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[libc++] Refactor basic_filebuf::overflow() #144793

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Merged
merged 2 commits into from
Jun 24, 2025
Merged

[libc++] Refactor basic_filebuf::overflow() #144793

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[libc++] Refactor basic_filebuf::overflow()
ldionne Jun 17, 2025
98f6169
Use early return
ldionne Jun 20, 2025
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57 changes: 36 additions & 21 deletions libcxx/include/fstream
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Original file line number Diff line number Diff line change
Expand Up @@ -835,35 +835,50 @@ typename basic_filebuf<_CharT, _Traits>::int_type basic_filebuf<_CharT, _Traits>
}
if (this->pptr() != this->pbase()) {
if (__always_noconv_) {
size_t __nmemb = static_cast<size_t>(this->pptr() - this->pbase());
if (std::fwrite(this->pbase(), sizeof(char_type), __nmemb, __file_) != __nmemb)
size_t __n = static_cast<size_t>(this->pptr() - this->pbase());
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@philnik777 philnik777 Jun 19, 2025

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Maybe name this __put_buffer_size?

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@ldionne ldionne Jun 20, 2025

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Hmm. This isn't really the size of the put area though, as that would be epptr() - pbase(). This is really the number of characters inside the put area that we want to write to the underlying file stream.

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@philnik777 philnik777 Jun 23, 2025

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Wouldn't epptr() - pbase() be the capacity? Maybe the terminology is ambiguous here.

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@ldionne ldionne Jun 24, 2025

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Yes, I guess if you use vector terminology, then epptr() - pbase() would be the capacity, and pptr() - pbase() would be the size. But here __n also corresponds to the number of characters we want to commit, which is why I kinda like __n.

I am fine with renaming this post-commit if we find something better.

if (std::fwrite(this->pbase(), sizeof(char_type), __n, __file_) != __n)
return traits_type::eof();
} else {
char* __extbe = __extbuf_;
codecvt_base::result __r;
if (!__cv_)
std::__throw_bad_cast();

// See [filebuf.virtuals]
char_type* __b = this->pbase();
char_type* __p = this->pptr();
const char_type* __end;
char* __extbuf_end = __extbuf_;
do {
if (!__cv_)
std::__throw_bad_cast();

const char_type* __e;
__r = __cv_->out(__st_, this->pbase(), this->pptr(), __e, __extbuf_, __extbuf_ + __ebs_, __extbe);
if (__e == this->pbase())
codecvt_base::result __r = __cv_->out(__st_, __b, __p, __end, __extbuf_, __extbuf_ + __ebs_, __extbuf_end);
if (__end == __b)
return traits_type::eof();

// No conversion needed: output characters directly to the file, done.
if (__r == codecvt_base::noconv) {
size_t __nmemb = static_cast<size_t>(this->pptr() - this->pbase());
if (std::fwrite(this->pbase(), 1, __nmemb, __file_) != __nmemb)
size_t __n = static_cast<size_t>(__p - __b);
if (std::fwrite(__b, 1, __n, __file_) != __n)
return traits_type::eof();
} else if (__r == codecvt_base::ok || __r == codecvt_base::partial) {
size_t __nmemb = static_cast<size_t>(__extbe - __extbuf_);
if (std::fwrite(__extbuf_, 1, __nmemb, __file_) != __nmemb)
break;

// Conversion successful: output the converted characters to the file, done.
} else if (__r == codecvt_base::ok) {
size_t __n = static_cast<size_t>(__extbuf_end - __extbuf_);
if (std::fwrite(__extbuf_, 1, __n, __file_) != __n)
return traits_type::eof();
break;

// Conversion partially successful: output converted characters to the file and repeat with the
// remaining characters.
} else if (__r == codecvt_base::partial) {
size_t __n = static_cast<size_t>(__extbuf_end - __extbuf_);
if (std::fwrite(__extbuf_, 1, __n, __file_) != __n)
return traits_type::eof();
if (__r == codecvt_base::partial) {
this->setp(const_cast<char_type*>(__e), this->pptr());
this->__pbump(this->epptr() - this->pbase());
}
} else
__b = const_cast<char_type*>(__end);
continue;

} else {
return traits_type::eof();
} while (__r == codecvt_base::partial);
}
} while (true);
}
this->setp(__pb_save, __epb_save);
}
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