Value Extraction

Functions for extracting data from Nix values. More...

Functions
ValueType	nix_get_type (nix_c_context *context, const nix_value *value)
	Get value type.
const char *	nix_get_typename (nix_c_context *context, const nix_value *value)
	Get type name of value as defined in the evaluator.
bool	nix_get_bool (nix_c_context *context, const nix_value *value)
	Get boolean value.
nix_err	nix_get_string (nix_c_context *context, const nix_value *value, nix_get_string_callback callback, void *user_data)
	Get the raw string.
const char *	nix_get_path_string (nix_c_context *context, const nix_value *value)
	Get path as string.
unsigned int	nix_get_list_size (nix_c_context *context, const nix_value *value)
	Get the length of a list.
unsigned int	nix_get_attrs_size (nix_c_context *context, const nix_value *value)
	Get the element count of an attrset.
double	nix_get_float (nix_c_context *context, const nix_value *value)
	Get float value in 64 bits.
int64_t	nix_get_int (nix_c_context *context, const nix_value *value)
	Get int value.
ExternalValue *	nix_get_external (nix_c_context *context, nix_value *value)
	Get external reference.
nix_value *	nix_get_list_byidx (nix_c_context *context, const nix_value *value, EvalState *state, unsigned int ix)
	Get the ix'th element of a list.
nix_value *	nix_get_list_byidx_lazy (nix_c_context *context, const nix_value *value, EvalState *state, unsigned int ix)
	Get the ix'th element of a list without forcing evaluation of the element.
nix_value *	nix_get_attr_byname (nix_c_context *context, const nix_value *value, EvalState *state, const char *name)
	Get an attr by name.
nix_value *	nix_get_attr_byname_lazy (nix_c_context *context, const nix_value *value, EvalState *state, const char *name)
	Get an attribute value by attribute name, without forcing evaluation of the attribute's value.
bool	nix_has_attr_byname (nix_c_context *context, const nix_value *value, EvalState *state, const char *name)
	Check if an attribute name exists on a value.
nix_value *	nix_get_attr_byidx (nix_c_context *context, nix_value *value, EvalState *state, unsigned int i, const char **name)
	Get an attribute by index.
nix_value *	nix_get_attr_byidx_lazy (nix_c_context *context, nix_value *value, EvalState *state, unsigned int i, const char **name)
	Get an attribute by index, without forcing evaluation of the attribute's value.
const char *	nix_get_attr_name_byidx (nix_c_context *context, nix_value *value, EvalState *state, unsigned int i)
	Get an attribute name by index.

Detailed Description

Functions for extracting data from Nix values.

Function Documentation

nix_get_attr_byidx()

nix_value * nix_get_attr_byidx	(	nix_c_context *	context,
		nix_value *	value,
		EvalState *	state,
		unsigned int	i,
		const char **	name )

Get an attribute by index.

Also gives you the name.

Attributes are returned in an unspecified order which is NOT suitable for reproducible operations. In Nix's domain, reproducibility is paramount. The caller is responsible for sorting the attributes or storing them in an ordered map to ensure deterministic behavior in your application.

Note

When Nix does sort attributes, which it does for virtually all intermediate operations and outputs, it uses byte-wise lexicographic order (equivalent to lexicographic order by Unicode scalar value for valid UTF-8). We recommend applying this same ordering for consistency.

Call nix_value_decref() when you're done with the pointer

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect
[in]	state	nix evaluator state
[in]	i	attribute index
[out]	name	will store a pointer to the attribute name, valid until state is freed

Returns

value, NULL in case of errors

nix_get_attr_byidx_lazy()

nix_value * nix_get_attr_byidx_lazy	(	nix_c_context *	context,
		nix_value *	value,
		EvalState *	state,
		unsigned int	i,
		const char **	name )

Get an attribute by index, without forcing evaluation of the attribute's value.

Also gives you the name.

Returns the attribute value without forcing its evaluation, allowing access to lazy values. The attribute set value itself must already have been evaluated.

Attributes are returned in an unspecified order which is NOT suitable for reproducible operations. In Nix's domain, reproducibility is paramount. The caller is responsible for sorting the attributes or storing them in an ordered map to ensure deterministic behavior in your application.

Note

When Nix does sort attributes, which it does for virtually all intermediate operations and outputs, it uses byte-wise lexicographic order (equivalent to lexicographic order by Unicode scalar value for valid UTF-8). We recommend applying this same ordering for consistency.

Call nix_value_decref() when you're done with the pointer

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect (must be an evaluated attribute set)
[in]	state	nix evaluator state
[in]	i	attribute index
[out]	name	will store a pointer to the attribute name, valid until state is freed

Returns

value, NULL in case of errors

nix_get_attr_byname()

nix_value * nix_get_attr_byname	(	nix_c_context *	context,
		const nix_value *	value,
		EvalState *	state,
		const char *	name )

Get an attr by name.

