Bug 10692 - Buggy implementation of Decoder.Convert() method
Summary: Buggy implementation of Decoder.Convert() method
Alias: None
Product: Class Libraries
Classification: Mono
Component: mscorlib ()
Version: unspecified
Hardware: All All
: --- normal
Target Milestone: Untriaged
Assignee: marcos.henrich
Depends on:
Reported: 2013-02-26 12:28 UTC by Gerardo García Peña
Modified: 2016-02-15 17:49 UTC (History)
2 users (show)

Is this bug a regression?: ---
Last known good build:

a test case with the different behaviour seen in Mono and MS.NET (1.99 KB, application/x-zip-compressed)
2013-02-26 12:29 UTC, Gerardo García Peña

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Description Gerardo García Peña 2013-02-26 12:28:10 UTC
The Mono implementation of Decoder.Convert() method differs from the Microsoft .NET implementation and of its expected behaviour.

If we read the following byte stream with the microsoft implementation:

  0x20 0xC3 0xA1 0xC3 0xA9

  We read
    - byte 0x20 and character ' '
    - bytes 0xC3 0xA1 and character 'á'
    - bytes 0xC3 0xA9 and character 'é'

But with the same code (or binary) using the mono class libraries we obtain the following behaviour:

  We read
    - byte 0x20 0xC3 and get the char ' ' (?)
    - bytes 0xA1 0xC3 and we get tha char 'á' (???)
    - byte 0xA9 and now we got 'é' (??WHAT??)

It seems that the Mono implementation of Convert is broken twice:

  - it does not honour the 'flush()' flag -- which makes possible to decode the shown byte stream in this way
  - and consumes more bytes of needed when is decoding a one-byte utf8 char.

I attach a simple test with the output of the Microsoft .NET execution (msnet) and the output of the same binary running under Mono. The binary is compiled with the 'mono-csc' compiler.
Comment 1 Gerardo García Peña 2013-02-26 12:29:34 UTC
Created attachment 3482 [details]
a test case with the different behaviour seen in Mono and MS.NET
Comment 2 marcos.henrich 2016-02-15 17:49:02 UTC
I ran the use case with mono 4.2, and the output was now identical to the one generated in .NET.