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+[streambuf.virtuals]
+
+# 31 Input/output library [[input.output]](./#input.output)
+
+## 31.6 Stream buffers [[stream.buffers]](stream.buffers#streambuf.virtuals)
+
+### 31.6.3 Class template basic_streambuf [[streambuf]](streambuf#virtuals)
+
+#### 31.6.3.5 Virtual functions [streambuf.virtuals]
+
+#### [31.6.3.5.1](#streambuf.virt.locales) Locales [[streambuf.virt.locales]](streambuf.virt.locales)
+
+[ð](#lib:imbue,basic_streambuf)
+
+`void imbue(const locale&);
+`
+
+[1](#streambuf.virt.locales-1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3594)
+
+*Effects*: Change any translations based on locale[.](#streambuf.virt.locales-1.sentence-1)
+
+[2](#streambuf.virt.locales-2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3598)
+
+*Remarks*: Allows the derived class to be informed of changes in locale at the
+time they occur[.](#streambuf.virt.locales-2.sentence-1)
+
+Between invocations of this function a class derived
+from streambuf can safely cache results of calls to locale functions
+and to members of facets so obtained[.](#streambuf.virt.locales-2.sentence-2)
+
+[3](#streambuf.virt.locales-3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3606)
+
+*Default behavior*: Does nothing[.](#streambuf.virt.locales-3.sentence-1)
+
+#### [31.6.3.5.2](#streambuf.virt.buffer) Buffer management and positioning [[streambuf.virt.buffer]](streambuf.virt.buffer)
+
+[ð](#lib:setbuf,basic_streambuf)
+
+`basic_streambuf* setbuf(char_type* s, streamsize n);
+`
+
+[1](#streambuf.virt.buffer-1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3619)
+
+*Effects*: Influences stream buffering in a way that is defined separately for each class
+derived frombasic_streambuf in this Clause ([[stringbuf.virtuals]](stringbuf.virtuals "31.8.2.5 Overridden virtual functions"), [[filebuf.virtuals]](filebuf.virtuals "31.10.3.5 Overridden virtual functions"))[.](#streambuf.virt.buffer-1.sentence-1)
+
+[2](#streambuf.virt.buffer-2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3626)
+
+*Default behavior*: Does nothing[.](#streambuf.virt.buffer-2.sentence-1)
+
+Returnsthis[.](#streambuf.virt.buffer-2.sentence-2)
+
+[ð](#lib:seekoff,basic_streambuf)
+
+`pos_type seekoff(off_type off, ios_base::seekdir way,
+                 ios_base::openmode which
+                   = ios_base::in | ios_base::out);
+`
+
+[3](#streambuf.virt.buffer-3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3641)
+
+*Effects*: Alters the stream positions within one or more of
+the controlled sequences in a way that is defined separately for each class
+derived frombasic_streambuf in this Clause ([[stringbuf.virtuals]](stringbuf.virtuals "31.8.2.5 Overridden virtual functions"), [[filebuf.virtuals]](filebuf.virtuals "31.10.3.5 Overridden virtual functions"))[.](#streambuf.virt.buffer-3.sentence-1)
+
+[4](#streambuf.virt.buffer-4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3649)
+
+*Default behavior*: Returnspos_type(off_type(-1))[.](#streambuf.virt.buffer-4.sentence-1)
+
+[ð](#lib:seekpos,basic_streambuf)
+
+`pos_type seekpos(pos_type sp,
+                 ios_base::openmode which
+                   = ios_base::in | ios_base::out);
+`
+
+[5](#streambuf.virt.buffer-5)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3663)
+
+*Effects*: Alters the stream positions within one or more of
+the controlled sequences in a way that is defined separately for each class
