Change the return type to a std::pair<bool, QPDFObjectHandle> in order to
allow a default constructed object handle (which is currently returned to
indicate failure) to become a valid object.
1. Make class final
2. Pass og parameter by value
3. Properly initialize qpdf and og
Also, tweak QPDF::replaceObject to allow stream replacement without
violating the requirement that streams must always be indirect objects.
Also, remove QPDF::reserveStream as it does not do what the name implies
and having this as a separate methods does not aid code readability.
Given that the PDF spec requires the xref table to contain entries for all
object ids <= the maximum id present in a PDF document, max_size is a
qpdf implementation limitation for legitimate object ids.
QPDF::read_xrefTable ignores type 0 entries for objects in a section if an
associates XRefStm has an entry for the same object.
The spec states:
When the conforming reader searches for an object, if an entry is not
found in any given standard cross-reference section, the search shall
proceed to a cross-reference stream specified by the XRefStm entry
before looking in the previous cross-reference section,
If a deleted entry is found in a section, the XRefStm is not searched
according to the standard.
Create unresolved objects only for objects in the xref table (except during
parsing of the xref table). Do not add indirect nulls into the the object
cache as the result of a cache miss during a call to getObject except
during parsing or creation/updating from JSON. To support this behaviour,
add new private methods getObjectForParser and getObjectForJSON.
As a result of this change, dangling references are treated as direct nulls
rather than indirect nulls.
Prepare for treating indirect references differently depending on whether
we are parsing a PDF file (in which case reference to objects not in the
xref table are null even if they are in the object cache) or whether parse
from user code (in which case an indirect reference can refer to a user
created object).
