Import from stackprof to convenient in-memory format

stackprof.ts

@@ -0,0 +1,47 @@
+// https://github.com/tmm1/stackprof
+
+import {Profile, Frame} from './profile'
+
+interface StackprofFrame {
+  name: string
+  file?: string
+  line?: number
+}
+
+export interface StackprofProfile {
+  frames: {[number: string]: StackprofFrame}
+  raw: number[]
+  raw_timestamp_deltas: number[]
+}
+
+export function importFromStackprof(contents: string): Profile {
+  const stackprofProfile = JSON.parse(contents) as StackprofProfile
+
+  const duration = stackprofProfile.raw_timestamp_deltas.reduce((a, b) => a + b, 0)
+  const profile = new Profile(duration)
+
+  const {frames, raw, raw_timestamp_deltas} = stackprofProfile
+  let sampleIndex = 0
+  for (let i = 0; i < raw.length;) {
+    const stackHeight = raw[i++]
+
+    const stack: Frame[] = []
+    for (let j = 0; j < stackHeight; j++) {
+      const id = raw[i++]
+      stack.push({
+        key: id,
+         ...frames[id]
+      })
+    }
+    const nSamples = raw[i++]
+
+    let sampleDuration = 0
+    for (let j = 0; j < nSamples; j++) {
+      sampleDuration += raw_timestamp_deltas[sampleIndex++]
+    }
+
+    profile.appendSample(stack, sampleDuration)
+  }
+
+  return profile
+}