ASCII characters and behave the same
anyways.)
Previously we assumed a default precision of 6, which made the printed
values quite odd in some cases.
This commit changes that default to print them with just enough
precision to produce the exact same float when roundtripped.
This commit adds some new tests that assert exact format outputs, which
have to be modified if we decide to change the default behaviour.
This dict contains some metadata in some files.
Newer files also contain XMP metadata, but it's recommended to
still include this dict as well, for compatibility with older readers.
And it's much less complex than XMP, so let's support it.
Previously, get_inheritable_object would always try to find the object
and throw an error if it couldn't. The spec tells us that some page
attributes, like CropBox, are optional but also inheritable. Others,
like the media box and resources, are technically required by the spec,
but omitted by some documents.
In both cases, we are now able to search for inheritable objects and
find a suitable replacement if there wasn't one.
This class had slightly confusing semantics and the added weirdness
doesn't seem worth it just so we can say "." instead of "->" when
iterating over a vector of NNRPs.
This patch replaces NonnullRefPtrVector<T> with Vector<NNRP<T>>.
When parsing streams we rely on a /Length item being defined in the
stream's dictionary to know how much data comprises the stream. Its
value is usually a direct value, but it can be indirect. There was
however a contradiction in the code: the condition that allowed it to
read and use the /Length value required it to be a direct value, but the
actual code using the value would have worked with indirect ones. This
meant that indirect /Length values triggered the fallback, "manual"
stream parsing code.
On the other hand, this latter code was also buggy, because it relied on
the "endstream" keyword to appear on a separate line, which isn't always
the case.
This commit both fixes the bug in the manual stream parsing scenario,
while also allowing for indirect /Length values to be used to parse
streams more directly and avoid the manual approach. The main caveat to
this second change is that for a brief period of time the Document is
not able to resolve references (i.e., before the xref table itself is
not parsed). Any parsing happening before that (e..g, the linearization
dictionary) must therefore use the manual stream parsing approach.
DeprecatedFlyString relies heavily on DeprecatedString's StringImpl, so
let's rename it to A) match the name of DeprecatedString, B) write a new
FlyString class that is tied to String.
PDF allows for named destinations to be provided as string. These can be
either found in the Dests dictionary in the document catalogue (as
already implemented), or in the Name Tree specified by the Dests key in
the Names dictionary of the document catalogue (missing).
This commit adds this missing case. Once the named destination is found
in the name tree, its value is interpreted just like in the first case,
so a new utility method encapsulates the common behavior.
Name Trees are hierarchical, string-keyed, sorted-by-key dictionary
structures in PDF where each node (except the root) specifies the bounds
of the values it holds, and either its kids (more nodes) or the
key/value pairs it contains.
This commit implements a series of lookup calls for finding a key in
such name trees. This implementation follows the tree as needed on each
lookup, but if that becomes inefficient in the long run we can switch to
creating a HashMap with all the contents, which as a drawback will
require more memory.
This functionality was previously part of the resolve_to() Document
method, and thus only available only when resolving objects through the
Document class. There are many use cases where this casting can be used,
but no resolution is needed.
This commit moves this functionality into a new cast_to function, and
makes the resolve_to function call it internally. With this new function
in place we can now offer new versions of DictObject::get_* and
ArrayObject::get_*_at that don't perform Document resolution
unnecessarily when not required.
Destination arrays contain a page number, a mode name, and parameters
specific to that mode. In many cases these parameters can be set to
"null", which our code wasn't taking into consideration.
This commit parses these parameters taking into account whether they are
null or actual numbers, and stores them as Optional<float> instead of
plain floats. The parameters are not yet used anywhere else other than
when formatting a Destination object, so the change is fairly small.
The Value previously stored corresponded to a Reference to a Page object
in the PDF document. This isn't useful information, since what we want
to display at the end of the day is the page an outline item refers to.
This commit changes the page member on OutlineItem to be a Optional<u32>
(some destinations don't necessarily refer to a Page), which we resolve
while building OutlineItems.
