Module packing 

Shared utilities for packing and unpacking values in EVM storage slots.

This module provides helper functions for bit-level manipulation of storage slots, enabling efficient packing of multiple small values into single 32-byte slots.

Packing only applies to primitive types where LAYOUT::Bytes(count) && count < 32. Non-primitives (structs, fixed-size arrays, dynamic types) have LAYOUT = Layout::Slot.

Solidity Compatibility

This implementation matches Solidity’s value packing convention:

• Values are right-aligned within their byte range
• Types smaller than 32 bytes can pack multiple per slot when dimensions align

Structs

FieldLocation

Location information for a packed field within a storage slot.

PackedSlot

A helper struct to support packing elements into a single slot. Represents an in-memory storage slot value.

Functions

calc_element_loc

Calculate the element location within a slot for an array element at index idx.

calc_element_offset

Calculate the byte offset within a slot for an array element at index idx.

calc_element_slot

Calculate which slot an array element at index idx starts in.

calc_packed_slot_count

Calculate the total number of slots needed for an array.

create_element_mask

Create a bit mask for a value of the given byte size.

extract_packed_value

Extract a packed value from a storage slot at a given byte offset.

gen_word_fromtest-utils

Test helper function for constructing EVM words from hex string literals.

insert_packed_value

Insert a packed value into a storage slot at a given byte offset.

zero_packed_value

Zero out a packed value in a storage slot at a given byte offset.