Diffstat (limited to 'docs/Architecture')
1 files changed, 83 insertions, 0 deletions
diff --git a/docs/Architecture b/docs/Architecture
new file mode 100644
@@ -0,0 +1,83 @@
+Hubbub parser architecture
+ Hubbub is a flexible HTML parser. It offers two interfaces:
+ * a SAX-style event interface
+ * a DOM-style tree-based interface
+ Hubbub is comprised of four parts:
+ * a charset handler
+ * an input stream veneer
+ * a tokeniser
+ * a tree builder
+ Charset handler
+ The charset handler converts the raw data input into a requested encoding.
+ Input stream veneer
+ The input stream veneer provides an abstract stream-like interface over
+ the document buffer. This is used by the tokeniser. The document buffer
+ will be encoded in either UTf-8 or UTF-16 (this is client-selectable).
+ The tokeniser divides the data held in the document buffer into chunks.
+ It sends SAX-style events for each chunk. The tokeniser is agnostic to
+ the charset the document buffer is stored in.
+ Tree builder
+ The tree builder constructs a DOM tree from the SAX events emitted by the
+ tokeniser. The tree builder is tied to the document buffer charset.
+Memory usage and ownership
+ Memory usage within the library is well defined, as is ownership of allocated
+ Raw input data provided by the library client is owned by the client.
+ The document buffer is allocated on the fly by the library.
+ The document buffer is created and resized by the charset handler. Its
+ location is passed to the tree builder through a dedicated event. While
+ parsing is occurring, the ownership of the document buffer lies with the
+ charset handler. Upon parse completion, the tree builder may request
+ ownership of the buffer. If it does not, the buffer will be freed on parser
+ SAX events which refer to document segments contain direct references into
+ the document buffer (i.e. no copying of data held in the document buffer
+ The tree builder will allocate memory for use as DOM nodes. References to
+ strings in the document buffer will be direct and will operate a
+ copy-on-write strategy. All strings (excepting those which comprise part of
+ the document buffer) and nodes within the DOM are reference counted. Upon a
+ reference count reaching 0, the item is freed.
+ The above strategy permits data copying to be kept to a minimum, hence
+ minimising memory usage.
+ Notification of parse errors is made through a dedicated event similar to
+ that used for notification of movement of the document buffer. This event
+ contains the line/column offset of the error location, along with a message
+ detailing the error.