Externals

Externals let Nix expressions work with foreign values that aren't part of the normal Nix value data model. More...

Files
file	nix_api_external.h
	libexpr C bindings dealing with external values

Data Structures
struct	NixCExternalValueDesc
	Definition for a class of external values. More...
struct	ExternalValue
	External Value. More...

Typedefs
typedef struct nix_string_return	nix_string_return
	Represents a string owned by the Nix language evaluator.
typedef struct nix_printer	nix_printer
	Wraps a stream that can output multiple string pieces.
typedef struct nix_string_context	nix_string_context
	A list of string context items.
typedef struct NixCExternalValueDesc	NixCExternalValueDesc
	Definition for a class of external values.

Functions
void	nix_set_string_return (nix_string_return *str, const char *c)
	Sets the contents of a nix_string_return.
nix_err	nix_external_print (nix_c_context *context, nix_printer *printer, const char *str)
nix_err	nix_external_add_string_context (nix_c_context *context, nix_string_context *string_context, const char *c)
ExternalValue *	nix_create_external_value (nix_c_context *context, NixCExternalValueDesc *desc, void *v)
	Create an external value, that can be given to nix_init_external.
void *	nix_get_external_value_content (nix_c_context *context, ExternalValue *b)
	Extract the pointer from a Nix C API external value.

Detailed Description

Externals let Nix expressions work with foreign values that aren't part of the normal Nix value data model.

Typedef Documentation

nix_string_return

typedef struct nix_string_return nix_string_return

Represents a string owned by the Nix language evaluator.

See also

nix_set_owned_string

NixCExternalValueDesc

typedef struct NixCExternalValueDesc NixCExternalValueDesc

Definition for a class of external values.

Create and implement one of these, then pass it to nix_create_external_value Make sure to keep it alive while the external value lives.

Optional functions can be set to NULL

See also

nix_create_external_value

Function Documentation

nix_create_external_value()

ExternalValue * nix_create_external_value	(	nix_c_context *	context,
		NixCExternalValueDesc *	desc,
		void *	v )

Create an external value, that can be given to nix_init_external.

Call nix_gc_decref() when you're done with the pointer.

Parameters

[out]	context	Optional, stores error information
[in]	desc	a NixCExternalValueDesc, you should keep this alive as long as the ExternalValue lives
[in]	v	the value to store

Returns

external value, owned by the garbage collector

See also

nix_init_external

nix_external_add_string_context()

nix_err nix_external_add_string_context	(	nix_c_context *	context,
		nix_string_context *	string_context,
		const char *	c )

Add string context to the nix_string_context object

Parameters

[out]	context	Optional, stores error information
[out]	string_context	The nix_string_context to add to
[in]	c	The context string to add

Returns

NIX_OK if everything worked

nix_external_print()

nix_err nix_external_print	(	nix_c_context *	context,
		nix_printer *	printer,
		const char *	str )

Print to the nix_printer

Parameters

[out]	context	Optional, stores error information
[out]	printer	The nix_printer to print to
[in]	str	The string to print

Returns

NIX_OK if everything worked

nix_get_external_value_content()

void * nix_get_external_value_content	(	nix_c_context *	context,
		ExternalValue *	b )

Extract the pointer from a Nix C API external value.

Parameters

[out]	context	Optional, stores error information
[in]	b	The external value

Returns

The pointer, valid while the external value is valid, or null if the external value was not from the Nix C API.

See also

nix_get_external

nix_set_string_return()

void nix_set_string_return	(	nix_string_return *	str,
		const char *	c )

Sets the contents of a nix_string_return.

Copies the passed string.

Parameters

[out]	str	the nix_string_return to write to
[in]	c	The string to copy