stevedlawrence commented on code in PR #1603:
URL: https://github.com/apache/daffodil/pull/1603#discussion_r2627353381
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daffodil-core/src/main/scala/org/apache/daffodil/runtime1/processors/parsers/StringLengthParsers.scala:
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@@ -86,8 +87,25 @@ trait StringOfSpecifiedLengthMixin extends
PaddingRuntimeMixin with CaptureParsi
protected final def parseString(start: PState): String = {
val dis = start.dataInputStream
- val maxLen = start.tunable.maximumSimpleElementSizeInCharacters
val startBitPos0b = dis.bitPos0b
+ val bitLimit0b = dis.bitLimit0b
+
+ // We want to limit the maximum length passed into getSomeString since
that function can
+ // pre-allocate a buffer that size even if it won't find that many
characters. So we
+ // calculate the maximum number of characters that we could possibly
decode based on the
+ // number of a available bits and the character set. Note that some
character sets have
+ // variable width encodings, so we can't always know for sure how many
characters will be
+ // found. But we can calculate a maximum based on the smallest possible
code unit for the
Review Comment:
The code isn't calculating the maximum width, it's calculating the maximum
number of characters that the available number of bits/bytes could decode to.
With UTF8, we get the maximum number of characters with the minimum single
character length. So N bytes could potentially decode to N characters. It might
decode to less characters if there are any multibte chars, but it can't
possible decode to more than N characters.
I'll update this comment to make this more clear.
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