Compress, encrypt, decrypt, and say what a file allows

[tannevaled]

Four verbs the reader has been able to support since it learned to encrypt on writing, and which nothing was offering.

func (d *Doc) Compress()
func (d *Doc) Encrypt(e reader.Encryption)
func (d *Doc) Decrypt()
func (d *Doc) Protection() (reader.Protection, bool)

and on the command line:

pdfops compress in.pdf out.pdf
pdfops encrypt -user letmein -owner iownit -allow print,copy in.pdf out.pdf
pdfops -password letmein decrypt in.pdf out.pdf
pdfops -password letmein permissions in.pdf

protection AES-256, revision 6
opened as  the user
allows     print, copy

Measured on the whole corpus, on the pages rather than the exit status

Every file is opened, written, compressed and read back; then encrypted, reopened with each password, and written out plain again. What is compared at every step is a hash of what every page says.

files            118833
compressed       118833
  smaller        118746
  size           35202918151 -> 33576501245 (95.4%)
encrypted        118833
round-tripped    118833
took             6m55s

Nothing failed, nothing panicked, and no page changed by a byte at any step.

Needs reader v0.4.0 for Document.Protection. 100% statement coverage, go vet and gofmt clean.