OpenSystemsDevelopment / qpdf

Use QPDF_Stream::writeStreamJSON.
Factor out the json_stream_data == qpdf_sj_file case.

(Replacing the temporary implementation from the last commit.)

writeStreamJSON is a temporary implementation minimally adapted from
getStreamJSON.

Provide a custom method to check whether a name is valid utf8. Integrate
checking for characters that need to be escaped in JSON.

Create an alternative to getJSON to allow an object handle to be written as JSON without the overhead of creating a JSON object.

Create a simple utility class for writing JSON to a pipeline.

A parse error in stream data in which stream data contained a nested
object would cause a crash because qpdf was not correctly updating its
internal state. Rework the QPDF json reactor to not be sensitive to
parse errors in this way.

Allow "n:/pdf-syntax" JSON syntax for dictionary keys

Also, modernize for loop.

Instead of overwriting cur_row.data() use clear and insert.

Tighten checks for invalid indirect references  during xref reconstru…

Fix two errors introduced in #1110 and #1112. Since
#1110, encountering the invalid indirect reference #1110
-2147483648 n R produces an integer underflow which, if
 undetected, immediately trigger a logic error. Since
 #1112, object -1 0 R may be incorrectly identified as
 an earlier generation of itself and deleted,
 invalidating a live iterator.

Use std::vector instead of list and move shared pointers

This is just QPDFJob wiring.