Module NetstreamSource

A netstream is an input channel that is read block by block. The * fragment of the channel currently loaded into memory is called the * current window of the netstream. The window can be thought as * look-ahead buffer. * * Picture: * *

* 0                pos_in        pos_in + window_length            EOF
* +------------------+-------------------+--------------------------+
*                    ====================
*                     The current window
* 

* * You can use a netstream like an in_obj_channel, and read characters * and strings from the stream. The bytes come first from the look-ahead * buffer, and if there are not enough bytes, they are loaded from the * underlying channel. After every read operation it is tried to enlarge * the window such that it contains at least one block. * * If you want that the window becomes larger, you can call want (to * enlarge the window to a certain size) or want_another_block (to load * just another block from the underlying channel). Note that this affects only * the current window and not the future size of the window. * * Note Buffer_underrun: netstreams can cope with underruns of underlying * channels. An underrun happens when it is not possible to ensure the * minimum window size. However, it is possible that the window size * sinks under the minimum, but the Buffer_underrun is deferred until the * next call of an input method. Furthermore, there is a problem in the skip * method which may only be partially executed, i.e. the method skips some * bytes and then raises Buffer_underrun.