iOS处理器的小端模式

Tags
iOS
Date
Jun 15, 2020
iOS 设备的处理器是基于 ARM 架构的,采用小端模式(低字节放低位)读取数据的。
notion image
可以在一个ViewController里断点实验,可以看到
  • 这个vc的地址是0x7f8974f0c830
  • 这个vc的第一个8字节是0x000000010a9a2390,在内存中的显示为90 23 9a 0a 01 00 00 00
    • 这个8字节表示的是vc的isa,即[ViewController class]的地址
  • 这个vc的第二个8字节是0x00007f8974d18750,在内存中的显示为50 87 d1 74 89 7f 00 00
    • 这个8字节表示是vc.view
(lldb) po self <ViewController: 0x7f8974f0c830> (lldb) x self 0x7f8974f0c830: 90 23 9a 0a 01 00 00 00 00 00 00 00 00 00 00 00 .#.............. 0x7f8974f0c840: 00 00 00 00 00 00 00 00 50 87 d1 74 89 7f 00 00 ........P..t.... (lldb) x/4 self 0x7f8974f0c830: 0x000000010a9a2390 0x0000000000000000 0x7f8974f0c840: 0x0000000000000000 0x00007f8974d18750 (lldb) po 0x000000010a9a2390 ViewController (lldb) x 0x000000010a9a2390 0x10a9a2390: b8 23 9a 0a 01 00 00 00 d0 f7 7d 89 ff 7f 00 00 .#........}..... 0x10a9a23a0: 00 d2 82 75 89 7f 00 00 7f 00 00 00 5c 83 32 00 ...u........\.2. (lldb) x self.class 0x10a9a2390: b8 23 9a 0a 01 00 00 00 d0 f7 7d 89 ff 7f 00 00 .#........}..... 0x10a9a23a0: 00 d2 82 75 89 7f 00 00 7f 00 00 00 5c 83 32 00 ...u........\.2. (lldb) po 0x00007f8974d18750 <UIView: 0x7f8974d18750; frame = (0 0; 375 667); autoresize = W+H; layer = <CALayer: 0x6000012c92e0>> (lldb) x 0x00007f8974d18750 0x7f8974d18750: 58 f9 80 89 ff 7f 00 00 00 00 00 00 00 00 00 00 X............... 0x7f8974d18760: 00 00 00 00 00 00 00 00 40 08 7f 02 00 60 00 00 [email protected]`.. (lldb) x self.view 0x7f8974d18750: 58 f9 80 89 ff 7f 00 00 00 00 00 00 00 00 00 00 X............... 0x7f8974d18760: 00 00 00 00 00 00 00 00 40 08 7f 02 00 60 00 00 [email protected]`..
 

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