Kaitai Struct Parameter Type - kaitai-struct

I am trying to pass a parameter to ksy file. The parameter is of type another ksy file. The reason is that i need to access all the fields from the ksy file passed as parameter.
Is that possible?
If yes, would you please provide me with syntax code snippet so I can mimic it.
If no, what would be another solution?
Thank You.

Affiliate disclaimer: I'm a Kaitai Struct maintainer (see my GitHub profile).
First, I recommend always using the development version of the Kaitai Struct Web IDE (https://ide.kaitai.io/devel/), not the stable one. The stable IDE deployed at https://ide.kaitai.io/ has KS compiler of version 0.8, which is indeed the latest stable version, but already 2 years old at the moment. But the project is under active development, new bug fixes and improvements are coming every week, so the stable Web IDE is pretty much outdated. And thanks to the recent infrastructure enhancement, the devel Web IDE now gets rebuilt every time the compiler is updated, so you can use even the most recent features.
However, you won't be able to simulate the particular situation you describe in the Web IDE, because it can't currently handle top-level parameteric types (there is no hook where you can pass your own values as arguments). But it should work in a local environment. You can compile the commontype.ksy and pty.ksy specs in the Web IDE to the target language you want to use (the manual shows how to do it). The code putting it together could look like this (Java):
Commontype ct = new Commontype(new ByteBufferKaitaiStream(new byte[] { 80, 75 }));
Pty r = new Pty(
new ByteBufferKaitaiStream(new byte[] { 80 }), // IO stream
ct // commonword
);
Note that the actual parameter order of the Pty constructor may be different, e.g. in Python come the custom params (commonword) first and then the IO object. Check the generated code in your particular language.

Related

`#babel/runtime` and `#babel/plugin-transform-runtime` versions

Are #babel/runtime and #babel/plugin-transform-runtime supposed to be on the same version (e.g. both 7.2.0 exactly)? Or can I (as a library author) specify #babel/runtime dependency as ^7.0.0, whilst having the latest #babel/plugin-transform-runtime?
I'm aware that during the beta versions of Babel 7, there was a breaking change in beta.56 (see https://stackoverflow.com/a/51686837/2148762), but I'm guessing this should no longer be the case with the current stable version?
The reason I ask this is I'd ideally want the helpers from #babel/runtime to be shared across different packages, and to me leaving the version range open seems like a good idea. But at the same time, I'm not sure how low I should go (^7.0.0 or ^7.2.0), and whether there's an implicit contract between #babel/runtime and #babel/plugin-transform-runtime with regards to version numbers.
By default, #babel/plugin-transform-runtime is only allowed to output references to #babel/runtime that work on ^7.0.0 because it does not know what version you'd otherwise want to use, and doing anything else would cause lots of issues for users. This means that what you want to do is safe. The downside of this is that, if we add new helpers moving forward, your code would not be able to take advantage of the #babel/runtime version of them (because you might still be using a #babel/runtime version that doesn't have them.
Users can specify the version in the arguments for the transform, if you want to specifically make use of helpers that may have been added to Babel since 7.0.0, e.g.
{
"plugins": [
["#babel/plugin-transform-runtime", { version: "^7.2.0" }],
]
}
would then require you to have "#babel/runtime": "^7.2.0" in your package.json.
For instance, since support for the newer decorators proposal didn't land until Babel 7.1.5, if you use transform-runtime and non-legacy decorators, the decorators helper will still be inserted into every file where you use decorators, instead of importing it from #babel/runtime. To get the shared helper, you need to specify version: "^7.1.5" in your options for transform-runtime.
Can I (as a library author) specify #babel/runtime dependency as ^7.0.0, whilst having the latest #babel/plugin-transform-runtime?
Yes, this is safe.
I'm guessing this should no longer be the case with the current stable version?
Correct, that issue was because people failed to take the beta versioning into account.

More than one V4L-DVB driver on the same host machine

I have a question related to V4L-DVB drivers. Following the
Building/Compiling the Latest V4L-DVB Source Code link, there are 3 ways to
compile. I am curious about the last approach (More "Manually
Intensive" Approach). It allows me to choose the components that I
wish to build and install using the "make menuconfig". Some of these components (i.e. "CONFIG_MEDIA_ATTACH") are used in pre-processor directives that define a function in one shape if defined, and a function in another if not defined (i.e.
dvb_attach, dvb_detach) in the resulting modules (i.e. dvb_core.ko)
that will be loaded by most of the DVB drivers. What happens if there are two
drivers (*.ko modules) on the same host machine, one that needs dvb_core.ko with
CONFIG_MEDIA_ATTACH defined and another that needs dvb_core.ko with
CONFIG_MEDIA_ATTACH undefined, is there a clean way to handle this?
What is also not clear to me is: Since the V4L compilation environment seems very customizable (by setting the .config file), if I develop a driver using V4L-DVB structures, there is a big chance that it has conflicts with other drivers since each driver has its own custom settings. Is my understanding correct?
Thanks!
Dave

How does Server.call work in elixir-mongo?

