webpack/lib/util/publicPathPlaceholder.js

Packs ECMAScript/CommonJs/AMD modules for the browser. Allows you to split your codebase into multiple bundles, which can be loaded on demand. Supports loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
*/

"use strict";

// Placeholders embedded into asset `url()` / HTML chunk URLs at code-generation
// time, when the final public path can't be resolved yet, then substituted
// later once the information is available:
// - PUBLIC_PATH_AUTO    — stands in for `output.publicPath: "auto"`; replaced
//   with the per-output-file undo path (relative `../` segments back to the
//   output root) during chunk/asset render.
// - PUBLIC_PATH_FULL_HASH — stands in for `[fullhash]`/`[hash]` in a public
//   path before the compilation hash exists. Form: `<prefix><len>__`, where
//   `<len>` is the requested hash length (`0` means the full hash). Replaced
//   with the real hash (build-time, e.g. CSS `.css` files) or a runtime
//   `__webpack_require__.h()` expression (inlined CSS in JS).
const PUBLIC_PATH_AUTO = "__WEBPACK_CSS_PUBLIC_PATH_AUTO__";
const PUBLIC_PATH_FULL_HASH = "__WEBPACK_CSS_PUBLIC_PATH_FULL_HASH_";

/**
 * Scan `content` for `PUBLIC_PATH_FULL_HASH` placeholders and invoke `onMatch`
 * once per well-formed occurrence. The placeholder spans the half-open range
 * `[start, end)` and encodes the requested hash length (`0` means the full
 * hash). Callers substitute the build-time hash or a runtime expression
 * depending on context.
 * @param {string} content text to scan
 * @param {(start: number, end: number, length: number) => void} onMatch placeholder callback
 * @returns {void}
 */
const walkFullHashPlaceholders = (content, onMatch) => {
	const prefix = PUBLIC_PATH_FULL_HASH;
	const prefixLen = prefix.length;
	const len = content.length;
	let idx = content.indexOf(prefix);
	while (idx !== -1) {
		let digitEnd = idx + prefixLen;
		while (digitEnd < len) {
			const cc = content.charCodeAt(digitEnd);
			if (cc < 48 || cc > 57) break;
			digitEnd++;
		}
		// Well-formed placeholder: at least one digit followed by `__`.
		if (
			digitEnd > idx + prefixLen &&
			digitEnd + 1 < len &&
			content.charCodeAt(digitEnd) === 95 &&
			content.charCodeAt(digitEnd + 1) === 95
		) {
			const length = Number.parseInt(
				content.slice(idx + prefixLen, digitEnd),
				10
			);
			onMatch(idx, digitEnd + 2, length);
			idx = content.indexOf(prefix, digitEnd + 2);
		} else {
			idx = content.indexOf(prefix, idx + prefixLen);
		}
	}
};

module.exports.PUBLIC_PATH_AUTO = PUBLIC_PATH_AUTO;
module.exports.PUBLIC_PATH_FULL_HASH = PUBLIC_PATH_FULL_HASH;
module.exports.walkFullHashPlaceholders = walkFullHashPlaceholders;