RFR: 8329623: NegativeArraySizeException encoding large String to UTF-8

[Roger Riggs]

On Mon, 8 Apr 2024 08:54:21 GMT, Raffaello Giulietti <rgiulietti at openjdk.org> wrote:

>> When encoding a vary large string in String.getBytes(StandardCharset.UTF_8) computation of the buffer size may exceed the range of a positive 32-bit Integer.
>> If the estimated size for the result byte array is too large, pre-compute the exact buffer size. 
>> If that exceeds the range, then throw OutOfMemoryError.
>
> test/jdk/java/lang/String/CompactString/MaxSizeUTF16String.java line 143:
> 
>> 141:         // Strings of size min+1...min+2, throw OOME
>> 142:         // The resulting byte array would exceed implementation limits
>> 143:         for (int count = min + 1; count < max; count++) {
> 
> The case `min + 1` cannot lead to a `NegativeArraySizeException` in the current code, since `3 * (min + 1) <= MAX_VALUE`. In theory, it should succeed by returning the encoded `byte[]`, although It throws `OOME` for exceeding VM limits. That is, this case does not trigger the invocation of `computeSizeUTF8_UTF16()` in the proposed fix.
> 
> Only `min + 2` throws `NegativeArraySizeException` in the current code, and thus the invocation of `computeSizeUTF8_UTF16()` in the proposed fix.

Indeed, different OOMEs are thrown in the two cases triggered by different limits, min +2 is due to integer overflow, while min +1  is due a VM limit on the size of byte[Integer.MAX_VALUE]. Different VM implementations may have different limits. on the max size of a byte array.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18663#discussion_r1555866610