58 lines
2.0 KiB
JavaScript
58 lines
2.0 KiB
JavaScript
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// A framework for simple tokenizers. Takes care of newlines and
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// white-space, and of getting the text from the source stream into
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// the token object. A state is a function of two arguments -- a
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// string stream and a setState function. The second can be used to
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// change the tokenizer's state, and can be ignored for stateless
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// tokenizers. This function should advance the stream over a token
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// and return a string or object containing information about the next
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// token, or null to pass and have the (new) state be called to finish
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// the token. When a string is given, it is wrapped in a {style, type}
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// object. In the resulting object, the characters consumed are stored
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// under the content property. Any whitespace following them is also
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// automatically consumed, and added to the value property. (Thus,
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// content is the actual meaningful part of the token, while value
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// contains all the text it spans.)
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function tokenizer(source, state) {
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// Newlines are always a separate token.
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function isWhiteSpace(ch) {
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// The messy regexp is because IE's regexp matcher is of the
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// opinion that non-breaking spaces are no whitespace.
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return ch != "\n" && /^[\s\u00a0]*$/.test(ch);
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}
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var tokenizer = {
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state: state,
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take: function(type) {
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if (typeof(type) == "string")
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type = {style: type, type: type};
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type.content = (type.content || "") + source.get();
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if (!/\n$/.test(type.content))
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source.nextWhile(isWhiteSpace);
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type.value = type.content + source.get();
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return type;
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},
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next: function () {
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if (!source.more()) throw StopIteration;
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var type;
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if (source.equals("\n")) {
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source.next();
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return this.take("whitespace");
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}
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if (source.applies(isWhiteSpace))
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type = "whitespace";
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else
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while (!type)
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type = this.state(source, function(s) {tokenizer.state = s;});
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return this.take(type);
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}
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};
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return tokenizer;
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}
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