one/dist/esm/server/assetRange.mjs

One is a React framework for web, iOS, and Android apps.

async function withRange(request, response) {
	const range = request.headers.get("range");
	if (!range || request.method !== "GET" || response.status !== 200 || !response.body || response.headers.has("content-range") || response.headers.has("content-encoding") || !ifRangeMatches(request.headers.get("if-range"), response.headers)) {
		return response;
	}
	const match = /^bytes=(\d*)-(\d*)$/.exec(range.trim());
	if (!match || !match[1] && !match[2]) return response;
	const length = response.headers.get("content-length");
	const known = length && /^\d+$/.test(length) ? Number(length) : void 0;
	const headers = new Headers(response.headers);
	headers.set("accept-ranges", "bytes");
	headers.delete("content-length");
	const { size, kept, keptStart } = await readRange(response.body, match, known);
	const span = resolve(match, size);
	if (!span) {
		headers.set("content-range", `bytes */${size}`);
		return new Response(null, {
			status: 416,
			headers
		});
	}
	headers.set("content-range", `bytes ${span.start}-${span.end}/${size}`);
	headers.set("content-length", String(span.end - span.start + 1));
	return new Response(kept.subarray(span.start - keptStart, span.end - keptStart + 1), {
		status: 206,
		headers
	});
}
function ifRangeMatches(ifRange, headers) {
	if (!ifRange) return true;
	const value = ifRange.trim();
	if (value.startsWith("\"")) {
		const etag = headers.get("etag");
		return !!etag && !etag.startsWith("W/") && etag === value;
	}
	if (value.startsWith("W/")) return false;
	return headers.get("last-modified") === value;
}
function resolve(match, size) {
	let start;
	let end;
	if (!match[1]) {
		start = Math.max(0, size - Number(match[2]));
		end = size - 1;
	} else {
		start = Number(match[1]);
		end = match[2] ? Math.min(Number(match[2]), size - 1) : size - 1;
	}
	if (start >= size || start > end) return;
	return {
		start,
		end
	};
}
async function readRange(body, match, known) {
	const span = known === void 0 ? void 0 : resolve(match, known) ?? {
		start: known,
		end: -1
	};
	const suffix = !span && !match[1] ? Number(match[2]) : 0;
	const from = span ? span.start : match[1] ? Number(match[1]) : 0;
	const to = span ? span.end : match[2] && match[1] ? Number(match[2]) : Number.POSITIVE_INFINITY;
	const chunks = [];
	let keptBytes = 0;
	let size = 0;
	const reader = body.getReader();
	while (known === void 0 || size <= to) {
		const { done, value } = await reader.read();
		if (done) break;
		const chunkStart = size;
		size += value.byteLength;
		if (suffix) {
			chunks.push(value);
			keptBytes += value.byteLength;
			while (chunks.length > 1 && keptBytes - chunks[0].byteLength >= suffix) {
				keptBytes -= chunks.shift().byteLength;
			}
			continue;
		}
		const lo = Math.max(from, chunkStart);
		const hi = Math.min(to + 1, size);
		if (hi > lo) {
			chunks.push(value.subarray(lo - chunkStart, hi - chunkStart));
			keptBytes += hi - lo;
		}
	}
	if (known !== void 0) {
		await reader.cancel();
		size = known;
	}
	const kept = new Uint8Array(keptBytes);
	let at = 0;
	for (const chunk of chunks) {
		kept.set(chunk, at);
		at += chunk.byteLength;
	}
	return {
		size,
		kept,
		keptStart: suffix ? size - keptBytes : from
	};
}

export { withRange };
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