+derived frombasic_streambuf in this Clause ([[stringbuf]](stringbuf "31.8.2 Class template basic_stringbuf"), [[filebuf]](filebuf "31.10.3 Class template basic_filebuf"))[.](#streambuf.virt.buffer-5.sentence-1)
+
+[6](#streambuf.virt.buffer-6)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3671)
+
+*Default behavior*: Returnspos_type(off_type(-1))[.](#streambuf.virt.buffer-6.sentence-1)
+
+[ð](#lib:sync,basic_streambuf)
+
+`int sync();
+`
+
+[7](#streambuf.virt.buffer-7)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3683)
+
+*Effects*: Synchronizes the controlled sequences with the arrays[.](#streambuf.virt.buffer-7.sentence-1)
+
+That is, ifpbase() is non-null the characters betweenpbase() andpptr() are written to the controlled sequence[.](#streambuf.virt.buffer-7.sentence-2)
+
+The pointers may then be reset as appropriate[.](#streambuf.virt.buffer-7.sentence-3)
+
+[8](#streambuf.virt.buffer-8)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3695)
+
+*Returns*: -1 on failure[.](#streambuf.virt.buffer-8.sentence-1)
+
+What constitutes failure is determined by each derived class ([[filebuf.virtuals]](filebuf.virtuals "31.10.3.5 Overridden virtual functions"))[.](#streambuf.virt.buffer-8.sentence-2)
+
+[9](#streambuf.virt.buffer-9)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3700)
+
+*Default behavior*: Returns zero[.](#streambuf.virt.buffer-9.sentence-1)
+
+#### [31.6.3.5.3](#streambuf.virt.get) Get area [[streambuf.virt.get]](streambuf.virt.get)
+
+[ð](#lib:showmanyc,basic_streambuf)
+
+`streamsize showmanyc();[267](#footnote-267 "The morphemes of showmanyc are âes-how-many-seeâ, not âshow-manicâ.")
+`
+
+[1](#streambuf.virt.get-1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3716)
+
+*Returns*: An estimate of the number of
+characters available in the sequence, or â1[.](#streambuf.virt.get-1.sentence-1)
+
+If it returns
+a positive value, then successive calls tounderflow() will not returntraits::eof() until at least that number of characters have been
+extracted from the stream[.](#streambuf.virt.get-1.sentence-2)
+
+Ifshowmanyc() returns â1, then calls tounderflow() oruflow() will fail[.](#streambuf.virt.get-1.sentence-3)[268](#footnote-268 "underflow or uflow can fail by throwing an exception prematurely. The intention is not only that the calls will not return eof() but that they will return âimmediatelyâ.")
+
+[2](#streambuf.virt.get-2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3744)
+
+*Default behavior*: Returns zero[.](#streambuf.virt.get-2.sentence-1)
+
+[3](#streambuf.virt.get-3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3748)
+
+*Remarks*: Usestraits::eof()[.](#streambuf.virt.get-3.sentence-1)
+
+[ð](#lib:xsgetn,basic_streambuf)
+
+`streamsize xsgetn(char_type* s, streamsize n);
+`
+
+[4](#streambuf.virt.get-4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3760)
+
+*Effects*: Assigns up to n characters to successive elements of
+the array whose first element is designated by s[.](#streambuf.virt.get-4.sentence-1)
+
+The characters assigned are read from the input sequence as if
+by repeated calls tosbumpc()[.](#streambuf.virt.get-4.sentence-2)
+
+Assigning stops when either n characters
+have been assigned or a call tosbumpc() would returntraits::eof()[.](#streambuf.virt.get-4.sentence-3)
+
+[5](#streambuf.virt.get-5)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3773)
+
+*Returns*: The number of characters assigned[.](#streambuf.virt.get-5.sentence-1)[269](#footnote-269 "Classes derived from basic_streambuf can provide more efficient ways to implement xsgetn() and xsputn() by overriding these definitions from the base class.")