While the Outline Items making up the document's Outline have all sorts
of cross-references (parent, first/last chlid, next/previous sibling,
etc), not all documents out there have fully-consistent references. Our
implementation already discarded some of that information too (e.g.,
/Parent and /Prev were never read), and trusted that /First and /Next
were good enough to traverse the whole hierarchy.
Where the current implementation failed was in assuming that /Last was
also a good source of information. There are documents out there were
/Last also points to dead ends, and were therefore causing a crash when
we verified that the last child found on a chain was the /Last child
declared by the parent. To fix this I'm simply removing the check, and
simplifying the function call to remove any references to /Last. This
way we affirm our commitment to /First and /Next as the main sources of
information.
This will make it easier to support both string types at the same time
while we convert code, and tracking down remaining uses.
One big exception is Value::to_string() in LibJS, where the name is
dictated by the ToString AO.
We have a new, improved string type coming up in AK (OOM aware, no null
state), and while it's going to use UTF-8, the name UTF8String is a
mouthful - so let's free up the String name by renaming the existing
class.
Making the old one have an annoying name will hopefully also help with
quick adoption :^)
The Parser class is now a generic PDF object parser, of which the new
DocumentParser class derives. DocumentParser now takes over all
functions relating to linearization, pages, xref and trailer handling.
This allows the use of multiple parsers in the same document's
context, which will be needed in order to handle PDF object streams.
Each of these strings would previously rely on StringView's char const*
constructor overload, which would call __builtin_strlen on the string.
Since we now have operator ""sv, we can replace these with much simpler
versions. This opens the door to being able to remove
StringView(char const*).
No functional changes.
These are mostly minor mistakes I've encountered while working on the
removal of StringView(char const*). The usage of builder.put_string over
Format<FormatString>::format is preferrable as it will avoid the
indirection altogether when there's no formatting to be done. Similarly,
there is no need to do format(builder, "{}", number) when
builder.put_u64(number) works equally well.
Additionally a few Strings where only constant strings were used are
replaced with StringViews.
Security handlers manage encryption and decription of PDF files. The
standard security handler uses RC4/MD5 to perform its crypto (AES as
well, but that is not yet implemented).
This isn't a complete conversion to ErrorOr<void>, but a good chunk.
The end goal here is to propagate buffer allocation failures to the
caller, and allow the use of TRY() with formatting functions.
Old situation:
Object.h defines Object
Object.h defines ArrayObject
ArrayObject requires the definition of Object
ArrayObject requires the definition of Value
Value.h defines Value
Value requires the definition of Object
Therefore, a file with the single line "#include <Value.h>" used to
raise compilation errors; certainly not something that one might expect
from a library.
This patch splits up the definitions in Object.h to break the cycle.
Now, Object.h only defines Object, Value.h still only defines Value (and
includes Object.h), and the new header ObjectDerivatives.h defines
ArrayObject (and includes both Object.h and Value.h).
This is a big step, as most PDFs which are downloaded online will be
linearized. Pretty much the only difference is that the xref structure
is slightly different.
The Parser should hold information relevant for parsing, whereas the
Document should hold information relevant for displaying pages.
With this in mind, there is no reason for the Document to hold the
xref table and trailer. These objects have been moved to the Parser,
which allows the Parser to expose less public methods (which will be
even more evident once linearized PDFs are supported).
We now follow nested page tree nodes to find all of the actual
page dicts, whereas previously we just assumed the root level
page tree node contained all of the page children directly.
This commit introduces the ability to parse the document catalog dict,
as well as the page tree and individual pages. Pages obviously aren't
fully parsed, as we won't care about most of the fields until we
start actually rendering PDFs.
One of the primary benefits of the PDF format is laziness. PDFs are
not meant to be parsed all at once, and the same is true for pages.
When a Document is constructed, it builds a map of page number to
object index, but it does not fetch and parse any of the pages. A page
is only parsed when a caller requests that particular page (and is
cached going forwards).
Additionally, this commit also adds an object_cast function which
logs bad casts if DEBUG_PDF is set. Additionally, utility functions
were added to ArrayObject and DictObject to get all types of objects
from the collections to avoid having to manually cast.
