> Strings, after construction, are immutable but may be constructed from 
> mutable arrays of bytes, characters, or integers.
> The string constructors should guard against the effects of mutating the 
> arrays during construction that might invalidate internal invariants for the 
> correct behavior of operations on the resulting strings. In particular, a 
> number of operations have optimizations for operations on pairs of latin1 
> strings and pairs of non-latin1 strings, while operations between latin1 and 
> non-latin1 strings use a more general implementation. 
> 
> The changes include:
> 
> - Adding a warning to each constructor with an array as an argument to 
> indicate that the results are indeterminate 
>   if the input array is modified before the constructor returns. 
>   The resulting string may contain any combination of characters sampled from 
> the input array.
> 
> - Ensure that strings that are represented as non-latin1 contain at least one 
> non-latin1 character.
>   For latin1 inputs, whether the arrays contain ASCII, ISO-8859-1, UTF8, or 
> another encoding decoded to latin1 the scanning and compression is unchanged.
>   If a non-latin1 character is found, the string is represented as non-latin1 
> with the added verification that a non-latin1 character is present at the 
> same index.
>   If that character is found to be latin1, then the input array has been 
> modified and the result of the scan may be incorrect.
>   Though a ConcurrentModificationException could be thrown, the risk to an 
> existing application of an unexpected exception should be avoided.
>   Instead, the non-latin1 copy of the input is re-scanned and compressed; 
> that scan determines whether the latin1 or the non-latin1 representation is 
> returned.
> 
> - The methods that scan for non-latin1 characters and their intrinsic 
> implementations are updated to return the index of the non-latin1 character.
> 
> - String construction from StringBuilder and CharSequence must also be 
> guarded as their contents may be modified during construction.

Roger Riggs has updated the pull request incrementally with two additional 
commits since the last revision:

 - Merge pull request #4 from cl4es/8311906_x64_intr_opt
   
   Simplified and slightly optimized x86 char_array_compress
 - Simplified and slightly optimized x86 char_array_compress

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/16425/files
  - new: https://git.openjdk.org/jdk/pull/16425/files/04d58779..0256b9e0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16425&range=10
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16425&range=09-10

  Stats: 61 lines in 1 file changed: 7 ins; 20 del; 34 mod
  Patch: https://git.openjdk.org/jdk/pull/16425.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16425/head:pull/16425

PR: https://git.openjdk.org/jdk/pull/16425

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