Xcode 使用 chisel 插件及 chisel 源码解读

作者: who_young | 来源:发表于2020-01-03 20:03 被阅读0次

LLDB 是 Xcode 中自带的一个调试工具，chisel 是 facebook 开源的一个 LLDB 命令的集合，它简化和扩展了 LLDB 的命令，使用方法在 chisel github 中介绍的也比较详细。我在这里简单介绍一下，并结合我的使用经验，做些说明。

1. 安装 (安装工具：终端)

若未安装 homebrew , 则先执行 /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)" 安装 homebrew
brew update
brew install chisel
touch ~/.lldbinit
open ~/.lldbinit
将 command script import /usr/local/opt/chisel/libexec/fblldb.py 这条命令粘贴到 ~/.lldbinit 文件中
重启 Xcode 即可。
提示：若重启 Xcode 后，未生效，可以将 chisel 下载到本地，并将 command script import /path/to/fblldb.py 添加到 ~/.lldbinit 文件中。/path/to/fblldb.py 替换为 fblldb.py 所在的真实路径

2. Command 介绍

在 Xcode 控制台可以使用 help 命令查看所有支持的命令。这里只介绍下面一些常用的命令：

Command	Description	iOS	OS X
pviews	递归打印 key window 上的 View	Yes	Yes
pvc	递归打印 key window 上的 View Controller	Yes	No
visualize	在 Mac 的预览 APP 中打开 `UIImage`, `CGImageRef`, `UIView`, `CALayer`, `NSData` (of an image), `UIColor`, `CIColor`, or `CGColorRef`	Yes	No
fv	在视图层级中，找到类名包含要搜索类名的所有 View	Yes	No
fvc	在视图层级中，找到类名包含要搜索类名的所有 View Controller	Yes	No
show/hide	显示或隐藏指定的 View 或者 Layer	Yes	Yes
mask/unmask	在 View 或者 Layer 的上方添加/隐藏一个透明的蒙版	Yes	No
border/unborder	给 View 或者 Layer 添加/隐藏一个边框	Yes	Yes
caflush	重新渲染页面	Yes	Yes
bmessage	给类方法或实例方法添加一个断点，即使这个类没有实现该方法(父类实现了该方法)	Yes	Yes
presponder	打印从指定对象开始的响应链	Yes	Yes

上述 Command 的实现源码在 /chisel/commands/目录下

3. Command 使用例子

使用 help <command> 可以查看具体使用方法
pvc

<RootTabBarController 0x7fd9fe80cc00>, state: appeared, view: <UILayoutContainerView 0x7fda00006390>
   | <BaseNavigationController 0x7fd9fd805e00>, state: appeared, view: <UILayoutContainerView 0x7fd9fd402df0>
   |    | <RootTableViewController 0x7fd9fd402a60>, state: disappeared, view: <UITableView 0x7fd9ff828200> not in the window
   |    | <EnumerateDemoViewController 0x7fda02001140>, state: appeared, view: <UIView 0x7fda0000d760>

pviews

<UIWindow: 0x7fd9fd602070; frame = (0 0; 375 667); gestureRecognizers = <NSArray: 0x600002918ba0>; layer = <UIWindowLayer: 0x6000027602a0>>
   | <UITransitionView: 0x7fda0201a040; frame = (0 0; 375 667); autoresize = W+H; layer = <CALayer: 0x60000272ef00>>
   |    | <UIDropShadowView: 0x7fda02016630; frame = (0 0; 375 667); clipsToBounds = YES; autoresize = W+H; layer = <CALayer: 0x60000272f040>>
   |    |    | <UILayoutContainerView: 0x7fda00006390; frame = (0 0; 375 667); autoresize = W+H; layer = <CALayer: 0x6000027592a0>>
   |    |    |    | <UITransitionView: 0x7fda00006f50; frame = (0 0; 375 667); clipsToBounds = YES; autoresize = W+H; layer = <CALayer: 0x600002759300>>
  ......
   |    |    |    |    |    |    | <_UIVisualEffectContentView: 0x7fd9fd7052f0; frame = (0 0; 371 48); autoresize = W+H; tintColor = UIExtendedGrayColorSpace 1 1; layer = <CALayer: 0x600002765700>> disablesGroupFiltering
   |    |    |    |    |    | <UITabBarSwappableImageView: 0x7fda0200eaa0; frame = (174.5 4; 21 28); opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x60000272ec40>>
   |    |    |    |    |    | <UITabBarButtonLabel: 0x7fda02401f50; frame = (158 34.5; 54.5 12); text = 'Downloads'; opaque = NO; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x60000047ce60>>

pviews 打印的东西太多，"......" 省略了许多内容。想查找关心的 view，比较难查找，我们通过 help pviews 可以查看更详细的使用方法。

help pviews

     Print the recursion description of <aView>.  Expects 'raw' input (see
     'help raw-input'.)