+
+[6](#streambuf.virt.get-6)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3786)
+
+*Remarks*: Usestraits::eof()[.](#streambuf.virt.get-6.sentence-1)
+
+[ð](#lib:underflow,basic_streambuf)
+
+`int_type underflow();
+`
+
+[7](#streambuf.virt.get-7)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3798)
+
+The[*pending sequence*](#def:pending_sequence) of characters is defined as the concatenation of
+
+- [(7.1)](#streambuf.virt.get-7.1)
+
+the empty sequence if gptr() is null, otherwise the
+characters in
+[gptr(), egptr()),
+followed by
+
+- [(7.2)](#streambuf.virt.get-7.2)
+
+some (possibly empty) sequence of characters read from the input sequence[.](#streambuf.virt.get-7.sentence-1)
+
+[8](#streambuf.virt.get-8)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3811)
+
+The[*result character*](#def:result_character) is
+the first character of the pending sequence if it is non-empty,
+otherwise
+the next character that would be read from the input sequence[.](#streambuf.virt.get-8.sentence-1)
+
+[9](#streambuf.virt.get-9)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3819)
+
+The[*backup sequence*](#def:backup_sequence) is the empty sequence if eback() is null, otherwise the
+characters in
+[eback(), gptr())[.](#streambuf.virt.get-9.sentence-1)
+
+[10](#streambuf.virt.get-10)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3826)
+
+*Effects*: The function sets up thegptr() andegptr() such that
+if the pending sequence is non-empty, thenegptr() is non-null and
+the characters in [gptr(), egptr()) are
+the characters in the pending sequence,
+otherwise
+either gptr() is null orgptr() == egptr()[.](#streambuf.virt.get-10.sentence-1)
+
+[11](#streambuf.virt.get-11)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3843)
+
+Ifeback() andgptr() are non-null then the function is not constrained as to their contents, but the âusual backup conditionâ is that either
+
+- [(11.1)](#streambuf.virt.get-11.1)
+
+the backup sequence contains at leastgptr() - eback() characters, in which case the characters in
+[eback(), gptr())
+agree with the lastgptr() - eback() characters of the backup sequence, or
+
+- [(11.2)](#streambuf.virt.get-11.2)
+
+the characters in [gptr() - n, gptr())
+agree with the backup sequence (where n is the length of the backup sequence)[.](#streambuf.virt.get-11.sentence-1)
+
+[12](#streambuf.virt.get-12)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3863)
+
+*Returns*: traits::to_int_type(c),
+where c is the first*character* of the[*pending sequence*](#def:pending_sequence),
+without moving the input sequence position past it[.](#streambuf.virt.get-12.sentence-1)
+
+If the pending sequence is null then the function returnstraits::eof() to indicate failure[.](#streambuf.virt.get-12.sentence-2)
+
+[13](#streambuf.virt.get-13)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3875)
+
+*Default behavior*: Returnstraits::eof()[.](#streambuf.virt.get-13.sentence-1)
+
+[14](#streambuf.virt.get-14)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3880)
+
+*Remarks*: The public members ofbasic_streambuf call this virtual function only ifgptr() is null orgptr() >= egptr()[.](#streambuf.virt.get-14.sentence-1)
+
+[ð](#lib:uflow,basic_streambuf)
+
+`int_type uflow();
+`
+
+[15](#streambuf.virt.get-15)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3896)
+
+*Preconditions*: The constraints are the same as forunderflow(),
+except that the result character is transferred from the pending
+sequence to the backup sequence, and the pending sequence is not empty before the transfer[.](#streambuf.virt.get-15.sentence-1)
+
+[16](#streambuf.virt.get-16)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3903)
+
+*Default behavior*: Callsunderflow()[.](#streambuf.virt.get-16.sentence-1)
+
+Ifunderflow() returnstraits::eof(),
+returnstraits::eof()[.](#streambuf.virt.get-16.sentence-2)
+
+Otherwise, returns the value oftraits::to_int_type(*gptr()) and increments the value of the next pointer for the input sequence[.](#streambuf.virt.get-16.sentence-3)
+
