Implement QPDFObjectHandle::parse

Move object parsing code from QPDF to QPDFObjectHandle and
parameterize the parts of it that are specific to a QPDF object.
Provide a version that can't handle indirect objects and that can be
called on an arbitrary string.

A side effect of this change is that the offset used when reporting
invalid stream length has changed, but since the new value seems like
a better value than the old one, the test suite has been updated
rather than making the code backward compatible.  This only effects
the offset reported for invalid streams that lack /Length or have an
invalid /Length key.

Updated some test code and exmaples to use QPDFObjectHandle::parse.

Supporting changes include adding a BufferInputSource constructor that
takes a string.

1 files changed, 2 insertions, 4 deletions

diff --git a/TODO b/TODO
index cf752daf..42d5e7a6 100644
--- a/TODO
+++ b/TODO
@@ -20,16 +20,14 @@ Next
  * Make sure that the release notes call attention to the one API
    breaking change: removal of length from replaceStreamData.
 
- * Add a way to create new QPDFObjectHandles with a string
-   representation of them, such as
-   QPDFObjectHandle::parse("<< /a 1 /b 2 >>");
-
  * Document thread safety: One individual QPDF or QPDFWriter object
    can only be used by one thread at a time, but multiple threads can
    simultaneously use separate objects.
 
  * Write some documentation about the design of copyForeignObject.
 
+ * Mention QPDFObjectHandle::parse in the documentation.
+
  * copyForeignObject still to do:
 
     - qpdf command