# 3.3 Data Conventions

_Peios / Advanced Peios / Conventions / Specification Structure_

> The conventions every book in this anthology inherits — byte order, sizes, layout tables, notation, strings, hashes and timestamps.

The conventions below hold across every book in this anthology. A book
MUST NOT restate them, and MUST state any point on which it differs.

## 3.3.1 Byte order

All multi-byte integer fields are little-endian unless explicitly stated
otherwise.

## 3.3.2 Sizes

All sizes and offsets are in bytes. `u8`, `u16`, `u32`, and `u64` denote
unsigned integers of 8, 16, 32, and 64 bits.

## 3.3.3 Layout tables

A field layout is given as a table in declaration order. **A layout
table is normative**: fields appear on the wire in the order listed,
with no padding between them.

## 3.3.4 Notation

Hexadecimal values carry the `0x` prefix. Byte sequences are written as
space-separated hex pairs: `0a 0b 0c`.

## 3.3.5 Strings

Strings are UTF-8 (RFC 3629). String comparison is byte-for-byte
equality unless stated otherwise.

## 3.3.6 Hashes and signatures

Hash values are lowercase hexadecimal unless stated otherwise, and hash
algorithms are named by their IANA-registered identifiers.

## 3.3.7 Timestamps

Timestamps are RFC 3339, in UTC, and end with `Z`.

## 3.3.8 What a book's conventions article carries

Given the above, a book's conventions article (§3.1) is short. It MUST
carry the book's RFC 2119 declaration, and SHOULD carry only:

- notation the book introduces that is not listed here;
- any point on which the book departs from this article;
- pseudocode conventions, if the book uses pseudocode (§2.3).

> [!NOTE]
> Before this article existed, four books each carried a near-identical
> conventions chapter. Three of them listed the same seven headings.
> Duplicated text of that kind does not stay identical: it is where
> contradictions breed, and the contradiction is invisible because
> nobody reads two copies of the same thing side by side.