Endianness

As explained in Latency

Byte order is the ordering of the bytes that represent a multi-byte value in memory or in a serialized representation.

Endianness is the ordering of bytes used to represent a multi-byte value in memory or a serialized representation. CPU architecture determines in-memory byte order, so mismatches can require transformation during serialization and deserialization. section 7.3

A 32-bit value can be arranged in two principal orders:

• Little-endian stores lower-order bits first and higher-order bits last; 0xE011CFD0 becomes 0xD0, 0xCF, 0x11, 0xE0 in memory. section 7.3
• Big-endian stores higher-order bits first and lower-order bits last; 0xE011CFD0 becomes 0xE0, 0x11, 0xCF, 0xD0. section 7.3

Order identifier in memory

A Rust order structure stores orderId 1001 as the four bytes 0xE9, 0x03, 0x00, and 0x00 under little-endian order. Serialization presents the same value as JSON 0x000003E9, while deserialization reverses the transformation. section 7.3

Figure 7.2 Serialization transforms the in-memory representation of data (shown on the left as a Rust struct) to a serialized format such as JSON (shown on the right). Deserialization performs the opposite transformation from a serialized format to an in-memory representation.

Compare the in-memory Rust struct with its JSON representation and the reverse deserialization path. section 7.3

How Latency covers it

How deep it goes

Defines little- and big-endian layouts with 32-bit examples, but stops short of implementation code or measurement procedures.

Examples

Uses a Rust order structure, a 32-bit order identifier, hexadecimal byte sequences, and JSON serialization.

What you can do after

Evaluate how little- or big-endian layout changes the byte representation and transformation work for serialized values.

How it connects

Connects byte order to CPU architecture, serialization, deserialization, memory copies, JSON, and network protocols.

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Also explained in

• 

  liveBookmanning.com
  Modern C, Third EditionEndianness is the ordering convention used to encode the bytes of multi-byte values in a representation.
• 

  liveBookmanning.com
  Rust in Action: Systems programming concepts and techniquesEndianness is the convention governing the order in which the bytes of a multibyte value are laid out in memory.

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Related concepts

• big-endianincludes · Big-endian is an ordering convention in which the most significant byte or component of a multibyte value comes before its less significant components.
• little-endianincludes · Little-endian is a byte-order convention in which the least significant byte of a multibyte value comes first, at the lowest address or earliest position.
• implementation definedconfigures · Implementation-defined behavior is behavior for which a language standard permits an implementation to choose among specified alternatives and requires it to document its choice.

This explainer was generated by Manning's knowledge graph from the text of Latency. The section links point to the parts of the book it draws on.