I'm learning Elixir and attempting to use the elixir-mongo library. During the auth/1 command, A the function uses Server.call, piping in the MongoDB request string. looking at the Mongo.Server class, it does not appear to be an actual genserver, nor have a method to match call/1. How is this working?
With high probability it doesn't work. Mongo.Server module doesn't export call function. There are no macros that generate it magically. My guess is that master branch is currently broken. If you are using the library and want to dig into the sources make sure you are looking at the same tag as the version you are using in your project.
Also, there are no classes and methods in Elixir. There are modules and functions :)

Build Scala against different versions of external API

I'm writing a small library which I'd like to be backwards compatible with older versions of an API, yet use features of the latest API when possible.
So for example, I have a project which uses an external API, which I'll call FooFoo_v1.
Initially, my code looked like this:
// in Widget.scala
val f = new Foo
f.bar
Foo has since released a new version of their API, FooFoo_v2, which adds the bat method. So long as I'm compiling against the new version, this works fine:
// in Widget.scala
val f = new Foo
f.bar
f.bat
But if you try to build against FooFoo_v1, the build obviously fails. Since the bat feature is truly optional, and I'd like to allow folks to build my code against FooFoo_v1 or FooFoo_v2.
Ignoring the details of the dependency management, what's the right high level approach for something like this? My aim is to keep it as simple as possible.
I think you should split your library in two pieces - one with features used from FooFoo_v1, another depending on the first one and on FooFoo_v2 and using features from FooFoo_v2. How to accomplish it depends on your code... If it's too difficult it's better to follow #rex-kerr advice - to maintain two branches.
I would simply keep separate branches of the project in a repository (one which is sufficiently robust to allow you to edit one and merge effortlessly into the others--git would be my first choice).
If you must do the selection at runtime, then you're limited to using reflection for any new methods.

How to compare files programmatically in eclipse?

I am developing an eclipse plugin that runs code violation checker on the difference of two versions of a file. Right now I am using diff.exe to get the difference between the two files. But as diff.exe is an extrenal app, I realized that its better to use eclipse built-in compare tool to get the file difference.
So I used org.eclipse.compare and reached up to this point:
public static List<Patch> compare(String old, String recent) {
try{
IRangeComparator left = new TokenComparator(old); //what exactly to be passed in this constructor, a file path, a literal value or something else?
IRangeComparator right = new TokenComparator(recent);
RangeDifference[] diffs = RangeDifferencer.findDifferences(left, right); // This line is throwing NPE
//..
// Process RangeDifferences into Collection of Patch collection
//..
}catch(Exception e){}
//Returns a collection of file differences.
return null;
}
Now the problem is I am not sure what exactly to be passed in the constructor TokenComparator(String). The document says this constructor Creates a TokenComparator for the given string. But it is not written what exactly to be passed in this constructor, a file path, a literal value or something else? When I'm passing a file path or a string literal I am getting NullPointerException on the next line of finding differences.
java.lang.NullPointerException
at org.eclipse.compare.internal.core.LCS.isCappingDisabled(LCS.java:98)
at org.eclipse.compare.internal.core.LCS.longestCommonSubsequence(LCS.java:55)
at org.eclipse.compare.rangedifferencer.RangeComparatorLCS.longestCommonSubsequence(RangeComparatorLCS.java:186)
at org.eclipse.compare.rangedifferencer.RangeComparatorLCS.findDifferences(RangeComparatorLCS.java:31)
at org.eclipse.compare.rangedifferencer.RangeDifferencer.findDifferences(RangeDifferencer.java:98)
at org.eclipse.compare.rangedifferencer.RangeDifferencer.findDifferences(RangeDifferencer.java:82)
at org.eclipse.compare.rangedifferencer.RangeDifferencer.findDifferences(RangeDifferencer.java:67)
at com.dassault_systemes.eclipseplugin.codemonview.util.CodeMonDiff.compare(CodeMonDiff.java:48)
at com.dassault_systemes.eclipseplugin.codemonview.util.CodeMonDiff.main(CodeMonDiff.java:56)
Someone please tell what is right way to proceed.
If the question is What value the token comparators constructor takes then the answer is it takes the input string to compare. Specified in javadoc here http://help.eclipse.org/indigo/index.jsp?topic=%2Forg.eclipse.platform.doc.isv%2Freference%2Fapi%2Forg%2Feclipse%2Fcompare%2Fcontentmergeviewer%2FTokenComparator.html
TokenComparator(String text)
Creates a TokenComparator for the given string.
And the null pointer yo are getting is because in function isCappingDisabled it tries to open the compare plugin which seems to be null. You seem to be missing a direct dependency to the plugin "org.eclipse.compare.core"
The org.eclipse.compare plugin was never meant to be used in standalone : many of its functionalities require a running instance of Eclipse. Furthermore, it mixes core and UI code within the same plugin, which will lead to unexpected behavior if you are not very careful about what you use and what dependencies are actually available in your environment.
You mentionned that you were developping an Eclipse plugin. However, the NPE you get indicates that you are not running your code as an Eclipse plugin, but rather as a standard Java program. In an Eclipse environment, ComparePlugin.getDefault() cannot return null : the plugin needs to be started for that call to return anything but null.... and the mere loading of the ComparePlugin class within Eclipse is enough to start it.
The answer will be a choice :
You need your code to run as a standalone Java program out of Eclipse. In such an event, you cannot use org.eclipse.compare and diff.exe is probably your best choice (or you could switch to an implementation of diff that was implemented in Java in order to be independent of the platform).
You do not need your program to work in a standalone environment, only as an Eclipse plugin. In this case, you can keep the code you're using. However, when you run your code, you have to launch it as a new "Eclipse application" instead of "Java Application". You might want to look at a tutorial on how to develop Eclipse plugins for this, This simple tutorial from Lars Vogel shows how to run a new Eclipse Application to test an Hello World plugin. You will need a similar code, with a menu entry to launch your plugin somewhere (right-click on a file then select "check violations" in your case?).