78 lines
2.4 KiB
JavaScript
78 lines
2.4 KiB
JavaScript
/**
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* Cooperative advisory **`fcntl`** lock slot + **`F_SETLKW`** waiter drain (**FIFO** per path).
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* Used by **`packages/bare-os-booter/index.js`** **`bareOsSyscall('fcntl')`**.
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*/
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/**
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* @param {{ readers: Set<string>; writer: string | null }} slot
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* @param {string} owner
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* @param {boolean} wantWrite
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*/
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export function bareOsTryAcquireCooperativeLock(slot, owner, wantWrite) {
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if (wantWrite) {
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if (slot.writer && slot.writer !== owner) return false
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if (
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slot.readers.size > 0 &&
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[...slot.readers].some((sid) => sid !== owner)
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) {
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return false
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}
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slot.readers.clear()
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slot.writer = owner
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return true
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}
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if (slot.writer && slot.writer !== owner) return false
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slot.readers.add(owner)
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return true
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}
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/**
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* @param {Record<string, unknown>} c
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* @param {string} lockPath
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* @param {{ resolve: (v: unknown) => void, timer: ReturnType<typeof setTimeout> | null, owner: string, wantWrite: boolean }} entry
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*/
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export function bareOsRemoveFcntlWaiter(c, lockPath, entry) {
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const m = /** @type {Record<string, unknown>} */ (c)
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const qm = m.bareOsFcntlLockWaitQueues
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if (!qm || typeof qm !== 'object') return
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const q = /** @type {unknown[]} */ (qm[lockPath])
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if (!Array.isArray(q)) return
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const i = q.indexOf(entry)
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if (i >= 0) q.splice(i, 1)
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if (q.length === 0) delete qm[lockPath]
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}
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/**
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* @param {Record<string, unknown>} c
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* @param {string} lockPath
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*/
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export function bareOsDrainFcntlLockWaiters(c, lockPath) {
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const locks = /** @type {Record<string, { readers: Set<string>; writer: string | null }>} */ (
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c.bareOsCooperativeLocks
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)
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const slot = locks?.[lockPath]
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if (!slot) return
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const m = /** @type {Record<string, unknown>} */ (c)
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const qm = m.bareOsFcntlLockWaitQueues
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const q = qm?.[lockPath]
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if (!Array.isArray(q) || q.length === 0) return
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while (q.length > 0) {
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const w = /** @type {{ resolve: (v: unknown) => void, timer: ReturnType<typeof setTimeout> | null, owner: string, wantWrite: boolean }} */ (
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q[0]
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)
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if (!bareOsTryAcquireCooperativeLock(slot, w.owner, w.wantWrite)) break
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q.shift()
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if (w.timer) clearTimeout(w.timer)
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w.resolve({
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ok: true,
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op: 'fcntl',
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cmd: 'F_SETLKW',
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path: lockPath,
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cooperative: true,
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locked: w.wantWrite ? 'write' : 'read',
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blockedWait: true
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})
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}
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if (q.length === 0 && qm && typeof qm === 'object') delete qm[lockPath]
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}
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