Extracts up tocount immediately available characters from the input stream. The extracted characters are stored into the character array pointed to bys.

Behaves asUnformattedInputFunction. After constructing and checking the sentry object,

• Ifrdbuf()->in_avail()==-1, callssetstate(eofbit) and extracts no characters.

• Ifrdbuf()->in_avail()==0, extracts no characters.

• Ifrdbuf()->in_avail()>0, extractsstd::min(rdbuf()->in_avail(), count) characters and stores them into successive locations of the character array whose first element is pointed to bys.

[edit]Parameters

[edit]Return value

The number of characters actually extracted.

[edit]Exceptions

If an internal operation throws an exception, it is caught andbadbit is set. Ifexceptions() is set forbadbit, the exception is rethrown.

[edit]Notes

The behavior of this function is highly implementation-specific. For example, usingreadsome() withstd::ifstream leads to significant, implementation-specific outcomes. Some library implementations fill the underlyingfilebuf with data as soon asstd::ifstream opens a file, which meansreadsome() always reads data and could even read the entire file. With other implementations,std::ifstream only reads from a file when an input operation is invoked, which means callingreadsome() immediately after opening the file never extracts any characters. Similarly, callingstd::cin.readsome() may return all pending, unprocessed console input or may always return zero and extract no characters.

[edit]Example

#include <cassert>#include <iostream>#include <sstream> int main(){char c[10]="*********";// c[9] == '\0' // std::stringbuf makes its entire buffer available for unblocking readstd::istringstream input("This is sample text."); auto r= input.readsome(c,5);// reads 'This ' and stores in c[0] .. c[4]assert(r==5);std::cout<< c<<'\n';     r= input.readsome(c,9);// reads 'is sample' and stores in c[0] .. c[8]assert(r==9);std::cout<< c<<'\n';}

This ****is sample

[edit]See also

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