mirror of
https://github.com/vercel-labs/scriptc.git
synced 2026-10-26 06:34:20 +08:00
Malte Ubl
1a14263b5f
Every ScrArr carried sixteen words, seven of them (sparse slots, their length and capacity, noncanonical numeric properties with length and capacity, and match-result metadata) used only by sparse arrays, arrays with numeric non-index properties and regex match results. They now live in a ScrArrExt the array points at, allocated on first use: a dense array shrinks from 128 to 80 bytes, and a cycle-capable one (with its 16-byte collector header) from 144 to 96. Runtime readers go through a shared empty ext; writers allocate it. The backend mirror loses the seven fields, tagged-template arrays are emitted with a NULL ext, live stream commits swap the ext pointer (which swapped all seven fields before), and the cached typed-view refresh swaps sparse slots and properties through scr_arr_swap_indexed_ext, keeping each array's metadata as before. The program-object ABI marker moves to scr_runtime_abi_v11. A corpus program (4610-array-ext-dyn-refresh.ts, with its order baseline) pins numeric non-index properties of a dynamically typed array through its refreshed typed view, sparse slots written directly and through a live reference, truncation, and regex match metadata read directly, through `any` and after a copy.
45 lines
1.7 KiB
TypeScript
45 lines
1.7 KiB
TypeScript
// Sparse slots, noncanonical numeric properties and regex match metadata
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// live in an array's out-of-line storage: they keep their values through
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// typed views of dynamically typed arrays, writes through live references,
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// truncation and copies.
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function asNumbers(value: any): number[] {
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return value as number[];
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}
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const parsed: any = JSON.parse("[1, 2, 3]");
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const first = asNumbers(parsed);
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console.log("first", first.length, first[0], first[2]);
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parsed[-1] = 9;
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parsed["1.5"] = 11;
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parsed.push(4);
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const second = asNumbers(parsed);
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console.log("properties", second.length, second[3], parsed[-1], parsed["1.5"], "-1" in parsed, Object.keys(parsed).length);
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delete parsed[-1];
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parsed.push(5);
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const third = asNumbers(parsed);
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console.log("third", third.length, third[4], parsed[-1], "-1" in parsed, "1.5" in parsed);
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const sparse: number[] = [1, 2, 3];
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sparse[4_000_000] = 7;
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console.log("sparse", sparse.length, sparse[4_000_000], 3_999_999 in sparse, 4_000_000 in sparse);
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sparse.length = 3;
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console.log("sparse truncated", sparse.length, sparse[4_000_000], 4_000_000 in sparse);
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const typed: number[] = [5, 6];
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typed[3_000_000] = 1;
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const viaAny: any = typed;
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viaAny[3_000_001] = 2;
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console.log("typed", typed.length, typed[3_000_000], typed[3_000_001], 3_000_001 in typed);
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typed.length = 2;
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console.log("typed truncated", typed.length, typed[3_000_000], viaAny.length);
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const match = /(b)(c)?/.exec("abd")!;
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console.log("match", match.index, match.input, match.length, match[1], match[2]);
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const loose: any = match;
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console.log("match via any", loose.index, loose.input, loose[1], loose.length);
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const copy = match.slice();
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console.log("copy", copy.length, copy[0], copy[1]);
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