Syntax: pviews
Print the recursion description of <aView>.

Arguments:
  <aView>; Type: UIView*/NSView*; The view to print the description of.

Options:
  --up/-u ; Print only the hierarchy directly above the view, up to its window.
  --depth/-d <depth>; Type: int; Print only to a given depth. 0 indicates
  infinite depth.
  --window/-w <window>; Type: int; Specify the window to print a description
  of. Check which windows exist with "po (id)[[UIApplication sharedApplication]
  windows]".
  --short/-s ; Print a short description of the view
  --medium/-m ; Print a medium description of the view

Syntax: pviews [--up] [--depth=depth] [--window=window] [--short] [--medium]
<aView>

This command is implemented as FBPrintViewHierarchyCommand in
/Users/yanghu/chisel/commands/FBPrintCommands.py.

我们加上 <aView> 和 -m 参数
pviews 0x7fda0000d760 -m

<UIView: 0x7fda0000d760>
   | <UIButton: 0x7fda0000d8c0>
   |    | <UIButtonLabel: 0x7fd9fd40d0b0>
   | <UIButton: 0x7fda0000e7f0>
   |    | <UIButtonLabel: 0x7fd9fd40ce20>
   | <UIButton: 0x7fda0000ea90>
   |    | <UIButtonLabel: 0x7fd9fd40cb90>
   | <UIButton: 0x7fda0000ed30>
   |    | <UIButtonLabel: 0x7fd9fd40c6f0>

visualize

visualize 0x7fda0000e7f0

visualize.png

fvc enum

0x7fda02001140 EnumerateDemoViewController

fv UIButton

0x7fda0000d8c0 UIButton
0x7fd9fd40d0b0 UIButtonLabel
0x7fda0000e7f0 UIButton
0x7fd9fd40ce20 UIButtonLabel
0x7fda0000ea90 UIButton
0x7fd9fd40cb90 UIButtonLabel
0x7fda0000ed30 UIButton
0x7fd9fd40c6f0 UIButtonLabel
0x7fda00013880 _UIButtonBarButton
0x7fda000153e0 UIButtonLabel

