hid: inline file system ignores empty lines in quoted content

[jschlatow]

While switching to HID by default, I came across the issue that stdin2out fails to read some content from an inline-specified file. Looking into this, I noticed that empty quoted lines are simply dropped. Let's have a look at an example:

+ vfs
  + inline source.txt
  | : 
  | : foo
  | : 
  | : bar
  | :

I instrumented Vfs_inline::File_system::Buffered_data::unquoted_content(). When I log() the entire node provided as argument, I get the same HID as shown above. When I use for_each_quoted_line(), however, only the lines containing foo and bar are iterated.

@nfeske Is this intentional? Is there a way to iterate the quoted content including empty lines?

[nfeske]

That's not intentional. I'm afraid it's a bug.

[nfeske]

Could you try mimicking the situation using base/src/test/hid/? I'm a little bit surprised because the test actually covers empty quoted lines.

build/x86_64$ make run/test PKG=test-hid KERNEL=linux BOARD=linux

[nfeske]

...but maybe only at the generator side (?)

[jschlatow]

Commit 01a08d3 adds the corresponding test case.

[nfeske]

@jschlatow Excellent! Are you planning to dig deeper?

[jschlatow]

I tried but only got as far as suspecting the seg.num_bytes in the following line:

genode/repos/base/include/util/hid.h

Line 187 in 13aeca8

if (seg.num_bytes && prefix.type != Prefix::COMMENT)

Changing this, however, did not have any effect. I tried instrumenting with log(), but this only caused segfaults. Unfortunately, I cannot get back to this before tomorrow afternoon.

[jschlatow]

@nfeske As it turns out, the implementation perfectly conforms to the HID documentation:

Content must be separated from the ':' character with a single space.

Thus, it is possible to add an empty line to the quoted content by adding a space after the ':'. Yet, I'm afraid this is going to be a common pitfall that we should rather prevent. What is your opinion?

[jschlatow]

the implementation perfectly conforms to the HID documentation

Well, not quite. I forgot that append_quoted already adds a space after the :. I therefore tested with two spaces.

[nfeske]

Pitfalls are no good. We should definitely interpret colon lines without a trailing space as valid empty lines.
Strictly speaking, the documentation tells "content must be separated". If there is no content, there should be no need for a separating character.

[jschlatow]

Commit c9b161d fixes this (at least for test/hid, I'm currently testing whether this also works for the inline file system). Please note that I also pushed fixup adc7ff2 for test/hid, as I got the line count wrong.