125 lines
3.5 KiB
Plaintext
125 lines
3.5 KiB
Plaintext
October 2001, --Jcid
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Last update: Jul 2009
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---------------
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THE HTML PARSER
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---------------
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Dillo's parser is more than just a HTML parser, it does XHTML
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and plain text also. It has parsing 'modes' that define its
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behaviour while working:
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typedef enum {
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DILLO_HTML_PARSE_MODE_INIT = 0,
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DILLO_HTML_PARSE_MODE_STASH,
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DILLO_HTML_PARSE_MODE_STASH_AND_BODY,
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DILLO_HTML_PARSE_MODE_BODY,
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DILLO_HTML_PARSE_MODE_VERBATIM,
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DILLO_HTML_PARSE_MODE_PRE
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} DilloHtmlParseMode;
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The parser works upon a token-grained basis, i.e., the data
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stream is parsed into tokens and the parser is fed with them. The
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process is simple: whenever the cache has new data, it is
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passed to Html_write, which groups data into tokens and calls the
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appropriate functions for the token type (tag, space, or word).
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Note: when in DILLO_HTML_PARSE_MODE_VERBATIM, the parser
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doesn't try to split the data stream into tokens anymore; it
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simply collects until the closing tag.
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------
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TOKENS
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------
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* A chunk of WHITE SPACE --> Html_process_space
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* TAG --> Html_process_tag
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The tag-start is defined by two adjacent characters:
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first : '<'
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second: ALPHA | '/' | '!' | '?'
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Note: comments are discarded ( <!-- ... --> )
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The tag's end is not as easy to find, nor to deal with!:
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1) The HTML 4.01 sec. 3.2.2 states that "Attribute/value
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pairs appear before the final '>' of an element's start tag",
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but it doesn't define how to discriminate the "final" '>'.
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2) '<' and '>' should be escaped as '<' and '>' inside
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attribute values.
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3) The XML SPEC for XHTML states:
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AttrValue ::== '"' ([^<&"] | Reference)* '"' |
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"'" ([^<&'] | Reference)* "'"
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Current parser honors the XML SPEC.
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As it's a common mistake for human authors to mistype or
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forget one of the quote marks of an attribute value; the
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parser solves the problem with a look-ahead technique
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(otherwise the parser could skip significant amounts of
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properly-written HTML).
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* WORD --> Html_process_word
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A word is anything that doesn't start with SPACE, that's
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outside of a tag, up to the first SPACE or tag start.
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SPACE = ' ' | \n | \r | \t | \f | \v
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-----------------
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THE PARSING STACK
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-----------------
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The parsing state of the document is kept in a stack:
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class DilloHtml {
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[...]
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lout::misc::SimpleVector<DilloHtmlState> *stack;
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[...]
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};
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struct _DilloHtmlState {
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CssPropertyList *table_cell_props;
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DilloHtmlParseMode parse_mode;
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DilloHtmlTableMode table_mode;
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bool cell_text_align_set;
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DilloHtmlListMode list_type;
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int list_number;
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/* TagInfo index for the tag that's being processed */
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int tag_idx;
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dw::core::Widget *textblock, *table;
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/* This is used to align list items (especially in enumerated lists) */
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dw::core::Widget *ref_list_item;
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/* This is used for list items etc; if it is set to TRUE, breaks
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have to be "handed over" (see Html_add_indented and
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Html_eventually_pop_dw). */
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bool hand_over_break;
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};
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Basically, when a TAG is processed, a new state is pushed into
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the 'stack' and its 'style' is set to reflect the desired
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appearance (details in DwStyle.txt).
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That way, when a word is processed later (added to the Dw), all
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the information is within the top state.
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Closing TAGs just pop the stack.
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