How to get a shifted multibyte state

Krzysztof Żelechowski 41

1.Is it possible to perform a sequence of operations on a wide-character stream so that its multibyte status will become shifted?
2. If you perform an operation on a narrow-character stream under a multi-byte locale and that operation stops in the middle of a compound character, will its multibyte status become shifted?

David Lowndes 4,711 Reputation points

2020-10-03T22:12:32.99+00:00

I think you need to clarify your questions with more detail - it's not clear to me what you're asking.
Krzysztof Żelechowski 41 Reputation points

2020-10-03T22:24:29.067+00:00

If (s) is a stream then (s .tellg () .state ()) is its multibyte state. Using the codecvt facet of the stream’s locale, it is possible to test whether this state is shifted or not. Design an experiment where the expected result will be shifted.
Barrnet Zhou-MSFT 171 Reputation points

2020-10-05T08:07:39.837+00:00

I would appreciate it if you could describe the problem in more detail, such as the functions involved, your needs, the purpose and so on. @Krzysztof Żelechowski
Krzysztof Żelechowski 41 Reputation points

2020-10-05T16:47:50.117+00:00

The functions involved are istream ::tellg (), streampos ::state () and codecvt ::unshift (). I am trying to store stream position in a file — but the shift state cannot be stored in a file, so I need to make sure there is no shift.
Barrnet Zhou-MSFT 171 Reputation points

2020-10-07T07:29:58.083+00:00

I suggest that you could use _lseek and _tell to check the offset. _lseek(fd,0, SEEK_END) can move to the end of the file. _tell(fd) can detect where it is. @Krzysztof Żelechowski
Krzysztof Żelechowski 41 Reputation points

2020-10-07T11:01:19.367+00:00

I meant in C++, not in POSIX.
Barrnet Zhou-MSFT 171 Reputation points

2020-10-14T08:23:03.567+00:00

You could try to use mbstate_t and mbsinit. They are in C runtime library. @Krzysztof Żelechowski
Krzysztof Żelechowski 41 Reputation points

2020-10-14T11:23:53.527+00:00

How can I use mbsinit to get a shifted state?
Barrnet Zhou-MSFT 171 Reputation points

2020-10-15T06:23:17.097+00:00

You could refer to this link about mbsinit. @Krzysztof Żelechowski

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How to get a shifted multibyte state