Support .cpuprofile of node --cpu-prof (#256)

* Support `.cpuprofile` of `node --cpu-prof`

* `convert_cpu_prof` -> `convertCpuProf`

* Do separate test script for `node --cpu-prof`

* Fix linter `const` error

* Format code according to `standard`

examples/cpu-profiler/.gitignore

@@ -5,5 +5,5 @@ node_modules
 win
 todo
 .vscode
-flamegraph.html
+flamegraph*.html
 v8-profile.json

examples/cpu-profiler/cpu-prof-test.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+
+node --cpu-prof --cpu-prof-name=samples-cpu-prof.cpuprofile index.js &
+
+sleep 1
+node_modules/.bin/autocannon -l -R 200000 -c 2000 -d 20 http://localhost:3000
+curl -v http://localhost:3000/stop-server
+wait
+
+node node_modules/.bin/0x --name=flamegraph-cpu-prof --visualize-cpu-profile samples-cpu-prof.cpuprofile

examples/cpu-profiler/index.js

@@ -29,8 +29,12 @@ router.get('/stop-profiling', async (ctx, next) => {
   }
 })
 
+router.get('/stop-server', (ctx, next) => {
+  server.close()
+})
+
 app
   .use(router.routes())
   .use(router.allowedMethods())
 
-app.listen(3000)
+const server = app.listen(3000)

lib/cpu-profile-to-tree.js

@@ -21,8 +21,44 @@ function convert (profile) {
   return converted
 }
 
+function id2IndexMap (nodes) {
+  const map = new Array(nodes.length + 1)
+  for (let i = 0; i < nodes.length; i++) {
+    const node = nodes[i]
+    map[node.id] = i
+  }
+  return map
+}
+
+function convertCpuProf (nodes, id2Index, id) {
+  const node = nodes[id2Index[id]]
+  const name = node.callFrame.functionName
+  const url = node.callFrame.url
+  const lineNumber = node.callFrame.lineNumber
+  const childrenLength = node.children ? node.children.length : 0
+  const converted = {
+    children: new Array(childrenLength),
+    name: `${name}${url ? ' ' + url : ''}${lineNumber > 0 ? `:${lineNumber}` : ''}`,
+    top: node.hitCount,
+    value: node.hitCount,
+    S: 0
+  }
+  if (name[0] === '(' && childrenLength === 0) {
+    // filter out (garbage collector) and (idle)
+    converted.top = 0
+    converted.value = 0
+  }
+  for (let i = 0; i < childrenLength; i++) {
+    converted.children[i] = convertCpuProf(nodes, id2Index, node.children[i])
+    converted.value += converted.children[i].value
+  }
+  return converted
+}
+
 function cpuProfileToTree (profile) {
-  const converted = convert(profile.head)
+  const converted = profile.head
+    ? convert(profile.head)
+    : convertCpuProf(profile.nodes, id2IndexMap(profile.nodes), 1)
   return {
     merged: converted,
     unmerged: converted