OpenSystemsDevelopment / qpdf

… shared helper retrieval, validation methods, and update usages across the codebase. Remove unused test coverage entries.

…t. Add shared helper retrieval, validation methods, and update usages across the codebase.

…le handling. Add shared helper retrieval, validation methods, and update usages across the codebase.

Integrate `QPDFPageLabelDocumentHelper` with `QPDF` for improved page label handling. Add methods for retrieving shared helper instances, validating page label structures, and streamline usage throughout the codebase.

…, remove redundant `QTC::TC` call, and simplify type usage.

…ated `acroform()` method and update related references for improved performance, consistency and maintainability.

…mplify control flow, and update method returns.

…dding error counting and leveraging `reconstructed_xref` for improved robustness, limiting the acceptable number of errors for damaged files.

…std::string_view`, improving performance and code clarity.

…ys with `std::string`, and simplify related password handling logic.

…`, simplify method signatures, and centralize logic in `QPDF::EncryptionData` for improved maintainability.

…ling, and improve maintainability.

…Perms_value_V5` methods; inline their logic into `setV5EncryptionParameters` to simplify encryption data processing.

…dom_string`, improve readability of salts and keys handling, and streamline `compute_Perms_value_V5_clear` logic by returning strings directly.

…std::bitset`, reorganizing related methods, and simplifying access to improve clarity and maintainability.

…, transition `interpretCF` to a class method, and eliminate redundant parameter passing for improved clarity and maintainability.

…rs::initialize` and replacing shared pointers with references for improved clarity and maintainability.

…t parameter passing, and improve maintainability. Change static functions and QPDF methods to EncryptionData methods.

Simplify `readObjectAtOffset` by splitting responsibilities into separate functions: `read_object_start` and a streamlined `readObjectAtOffset`. Remove redundant parameters and improve code readability, ensuring better modularity for object reading operations.

When validating the pages tree after xref recovery do not tree dictionaries
as page objects if more than 2 of the following are true:

- the dictionary is direct
- the /Type entry is missing or is not /Page
- the dictionary does not contain a valid /Parent entry
- the dictionary does not contain or inherit a valid /MediaBox
- the dictionary does not contain or inherit a /Resources dictionary

Such dictionaries are very unlikely to be page objects and trying to
process them may cause excessive run time and memory usage.

During xref table reconstruction ignore uncompressed object entries found
in xref streams. The xref table gets populated with entries for the
objects actually found in the file. The entries for uncompressed object in
xref streams are redundant and potentially incorrect.

Only top-level XMP metadata is supposed to be left unencrypted. All
other metadata is not treated specially.

... containing objects with no white-space between them.

To enforce the rule that objects end at the start-offset of the next
object, each object is parsed in it own object stream.

To facilitate this, a new private API input source is::OffsetBuffer has
been added which only contains the object but reports offsets relative to
the start of the object stream. This is adapted from OffsetInputSource by
changing the direction of the offset, endowing it with its own
BufferInputSource and striooing out checks duplicated in BufferInputSource.

Fixes the expected failure in the test case added in #1266.

Only build strings when needed.

If startxref cannot be found in the last 1024 try finding it in the
whole file and check whether it is valid.

Split reconstruction into three passes - scanning of input for objects and
trailer, insertion of objects into the xref table, and loading the trailer.

This allows insertion to take place in the usual reverse order and removes
the need for a separate insertReconstructedXrefEntry method.

It also allows trailer to be tried from most recent to oldest.

Ignore any found trailers without /Root entry.

- Remove unnecessary QPDF_DLLs
- make deleted constructors public
- move some comments to support tooltips
- modernise some constructors and destructors
- change some member shared pointers to unique pointers

Move all stream-specific methods to new class qpdf::Stream

Except for virtual functions to avoid the need for users to update code.

This reverts commit ff2a78f579ebdd06b417e34260a17dba06e71137, reversing
changes made to 8f54319f7a6514110f4b05cbbf1cb1c9fc8cb6a0.

This reverts commit c648b9a018105a3c30b3e7f3c5f8a058d3ddd92c, reversing
changes made to 12b67a3227df6b6df3a4f5f098e11cce173ff7d5.