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/**
* DON'T depend on anything from the outside like `promiseTry`, as this module is part of a separate lazy-loaded chunk.
*
* Including anything from the main chunk would include the whole chunk by default.
* Even it it would be tree-shaken during build, it won't be tree-shaken in dev.
*
* In the future consider separating common utils into a separate shared chunk.
*/
import loadWoff2 from "./woff2/woff2-loader";
import loadHbSubset from "./harfbuzz/harfbuzz-loader";
/**
* Shared commands between the main thread and worker threads.
*/
export const Commands = {
Subset: "SUBSET",
} as const;
/**
* Used by browser (main thread), node and jsdom, to subset the font based on the passed codepoints.
*
* @returns woff2 font as a base64 encoded string
*/
export const subsetToBase64 = async (
arrayBuffer: ArrayBuffer,
codePoints: Array<number>,
): Promise<string> => {
try {
const buffer = await subsetToBinary(arrayBuffer, codePoints);
return toBase64(buffer);
} catch (e) {
console.error("Skipped glyph subsetting", e);
// Fallback to encoding whole font in case of errors
return toBase64(arrayBuffer);
}
};
/**
* Used by browser (worker thread) and as part of `subsetToBase64`, to subset the font based on the passed codepoints.
*
* @eturns woff2 font as an ArrayBuffer, to avoid copying large strings between worker threads and the main thread.
*/
export const subsetToBinary = async (
arrayBuffer: ArrayBuffer,
codePoints: Array<number>,
): Promise<ArrayBuffer> => {
// lazy loaded wasm modules to avoid multiple initializations in case of concurrent triggers
// IMPORTANT: could be expensive, as each new worker instance lazy loads these to their own memory ~ keep the # of workes small!
const { compress, decompress } = await loadWoff2();
const { subset } = await loadHbSubset();
const decompressedBinary = decompress(arrayBuffer).buffer;
const snftSubset = subset(decompressedBinary, new Set(codePoints));
const compressedBinary = compress(snftSubset.buffer);
return compressedBinary.buffer;
};
/**
* Util for isomoprhic browser (main thread), node and jsdom usage.
*
* Isn't used inside the worker to avoid copying large binary strings (as dataurl) between worker threads and the main thread.
*/
export const toBase64 = async (arrayBuffer: ArrayBuffer) => {
let base64: string;
if (typeof Buffer !== "undefined") {
// node, jsdom
base64 = Buffer.from(arrayBuffer).toString("base64");
} else {
// browser (main thread)
// it's perfectly fine to treat each byte independently,
// as we care only about turning individual bytes into codepoints,
// not about multi-byte unicode characters
const byteString = String.fromCharCode(...new Uint8Array(arrayBuffer));
base64 = btoa(byteString);
}
return `data:font/woff2;base64,${base64}`;
};
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