Key Expression

class KeyExpr : public zenoh::Owned<::z_owned_keyexpr_t>

A Zenoh key expression .

Key expression can be registered in the zenoh::Session object with zenoh::Session::declare_keyexpr method. The unique id is internally assinged to the key expression string in this case. This allows to reduce bandwith usage when transporting key expressions.

Methods

typedef ::z_keyexpr_intersection_level_t IntersectionLevel

Intersection level of 2 key expressions.

Values:

  • Z_KEYEXPR_INTERSECTION_LEVEL_DISJOINT: 2 key expression do not intersect.

  • Z_KEYEXPR_INTERSECTION_LEVEL_INTERSECTS: 2 key expressions intersect, i.e. there exists at least one key that is included by both.

  • Z_KEYEXPR_INTERSECTION_LEVEL_INCLUDES: First key expression is the superset of second one.

  • Z_KEYEXPR_INTERSECTION_LEVEL_EQUALS: 2 key expressions are equal.

Warning

This API has been marked as unstable: it works as advertised, but it may be changed in a future release.

inline std::string_view as_string_view() const

Get underlying key expression string.

Returns:

The key expression as a string_view.

inline bool includes(const KeyExpr &other)

Check if a given KeyExpr includes the other.

Parameters:

other – the KeyExpr to compare with

Returns:

true if current key expression includes other, i.e. contains every key belonging to the other.

inline KeyExpr concat(std::string_view s, ZResult *err = nullptr) const

Construct new key expression by concatenating the current one with a string.

Parameters:

  • s – a string to concatenate with the key expression.

  • err – if not null, the result code will be written to this location, otherwise ZException exception will be thrown in case of error.

Returns:

a new key expression.

inline KeyExpr join(const KeyExpr &other, ZResult *err = nullptr) const

Construct new key expression by joining it with another one.

Parameters:

  • other – the KeyExpr to append.

  • err – if not null, the result code will be written to this location, otherwise ZException exception will be thrown in case of error.

inline bool intersects(const KeyExpr &other) const

Check if 2 key expressions intersect.

Returns:

true if there is at least one non-empty key that is contained in both key expressions, false otherwise.

inline IntersectionLevel relation_to(const KeyExpr &other)

Returns the relation between this and other from this’s point of view.

static inline bool is_canon(std::string_view s)

Check if the string represents a canonical key expression.

Constructors

inline KeyExpr(std::string_view key_expr, bool autocanonize = true, ZResult *err = nullptr)

Create a new instance from a string.

Parameters:

  • key_expr – string representing key expression.

  • autocanonize – if true the key_expr will be autocanonized, prior to constructing key expression.

  • err – if not null, the result code will be written to this location, otherwise ZException exception will be thrown in case of error.

inline KeyExpr(const std::string &key_expr, bool autocanonize = true, ZResult *err = nullptr)

Create a new instance from a string.

Parameters:

  • key_expr – string representing key expression.

  • autocanonize – if true the key_expr will be autocanonized, prior to constructing key expression.

  • err – if not null, the result code will be written to this location, otherwise ZException exception will be thrown in case of error.

inline KeyExpr(const char *key_expr, bool autocanonize = true, ZResult *err = nullptr)

Create a new instance from a null-terminated string.

Parameters:

  • key_expr – null-terminated string representing key expression.

  • autocanonize – if true the key_expr will be autocanonized, prior to constructing key expression.

  • err – if not null, the result code will be written to this location, otherwise ZException exception will be thrown in case of error.

inline KeyExpr(const KeyExpr &other)

Copy constructor.

Operators

inline bool operator==(std::string_view other) const

Key expression to string equality relation.

Parameters:

other – a string to compare with.

Returns:

true if the key expression string representation is equal to other, false otherwise.

inline bool operator!=(std::string_view other) const

Key expression to string inequality relation.

Parameters:

other – a string to compare with.

Returns:

false if the key expression string representation is equal to other, true otherwise.

inline bool operator==(const std::string &other) const

Key expression to string equality relation.

Parameters:

other – a string to compare with.

Returns:

true if the key expression string representation is equal to other, false otherwise.

inline bool operator!=(const std::string &other) const

Key expression to string inequality relation.

Parameters:

other – a string to compare with.

Returns:

false if the key expression string representation is equal to other, true otherwise.

inline bool operator==(const char *other) const

Key expression to string equality relation.

Parameters:

other – a null-terminated string to compare with.

Returns:

true if the key expression string representation is equal to other, false otherwise.

inline bool operator!=(const char *other) const

Key expression to string inequality relation.

Parameters:

other – a null-terminated string to compare with.

Returns:

false if the key expression string representation is equal to other, true otherwise.

inline bool operator==(const KeyExpr &other) const

Equality relation.

Parameters:

other – a key expression to compare with.

Returns:

true if both key expressions are equal (i.e. they represent the same set of resources), false otherwise.

inline bool operator!=(const KeyExpr &other) const

Inequality relation.

Parameters:

other – a key expression to compare with.

Returns:

false if both key expressions are equal (i.e. they represent the same set of resources), true otherwise.

inline KeyExpr &operator=(const KeyExpr &other)

Assignment operator.