refactor(processes): extract Linux start-time capture

src/shared/linux-process-start-times.ts

@@ -0,0 +1,38 @@
+import { readFile } from 'node:fs/promises'
+import type { ProcessTableRow } from './process-table-snapshot'
+
+/** Read Linux's stable PID start-time ticks without spawning another process. */
+export async function readLinuxProcessStartTimes(
+  rows: readonly ProcessTableRow[]
+): Promise<ReadonlyMap<number, string> | undefined> {
+  if (process.platform !== 'linux') {
+    return undefined
+  }
+  const candidates = rows.filter((row) => row.tty !== undefined && row.tty !== '?')
+  const starts = await Promise.all(
+    candidates.map(async (row) => {
+      try {
+        const stat = await readFile(`/proc/${row.pid}/stat`, 'utf8')
+        const closingParen = stat.lastIndexOf(')')
+        if (closingParen === -1) {
+          return null
+        }
+        const tail = stat
+          .slice(closingParen + 1)
+          .trim()
+          .split(/\s+/)
+        const startTime = tail[19]
+        return startTime ? ([row.pid, startTime] as const) : null
+      } catch {
+        return null
+      }
+    })
+  )
+  const result = new Map<number, string>()
+  for (const entry of starts) {
+    if (entry) {
+      result.set(entry[0], entry[1])
+    }
+  }
+  return result
+}

src/shared/process-table-snapshot-reader.ts

@@ -1,6 +1,6 @@
 import { execFile as execFileCb } from 'node:child_process'
-import { readFile } from 'node:fs/promises'
 import { promisify } from 'node:util'
+import { readLinuxProcessStartTimes } from './linux-process-start-times'
 import {
   PS_ARGS,
   PS_MAX_BUFFER_BYTES,
@@ -217,42 +217,6 @@ function assertWholeCapture(stdout: string): string {
   return stdout
 }
 
-/** Read Linux's stable PID start-time ticks without spawning another process. */
-async function readLinuxProcessStartTimes(
-  rows: readonly ProcessTableRow[]
-): Promise<ReadonlyMap<number, string> | undefined> {
-  if (process.platform !== 'linux') {
-    return undefined
-  }
-  const candidates = rows.filter((row) => row.tty !== undefined && row.tty !== '?')
-  const starts = await Promise.all(
-    candidates.map(async (row) => {
-      try {
-        const stat = await readFile(`/proc/${row.pid}/stat`, 'utf8')
-        const closingParen = stat.lastIndexOf(')')
-        if (closingParen === -1) {
-          return null
-        }
-        const tail = stat
-          .slice(closingParen + 1)
-          .trim()
-          .split(/\s+/)
-        const startTime = tail[19]
-        return startTime ? ([row.pid, startTime] as const) : null
-      } catch {
-        return null
-      }
-    })
-  )
-  const result = new Map<number, string>()
-  for (const entry of starts) {
-    if (entry) {
-      result.set(entry[0], entry[1])
-    }
-  }
-  return result
-}
-
 const processTableReader = createProcessTableSnapshotReader<ProcessTableCapture>({
   runPs: () => captureProcessTable(PS_ARGS),
   now: () => Date.now()