geodesk::Key Class Reference

A lightweight wrapper for a key string. More...

#include <Key.h>

Public Member Functions
	Key ()
	Creates a null Key.
const char *	data () const noexcept
	The character data of the key string.
uint32_t	size () const noexcept
	The size of the key string (in bytes, not characters).
int	code () const noexcept
	The global-string code of this Key, or -1 if it is not in the global-string table.
bool	operator== (const Key &) const =default
bool	operator!= (const Key &) const =default

Detailed Description

A lightweight wrapper for a key string.

A Key is constructed from a std::string_view via Features::key() and is valid for all features within the same GOL. A Key created for one GOL cannot be used for lookups in another.

A Key object is useful in scenarios requiring lookups of the same tag across multiple features. It avoids the overhead of resolving the tag's global-string code on every lookup, leading to a performance boost of about 2x to 4x.

Key houseNumber = buildings.key("addr:housenumber");
for(Feature building: buildings)
{
    TagValue hn = building[houseNumber];
    // This is faster than:
    TagValue hnSlow = building["addr:housenumber"];
}

Key converts implicitly to std::string_view.

Warning

The memory backing the std::string_view used to create this Key must remain unchanged and valid for the Key's entire lifetime to avoid undefined behavior.

See also

Tags, Feature

Constructor & Destructor Documentation

Key()

geodesk::Key::Key ( )

inline

Creates a null Key.

Any lookup with a null Key returns an empty TagValue. Calling hasTag() with a null Key always returns false.

Member Function Documentation

code()

int geodesk::Key::code ( ) const

inlinenoexcept

The global-string code of this Key, or -1 if it is not in the global-string table.

data()

const char * geodesk::Key::data ( ) const

inlinenoexcept

The character data of the key string.

Note: The string is not guaranteed to 0-terminated.

operator!=()

bool geodesk::Key::operator!= ( const Key & ) const

default

operator==()

bool geodesk::Key::operator== ( const Key & ) const

default

size()

uint32_t geodesk::Key::size ( ) const

inlinenoexcept

The size of the key string (in bytes, not characters).

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The documentation for this class was generated from the following file:

• C:/dev/libgeodesk/include/geodesk/feature/Key.h