Several integer key values do not state explicit valid ranges

petervwyatt commented 3 years ago

Several integer keys in dictionaries do not state any explicit valid ranges, such as "positive integer ..." or "non-negative integer ...".

One way to fix this quickly may be to simply state once up the front of ISO 32K somewhere (where?) that key values that represent counts, sizes, widths, heights, file byte offsets, object numbers, page numbers and <anything else that is common?> are non-negative unless stated otherwise.

Or we could review each and add the explicit wording in place.

Here is an incomplete list (from a search of ISO 32000-2 for "integer" up to about Table 100 - more to be added later):

Table 11 Columns: unstated non-negative
Table 11 Rows: unstated non-negative
Table 11 DamagedRowsBeforeError: unstated non-negative
Table 15: Size: unstated positive
Table 15: Prev: unstated non-negative or positive??
Table 16: N: unstated non-negative / positive??
Table 16: First: unstated non-negative / positive??
Table 17: Size: unstated > 1 (since has to be +1 on highest object# and PDFs need at least 1 object (technically more!))
Table 17: Prev: unstated non-negative or positive??
Table 19: XRefStm: unstated non-negative (just "byte offset")
Table 30: Count: unstated non-negative or positive?? (just "count of leaf nodes" - does it include Template pages?)
Table 31: StructParents: ?? is there a valid range ??
Table 45: Size: unstated non-negative
Table 87 (Image XObject): Width: unstated non-negative
Table 87 (Image XObject): Height: unstated non-negative
Table 87 (Image XObject): StructParent ?? is there a valid range ??
Table 93 (Form XObject): StructParent ?? is there a valid range ??
Table 87 (Form XObject): StructParents ?? is there a valid range ??
Table 95 (Reference dict): Page: unstated non-negative

petervwyatt commented 3 years ago

More:

Table 109, 110: FirstChar, LastChar : unstated non-negative ??
Table 114: Supplement - ?? nothing ??
Table 125: Length, Length2, Length3 : unstated non-negative
Table 129, 130: Width, Height : unstated positive
Table 131: Width, Height, Width2, Height2 : unstated positive
Table 147: NumCopies: unstated positive
Table 166: StructParent: ??

petervwyatt commented 3 years ago

More:

Table 232: MaxLen - is a 0-length text field useful or invalid???
Table 255: R, V - no info is given as to valid ranges for these versions
Table 255: Prop_AuthTime - assume 0 is valid so should be described as a "non-negative integer"?
Table 305: C, B - looks like 0 would be invalid so should be described as "positive integers"?

pesco commented 2 years ago

Also Table 8: Columns (positive)?

It doesn't make any sense to allow a value of 0 here, does it? FWIW, I'll come out to admit that I managed to produce a segfault if 0 was given.

Similarly for the Columns entry in Table 11 (you wrote non-negative above)?