Minicap数据解析（js）

var WebSocketServer = require('ws').Server
  , http = require('http')
  , express = require('express')
  , path = require('path')
  , net = require('net')
  , app = express()

var PORT = process.env.PORT || 9002

app.use(express.static(path.join(__dirname, '/public')))

var server = http.createServer(app)
var wss = new WebSocketServer({ server: server })

wss.on('connection', function(ws) {
  console.info('Got a client')

  var stream = net.connect({
    port: 1717
  })

  stream.on('error', function() {
    console.error('Be sure to run `adb forward tcp:1717 localabstract:minicap`')
    process.exit(1)
  })

  var readBannerBytes = 0
  var bannerLength = 2
  var readFrameBytes = 0
  var frameBodyLength = 0
  var frameBody = new Buffer(0)
  var banner = {
    version: 0
  , length: 0
  , pid: 0
  , realWidth: 0
  , realHeight: 0
  , virtualWidth: 0
  , virtualHeight: 0
  , orientation: 0
  , quirks: 0
  }

  function tryRead() {
    for (var chunk; (chunk = stream.read());) {
      console.info('chunk(length=%d)', chunk.length)
      for (var cursor = 0, len = chunk.length; cursor < len;) {
        if (readBannerBytes < bannerLength) {
          switch (readBannerBytes) {
          case 0:
            // version
            banner.version = chunk[cursor]
            break
          case 1:
            // length
            banner.length = bannerLength = chunk[cursor]
            break
          case 2:
          case 3:
          case 4:
          case 5:
        // pid
        banner.pid +=
          (chunk[cursor] << ((readBannerBytes - 2) * 8)) >>> 0
        break
      case 6:
      case 7:
      case 8:
      case 9:
        // real width
        banner.realWidth +=
          (chunk[cursor] << ((readBannerBytes - 6) * 8)) >>> 0
        break
      case 10:
      case 11:
      case 12:
      case 13:
        // real height
        banner.realHeight +=
          (chunk[cursor] << ((readBannerBytes - 10) * 8)) >>> 0
        break
      case 14:
      case 15:
      case 16:
      case 17:
        // virtual width
        banner.virtualWidth +=
          (chunk[cursor] << ((readBannerBytes - 14) * 8)) >>> 0
        break
      case 18:
      case 19:
      case 20:
      case 21:
        // virtual height
        banner.virtualHeight +=
          (chunk[cursor] << ((readBannerBytes - 18) * 8)) >>> 0
        break
      case 22:
        // orientation
        banner.orientation += chunk[cursor] * 90
        break
      case 23:
        // quirks
        banner.quirks = chunk[cursor]
        break
      }

      cursor += 1
      readBannerBytes += 1

      if (readBannerBytes === bannerLength) {
        console.log('banner', banner)
      }
    }
    else if (readFrameBytes < 4) {
      frameBodyLength += (chunk[cursor] << (readFrameBytes * 8)) >>> 0
      cursor += 1
      readFrameBytes += 1
      console.info('headerbyte%d(val=%d)', readFrameBytes, frameBodyLength)
    }
    else {
      if (len - cursor >= frameBodyLength) {
        console.info('bodyfin(len=%d,cursor=%d)', frameBodyLength, cursor)

        frameBody = Buffer.concat([
          frameBody
        , chunk.slice(cursor, cursor + frameBodyLength)
        ])

        // Sanity check for JPG header, only here for debugging purposes.
        if (frameBody[0] !== 0xFF || frameBody[1] !== 0xD8) {
          console.error(
            'Frame body does not start with JPG header', frameBody)
          process.exit(1)
        }

        ws.send(frameBody, {
          binary: true
        })

        cursor += frameBodyLength
        frameBodyLength = readFrameBytes = 0
        frameBody = new Buffer(0)
      }
      else {
        console.info('body(len=%d)', len - cursor)

        frameBody = Buffer.concat([
          frameBody
        , chunk.slice(cursor, len)
        ])

        frameBodyLength -= len - cursor
        readFrameBytes += len - cursor
        cursor = len
          }
        }
      }
    }
  }

  stream.on('readable', tryRead)

  ws.on('close', function() {
console.info('Lost a client')
stream.end()
  })
})

server.listen(PORT)
console.info('Listening on port %d', PORT)