hide 0x7fda0000d8c0

show 0x7fda0000d8c0

caflush

e (void)[0x7fda0000d8c0 setBackgroundColor:[UIColor redColor]]
caflush

border

border 0x7fda0000e7f0 -c 'blue' -w 5
caflush

border.png

unborder

unborder 0x7fda0000e7f0
caflush

mask 0x7fda0000e7f0

mask.png

unmask 0x7fda0000e7f0

presponder 0x7fda00015db0

<UIButton: 0x7fda00015db0; frame = (40 80; 295 40); clipsToBounds = YES; opaque = NO; layer = <CALayer: 0x600002734660>>
   | <UIView: 0x7fda00006840; frame = (0 0; 375 667); autoresize = W+H; layer = <CALayer: 0x600002734500>>
   |    | <EnumerateDemoViewController: 0x7fda0000dc80>
   |    |    | <UIViewControllerWrapperView: 0x7fda02007ee0; frame = (0 0; 375 667); autoresize = W+H; layer = <CALayer: 0x600002730340>>
   |    |    |    | <UINavigationTransitionView: 0x7fd9fd408ba0; frame = (0 0; 375 667); clipsToBounds = YES; autoresize = W+H; layer = <CALayer: 0x600002755fc0>>
   |    |    |    |    | <UILayoutContainerView: 0x7fd9fd402df0; frame = (0 0; 375 667); clipsToBounds = YES; autoresize = W+H; gestureRecognizers = <NSArray: 0x600002939800>; layer = <CALayer: 0x600002756820>>
   |    |    |    |    |    | <BaseNavigationController: 0x7fd9fd805e00>
   |    |    |    |    |    |    | <UIViewControllerWrapperView: 0x7fda02016e70; frame = (0 0; 375 667); autoresize = W+H; layer = <CALayer: 0x60000272ece0>>
   |    |    |    |    |    |    |    | <UITransitionView: 0x7fda00006f50; frame = (0 0; 375 667); clipsToBounds = YES; autoresize = W+H; layer = <CALayer: 0x600002759300>>
   |    |    |    |    |    |    |    |    | <UILayoutContainerView: 0x7fda00006390; frame = (0 0; 375 667); autoresize = W+H; layer = <CALayer: 0x6000027592a0>>
   |    |    |    |    |    |    |    |    |    | <RootTabBarController: 0x7fd9fe80cc00>
   |    |    |    |    |    |    |    |    |    |    | <UIDropShadowView: 0x7fda02016630; frame = (0 0; 375 667); clipsToBounds = YES; autoresize = W+H; layer = <CALayer: 0x60000272f040>>
   |    |    |    |    |    |    |    |    |    |    |    | <UITransitionView: 0x7fda0201a040; frame = (0 0; 375 667); autoresize = W+H; layer = <CALayer: 0x60000272ef00>>
   |    |    |    |    |    |    |    |    |    |    |    |    | <UIWindow: 0x7fd9fd602070; frame = (0 0; 375 667); gestureRecognizers = <NSArray: 0x600002918ba0>; layer = <UIWindowLayer: 0x6000027602a0>>
   |    |    |    |    |    |    |    |    |    |    |    |    |    | <UIWindowScene: 0x7fda02004a80; scene = <FBSSceneImpl: 0x600000960400; identifier: sceneID:com.yanghu.YHDailyDemo-default>; persistentIdentifier = B5525011-A1BC-40F3-AFB4-D8A8187B7102; activationState = UISceneActivationStateForegroundActive; settingsCanvas = <UIWindowScene: 0x7fda02004a80>; windows = (
    "<UIWindow: 0x7fd9fd602070; frame = (0 0; 375 667); gestureRecognizers = <NSArray: 0x600002918ba0>; layer = <UIWindowLayer: 0x6000027602a0>>",
    "<UITextEffectsWindow: 0x7fda02109f60; frame = (0 0; 375 667); opaque = NO; autoresize = W+H; layer = <UIWindowLayer: 0x6000027708a0>>"
)>
   |    |    |    |    |    |    |    |    |    |    |    |    |    |    | <UIApplication: 0x7fd9fd600820>
   |    |    |    |    |    |    |    |    |    |    |    |    |    |    |    | <AppDelegate: 0x600002774220>

bmessage

bmessage "-[EnumerateDemoViewController viewDidAppear:]"

bmessage.png

4. 自定义 Command

新建 Python 文件 , 例 /path/to/test.py
添加 script fblldb.loadCommandsInDirectory('/path/to/') 到 ~/.lldbinit 文件中。注意：/path/to/ 要使用绝对路径，否则会报错。
重启 Xcode 或者在 Xcode 的控制台输入命令 command source ~/.lldbinit

加载自定义 command 的过程，参考源码：fblldb.py : loadCommandsInDirectory()

实例：新建 Python 文件： ~/lldbCustom/threadcheck.py , 修改 ~/.lldbinit 文件：

# ~/.lldbinit

command script import ~/chisel/fblldb.py
script fblldb.loadCommandsInDirectory('/Users/yanghu/lldbCustom/')

添加 yhct 命令，打印当前线程；添加 yhctm 命令，打印当前线程是否是主线程；

#!/usr/bin/python

# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.

import os

import lldb
import fblldbbase as fb

def lldbcommands():
  return [
    YHCurrentThreadCheckCommand(),
    YHCurrentThreadMainCheckCommand()
  ]

class YHCurrentThreadCheckCommand(fb.FBCommand):
  def name(self):
    return 'yhct'

  def description(self):
    return 'print current thread'

  def run(self, arguments, options):
    command = 'po [NSThread currentThread]'
    lldb.debugger.HandleCommand(command)
      
class YHCurrentThreadMainCheckCommand(fb.FBCommand):
  def name(self):
    return 'yhctm'

  def description(self):
    return 'check current thread is or is not equal to main thread'

  def run(self, arguments, options):
    command = 'po [NSThread currentThread].isMainThread'
    lldb.debugger.HandleCommand(command)

5. Command 源码解读 ( 以 visualize 为例)

在 Xcode 控制台执行 help visualize 命令，控制台打印如下：

Open a UIImage, CGImageRef, UIView, or CALayer in Preview.app on your Mac.
     Expects 'raw' input (see 'help raw-input'.)

