Peekable

Description

A Peekable Device allows a character read from the input sequence to be putback.

The name of the concept is based on the observation that a PeekableDevice allow the user to peek at the first character in the sequence it controls by calling get or read followed by putback. The names Putbackable and InputRevertable were considered but rejected.

Refinement of

Source.

Associated Types

Same as Source.

Notation

`P`	-	A type which is a model of Peekable
`p`	-	Object of type `P`
`c`	-	Object of type equal to the character type of `P`
`io`	-	Alias for namespace `boost::iostreams`

Valid Expressions / Semantics

Expression	Expression Type	Precondition	Semantics	Postcondition
`io::putback(p, c)`	`bool`	One or more characters has been read from `p` using `io::get` or `io::read`, with no intervening i/o operations having been performed	Attempts to put back `c` to `p`, returning `true` for success	If putback returns `true`, the next character read from `p` using `io::get` or `io::read` will be equal to `c`

Exceptions

Errors which occur during the execution of putback are be indicated by throwing exceptions.

Models

Standard input streams and stream buffers.

Revised 20 May, 2004

Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)