std::streamsize readsome( char_type* s, std::streamsize count ); |
Extracts up to count
immediately available characters from the input stream. The extracted characters are stored into the character array pointed to by s
.
Behaves as UnformattedInputFunction
. After constructing and checking the sentry object,
- If
rdbuf()->in_avail() == -1
, callssetstate(eofbit)
and extracts no characters. - If
rdbuf()->in_avail() == 0
, extracts no characters. - If
rdbuf()->in_avail() > 0
, extractsstd::min(rdbuf()->in_avail(), count)
characters and stores them into successive locations of the characater array whose first element is pointed to bys
.
Parameters
s | - | pointer to the character array to store the characters to |
count | - | maximum number of characters to read |
Return value
The number of characters actually extracted.
Exceptions
failure
if an error occurred (the error state flag is not goodbit
) and exceptions()
is set to throw for that state.
If an internal operation throws an exception, it is caught and badbit
is set. If exceptions()
is set for badbit
, the exception is rethrown.
Notes
The behavior of this function is highly implementation-specific. For example, when used with std::ifstream
, some library implementations fill the underlying filebuf with data as soon as the file is opened (and readsome() on such implementations reads data, potentially, but not necessarily, the entire file), while other implementations only read from file when an actual input operation is requested (and readsome() issued after file opening never extracts any characters). Likewise, a call to std::cin.readsome()
may return all pending unprocessed console input, or may always return zero and extract no characters.
Example
#include <iostream> #include <sstream> int main() { char c[10] = {}; std::istringstream input("This is sample text."); // std::stringbuf makes its entire // buffer available for unblocking read input.readsome(c, 5); // reads 'This ' and stores in c[0] .. c[4] input.readsome(c, 9); // reads 'is sample' and stores in c[0] .. c[8] std::cout << c; }
Output:
is sample
See also
extracts blocks of characters (public member function) | |
obtains the number of characters immediately available in the get area (public member function of std::basic_streambuf ) |
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