8366093: [lworld] Add preview mode to C++ classloader

[david-beaumont]

C++ changes for supporting preview mode when preview mode resources (with new location flags) are available.

At the moment, this code will operate on non-preview jimage files (1.0) and act as if no preview resources are available by virtue of the default value for missing attributes being zero (which matches location flags for "normal" entries).

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Progress

• Change must not contain extraneous whitespace

Issue

• JDK-8366093: [lworld] Add preview mode to C++ classloader (Sub-task - P4)

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8366093: [lworld] Add preview mode to C++ classloader

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[david-beaumont]

As discussed offline, there might be a neater expression for these flags with:

bit: 1 0
    [0,0] 0 = normal_entry (only)
    [0,1] 1 = normal_entry_with_preview_version
    [1,0] 2 = preview_entry (only)
    [1,1] 3 = preview_entry_with_normal_version
       ^-- has other version bit
     ^---- is preview version bit

[david-beaumont]

After remembering that these flags are also used in packages/xxx locations, where "is this a preview version" makes no conceptual sense, I no longer think it would be a good idea to change the flag definitions.

[mlbridge]

Webrevs

• 00: Full (9ca6c473)

[david-beaumont]

Also set on package directories if all its entries are preview only, but the C++ code doesn't need to know that because it's never dealing with those entries.

[david-beaumont]

Also set on package directories if any of its entries have preview content.