Atoms

Detailed Description

Atoms represent all strings within a Reduct expression, as such it also represents anything that a string can be, including integers, floats and intrinsics.

Interning

To improve performance, we "intern" all atoms. Meaning that instead of needing to use strcmp() or similar to compare atoms, we store all atoms in a hash map.

When a new string is encountered, we look it up in the map. As such, any instance of the same string will always be represented by the same reduct_atom_t structure. Turning a string comparison into a pointer comparison and avoiding redundant parsing of numeric or intrinsic values.

See also

Wikipedia String Interning

Data Structures
struct	reduct_atom_t
	Atom structure. More...

Macros
#define	REDUCT_ATOM_SMALL_MAX   15
	The maximum length of a small atom.
#define	REDUCT_FNV_PRIME   16777619U
	FNV-1a 32-bit prime.
#define	REDUCT_FNV_OFFSET   2166136261U
	FNV-1a 32-bit offset basis.

Enumerations
enum	reduct_atom_lookup_flags_t { REDUCT_ATOM_LOOKUP_NONE = 0 , REDUCT_ATOM_LOOKUP_QUOTED = 1 << 0 }
	Atom lookup flags. More...

Functions
static REDUCT_ALWAYS_INLINE reduct_uint32_t	reduct_hash (const char *str, reduct_size_t len)
	Hash a string.
static void	reduct_atom_init (reduct_atom_t *atom)
	Initialize an atom.
REDUCT_API void	reduct_atom_deinit (struct reduct *reduct, reduct_atom_t *atom)
	Deinitialize an atom.
static REDUCT_ALWAYS_INLINE reduct_bool_t	reduct_atom_is_equal (reduct_atom_t *atom, const char *str, reduct_size_t len)
	Check if an atom is equal to a string.
REDUCT_API reduct_atom_t *	reduct_atom_lookup_int (struct reduct *reduct, reduct_int64_t value)
	Lookup an atom by integer value.
REDUCT_API reduct_atom_t *	reduct_atom_lookup_float (struct reduct *reduct, reduct_float_t value)
	Lookup an atom by float value.
REDUCT_API reduct_atom_t *	reduct_atom_lookup (struct reduct *reduct, const char *str, reduct_size_t len, reduct_atom_lookup_flags_t flags)
	Lookup an atom in the Reduct structure.
REDUCT_API void	reduct_atom_normalize (struct reduct *reduct, reduct_atom_t *atom)
	Normalize an atom, determining its shape and parsing escape sequences.

Macro Definition Documentation

REDUCT_ATOM_SMALL_MAX

#define REDUCT_ATOM_SMALL_MAX   15

The maximum length of a small atom.

Definition at line 32 of file atom.h.

REDUCT_FNV_PRIME

#define REDUCT_FNV_PRIME   16777619U

FNV-1a 32-bit prime.

Definition at line 62 of file atom.h.

REDUCT_FNV_OFFSET

#define REDUCT_FNV_OFFSET   2166136261U

FNV-1a 32-bit offset basis.

Definition at line 63 of file atom.h.

Enumeration Type Documentation

reduct_atom_lookup_flags_t

enum reduct_atom_lookup_flags_t

Atom lookup flags.

Enumerator
REDUCT_ATOM_LOOKUP_NONE	No flags.
REDUCT_ATOM_LOOKUP_QUOTED	Atom should be explicitly quoted.

Definition at line 37 of file atom.h.

Function Documentation

reduct_hash()

static REDUCT_ALWAYS_INLINE reduct_uint32_t reduct_hash ( const char *  str, reduct_size_t  len  )

inlinestatic

Hash a string.

Parameters

str	The string to hash.
len	The length of the string.

Returns

The hash of the string.

Definition at line 72 of file atom.h.

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reduct_atom_init()

static void reduct_atom_init ( reduct_atom_t *  atom )

inlinestatic

Initialize an atom.

Parameters

atom	Pointer to the atom to initialize.

Definition at line 88 of file atom.h.

reduct_atom_deinit()

REDUCT_API void reduct_atom_deinit	(	struct reduct *	reduct,
		reduct_atom_t *	atom
	)

Deinitialize an atom.

Parameters

reduct	Pointer to the Reduct structure.
atom	Pointer to the atom to deinitialize.

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reduct_atom_is_equal()

static REDUCT_ALWAYS_INLINE reduct_bool_t reduct_atom_is_equal ( reduct_atom_t *  atom, const char *  str, reduct_size_t  len  )

inlinestatic

Check if an atom is equal to a string.

Parameters

atom	Pointer to the atom.
str	The string to compare.
len	The length of the string.

Returns

REDUCT_TRUE if the atom is equal to the string, REDUCT_FALSE otherwise.

Definition at line 112 of file atom.h.

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reduct_atom_lookup_int()

REDUCT_API reduct_atom_t * reduct_atom_lookup_int	(	struct reduct *	reduct,
		reduct_int64_t	value
	)

Lookup an atom by integer value.

Will create a new atom if it does not exist.

Parameters

reduct	Pointer to the Reduct structure.
value	The integer value.

Returns

A pointer to the atom.

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reduct_atom_lookup_float()

REDUCT_API reduct_atom_t * reduct_atom_lookup_float	(	struct reduct *	reduct,
		reduct_float_t	value
	)

Lookup an atom by float value.

Will create a new atom if it does not exist.

Parameters

reduct	Pointer to the Reduct structure.
value	The float value.

Returns

A pointer to the atom.

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reduct_atom_lookup()

REDUCT_API reduct_atom_t * reduct_atom_lookup	(	struct reduct *	reduct,
		const char *	str,
		reduct_size_t	len,
		reduct_atom_lookup_flags_t	flags
	)

Lookup an atom in the Reduct structure.

Will create a new atom if it does not exist.

Parameters

reduct	Pointer to the Reduct structure.
str	The string to lookup.
len	The length of the string.
flags	Lookup flags to alter the interning behavior.

Returns

A pointer to the atom.

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reduct_atom_normalize()

REDUCT_API void reduct_atom_normalize	(	struct reduct *	reduct,
		reduct_atom_t *	atom
	)

Normalize an atom, determining its shape and parsing escape sequences.

Warning

Should only be called on atoms stored in a reduct_item_t.

Parameters

reduct	Pointer to the Reduct structure.
atom	Pointer to the atom to normalize.

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