Syntax: visualize
Open a UIImage, CGImageRef, UIView, or CALayer in Preview.app on your Mac.

Arguments:
  <target>; Type: (id); The object to visualize.

Syntax: visualize <target>

This command is implemented as FBVisualizeCommand in
/Users/yanghu/chisel/commands/FBVisualizationCommands.py.

根据最后一行打印的路径，我们打开 FBVisualizationCommands.py 文件如下 ( "......" 省略了一些无关信息) ：

......
def _showImage(commandForImage):
  imageDirectory = '/tmp/xcode_debug_images/'

  imageName = time.strftime("%Y-%m-%d-%H-%M-%S", time.gmtime()) + ".png"
  imagePath = imageDirectory + imageName

  try:
    os.makedirs(imageDirectory)
  except OSError as e:
    if e.errno == errno.EEXIST and os.path.isdir(imageDirectory):
      pass
    else:
      raise

  toPNG = '(id)UIImagePNGRepresentation((id){})'.format(commandForImage)
  imageDataAddress = fb.evaluateExpressionValue(toPNG, tryAllThreads=True).GetValue()
  imageBytesStartAddress = fb.evaluateExpression('(void *)[(id)' + imageDataAddress + ' bytes]')
  imageBytesLength = fb.evaluateExpression('(NSUInteger)[(id)' + imageDataAddress + ' length]')

  address = int(imageBytesStartAddress, 16)
  length = int(imageBytesLength)

  if not (address or length):
    print('Could not get image data.')
    return

  process = lldb.debugger.GetSelectedTarget().GetProcess()
  error = lldb.SBError()
  mem = process.ReadMemory(address, length, error)

  if error is not None and str(error) != 'success':
    print(error)
  else:
    imgFile = open(imagePath, 'wb')
    imgFile.write(mem)
    imgFile.close()
    os.system('open ' + imagePath)

......

def _showLayer(layer):
  layer = '(' + layer + ')'
  size = '((CGRect)[(id)' + layer + ' bounds]).size'

  width = float(fb.evaluateExpression('(CGFloat)(' + size + '.width)'))
  height = float(fb.evaluateExpression('(CGFloat)(' + size + '.height)'))
  if width == 0.0 or height == 0.0:
    print('Nothing to see here - the size of this element is {} x {}.'.format(width, height))
    return

  fb.evaluateEffect('UIGraphicsBeginImageContextWithOptions(' + size + ', NO, 0.0)')
  fb.evaluateEffect('[(id)' + layer + ' renderInContext:(void *)UIGraphicsGetCurrentContext()]')

  result = fb.evaluateExpressionValue('(UIImage *)UIGraphicsGetImageFromCurrentImageContext()')
  if result.GetError() is not None and str(result.GetError()) != 'success':
    print(result.GetError())
  else:
    image = result.GetValue()
    _showImage(image)

  fb.evaluateEffect('UIGraphicsEndImageContext()')

......

def _visualize(target):
  target = fb.evaluateInputExpression(target)

  if fb.evaluateBooleanExpression('(unsigned long)CFGetTypeID((CFTypeRef)' + target + ') == (unsigned long)CGImageGetTypeID()'):
    _showImage('(id)[UIImage imageWithCGImage:' + target + ']')
  else:
    if objectHelpers.isKindOfClass(target, 'UIImage'):
      _showImage(target)
    elif objectHelpers.isKindOfClass(target, 'UIView'):
      _showLayer('[(id)' + target + ' layer]')
    elif objectHelpers.isKindOfClass(target, 'CALayer'):
      _showLayer(target)
    elif objectHelpers.isKindOfClass(target, 'UIColor') or objectHelpers.isKindOfClass(target, 'CIColor') or _colorIsCGColorRef(target):
      _showColor(target)
    elif objectHelpers.isKindOfClass(target, 'NSData'):
      if _dataIsImage(target):
        _showImage('(id)[UIImage imageWithData:' + target + ']')
      elif _dataIsString(target):
        print(fb.describeObject('[[NSString alloc] initWithData:' + target + ' encoding:4]'))
      else:
        print('Data isn\'t an image and isn\'t a string.')
    else:
      print('{} isn\'t supported. You can visualize UIImage, CGImageRef, UIView, CALayer, NSData, UIColor, CIColor, or CGColorRef.'.format(objectHelpers.className(target)))

class FBVisualizeCommand(fb.FBCommand):
  def name(self):
    return 'visualize'

  def description(self):
    return 'Open a UIImage, CGImageRef, UIView, or CALayer in Preview.app on your Mac.'

