Orginize

packages/bare-os-booter/lib/posix/bare-os-fcntl-cooperative-lock.js

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