OpenSystemsDevelopment / qpdf

Introduced explicit checks for empty streams and refined filtering conditions for improved clarity and correctness.

Refactor Stream::filterable and Stream::pipeStreamData

Replaced `std::shared_ptr` with `std::unique_ptr` in `SF_FlateLzwDecode` to improve memory management and clarify ownership semantics. Adjusted related code and function logic to accommodate the change, including moving pipelines into the vector.

Updated `SF_Crypt` class methods and destructor to use the `final` specifier for clarity and stricter override rules. Refactored `setDecodeParms` logic for better readability and accurate handling of dictionary keys. Other minor adjustments contribute to code maintainability and correctness.

Removed `expand_filter_name` method and integrated its functionality directly into `filter_factory` for improved clarity and maintainability. Consolidated filter handling logic to eliminate redundant operations and streamline code execution.

Replaced individual compression flags with a unified decode-level parameter for stream filtering. Introduced a helper function to handle filtering conditions, reducing redundancy and improving readability. Removed unused code and updated related tests to reflect these changes.

Stream provider logic has been streamlined by removing unnecessary variables and conditional checks. Adjusted handling of mismatched or missing stream lengths to improve code readability and maintainability.

Replaced shared_ptr with unique_ptr for pipeline management, reducing overhead and improving ownership semantics. Simplified conditional checks and modernized code to enhance readability by removing redundant variables and adjusting pointer usages. This refactor ensures better maintainability and minor performance gains in stream processing.

Moved `anyBadTokens` and `lastTokenWasBad` methods to inline definitions within the header file for improved readability and maintainability. Also marked the class and relevant methods as `final` to prevent further inheritance and overrides.

Refactored the handling of /DecodeParms by removing unnecessary vector creation and directly accessing elements in the decode array. This improves code clarity and maintains consistency with filters processing.

Simplified and reorganized logic for handling /DecodeParms in streams. Ensured proper initialization and updated filter checks for lossy and specialized compression, improving code clarity and maintainability.

Moved the conditional check for /DecodeParms inconsistency into the loop to ensure clearer handling when filters are non-empty. This improves code structure and maintains robustness for edge cases encountered in the wild.

Simplified the logic for handling /DecodeParms by using `as_array` and modernized code with `auto` and `emplace_back`. This improves code readability and aligns with modern C++ practices.

Removed the unnecessary `filterable` variable and streamlined the logic for handling stream decoding parameters. These changes eliminate redundant checks, improve readability, and ensure clarity in flow control for filter processing.

Replaced manual array handling with cleaner iteration using `as_array`. This improves code readability and ensures more robust processing of stream filter arrays.

Simplify and reorganize parsing logic to replace explicit filter name collection with direct filter creation. Added validation for unsupported filters, ensuring filters are cleared and errors returned when necessary. This improves code clarity and robustness.

Moved stream filter factory logic into `Members::filter_factory` for better encapsulation and maintainability. Removed redundant static filter factory map and improved error handling for invalid stream filter configurations.

Moved `expand_filter_name` calls to maintain uniformity and avoid redundant processing in filter handling. This ensures cleaner and more structured code without changing functionality.

Moved the filter abbreviation expansion logic from a static map to a new `expand_filter_name` method in `QPDF_Stream::Members`. This simplifies the code, improves maintainability, and consolidates the logic for easier testing and updates.

Bump version to 12.3.0 and C++ to C++-20

During xref recovery reject /Page objects with multiple errors

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.

Refine xref table reconstruction

Bump version to 12.2.1

Fix QPDFFormFieldObjectHelper::getChoices (fixes #1433)

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.

Add additional sanity check during xref recovery

Enhance Windows build for local dev

* Remove dependency on `perl`, now only required for maintenance
  activities and running the test suite.
* Exercise building qpdf and running executables from JetBrains CLion
  without any special additional tooling beyond pre-built external
  libraries.

This replaces the `copy_dlls` with a powershell script, written mostly
by ChatGPT, starting from the bash script below. The copy_dlls script
had a lot of logic that was no longer needed.

```bash
#!/bin/bash
set -eo pipefail
exe="$1"
dest="$2"
mingw_bin_dir="$3"
if [[ $mingw_bin_dir == "" ]]; then
    echo >&2 "Usage: $(basename $0) exe dest mingw-bin-dir"
    exit 2
fi

get_dlls() {
    objdump -p "$1" | grep 'DLL Name:' | awk '{print $NF}'
}
declare -a dlls
dlls=($(get_dlls "$exe"))
declare -A seen
while [[ ${#dlls[@]} -gt 0 ]]; do
    i="${dlls[0]}"
    dlls=("${dlls[@]:1}")
    if [[ ${seen[$i]} == 1 ]]; then
        continue
    fi
    seen[$i]=1
    full="$mingw_bin_dir/$i"
    if [[ -f "$full" ]]; then
        cp "$full" $dest/
        dlls+=($(get_dlls "$full"))
    fi
done
```

Return the display value if the choices entry is an array of strings rather
than a single string.

Test file is need-appearances.pdf modified to contain one array entry.

Do not copy duplicate pages during xref recovery.