Optionally read from stdin via cli (#99)

Test Plan:
- `./cli.js` opens speedscope in browser with no file selected
- `./cli.js sample/profiles/Chrome/65/simple-timeline.json` opens profile
- `cat sample/profiles/Chrome/65/simple-timeline.json | ./cli.js -` opens profile
- `node --prof-process --preprocess -j sample/profiles/node/8.5.0/isolate-0x102802600-v8.log | ./cli.js -` opens profile

Fixes #95

README.md

@@ -37,14 +37,10 @@ If you record profiling information like so:
 
     node --prof /path/to/my/script.js
 
-Then this will generate a bunch of `isolate*.log` files. Process one of them
-into usable JSON like so:
+Then this will generate one or more `isolate*.log` files. You can open
+the resulting profile in speedscope by running the following command:
 
-    node --prof-process -preprocess -j isolate*.log > profile.v8log.json
-
-Then drop the resulting `profile.v8log.json` file into speedscope, or run
-
-    speedscope profile.v8log.json
+    node --prof-process --preprocess -j isolate*.log | speedscope -
 
 ### Instruments.app
 

cli.js

@@ -2,73 +2,102 @@
 const path = require('path')
 const fs = require('fs')
 const os = require('os')
+const stream = require('stream')
+
 const opn = require('opn')
 
-const helpString = `
-Usage: speedscope [filepath]
+const helpString = `Usage: speedscope [filepath]
 
 If invoked with no arguments, will open a local copy of speedscope in your default browser.
 Once open, you can browse for a profile to import.
+
+If - is used as the filepath, will read from stdin instead.
+
+  cat /path/to/profile | speedscope -
 `
 
-if (process.argv.includes('--help') || process.argv.includes('-h')) {
-  console.log(helpString)
-  process.exit(0)
+function getProfileStream(relPath) {
+  const absPath = path.resolve(process.cwd(), relPath)
+  if (relPath === '-') {
+    // Read from stdin
+    return process.stdin
+  } else {
+    return fs.createReadStream(absPath)
+  }
 }
 
-if (process.argv.includes('--version') || process.argv.includes('-v')) {
-  console.log('v' + require('./package.json').version)
-  process.exit(0)
+function getProfileBuffer(relPath) {
+  const profileStream = getProfileStream(relPath)
+  const chunks = []
+  return new Promise((resolve, reject) => {
+    profileStream.pipe(
+      stream.Writable({
+        write(chunk, encoding, callback) {
+          chunks.push(chunk)
+          callback()
+        },
+        final() {
+          resolve(Buffer.concat(chunks))
+        },
+      }),
+    )
+    profileStream.on('error', ev => reject(ev))
+  })
 }
 
-if (process.argv.length > 3) {
-  console.log('At most one argument expected')
-  console.log(helpString)
-  process.exit(1)
+async function main() {
+  if (process.argv.includes('--help') || process.argv.includes('-h')) {
+    console.log(helpString)
+    return
+  }
+
+  if (process.argv.includes('--version') || process.argv.includes('-v')) {
+    console.log('v' + require('./package.json').version)
+    return
+  }
+
+  if (process.argv.length > 3) {
+    throw new Error('At most one argument expected')
+  }
+
+  let urlToOpen = 'file://' + path.resolve(__dirname, './dist/release/index.html')
+
+  if (process.argv.length === 3) {
+    const relPath = process.argv[2]
+    const sourceBuffer = await getProfileBuffer(relPath)
+    const filename = path.basename(relPath)
+    const sourceBase64 = sourceBuffer.toString('base64')
+    const jsSource = `speedscope.loadFileFromBase64(${JSON.stringify(filename)}, ${JSON.stringify(
+      sourceBase64,
+    )})`
+
+    const filePrefix = `speedscope-${+new Date()}-${process.pid}`
+    const jsPath = path.join(os.tmpdir(), `${filePrefix}.js`)
+    console.log(`Creating temp file ${jsPath}`)
+    fs.writeFileSync(jsPath, jsSource)
+    urlToOpen += `#localProfilePath=${jsPath}`
+
+    // For some silly reason, the OS X open command ignores any query parameters or hash parameters
+    // passed as part of the URL. To get around this weird issue, we'll create a local HTML file
+    // that just redirects.
+    const htmlPath = path.join(os.tmpdir(), `${filePrefix}.html`)
+    console.log(`Creating temp file ${htmlPath}`)
+    fs.writeFileSync(htmlPath, `<script>window.location=${JSON.stringify(urlToOpen)}</script>`)
+
+    urlToOpen = `file://${htmlPath}`
+  }
+
+  console.log('Opening', urlToOpen, 'in your default browser')
+
+  await opn(urlToOpen, {wait: false})
 }
 
-let urlToOpen = 'file://' + path.resolve(__dirname, './dist/release/index.html')
-
-if (process.argv.length === 3) {
-  const absPath = path.resolve(process.cwd(), process.argv[2])
-  let sourceBuffer
-  try {
-    sourceBuffer = fs.readFileSync(absPath)
-  } catch (e) {
-    console.log(e)
+main()
+  .then(() => {
+    process.exit(0)
+  })
+  .catch(e => {
+    console.log(e.stack + '\n')
     console.log(helpString)
     process.exit(1)
-  }
-  const filename = path.basename(absPath)
-  const sourceBase64 = sourceBuffer.toString('base64')
-  const jsSource = `speedscope.loadFileFromBase64(${JSON.stringify(filename)}, ${JSON.stringify(
-    sourceBase64,
-  )})`
-
-  const filePrefix = `speedscope-${+new Date()}-${process.pid}`
-  const jsPath = path.join(os.tmpdir(), `${filePrefix}.js`)
-  console.log(`Creating temp file ${jsPath}`)
-  fs.writeFileSync(jsPath, jsSource)
-  urlToOpen += `#localProfilePath=${jsPath}`
-
-  // For some silly reason, the OS X open command ignores any query parameters or hash parameters
-  // passed as part of the URL. To get around this weird issue, we'll create a local HTML file
-  // that just redirects.
-  const htmlPath = path.join(os.tmpdir(), `${filePrefix}.html`)
-  console.log(`Creating temp file ${htmlPath}`)
-  fs.writeFileSync(htmlPath, `<script>window.location=${JSON.stringify(urlToOpen)}</script>`)
-
-  urlToOpen = `file://${htmlPath}`
-}
-
-console.log('Opening', urlToOpen, 'in your default browser')
-
-opn(urlToOpen, {wait: false}).then(
-  () => {
-    process.exit(0)
-  },
-  err => {
-    console.error(err)
-    console.exit(1)
-  },
-)
+  })