Crate peekread[−][src]
Expand description
This crate allows you to take an arbitrary Read stream and ‘peek ahead’
into the stream without consuming the original stream.
This is done through the PeekRead trait which has the method
peek. When this method is called it returns a new PeekCursor object
implementing Read, BufRead and Seek that allows you to read from
the stream without affecting the original stream.
The PeekRead trait is directly
implemented on a select few types, but for most you will have to wrap your
type in a SeekPeekReader or BufPeekReader that implements the
peeking behavior using respectively seeking or buffering.
Examples
One could try various different parsers on the same stream until one succeeds:
let mut f = SeekPeekReader::new(File::open("ambiguous")?); // HTML is so permissive its parser never fails, so check for signature. if f.starts_with("<!DOCTYPE html>\n") { Ok(ParseResult::Html(parse_as_html(f))) } else { // Can pass PeekCursor to functions accepting T: Read without them // having to be aware of peekread. parse_as_jpg(f.peek()).map(ParseResult::Jpg) .or_else(|_| parse_as_png(f.peek()).map(ParseResult::Png)) .or_else(|_| parse_as_gif(f.peek()).map(ParseResult::Gif)) .or_else(|_| parse_as_javascript(f.peek()).map(ParseResult::Js)) }