istream (Input stream class)

Input stream class

Standard hierarchy

ios_base		ios		istream		iostream
						ifstream
						istringstream

Public member functions:

istream members:
(constructor)	Construct an object
operator>>	Perform formatted input operation (extraction)
gcount	Get number of characters extracted by last unformatted input operation
get	Extract unformatted data from stream
getline	Get a line from stream
ignore	Extract and discard characters
peek	Peek next character
putback	Put the last character back to stream
read	Read a block of data
readsome	Read a block of data
seekg	Set position of the get pointer
sync	Syncronize stream's buffer with source of characters
tellg	Get position of the get pointer
unget	Make last character got from stream available again
(destructor)	No-op [virtual]
members inherited from ios:
operator void *	Convert stream to pointer.
operator !	Evaluate stream object.
bad	Check if an unrecoverable error has occurred.
clear	Set control states.
copyfmt	Copy formatting information.
eof	Check if End-Of-File has been reached.
exceptions	Get/set the exception mask.
fail	Check if failure has occurred.
fill	Get/set the fill character.
good	Check if stream is good for i/o operations.
imbue	Imbue locale.
narrow	Narrow character.
rdbuf	Get/set the associated streambuf object.
rdstate	Get control state.
setstate	Set control state.
tie	Get/set the tied stream.
widen	Widen character.
members inherited from ios_base:
flags	Get/set format flags.
getloc	Get current locale.
imbue	Imbue locale.
iword	Get reference to a long element of the internal extensible array.
precision	Get/set floating-point decimal presision.
pword	Get reference to a void* element of the internal extensible array.
register_callback	Register event callback function.
setf	Set some format flags.
sync_with_stdio	Activates / Deactivates synchronization with cstdio functions. [static]
unsetf	Clear format flag.
width	Get/set field width.
xalloc	Return a new index for the internal extensible array. [static]

Description

istream provides member functions to assist in reading and interpreting input from a stream buffer. These members can be divided into two main groups:

Formatted input

These member functions extract formatted data that may be interpreted from a sequence of characters to any other type. All formatted input is done using the extraction operator (operator>>).

Unformatted input

Most of the other member functions of istream class are used to perform unformatted input, i.e. no interpretation is made on the characters got form input. These functions can get a dertermined number of characters from the input buffer (get, getline, peek, read, readsome), manipulate the get pointer (ignore, seekg, tellg, unget) or get information of last unformatted input operation (gcount).

  The input buffer may be syncronized with the external source of characters by calling member sync.

  Standard object cin is an instatiation of this class.