Use Encoder instead of Encoding in CsvParser #2106
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This improves the ByteCount logic when consuming surrogate characters because the Encoder maintains state across calls. Previously the default behaviour was that the Encoding would return the byte count having replaced the surrogate character with U+FFFD REPLACEMENT CHARACTER because on its own a surrogate character is invalid. For example, when reading the UTF-16 surrogate pair \uD83D\uDE17 corresponding to the Unicode character U+1F617, the (UTF-8) ByteCount would be 6 (the byte count of the sequence \uFFFD\uFFFD) instead of the correct value of 4 UTF-8 bytes.
An encoder with a custom EncoderReplacementFallback could easily require
a larger buffer, for example if its replacement string is "{LONG REPLACEMENT STRING}".
So the upper-bound of 16 bytes is not correct. Note that in this case
CsvParser.ByteCount would be nonsensical for input requiring the fallback, and
configuration.Encoding probably does not match the actual encoding, e.g we are reading
from a UTF-16 byte stream containing non-ASCII characters and we have set
configuration.Encoding to ASCII.
Nevertheless the safeguard is more sensible to have than not.
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I'm going to wait on this for now. I believe the SIMD code will completely change how this works. I will be counting blocks of bytes at a time instead of single characters. |
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closes #2088