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Virtual function (to be read s-how-many-c) called by other member functions to get an estimate on the number of characters available in the associated input sequence.
It is called by public member function basic_streambuf::in_avail when there are no read positions available at the get pointer (gptr).
The return value provides information on the possible behavior of the protected member functions underflow and uflow:
Its default behavior in basic_streambuf is to always return zero. basic_filebuf overrides this member function (see basic_filebuf::showmanyc).
streamsize is a signed integral type.
Reference
C library:
- <cassert> (assert.h)
- <cctype> (ctype.h)
- <cerrno> (errno.h)
-
<cfenv> (fenv.h)C++11
- <cfloat> (float.h)
-
<cinttypes> (inttypes.h)C++11
- <ciso646> (iso646.h)
- <climits> (limits.h)
- <clocale> (locale.h)
- <cmath> (math.h)
- <csetjmp> (setjmp.h)
- <csignal> (signal.h)
- <cstdarg> (stdarg.h)
-
<cstdbool> (stdbool.h)C++11
- <cstddef> (stddef.h)
-
<cstdint> (stdint.h)C++11
- <cstdio> (stdio.h)
- <cstdlib> (stdlib.h)
- <cstring> (string.h)
-
<ctgmath> (tgmath.h)C++11
- <ctime> (time.h)
-
<cuchar> (uchar.h)C++11
- <cwchar> (wchar.h)
- <cwctype> (wctype.h)
Containers:
-
<array>C++11
- <deque>
-
<forward_list>C++11
- <list>
- <map>
- <queue>
- <set>
- <stack>
-
<unordered_map>C++11
-
<unordered_set>C++11
- <vector>
-
Input/Output:
Multi-threading:
-
<atomic>C++11
-
<condition_variable>C++11
-
<future>C++11
-
<mutex>C++11
-
<thread>C++11
-
Other:
- <algorithm>
- <bitset>
-
<chrono>C++11
-
<codecvt>C++11
- <complex>
- <exception>
- <functional>
-
<initializer_list>C++11
- <iterator>
- <limits>
- <locale>
- <memory>
- <new>
- <numeric>
-
<random>C++11
-
<ratio>C++11
-
<regex>C++11
- <stdexcept>
- <string>
-
<system_error>C++11
-
<tuple>C++11
-
<type_traits>C++11
-
<typeindex>C++11
- <typeinfo>
- <utility>
- <valarray>
basic_streambuf
- basic_streambuf::~basic_streambuf
- basic_streambuf::basic_streambuf
public members
- basic_streambuf::getloc
- basic_streambuf::in_avail
- basic_streambuf::pubimbue
- basic_streambuf::pubseekoff
- basic_streambuf::pubseekpos
- basic_streambuf::pubsetbuf
- basic_streambuf::pubsync
- basic_streambuf::sbumpc
- basic_streambuf::sgetc
- basic_streambuf::sgetn
- basic_streambuf::snextc
- basic_streambuf::sputbackc
- basic_streambuf::sputc
- basic_streambuf::sputn
- basic_streambuf::sungetc
protected members
virtual protected members
- Reference
- <streambuf>
- basic_streambuf
- showmanyc
protected virtual member function
<streambuf> <iostream>
std::basic_streambuf::showmanyc
streamsize showmanyc();
Get number of characters available
It is called by public member function basic_streambuf::in_avail when there are no read positions available at the get pointer (gptr).
The return value provides information on the possible behavior of the protected member functions underflow and uflow:
| return value | description | expected behavior for underflow and uflow |
|---|---|---|
>0 | characters known to be available | Successive calls will succeed in retrieving characters until at least as many characters as the value returned have been extracted. |
0 | no information | Further calls may either retrieve more characters or return traits_type::eof(). |
-1 | sequence unavailable | Further calls will fail (either throwing or returning "immediately"). |
Its default behavior in basic_streambuf is to always return zero. basic_filebuf overrides this member function (see basic_filebuf::showmanyc).
Parameters
noneReturn Value
Returns zero.streamsize is a signed integral type.
Data races
Introduces no data races, but overriden versions in derived classes may.Exception safety
No-throw guarantee: this default definition never throws exceptions.See also
- basic_streambuf::in_avail
- Get number of character available to read (public member function)
- basic_streambuf::underflow
- Get character on underflow (protected virtual member function)
- basic_streambuf::uflow
- Get character on underflow and advance position (protected virtual member function)
- basic_filebuf::showmanyc
- Get number of characters available (public member function)
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Spotted an error? contact us