Struct Mapping 

pub struct Mapping;

A helper struct that provided the O(1) calculations to find the coordinates of a block that suits exactly the requested buffer size, or the next available one that can fit the message as well.

Implementations

impl Mapping

pub fn find_indices(size: u32) -> (u32, u32)

Maps a block size to its corresponding (First-Level, Second-Level) indices.

This function implements a two-level mapping strategy used for O(1) free-block lookup, optimized for both high-velocity small allocations and logarithmic scaling of large blocks.

Mapping Logic:

• Linear (Small): For sizes < 128, it uses a fixed FL (0) and 16-byte SL subdivisions. This minimizes fragmentation for tiny objects.
• Logarithmic (Large): For sizes >= 128, FL is the power of 2 (determined via leading_zeros), and SL is a 3-bit subdivider of the range between 2^n and 2^(n+1).

Mathematical Transformation:

• FL = log2(size)
• SL = (size - 2^FL) / (2^(FL - 3))

Bounds:

Indices are clamped to (31, 7) to prevent overflow in the matrix bitmask.

Arguments

• size - The total byte size of the memory block.

Returns

A tuple of (fl, sl) indices.