manifest: ensure that size always defaults to -1 in RaucImage

[jluebbe]

A size of -1 indicates that no size key was given in the manifest. Instead of hardcoding that in everywhere, create a r_new_image() constructor function and use it instead.

[ejoerns]

A size of -1 indicates that no size key was given in the manifest. Instead of hardcoding that in everywhere, create a r_new_image() constructor function and use it instead.

This does not replace any hard-coded setting of checksum.size as far as I can see (what the commit message suggests it does). So does this fix potential issues?

[jluebbe]

A size of -1 indicates that no size key was given in the manifest. Instead of hardcoding that in everywhere, create a r_new_image() constructor function and use it instead.

This does not replace any hard-coded setting of checksum.size as far as I can see (what the commit message suggests it does). So does this fix potential issues?

I have some patches in my stack that perform stricter checking of input manifests. They enforce that no checksum or size is set, so a default constructed RaucImage would have size 0 and fail (especially in the test cases).

But even right now it's inconsistent, as a default RaucImage would be written to a manifest with size=0.

[ejoerns]

So with mentioning the inconsistency in the commit message I'd be happy ;)

[jluebbe]

@ejoerns I've updated the commit message.

[ejoerns]

I just wanted to add that using r_rauc_image_free() or r_image_free() would better fit our naming conventions, but then noted that we have r_free_image() already. Thus we should better rename these together at any later point.