// ===================================================================
// header file

#define CRYPTX_ASN1_GETCLASS(flags)			((flag)>>1 & 0b11)
#define CRYPTX_ASN1_ISCONSTRUCTED(flags)		((flags) & 1)

typedef enum {
	ASN1_OK,
	ASN1_EOF,
	ASN1_INVALID_ARG,
	ASN1_LEN_OVERFLOW,
	ASN1_SPEC_MISMATCH
} asn1_error_t;

struct asn1_context {
	void *asn1_data_start;
	void *asn1_data_end;
	void *asn1_this;
	void *asn1_next;
};

asn1_error_t cryptx_asn1_start(struct asn1_context *ctx, void *asn1_data, size_t len);
asn1_error_t cryptx_asn1_decode(struct asn1_context *ctx, uint8_t **element, size_t *element_len, uint8_t *tag, uint8_t *flags);
asn1_error_t cryptx_asn1_next(struct asn1_context *ctx);


// ===================================================================
// demo code

int main(void)
{
	struct asn1_context asn1_state;
	asn1_error_t err;
	uint8_t *ptr;
	size_t elem_len;
	uint8_t tag;
	uint8_t flags;

	sprintf(CEMU_CONSOLE, "\n\n----------------------------------\nENCODEX ASN.1 Decoder Demo\n");

	err = cryptx_asn1_start(&asn1_state, asn1_demo, sizeof asn1_demo);
	sprintf(CEMU_CONSOLE, "\nASN.1 parser init complete. Exit code %u.\n",  err);
	if(err != ASN1_OK) return 1;

	while(err != ASN1_EOF){
		err = cryptx_asn1_decode(&asn1_state, &ptr, &elem_len, &tag, &flags);
		if(err)
			sprintf(CEMU_CONSOLE, "Decoder error %u\n", err);
		else
			sprintf(CEMU_CONSOLE, "Object Data, Tag Id: %u, Flags: %u, Size: %u, Addr: %p\n", tag, flags, elem_len, ptr);
		if(!CRYPTX_ASN1_ISCONSTRUCTED(flags)){
			err = cryptx_asn1_next(&asn1_state);
		}
	}


	return 0;
}

// ===================================================================
// output

ASN.1 parser init complete. Exit code 0.
Object Data, Tag Id: 16, Flags: 1, Size: 159, Addr: d1ab80
Object Data, Tag Id: 16, Flags: 1, Size: 13, Addr: d1ab82
Object Data, Tag Id: 6, Flags: 0, Size: 9, Addr: d1ab84
Object Data, Tag Id: 5, Flags: 0, Size: 0, Addr: d1ab8f
Object Data, Tag Id: 3, Flags: 0, Size: 141, Addr: d1ab92