dumbo's Introduction

dumbo

A planned C library for executing CSS selectors on HTML trees from a variety of libraries, including gumbo.

Goals

Portable: Uses C99 and autotools
Small: Focussed feature-set only for retrieving elements from HTML trees
Customisable: Allows compile-time toggling of HTML library support
Support CSS 3 (including the deprecated :contains() and non-standard ::attr(name))
Support selections on streaming HTML parsers (e.g., SAX parsers)

Implementation notes

As much as possible, dumbo shouldn't do any allocations. So, the API for executing selectors should be an iterator interface, and take void ** since client code should know what kind of tree they have (and thus, node type or te). Upon match, the library should just modify the out parameter to point to the element.

Example code:

#include <dumbo.h>
// ...
char *html = ...;
char *selector = ...;

MyTree *tree = mytree_parse(html);
MyTree *root = mytree_getroot(tree);

// Wrapped to store the tree, the library's tag (some internal enum), and
// library-specific context data for the current execution of the css selection.
dumbo_ctx ctx = DUMBO_CTX_WRAP_MYTREE(root);
dumbo_css *css = dumbo_css_parse(selector);

MyTree *node;
while (dumbo_css_exec(css, &ctx, &node) == 0) {
	// ...
}

// ...

// Execute again on different css selector (with the same tree).
dumbo_css_free(css);
selector = ...;
css = dumbo_css_parse(selector);
// Reuse the current context.
DUMBO_CTX_RESET_MYTREE(ctx);
while (dumbo_css_exec(css, &ctx, &node) == 0) {
	// ...
}

// ...

// Execute with different *tree* but the same selector.
mytree_free(tree);
html = ...;
tree = mytree_parse(html);
root = mytree_getroot(tree);
ctx = DUMBO_CTX_WRAP_MYTREE(root);
while (dumbo_css_exec(css, &ctx, &node) == 0) {
	// ...
}

// ...

dumbo_css_free(css);
mytree_free(tree);

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