lib/standard: Removed push_back_reader and replaced it by a peek operation on Buffere...

[nit.git] / lib / standard / stream.nit

diff --git a/lib/standard/stream.nit b/lib/standard/stream.nit
index e0d3a67..4ad6af1 100644 (file)
--- a/lib/standard/stream.nit
+++ b/lib/standard/stream.nit
@@ -392,6 +392,34 @@ abstract class BufferedReader
                return c.ascii
        end
 
+       # Peeks up to `n` bytes in the buffer, returns an empty string on EOF
+       #
+       # The operation does not consume the buffer
+       #
+       # ~~~nitish
+       #       var x = new FileReader("File.txt")
+       #       assert x.peek(5) == x.read(5)
+       # ~~~
+       fun peek(i: Int): String do
+               if eof then return ""
+               var b = new FlatBuffer.with_capacity(i)
+               while i > 0 and not eof do
+                       b.add _buffer[_buffer_pos]
+                       _buffer_pos += 1
+                       i -= 1
+               end
+               var nbuflen = b.length + (_buffer.length - _buffer_pos)
+               var nbuf = new FlatBuffer.with_capacity(nbuflen)
+               nbuf.append(b)
+               while _buffer_pos < _buffer.length do
+                       nbuf.add(_buffer[_buffer_pos])
+                       _buffer_pos += 1
+               end
+               _buffer_pos = 0
+               _buffer = nbuf
+               return b.to_s
+       end
+
        redef fun read(i)
        do
                if last_error != null then return ""