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Attempts to move the current position indicator of the controlled input sequence back to the character that precedes the current one.
Member function sungetc behaves in a similar way, but without taking any arguments.
Internally, the function calls the virtual protected member pbackfail if either there are no putback positions available at the get pointer (gptr), or if c does not match the character right before the current get position. Otherwise, the function uses the get pointer (gptr) directly, without calling virtual member functions.
Its behavior is the same as if implemented as:
The function returns the end-of-file value (
Member type int_type is an integral type able to represent any character value or the special end-of-file value.
This example gets characters form the standard input one by one. When the first numeric digit is found, sputback is called to restore the position in the stream to that digit in order to be extracted as part of a number using the extraction operator
Concurrent access to the same stream buffer object may introduce data races.
Reference
C library:
- <cassert> (assert.h)
- <cctype> (ctype.h)
- <cerrno> (errno.h)
-
<cfenv> (fenv.h)C++11
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<cstdbool> (stdbool.h)C++11
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<ctgmath> (tgmath.h)C++11
- <ctime> (time.h)
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<cuchar> (uchar.h)C++11
- <cwchar> (wchar.h)
- <cwctype> (wctype.h)
Containers:
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<array>C++11
- <deque>
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<forward_list>C++11
- <list>
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<unordered_map>C++11
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<unordered_set>C++11
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Input/Output:
Multi-threading:
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<atomic>C++11
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<future>C++11
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Other:
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basic_streambuf
- basic_streambuf::~basic_streambuf
- basic_streambuf::basic_streambuf
public members
- basic_streambuf::getloc
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- 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
- sputbackc
public member function
<streambuf> <iostream>
std::basic_streambuf::sputbackc
int_type sputbackc (char_type c);
Put character back
Member function sungetc behaves in a similar way, but without taking any arguments.
Internally, the function calls the virtual protected member pbackfail if either there are no putback positions available at the get pointer (gptr), or if c does not match the character right before the current get position. Otherwise, the function uses the get pointer (gptr) directly, without calling virtual member functions.
Its behavior is the same as if implemented as:
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Parameters
- c
- Character to be put back.
If this does not match the character at the put back position, the behavior depends on the pbackfail: it may either fail, be ignored, or override the character at that position.
Member type char_type is the type of the characters in the stream buffer (the first class template parameter).
Return Value
The value of the character put back, converted to a value of type int_type using member traits_type::to_int_type.The function returns the end-of-file value (
traits_type::eof()) on failure.Member type int_type is an integral type able to represent any character value or the special end-of-file value.
Example
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This example gets characters form the standard input one by one. When the first numeric digit is found, sputback is called to restore the position in the stream to that digit in order to be extracted as part of a number using the extraction operator
>>.Data races
Modifies the stream buffer object.Concurrent access to the same stream buffer object may introduce data races.
Exception safety
Basic guarantee: if an exception is thrown, the stream buffer is in a valid state (this also applies to standard derived classes).See also
- basic_streambuf::sungetc
- Decrease current position (public member function)
- basic_streambuf::sgetc
- Get current character (public member function)
- basic_streambuf::sbumpc
- Get current character and advance to next position (public member function)
- basic_streambuf::sputc
- Put character and advance to next position (public member function)
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