NixCExternalValueDesc Struct Reference

Definition for a class of external values. More...

#include <nix_api_external.h>

Data Fields
void(*	print )(void *self, nix_printer *printer)
	Called when printing the external value. More...
void(*	showType )(void *self, nix_string_return *res)
	Called on :t. More...
void(*	typeOf )(void *self, nix_string_return *res)
	Called on builtins.typeOf More...
void(*	coerceToString )(void *self, nix_string_context *c, int coerceMore, int copyToStore, nix_string_return *res)
	Called on "${str}" and builtins.toString. More...
int(*	equal )(void *self, void *other)
	Try to compare two external values. More...
void(*	printValueAsJSON )(void *self, State *, int strict, nix_string_context *c, bool copyToStore, nix_string_return *res)
	Convert the external value to json. More...
void(*	printValueAsXML )(void *self, State *, int strict, int location, void *doc, nix_string_context *c, void *drvsSeen, int pos)
	Convert the external value to XML. More...

Detailed Description

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

Field Documentation

coerceToString

void(* NixCExternalValueDesc::coerceToString) (void *self, nix_string_context *c, int coerceMore, int copyToStore, nix_string_return *res)

Called on "${str}" and builtins.toString.

The latter with coerceMore=true Optional, the default is to throw an error.

Parameters

[in]	self	the void* passed to nix_create_external_value
[out]	c	writable string context for the resulting string
[in]	coerceMore	boolean, try to coerce to strings in more cases instead of throwing an error
[in]	copyToStore	boolean, whether to copy referenced paths to store or keep them as-is
[out]	res	the return value. Not touching this, or setting it to the empty string, will make the conversion throw an error.

equal

int(* NixCExternalValueDesc::equal) (void *self, void *other)

Try to compare two external values.

Optional, the default is always false. If the other object was not a Nix C external value, this comparison will also return false

Parameters

[in]	self	the void* passed to nix_create_external_value
[in]	other	the void* passed to the other object's nix_create_external_value

Returns

true if the objects are deemed to be equal

print

void(* NixCExternalValueDesc::print) (void *self, nix_printer *printer)

Called when printing the external value.

Parameters

[in]	self	the void* passed to nix_create_external_value
[out]	printer	The printer to print to, pass to nix_external_print

printValueAsJSON

void(* NixCExternalValueDesc::printValueAsJSON) (void *self, State *, int strict, nix_string_context *c, bool copyToStore, nix_string_return *res)

Convert the external value to json.

Optional, the default is to throw an error

Parameters

[in]	self	the void* passed to nix_create_external_value
[in]	state	The evaluator state
[in]	strict	boolean Whether to force the value before printing
[out]	c	writable string context for the resulting string
[in]	copyToStore	whether to copy referenced paths to store or keep them as-is
[out]	res	the return value. Gets parsed as JSON. Not touching this, or setting it to the empty string, will make the conversion throw an error.

printValueAsXML

void(* NixCExternalValueDesc::printValueAsXML) (void *self, State *, int strict, int location, void *doc, nix_string_context *c, void *drvsSeen, int pos)

Convert the external value to XML.

Optional, the default is to throw an error

Todo:

The mechanisms for this call are incomplete. There are no C bindings to work with XML, pathsets and positions.

Parameters

[in]	self	the void* passed to nix_create_external_value
[in]	state	The evaluator state
[in]	strict	boolean Whether to force the value before printing
[in]	location	boolean Whether to include position information in the xml
[out]	doc	XML document to output to
[out]	c	writable string context for the resulting string
[in,out]	drvsSeen	a path set to avoid duplicating derivations
[in]	pos	The position of the call.

showType

void(* NixCExternalValueDesc::showType) (void *self, nix_string_return *res)

Called on :t.

Parameters

[in]	self	the void* passed to nix_create_external_value
[out]	res	the return value

typeOf

void(* NixCExternalValueDesc::typeOf) (void *self, nix_string_return *res)

Called on builtins.typeOf

Parameters

	self	the void* passed to nix_create_external_value
[out]	res	the return value

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

• src/libexpr/c/nix_api_external.h