This work has been split out from JDK-8328877: [JNI] The JNI Specification needs to address the limitations of integer UTF-8 String lengths
The modified UTF-8 format used by the VM can require up to six bytes to represent one unicode character, but six byte characters are stored as UTF-16 surrogate pairs. Hence the most bytes per character is 3, and so the maximum length is 3*`Integer.MAX_VALUE`. Though with compact strings this reduces to 2*`Integer.MAX_VALUE`. The low-level UTF8/UNICODE API should therefore define UTF8 lengths as `size_t` to accommodate all possible representations. Higher-level API's can still use `int` if they know the strings (eg symbols) are sufficiently constrained in length. See the comments in utf8.hpp that explain Strings, compact strings and the encoding. As the existing JNI `GetStringUTFLength` still requires the current truncating behaviour of ` UNICODE::utf8_length` we add back `UNICODE::utf8_length_as_int` for it to use. Note that some API's, like ` UNICODE::as_utf8(const T* base, size_t& length)` use `length` as an IN/OUT parameter: it is the incoming (int) length of the jbyte/jchar array, and the outgoing (size_t) length of the UTF8 sequence. This makes some of the call sites a little messy with casts. Testing: - tiers 1-4 - GHA ------------- Commit messages: - unnecessary cast - Fix comments - Fix off-by-one error - Rollback the GetLargeStringUTFLength addition. - Rollback the GetLargeStringUTFLength addition. - Initial commit before splitting out UTF8 changes Changes: https://git.openjdk.org/jdk/pull/20560/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20560&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8338257 Stats: 243 lines in 16 files changed: 116 ins; 5 del; 122 mod Patch: https://git.openjdk.org/jdk/pull/20560.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/20560/head:pull/20560 PR: https://git.openjdk.org/jdk/pull/20560
