[Feature] Some ways to soft-fail

[ershov]

What feature would you like to see?

I would like to be able to handle the errors in a soft way.

For example, in a file there is a data length, I specify u8 data[data_size] but the file is shorter than that. In this case the whole pattern will fail despite it's the last part of the file. I would like to be able to produce all items that were parsed successfully by that point.

Or another example, I specify a struct but the file is not long enough.

Also, I wasn't able to find a way to query the current cursor position to calculate min(pos, size) for data[...].

How will this feature be useful to you and others?

Easier pattern creation.

Request Type

• [ ] I can provide a PoC for this feature or am willing to work on it myself and submit a PR

Additional context?

No response

[WerWolv]

Hey You can use try-catch statements to catch errors like this and gracefully exit. They should be described in the documentation.

To query the current cursor position you can use the $ operator. Simply read from it like from a normal variable to get the current address

[ershov]

I tried try-catch. While it works, it's extremely bulky and not helping much in aborting on error while keeping everything up to the error point.

In order to make try-catch work for this purpose, one'd have to wrap every field of every struct in try-catch. That's not a viable solution.

Also, when I try to do

try {
    u8 data[... calculated size ...];
} catch {
    return;
}

it doesn't terminate the pattern execution as expected but rather tries to continue parsing the pattern which leads to overflow. The construct that does work is

try {
    u8 data[... calculated size ...];
} catch {
    u8 ERROR[std::mem::size() - $];
}

@WerWolv is there currently a way to do it better?

Maybe, some sort of a #pragma could do it better.

The mode that I would like to use the pattern is: Whenever an error happens, do the following:

1. Abort the pattern execution.
2. Keep everything that has been parsed up until the point.
3. At the end of the pattern add a field with indication of the error (maybe, at each level).

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