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cultcache-ts: the header peek is the one judge of a stamp; isStoreSnapshot is a shape test; byte-offset views, array16/32 and str16/32 leads and a spaced stamp pinned

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Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
This commit is contained in:
Meta Vens 2026-10-23 04:11:53 +02:00
commit 38dfa60804
2 changed files with 15 additions and 11 deletions
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12
packages/cultcache-ts/src/store-format.ts
View file

@ -16,16 +16,12 @@ const PERSISTED_RECORD_SLOTS = 4;
const STORE_SLOTS = 3;
/**
* True for a v1 or v3 snapshot, false for anything that is not a CultCache store header (the legacy
* envelope array). Any other `cultcache.store.*` header is refused by name.
* True for a decoded array that leads with a `cultcache.store.*` stamp, false for the legacy envelope array. It judges the
* shape only: the verdict on the stamp is {@link refuseUnreadStoreBytes}, which a reader calls on the bytes before it decodes,
* so the stamp of a decoded array it is given is one this runtime reads.
*/
export function isStoreSnapshot(decoded: unknown): decoded is [StoreFormat, ...unknown[]] {
if (!Array.isArray(decoded) || typeof decoded[0] !== "string" || !decoded[0].startsWith(STORE_FORMAT_PREFIX)) {
return false;
}
refuseUnreadFormat(decoded[0]);
return true;
return Array.isArray(decoded) && typeof decoded[0] === "string" && decoded[0].startsWith(STORE_FORMAT_PREFIX);
}
/**

14
packages/cultcache-ts/test/cult-cache.test.ts
View file

@ -2121,9 +2121,17 @@ test("a store's header is judged from its first bytes, in every MessagePack arra
assert.equal(headerRefused(storeStart([0x91], `cultcache.store.v4${"x".repeat(13)}`, "fix")), true);
assert.equal(headerRefused(storeStart([0x91], `cultcache.store.v4${"x".repeat(300)}`, "16")), true);
assert.equal(headerRefused(storeStart([0x91], `cultcache.store.v4${"x".repeat(300)}`, "32")), true);
// A view into a larger buffer is read from its own start.
const padded = new Uint8Array([9, 9, ...storeStart([0x91], "cultcache.store.v4", "fix")]);
assert.equal(headerRefused(padded.subarray(2)), true);
// A view into a larger buffer is read from its own start, in every form that reads a length through the DataView.
for (const lead of leads) {
for (const form of ["fix", "8", "16", "32"] as const) {
const padded = new Uint8Array([7, 7, 7, ...storeStart(lead, "cultcache.store.v4", form)]);
assert.equal(padded.subarray(3).byteOffset, 3);
assert.equal(headerRefused(padded.subarray(3)), true, `${lead} ${form} v4 at a byte offset`);
}
}
// The stamp is judged as written: a stamp with a space is not the stamp this runtime reads, and not one it ignores.
assert.equal(headerRefused(storeStart([0x91], "cultcache.store.v3 ", "fix")), true, "a v3 stamp with a trailing space is a header this runtime does not read");
assert.equal(headerRefused(storeStart([0x91], " cultcache.store.v4", "fix")), false, "a leading space makes it no cultcache.store.* header");
});
test("bytes with no readable store stamp are not refused", () => {