More complex array & struct style.

Hello guys,

Can someone explain me what's going on in
static const struct tlv_definition xyz_att_tlvdef?

Code:

//-------- .h file
enum tlv_type {
	TLV_TYPE_FIXED,
	TLV_TYPE_T,
	TLV_TYPE_TV,
	TLV_TYPE_TLV,
	TLV_TYPE_TL16V,
};

struct tlv_def {
	enum tlv_type type;
	u_int8_t fixed_len;
};

//-------- .c file
static const struct tlv_definition xyz_att_tlvdef = {
	.def = {
		[MOBILE_ID]	= { TLV_TYPE_TLV },
		[NAME_LONG]	= { TLV_TYPE_TLV },
		[NAME_SHORT]	= { TLV_TYPE_TLV },
		[UTC]		= { TLV_TYPE_TV },
		[NET_TIME_TZ]	= { TLV_TYPE_FIXED, 7 },
		[LSA_IDENT]	= { TLV_TYPE_TLV },
	},
};

I haven't seen this style of programming before, can someone provide me a link where such technique is explained? And what is the advantage of this style?

Code:

static const char *lm_cause_names[] = {
	[CAUSE_NORMAL]			= "Normal event",
	[CAUSE_ABNORMAL_UNSPEC]	= "Abnormal release, unspecified",
	[CAUSE_ABNORMAL_UNACCT]	= "Abnormal release, channel unacceptable",
	[CAUSE_ABNORMAL_TIMER]		= "Abnormal release, timer expired",
	[CAUSE_ABNORMAL_NOACT]		= "Abnormal release, no activity on radio path",
	[CAUSE_PREMPTIVE_REL]		= "Preemptive release",
};

Thank you.

This is C99's named initialization. The .def field of the struct is initialized to what's given, which also uses named initialization, so presumably the .def field is an array of some sort. The advantage over a normal initializer is that you don't have to know what the values of those constants are, and any "gaps" in the sequence are automatically filled to 0 for you.

Just so that's clear, this is an instance of a single struct, not a struct definition:

Code:

static const struct tlv_definition xyz_att_tlvdef =

Thank you for your replies,

But can someone give me a link so I can study it carefully?
Cause I'm a bit nervous when learning things only from examples. If someone put an article with some explanation what exactly is going on, than I know how such code behaves. I really feel satisfied when writing software that don't crash

regards,
Andaluz.