Reference

  • ARM Datasheet

https://www.freecodecamp.org/news/what-is-endianness-big-endian-vs-little-endian/
https://zhuanlan.zhihu.com/p/360037797

Background (Why)

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Endianness Overview (What)

  • BE stores the big-end first. When reading multiple bytes the first byte (or the lowest memory address) is the biggest - so it makes the most sense to people who read left to right.
  • LE stores the little-end first. When reading multiple bytes the first byte (or the lowest memory address) is the littlest - so it makes most sense to people who read right to left.
  • BE vs LE

  • image.png

    Examples (How)

  • X86 is LE; ARM is LE by defaut (but supports BE also).

  • 网络字节序

TCP/IP协议隆重出场，RFC1700规定使用“大端”字节序为网络字节序。

  • unsinged int 类型数据在内存的存储方式 （对于大于一个字节的基本数据类型，CPU都会以一定的 order 按 byte 读取数据）

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  • Struct 类型数据在内存的存储方式（对于复合数据类型，CPU按照其子元素的基本数据类型读取数据，另外会考虑内存对齐）

下面是在 X86_64 上实现的例子（小端模式）
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