+[17](#streambuf.virt.get-17)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3917)
+
+*Returns*: traits::eof() to indicate failure[.](#streambuf.virt.get-17.sentence-1)
+
+[267)](#footnote-267)[267)](#footnoteref-267)
+
+The morphemes of showmanyc are âes-how-many-seeâ, not âshow-manicâ[.](#footnote-267.sentence-1)
+
+[268)](#footnote-268)[268)](#footnoteref-268)
+
+underflow oruflow can fail by throwing an exception prematurely[.](#footnote-268.sentence-1)
+
+The intention is not only that the calls will not returneof() but that they will return âimmediatelyâ[.](#footnote-268.sentence-2)
+
+[269)](#footnote-269)[269)](#footnoteref-269)
+
+Classes derived frombasic_streambuf can provide more efficient ways to implementxsgetn() andxsputn() by overriding these definitions from the base class[.](#footnote-269.sentence-1)
+
+#### [31.6.3.5.4](#streambuf.virt.pback) Putback [[streambuf.virt.pback]](streambuf.virt.pback)
+
+[ð](#lib:pbackfail,basic_streambuf)
+
+`int_type pbackfail(int_type c = traits::eof());
+`
+
+[1](#streambuf.virt.pback-1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3931)
+
+The[*pending sequence*](#def:pending_sequence) is defined as forunderflow(),
+with the modifications that
+
+- [(1.1)](#streambuf.virt.pback-1.1)
+
+  Iftraits::eq_int_type(c, traits::eof()) returnstrue,
+then the input sequence is backed up one character before the pending sequence is determined[.](#streambuf.virt.pback-1.1.sentence-1)
+
+- [(1.2)](#streambuf.virt.pback-1.2)
+
+  Iftraits::eq_int_type(c, traits::eof()) returns false, then c is prepended[.](#streambuf.virt.pback-1.2.sentence-1)
+  Whether the input sequence is backed up or modified in any other way is unspecified[.](#streambuf.virt.pback-1.2.sentence-2)
+
+[2](#streambuf.virt.pback-2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3951)
+
+*Postconditions*: On return, the constraints ofgptr(),eback(),
+andpptr() are the same as forunderflow()[.](#streambuf.virt.pback-2.sentence-1)
+
+[3](#streambuf.virt.pback-3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3961)
+
+*Returns*: traits::eof() to indicate failure[.](#streambuf.virt.pback-3.sentence-1)
+
+Failure may occur because the input sequence could not be backed up, or if for some
+other reason the pointers cannot be set consistent with the constraints[.](#streambuf.virt.pback-3.sentence-2)
+
+pbackfail() is called only when put back has really failed[.](#streambuf.virt.pback-3.sentence-3)
+
+[4](#streambuf.virt.pback-4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3970)
+
+Returns some value other thantraits::eof() to indicate success[.](#streambuf.virt.pback-4.sentence-1)
+
+[5](#streambuf.virt.pback-5)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3975)
+
+*Default behavior*: Returnstraits::eof()[.](#streambuf.virt.pback-5.sentence-1)
+
+[6](#streambuf.virt.pback-6)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3980)
+
+*Remarks*: The public functions ofbasic_streambuf call this virtual function only whengptr() is null,gptr() == eback(),
+ortraits::eq(traits::to_char_type(c), gptr()[-1]) returnsfalse[.](#streambuf.virt.pback-6.sentence-1)
+
+Other calls shall also satisfy that constraint[.](#streambuf.virt.pback-6.sentence-2)
+
+#### [31.6.3.5.5](#streambuf.virt.put) Put area [[streambuf.virt.put]](streambuf.virt.put)
+
+[ð](#lib:xsputn,basic_streambuf)
+
+`streamsize xsputn(const char_type* s, streamsize n);
+`
+
+[1](#streambuf.virt.put-1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L4003)
+
+*Effects*: Writes up to n characters to the output sequence as if
+by repeated calls tosputc(c)[.](#streambuf.virt.put-1.sentence-1)
+
+The characters written are obtained from successive elements of
+the array whose first element is designated by s[.](#streambuf.virt.put-1.sentence-2)
+
+Writing stops when either n characters have been written or
+a call tosputc(c) would returntraits::eof()[.](#streambuf.virt.put-1.sentence-3)
+
+It is unspecified whether the function calls overflow() when pptr() == epptr() becomes true or whether it achieves the same effects by other means[.](#streambuf.virt.put-1.sentence-4)
