Struct BTreeKeyFormat 

pub struct BTreeKeyFormat {
    pub big_keys: bool,
    pub variable_index_keys: bool,
    pub max_key_len: u16,
}

Describes how a B-tree encodes its keys, so the shared split / grow / rotate machinery below can serve both the classic-HFS 1-byte-key catalog and the HFS+ 2-byte (“big key”) trees without forking the algorithm.

The classic path threads BTreeKeyFormat::CLASSIC_CATALOG and is byte-identical to the pre-descriptor code (the fixed 0x25 index key produced by normalize_catalog_index_key); HFS+ threads the matching HFSPLUS_* constant, which is what unlocks variable-length index keys so an HFS+ catalog can split past a single leaf level without corrupting.

Derived from the BTHeaderRec attributes bitfield + maxKeyLength.

Fields

big_keys: bool

kBTBigKeysMask: key-length prefix is 2 bytes (HFS+) vs 1 byte (classic).

variable_index_keys: bool

kBTVariableIndexKeysMask: index records store the child’s variable-length key verbatim. When clear, index keys are padded to max_key_len.

max_key_len: u16

Maximum key length — the fixed index-key width when variable_index_keys is clear (classic catalog: 0x25; HFS+ extents-overflow: 10).

Implementations

impl BTreeKeyFormat

pub const CLASSIC_CATALOG: BTreeKeyFormat

Classic HFS catalog: 1-byte key length, fixed 0x25-byte index keys.

pub const HFSPLUS_CATALOG: BTreeKeyFormat

HFS+/HFSX catalog: 2-byte key length, variable-length index keys (kHFSPlusCatalogKeyMaximumLength = 516).

pub const HFSPLUS_EXTENTS: BTreeKeyFormat

HFS+ extents-overflow: 2-byte key length, fixed 10-byte index keys (kHFSPlusExtentKeyMaximumLength = 10).

pub const HFSPLUS_ATTRIBUTES: BTreeKeyFormat

HFS+ attributes: 2-byte key length, variable-length index keys (kHFSPlusAttrKeyMaximumLength = 264).

pub const CLASSIC_EXTENTS: BTreeKeyFormat

Classic HFS extents-overflow: 1-byte key length, fixed 7-byte keys.

pub fn from_header(attributes: u32, max_key_len: u16) -> Self

Build a descriptor from a BTHeaderRec attributes bitfield and maxKeyLength. The attributes field on hand-built volumes can be 0 (no flags) even for HFS+ trees, so callers that know the tree’s identity should prefer the HFSPLUS_* / CLASSIC_CATALOG constants; this helper is for code paths that only have the raw header bytes.

pub fn header_attributes(&self) -> u32

The BTHeaderRec attributes bits implied by this format.

pub fn len_prefix(&self) -> usize

Bytes occupied by the key-length prefix (1 classic, 2 big-key).

pub fn key_len(&self, record: &[u8]) -> usize

Read the key length stored at the front of record.

pub fn key_portion(&self, record: &[u8]) -> Vec<u8>

The key portion of a record — the length prefix plus key_len key bytes. This is exactly the slice an index separator must carry, and what the split helpers extract from a leaf/child’s first record.

pub fn make_index_key(&self, first_key: &[u8]) -> Vec<u8>

Build the key bytes of an index record (length prefix + key) from a child node’s first-key portion.

• Classic HFS: the fixed 0x25 normalized key, identical to normalize_catalog_index_key.
• HFS+ variable-index-key trees (catalog, attributes): the key portion verbatim (2-byte length + key bytes).
• HFS+ fixed-index-key trees (extents-overflow): the key bytes padded to max_key_len, length field forced to max_key_len.

Trait Implementations

impl Clone for BTreeKeyFormat

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for BTreeKeyFormat

impl Debug for BTreeKeyFormat

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for BTreeKeyFormat

impl PartialEq for BTreeKeyFormat

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for BTreeKeyFormat