Call nix_value_decref() when you're done with the pointer

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect
[in]	state	nix evaluator state
[in]	name	attribute name

Returns

value, NULL in case of errors

nix_get_attr_byname_lazy()

nix_value * nix_get_attr_byname_lazy	(	nix_c_context *	context,
		const nix_value *	value,
		EvalState *	state,
		const char *	name )

Get an attribute value by attribute name, without forcing evaluation of the attribute's value.

Returns the attribute value without forcing its evaluation, allowing access to lazy values. The attribute set value itself must already be evaluated.

Call nix_value_decref() when you're done with the pointer

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect (must be an evaluated attribute set)
[in]	state	nix evaluator state
[in]	name	attribute name

Returns

value, NULL in case of errors

nix_get_attr_name_byidx()

const char * nix_get_attr_name_byidx	(	nix_c_context *	context,
		nix_value *	value,
		EvalState *	state,
		unsigned int	i )

Get an attribute name by index.

Returns the attribute name without forcing evaluation of the attribute's value.

Attributes are returned in an unspecified order which is NOT suitable for reproducible operations. In Nix's domain, reproducibility is paramount. The caller is responsible for sorting the attributes or storing them in an ordered map to ensure deterministic behavior in your application.

Note

When Nix does sort attributes, which it does for virtually all intermediate operations and outputs, it uses byte-wise lexicographic order (equivalent to lexicographic order by Unicode scalar value for valid UTF-8). We recommend applying this same ordering for consistency.

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect
[in]	state	nix evaluator state
[in]	i	attribute index

Returns

name string valid until state is freed, NULL in case of errors

nix_get_attrs_size()

unsigned int nix_get_attrs_size	(	nix_c_context *	context,
		const nix_value *	value )

Get the element count of an attrset.

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect

Returns

attrset element count, error info via context

nix_get_bool()

bool nix_get_bool	(	nix_c_context *	context,
		const nix_value *	value )

Get boolean value.

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect

Returns

true or false, error info via context

nix_get_external()

ExternalValue * nix_get_external	(	nix_c_context *	context,
		nix_value *	value )

Get external reference.

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect

Returns

reference valid while value is valid. Call nix_gc_incref() if you need it to live longer, then only in that case call nix_gc_decref() when done. NULL in case of error

nix_get_float()

double nix_get_float	(	nix_c_context *	context,
		const nix_value *	value )

Get float value in 64 bits.

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect

Returns

float contents, error info via context

nix_get_int()

int64_t nix_get_int	(	nix_c_context *	context,
		const nix_value *	value )

Get int value.

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect

Returns

int contents, error info via context

nix_get_list_byidx()

nix_value * nix_get_list_byidx	(	nix_c_context *	context,
		const nix_value *	value,
		EvalState *	state,
		unsigned int	ix )

Get the ix'th element of a list.

Call nix_value_decref() when you're done with the pointer

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect
[in]	state	nix evaluator state
[in]	ix	list element to get

Returns

value, NULL in case of errors

nix_get_list_byidx_lazy()

nix_value * nix_get_list_byidx_lazy	(	nix_c_context *	context,
		const nix_value *	value,
		EvalState *	state,
		unsigned int	ix )

Get the ix'th element of a list without forcing evaluation of the element.

Returns the list element without forcing its evaluation, allowing access to lazy values. The list value itself must already be evaluated.

Call nix_value_decref() when you're done with the pointer

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect (must be an evaluated list)
[in]	state	nix evaluator state
[in]	ix	list element to get

Returns

value, NULL in case of errors

nix_get_list_size()

unsigned int nix_get_list_size	(	nix_c_context *	context,
		const nix_value *	value )

Get the length of a list.

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect

Returns

length of list, error info via context

nix_get_path_string()

const char * nix_get_path_string	(	nix_c_context *	context,
		const nix_value *	value )

Get path as string.

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect

Returns

string valid while value is valid, NULL in case of error

nix_get_string()

nix_err nix_get_string	(	nix_c_context *	context,
		const nix_value *	value,
		nix_get_string_callback	callback,
		void *	user_data )

Get the raw string.

This may contain placeholders.

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect
[in]	callback	Called with the string value.
[in]	user_data	optional, arbitrary data, passed to the callback when it's called.

Returns

error code, NIX_OK on success.

nix_get_type()

ValueType nix_get_type	(	nix_c_context *	context,
		const nix_value *	value )

Get value type.

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect

Returns

type of nix value

nix_get_typename()

const char * nix_get_typename	(	nix_c_context *	context,
		const nix_value *	value )

Get type name of value as defined in the evaluator.

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect

Returns

type name string, free with free()

nix_has_attr_byname()

bool nix_has_attr_byname	(	nix_c_context *	context,
		const nix_value *	value,
		EvalState *	state,
		const char *	name )

Check if an attribute name exists on a value.

Parameters

[out]	context	Optional, stores error information
[in]	Value	Nix value to inspect
[in]	state	nix evaluator state
[in]	name	attribute name

Returns

value, error info via context