Struct Unit

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pub struct Unit(/* private fields */);

Expand description

An unit represents an element in a double-array.

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impl Unit

Unit represents one node of a double array trie. The bit width of each node is 32-bits.

The bit layout of a non-leaf node:

0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +—————+-+-+—————————————–+-+ | LABEL |H|E| OFFSET |I| +—————+-+-+—————————————–+-+

LABEL 8-bits value that represents a label of the double array node. HAS_LEAF (H) 1-bit flag that indicates whether the node has leaf nodes or not. EXTEND_OFFSET (E) 1-bit flag that indicates whether the offset should be extended or not. OFFSET 21-bits value that represents an offset of the double array node. IS_LEAF (I) 1-bit flag that indicates whether the node is a leaf node or not. This flag is always 0 in this case.

The bit layout of a leaf node:

0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +———————————————————––+-+ | VALUE |I| +———————————————————––+-+

VALUE 31-bits value that represents a value of the double array node. IS_LEAF (I) 1-bit flag that indicates whether the node is a leaf node or not. This flag is always 1 in this case.

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pub const fn new() -> Self

Creates a new Unit.

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pub fn from_u32(value: u32) -> Self

Creates a new Unit from value.

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pub fn as_u32(&self) -> u32

Returns an internal 32 bit integer.

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pub fn has_leaf(&self) -> bool

Returns true if the unit have a leaf as a child unit. Otherwise, returns false.

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pub fn is_leaf(&self) -> bool

Returns true if the unit is a leaf which have a value. Otherwise, return false.

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pub fn value(&self) -> u32

Returns a 31 bits unsigned integer value associated with the unit.

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pub fn label(&self) -> u32

Returns a label (<= 255) if the unit is not a leaf. Otherwise, returns an integer value greater than 255.

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pub fn offset(&self) -> u32

Returns an offset value within the unit. If the offset extension flag is true, returns the offset multiplied by 256.

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pub fn set_offset(&mut self, offset: u32)

Sets an offset to the unit. offset should be a value less than or equal to 29 bits. If the offset is greater than 21 bits, sets the offset extension flag and the offset without lower 8 bits (then, lower 8 bits of the given offset should be 0).

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