+
+[2](#streambuf.virt.put-2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L4017)
+
+*Returns*: The number of characters written[.](#streambuf.virt.put-2.sentence-1)
+
+[ð](#lib:overflow,basic_streambuf)
+
+`int_type overflow(int_type c = traits::eof());
+`
+
+[3](#streambuf.virt.put-3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L4028)
+
+*Effects*: Consumes some initial subsequence of the characters of the[*pending sequence*](#def:pending_sequence)[.](#streambuf.virt.put-3.sentence-1)
+
+The pending sequence is defined as the concatenation of
+
+- [(3.1)](#streambuf.virt.put-3.1)
+
+the empty sequence if pbase() is null, otherwise thepptr() - pbase() characters beginning atpbase(), followed by
+
+- [(3.2)](#streambuf.virt.put-3.2)
+
+the empty sequence
+iftraits::eq_int_type(c, traits::eof()) returnstrue, otherwise the sequence consisting of c[.](#streambuf.virt.put-3.sentence-2)
+
+[4](#streambuf.virt.put-4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L4047)
+
+*Preconditions*: Every overriding definition of this virtual function
+obeys the following constraints:
+
+- [(4.1)](#streambuf.virt.put-4.1)
+
+  The effect of consuming a character on the associated output sequence is
+specified[.](#streambuf.virt.put-4.1.sentence-1)[270](#footnote-270 "That is, for each class derived from a specialization of basic_streambuf in this Clause ([stringbuf], [filebuf]), a specification of how consuming a character effects the associated output sequence is given. There is no requirement on a program-defined class.")
+
+- [(4.2)](#streambuf.virt.put-4.2)
+
+  Letr be the number of characters in the pending sequence not consumed[.](#streambuf.virt.put-4.2.sentence-1)
+  Ifr is nonzero thenpbase() andpptr() are set so that:pptr() - pbase() == r and the r characters starting atpbase() are the associated output stream[.](#streambuf.virt.put-4.2.sentence-2)
+  In case r is zero (all characters of the pending sequence have been consumed)
+then eitherpbase() is set tonullptr,
+orpbase() andpptr() are both set to the same non-null value[.](#streambuf.virt.put-4.2.sentence-3)
+
+- [(4.3)](#streambuf.virt.put-4.3)
+
+  The function may fail if either
+appending some character to the associated output stream fails or
+if it is unable to establishpbase() andpptr() according to the above rules[.](#streambuf.virt.put-4.3.sentence-1)
+
+[5](#streambuf.virt.put-5)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L4097)
+
+*Returns*: traits::eof() or throws an exception
+if the function fails[.](#streambuf.virt.put-5.sentence-1)
+
+Otherwise,
+returns some value other thantraits::eof() to indicate success[.](#streambuf.virt.put-5.sentence-2)[271](#footnote-271 "Typically, overflow returns c to indicate success, except when traits::eq_int_type(c, traits::eof()) returns true, in which case it returns traits::not_eof(c).")
+
+[6](#streambuf.virt.put-6)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L4118)
+
+*Default behavior*: Returnstraits::eof()[.](#streambuf.virt.put-6.sentence-1)
+
+[7](#streambuf.virt.put-7)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L4123)
+
+*Remarks*: The member functionssputc() andsputn() call this function in case that
+no room can be found in the put buffer enough to accommodate the
+argument character sequence[.](#streambuf.virt.put-7.sentence-1)
+
+[270)](#footnote-270)[270)](#footnoteref-270)
+
+That is, for each class derived from a specialization ofbasic_streambuf in this Clause ([[stringbuf]](stringbuf "31.8.2 Class template basic_stringbuf"), [[filebuf]](filebuf "31.10.3 Class template basic_filebuf")),
+a specification of how consuming a character effects the associated output sequence is given[.](#footnote-270.sentence-1)
+
+There is no requirement on a program-defined class[.](#footnote-270.sentence-2)
+
+[271)](#footnote-271)[271)](#footnoteref-271)
+
+Typically,overflow returns c to indicate success, except whentraits::eq_int_type(c, traits::eof()) returnstrue,
+in which case it returnstraits::not_eof(c)[.](#footnote-271.sentence-1)