Converting from GB18030 encoded bytes to chars throws Exception #110521
Description
Description
Converting from GB18030 encoded data to string throws an exception in net9.
Reproduction Steps
This code throws the exception on net9 but not on net8.
using System.Text;
Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
var encoding = Encoding.GetEncoding("GB18030");
ReadOnlySpan<byte> encodedBytes = [0x95, 0x32, 0xB7, 0x37];
// This call throws, encoding GetString or GetChars as well.
var actual = encoding.GetCharCount(encodedBytes);
Console.WriteLine($"CharCount: {actual}");
var bytes = encoding.GetBytes("𠈓");
Console.WriteLine($"EncodedBytes of character match encodedBytes span: {bytes.AsSpan().SequenceEqual(encodedBytes)}");Expected behavior
The conversion from bytes to chars does not throw an exception.
Actual behavior
Unhandled exception. System.ArgumentException: The output char buffer is too small to contain the decoded characters, encoding 'Chinese Simplified (GB18030)' fallback 'System.Text.DecoderReplacementFallback'. (Parameter 'chars')
at System.Text.EncodingNLS.ThrowCharsOverflow()
at System.Text.EncodingNLS.ThrowCharsOverflow(DecoderNLS decoder, Boolean nothingDecoded)
at System.Text.EncodingCharBuffer.AddChar(Char ch1, Char ch2, Int32 numBytes)
at System.Text.GB18030Encoding.GetChars(Byte* bytes, Int32 byteCount, Char* chars, Int32 charCount, DecoderNLS baseDecoder)
at System.Text.GB18030Encoding.GetCharCount(Byte* bytes, Int32 count, DecoderNLS baseDecoder)
at System.Text.Encoding.GetCharCount(ReadOnlySpan`1 bytes)
at Program.<Main>$(String[] args) in C:\git\Receiver\SYC_Appliance\Test\GB18030DecodeFailure\Program.cs:line 12
Regression?
Yes
Known Workarounds
none
Configuration
.net 9
Windows
x64
Other information
There was a change (861164c) that modified the if statement in EncodingCharBuffer.AddChar. Maybe the logic for uninitialized chars and "counting" has changed.