Initial revision

[helm.git] / helm / DEVEL / pxp / netstring / netstream.mli

diff --git a/helm/DEVEL/pxp/netstring/netstream.mli b/helm/DEVEL/pxp/netstring/netstream.mli
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+(* $Id$
+ * ----------------------------------------------------------------------
+ *
+ *)
+
+
+(* 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.
+ *
+ * PICTURE:
+ *
+ * 0            window_position     current_length                  EOS
+ * +------------------+-------------------+--------------------------+
+ *                    ====================
+ *                     The current window
+ *
+ * window_length = current_length - window_position
+ *
+ * There is an automatism that the window has a certain length. If possible,
+ * the window is at least twice the block size long, where a "block" is
+ * the amount of data that is read from the input channel in one step.
+ *
+ * (The idea is that you choose as block size the number of bytes you want
+ * to analyze at once, and which must be loaded into memory. You can start
+ * your analysis at window_position and proceed until window_position +
+ * blocksize without having to check whether your window is large enough.
+ * Only when the first blocksize bytes of the window are already processed,
+ * the window must be enlarged by loading the next 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 input channel). Note that this affects only
+ * the current window and not future windows.
+ *
+ * If you do not need the first n bytes of the window anymore, you can
+ * call 'move' to move the beginning of the window by n bytes. If the
+ * window becomes too small after this operation, it is enlarged until
+ * it has twice the block size or until it reaches EOS.
+ *)
+
+type t
+
+val create_from_channel : in_channel -> int option -> int -> t
+    (* create_from_channel ch maxlength blocksize:
+     * The new netstream reads from the channel 'ch'. If maxlength = None,
+     * the channel is read until EOF. If maxlength = Some n, at most n bytes
+     * are read; i.e. the netstream reads until n bytes have been read or
+     * until EOF has been reached, whatever comes first. The blocksize 
+     * specifies the number of bytes to read at once.
+     *)
+
+val create_from_string : string -> t
+    (* Creates a new netstream from a string. The initial window of this
+     * netstream is a copy of the passed string.
+     *)
+
+val block_size : t -> int
+   (* Returns the (immutable) block size. *)
+
+val current_length : t -> int
+    (* Returns the number of bytes read so far. *)
+
+val at_eos : t -> bool
+    (* True iff EOS (end of stream) is reached, i.e. the last byte of the
+     * window is the last byte of the stream.
+     *)
+
+val window_position : t -> int
+    (* Returns the absolute position of the current window. *)
+
+val window_length : t -> int
+    (* Returns the length of the current window. *)
+
+val window : t -> Netbuffer.t
+    (* Returns the current window. *)
+
+val move : t -> int -> unit
+    (* move s n:
+     * Moves the window: The first n bytes of the current window are 
+     * discarded. If the window would become smaller than twice the
+     * blocksize and if the end of the stream is not yet reached, another
+     * block is read from the input channel and appended to the window.
+     * 
+     * PRECONDITION:
+     * - n <= window_length
+     *)
+
+val want : t -> int -> unit
+    (* want s n:
+     * If the window is smaller than n bytes, it is tried to enlarge
+     * the window such that it is at least n bytes long. The enlargement
+     * is not possible if the stream is not long enough; in this case
+     * the window becomes as large as possible.
+     *)
+
+val want_another_block : t -> unit
+    (* Enlarges the window by another block (if possible i.e. if the stream
+     * is long enough).
+     *)
+
+val print_stream : t -> unit
+
+(* ======================================================================
+ * History:
+ * 
+ * $Log$
+ * Revision 1.1  2000/11/17 09:57:27  lpadovan
+ * Initial revision
+ *
+ * Revision 1.2  2000/06/24 20:20:33  gerd
+ *     Added the toploop printer.
+ *
+ * Revision 1.1  2000/04/15 13:07:48  gerd
+ *     Initial revision.
+ *
+ * 
+ *)