Defined in header <iterator> | ||
---|---|---|
template< class CharT, class Traits = std::char_traits<CharT> > class istreambuf_iterator : public std::iterator< std::input_iterator_tag, CharT, typename Traits::off_type, /* unspecified, usually CharT* */, CharT > | (until C++17) | |
template< class CharT, class Traits = std::char_traits<CharT> > class istreambuf_iterator; | (since C++17) |
std::istreambuf_iterator
is a single-pass input iterator that reads successive characters from the std::basic_streambuf
object for which it was constructed. The actual read operation is performed when the iterator is incremented, not when it is dereferenced. The first character may be read when the iterator is constructed or when the first dereferencing is done. Otherwise, dereferencing only returns a copy of the most recently read character.
The default-constructed std::istreambuf_iterator
is known as the end-of-stream iterator. When a valid std::istreambuf_iterator
reaches the end of the underlying stream, it becomes equal to the end-of-stream iterator. Dereferencing or incrementing it further invokes undefined behavior.
std::istreambuf_iterator
has a trivial copy constructor, a constexpr default constructor, and a trivial destructor.
Member types
Member type | Definition |
---|---|
char_type | CharT |
traits_type | Traits |
int_type | typename traits::int_type |
streambuf_type | std::basic_streambuf<CharT, Traits> |
istream_type | std::basic_istream<CharT, Traits> |
Member functions
constructs a new istreambuf_iterator (public member function) | |
(destructor) (implicitly declared) | destructs an istreambuf_iterator (public member function) |
operator*operator->
(since C++11) | obtains a copy of the current character accesses a member of the current character, if CharT has members (public member function) |
advances the iterator (public member function) | |
tests if both istreambuf_iterator s are end-of-stream or if both are valid (public member function) |
Non-member functions
compares two istreambuf_iterator s (function template) |
Member types
Member type | Definition |
---|---|
value_type | CharT |
difference_type | Traits::off_type |
pointer | /* unspecified, usually CharT* */ |
reference | CharT |
iterator_category | std::input_iterator_tag |
Note: before C++17, these member types are required to be obtained by inheriting from std::iterator<std::input_iterator_tag,CharT,Traits::off_type,/* unspecified, usually CharT* */,CharT>
.
Example
#include <vector> #include <sstream> #include <iostream> #include <iterator> int main() { // typical use case: an input stream represented as a pair of iterators std::istringstream in("Hello, world"); std::vector<char> v( (std::istreambuf_iterator<char>(in)), std::istreambuf_iterator<char>() ); std::cout << "v has " << v.size() << " bytes. "; v.push_back('\0'); std::cout << "it holds \"" << &v[0] << "\"\n"; // demonstration of the single-pass nature std::istringstream s("abc"); std::istreambuf_iterator<char> i1(s), i2(s); std::cout << "i1 returns " << *i1 << '\n' << "i2 returns " << *i2 << '\n'; ++i1; std::cout << "after incrementing i1, but not i2\n" << "i1 returns " << *i1 << '\n' << "i2 returns " << *i2 << '\n'; ++i2; // this makes the apparent value of *i2 to jump from 'a' to 'c' std::cout << "after incrementing i2, but not i1\n" << "i1 returns " << *i1 << '\n' << "i2 returns " << *i2 << '\n'; }
Output:
v has 12 bytes. it holds "Hello, world" i1 returns a i2 returns a after incrementing i1, but not i2 i1 returns b i2 returns a after incrementing i2, but not i1 i1 returns b i2 returns c
See also
output iterator that writes to std::basic_streambuf (class template) | |
input iterator that reads from std::basic_istream (class template) |
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