[jdk8u] RFR: 8186801: Add regression test to test mapping based charsets (generated at build time)

[Severin Gehwolf]

On Fri, 16 Jun 2023 15:55:38 GMT, Andrew John Hughes <andrew at openjdk.org> wrote:

> This is a pre-requisite for [JDK-8301119](https://bugs.openjdk.org/browse/JDK-8301119) ("Support for GB18030-2022") and so is being proposed for inclusion in 8u382 during rampdown, so that the changes are in place for when GB18030-2022 enforcement begins in August. It introduces `GB18030.map`, containing the character mappings for GB18030, and tests to verify the correct mappings happen at run-time.
> 
> A number of changes were necessary for 8u. One main reason was the inclusion of [JDK-8186803](https://bugs.openjdk.org/browse/JDK-8186803) "Update Cp1140-Cp1149 EBEDIC euro charset to map \u000A to EBCDIC 0x15" as part of this fix in OpenJDK 10+. I have removed these changes in the 8u version so as to avoid making potentially incompatible library changes and focus on testing the current character mappings in 8u.
> 
> Another is that the character set data is spread across three files - `dbcs`, `sbcs` and `extsbcs` - in 8u, whereas it was amalgamated into a single file, `charsets`, during the introduction of modules. The coding test (`TestCharsetMapping.java`) has been adapted to use the 8u data format.
> 
> The detailed changes from the OpenJDK 10 patch are as follows:
> 
> 1. Drop the introduction of the `IBM114x.nr` files which implement JDK-8186803.
> 2. Drop the change to `charsets` which doesn't exist in 8u and any equivalent change may lead to compatibility issues
> 3. `EUC_TW.java` has slightly different context in 8u (no `pkg` argument) but the filename change is the same
> 4. Drop the alias changes in `MS932_0213.java` & `x-MS932_0213` to avoid a compatibility risk.
> 5. Changes to `EuroConverter.java` are dropped as they relate to JDK-8186803.
> 6. Detect the IBM0114x character sets in `TestCharsetMapping.java` and expect an additional 0xA -> 25 mapping rather than counting this as an error
> 7. Remove the parsing and checking of aliases in `TestCharsetMapping.java` as the 8u data files don't store them
> 8. Handle the internal character sets in `TestCharsetMapping.java` as they are not marked as such in the 8u data files
> 9. Change the data file parsing in `TestCharsetMapping.java` to handle the three 8u data files. `dbcs` has additional fields to the other two, but the first five fields that we actually use are mostly the same (`dbcs` has a type field, the other two assume a type of `sbcs`).
> 10. `TestEBCDICLineFeed.java` is modified to handle IBM0114x as is, without the JDK-8186803 change

My understanding is that this patch has no bearing on the product code (test only) since none of the added mappings are referenced in either of those `dbcs`, `sdcs` or `extsbcs` files. The main purpose of it would be to have the `GB18030.map` file available to move it to the cs test files used in `JDK-8301119` by `CoderTest.java`.

On that ground and by virtue of not introducing too much divergence from 11 code, this seems OK to me.

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Marked as reviewed by sgehwolf (Reviewer).

PR Review: https://git.openjdk.org/jdk8u/pull/43#pullrequestreview-1493616719