Values and results

Values by language

PLC type	Python	Rust (ciplink::Value)	C#	C++ (ciplink::Value)	C (JSON)
BOOL	bool	Bool	bool	bool	true / false
SINT, INT, DINT, LINT, USINT, UINT, UDINT	int	SInt … UDInt	long	int64_t	number
ULINT	int	ULInt	long, or ulong above long.MaxValue	int64_t, or uint64_t above INT64_MAX	number
REAL, LREAL	float	Real, LReal	double	double	number with . or e; {"$float": "NaN"} for non-finite values
STRING and custom strings	str	String	string	std::string	string
array, BOOL array	list	Array	object?[]	ciplink::Array	array
UDT, AOI, built-in structure	dict	Struct (an IndexMap, members in order)	Dictionary<string, object?>	ciplink::Struct	object, members in order
BYTE, WORD, DWORD, LWORD	list of bool, least significant bit first	Array of Bool	object?[] of bool	ciplink::Array of bool	array of booleans
raw bytes (generic message replies)	bytes	Bytes	byte[]	ciplink::Bytes	{"$bytes": "<hex>"}

Writes accept the same forms. Any number is accepted for a REAL and any integer for an integer type; the driver checks the range against the tag's type before sending. In C#, any IEnumerable works for an array and any IDictionary for a structure.

Results

Every read, write, description and generic message returns one result per item:

Field	Python Tag	Rust TagResult	C# Tag	C++ ciplink::Tag	C JSON
name	tag	tag	Name	tag	"tag"
value (none on error)	value	value: Option<Value>	Value	value (null)	"value"
data type	type	data_type	DataType	type	"type"
error message	error	error: Option<TagError>	Error	error->message	"error"."message"
error kind	error_kind	error.kind	ErrorKind	error->kind	"error"."kind"
CIP status, extended status	error.status, error.ext	error.status, error.ext	Status, ExtendedStatus	error->status, error->ext	"error"."status", "error"."ext"
success	bool(tag)	is_ok()	IsOk	bool(tag)	"error" is null

In Python, reading or writing one tag returns one Tag and several return a list. In the other languages the calls taking several tags return a list, and single-tag shortcuts (C# Read(string), C++ read_tag, write_tag) return one result.

The C ABI's JSON

The C functions take and return UTF-8 JSON text. Every char* the library returns belongs to the caller and is freed with ciplink_string_free; byte buffers from ciplink_send_connected and ciplink_send_unconnected are freed with ciplink_bytes_free. A tag result is:

{"tag": "Counter", "value": 42, "type": "DINT", "error": null}
{"tag": "NoSuchTag", "value": null, "type": null,
 "error": {"message": "...", "kind": "not_found", "status": 4, "ext": 0}}