  def args(self):
    return [ fb.FBCommandArgument(arg='target', type='(id)', help='The object to visualize.') ]

  def run(self, arguments, options):
    _visualize(arguments[0])

在控制台输入 visualize 0x7fda0000e7f0 命令，会执行 FBVisualizeCommand 类的 run(self, arguments, options) 方法 , 该方法实现里调用 _visualize(target) 方法。
_visualize(target) 方法的执行步骤如下：

确认传参符合要求 fb.evaluateInputExpression(target)
判断传参的类型 objectHelpers.isKindOfClass(target, 'class'), 不同类型执行不同的方法。该例中传参为一个 UIButton 对象，objectHelpers.isKindOfClass(target, 'UIView') 条件成立。因此执行 _showLayer('[(id)' + target + ' layer]') 方法。
_showLayer(layer) 方法内，开启了一个图片上下文，在该上下文里绘制一张图片。绘制成功后，调用 _showImage(commandForImage) 方法。
_showImage(commandForImage) 方法内，为图片创建一个临时存储路径，将图片流写入文件中 imgFile.write(mem) , 然后用 Mac 自带的预览工具打开该图片文件 os.system('open ' + imagePath)

自定义 Command 源码解读

自定义的 Command 需要添加脚本 script fblldb.loadCommandsInDirectory('/path/to/') 到 ~/.lldbinit 文件中, 该脚本中，重点调用了 fblldb.py 文件中的 loadCommandsInDirectory() 方法 ( "......" 省略了一些无关信息) :

def loadCommandsInDirectory(commandsDirectory):
  for file in os.listdir(commandsDirectory):
    fileName, fileExtension = os.path.splitext(file)
    if fileExtension == '.py':
      module = imp.load_source(fileName, os.path.join(commandsDirectory, file))

      if hasattr(module, 'lldbinit'):
        module.lldbinit()

      if hasattr(module, 'lldbcommands'):
        module._loadedFunctions = {}
        for command in module.lldbcommands():
          loadCommand(module, command, commandsDirectory, fileName, fileExtension)

def loadCommand(module, command, directory, filename, extension):
  func = makeRunCommand(command, os.path.join(directory, filename + extension))
  ......
  lldb.debugger.HandleCommand('script ' + functionName + ' = sys.modules[\'' + module.__name__ + '\']._loadedFunctions[\'' + key + '\']')
  lldb.debugger.HandleCommand('command script add --help "{help}" --function {function} {name}'.format(
    help=helpText.replace('"', '\\"'), # escape quotes
    function=functionName,
    name=name))

def makeRunCommand(command, filename):
  def runCommand(debugger, input, exe_ctx, result, _):
    ......
    if validateArgsForCommand(args, command):
      command.run(args, options)

  runCommand.__doc__ = helpForCommand(command, filename)
  return runCommand

该方法的执行步骤如下：

加载自定义 Command 文件 module = imp.load_source(fileName, os.path.join(commandsDirectory, file))
遍历自定义 Command 文件中 lldbcommands方法的类对象数组，对每个类对象调用 loadCommand(module, command, directory, filename, extension) 方法。
loadCommand(module, command, directory, filename, extension) 方法内调用 func = makeRunCommand(command, os.path.join(directory, filename + extension)) 方法，获取具体执行命令的方法。 makeRunCommand(command, filename) 方法调用类对象的 run(self, arguments, options) 方法，返回执行命令的方法。
调用 lldb.debugger.HandleCommand() 执行命令

Xcode 使用 chisel 插件及 chisel 源码解读

1. 安装 (安装工具：终端)

2. Command 介绍

3. Command 使用例子

4. 自定义 Command

5. Command 源码解读 ( 以 visualize 为例)

自定义 Command 源码解读

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