Struct Automaton

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pub struct Automaton { /* private fields */ }

Expand description

A minimal, deterministic automaton representing a JSONPath query.

Implementations§

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impl Automaton

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pub fn new(query: &JsonPathQuery) -> Result<Self, CompilerError>

Convert a JsonPathQuery into a minimal deterministic automaton.

§Errors

CompilerError::QueryTooComplex raised if the query is too complex and the automaton size was exceeded.
CompilerError::NotSupported raised if the query contains elements not yet supported by the compiler.

Source

pub fn is_select_root_query(&self) -> bool

Returns whether this automaton represents the select-root JSONPath query (‘$’).

§Examples

let query = rsonpath_syntax::parse("$").unwrap();
let automaton = Automaton::new(&query).unwrap();

assert!(automaton.is_select_root_query());

let query = rsonpath_syntax::parse("$.a").unwrap();
let automaton = Automaton::new(&query).unwrap();

assert!(!automaton.is_select_root_query());

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pub fn is_empty_query(&self) -> bool

Returns whether this automaton represents an empty JSONPath query that cannot accept anything.

A query like this can be created by, for example, putting a trivially false filter or an empty slice into the query.

§Examples

let query = rsonpath_syntax::parse("$[::0]").unwrap();
let automaton = Automaton::new(&query).unwrap();

assert!(automaton.is_empty_query());

let query = rsonpath_syntax::parse("$").unwrap();
let automaton = Automaton::new(&query).unwrap();

assert!(!automaton.is_empty_query());

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pub fn rejecting_state(&self) -> State

Returns the rejecting state of the automaton.

The state is defined as the unique state from which there exists no accepting run. If the query automaton reaches this state, the current subtree is guaranteed to have no matches.

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pub fn initial_state(&self) -> State

Returns the initial state of the automaton.

Query execution should start from this state.

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pub fn is_accepting(&self, state: State) -> bool

Returns whether the given state is accepting.

§Example

let query = rsonpath_syntax::parse("$.a").unwrap();
let automaton = Automaton::new(&query).unwrap();
let state_2 = automaton[automaton.initial_state()].member_transitions()[0].1;

assert!(automaton.is_accepting(state_2));

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pub fn has_any_array_item_transition(&self, state: State) -> bool

Returns whether the given state transitions to any list.

§Example

let query = rsonpath_syntax::parse("$[2]").unwrap();
let automaton = Automaton::new(&query).unwrap();
let state = automaton.initial_state();

assert!(automaton.has_any_array_item_transition(state));

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pub fn has_first_array_index_transition_to_accepting( &self, state: State, ) -> bool

Returns whether the given state is accepting the first item in a list.

§Example

let query = rsonpath_syntax::parse("$[0]").unwrap();
let automaton = Automaton::new(&query).unwrap();
let state = automaton.initial_state();

assert!(automaton.has_first_array_index_transition_to_accepting(state));

let query = rsonpath_syntax::parse("$[1]").unwrap();
let automaton = Automaton::new(&query).unwrap();
let state = automaton.initial_state();

assert!(!automaton.has_first_array_index_transition_to_accepting(state));

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pub fn has_array_index_transition_to_accepting( &self, state: State, match_index: &JsonUInt, ) -> bool

Returns whether the given state is accepting the item at a given index in a list.

§Example

let query = rsonpath_syntax::parse("$[1]").unwrap();
let automaton = Automaton::new(&query).unwrap();
let state = automaton.initial_state();
let match_index_1 = JsonUInt::try_from(1).unwrap();
let match_index_2 = JsonUInt::try_from(2).unwrap();

assert!(automaton.has_array_index_transition_to_accepting(state, &match_index_1));
assert!(!automaton.has_array_index_transition_to_accepting(state, &match_index_2));

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pub fn has_transition_to_accepting(&self, state: State) -> bool

Returns whether the given state has any transitions (labelled or fallback) to an accepting state.

§Example

let query = rsonpath_syntax::parse("$.a").unwrap();
let automaton = Automaton::new(&query).unwrap();

assert!(automaton.has_transition_to_accepting(automaton.initial_state()));

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pub fn is_rejecting(&self, state: State) -> bool

Returns whether the given state is rejecting, i.e. there exist no accepting runs from it.

§Example

let query = rsonpath_syntax::parse("$.a").unwrap();
let automaton = Automaton::new(&query).unwrap();

assert!(automaton.is_rejecting(automaton.rejecting_state()));

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pub fn is_unitary(&self, state: State) -> bool

Returns whether the given state is unitary. A unitary state is one that has exactly one labelled transition and its fallback targets the rejecting state.

Intuitively, there exists only one label that progresses towards acceptance from this state.

§Example

let query = rsonpath_syntax::parse("$.a").unwrap();
let automaton = Automaton::new(&query).unwrap();

assert!(automaton.is_unitary(automaton.initial_state()));