expand_bytes()

Decompose a sequence of bytes and store it in a variable.

Decompose a sequence of bytes and store it in a variable.

const uint8_t* expand_bytes(
        const uint8_t* b, const uint8_t* e, ...)

The expand_bytes() parameter is a combination of iterators of type uint8_t*. This specifies the next iterator after the beginning and end of the parsed target. If the parsing proceeds to the e position, nullptr is returned.

If there is no error in expansion, the next iterator to be read is returned.

The variable number parameters can be the following

Byte count	Data length	Explanation
uint8_t	1
uint16_t	2	Expand as a big-endian sequence
uint32_t	4	Expand as a big-endian sequence
uint8_t[N]	N	Fixed-length array of type uint8_t.
std::pair<char*,N>	N	Pairs of an array of type char*,uint8_t* and array length N can be generated with make_pair().

Example

auto&& rx = the_twelite.receiver.read();

char fourchars[5]{}; 
auto&& np = 
	expand_bytes(rx.get_payload().begin(), rx.get_payload().end()
		, make_pair((uint8_t*)fourchars, 4)
    );

// read rest of payload
uint8_t u8DI_BM_remote = 0xff;
uint16_t au16AI_remote[5];
expand_bytes(np, rx.get_payload().end()
	, u8DI_BM_remote
	, au16AI_remote[0]
	, au16AI_remote[1]
	, au16AI_remote[2]
	, au16AI_remote[3]
	, au16AI_remote[4]
);

In this example, a 4-byte string is read out first. Here, make_pair() is used to explicitly read 4 bytes of data.

The next data is read out based on the returned iterator np. The next data is of type uint8_t, followed by five more of type uint16_t.

Background

To simplify the description of byte arrays of type uint8_t used in generating data payloads and extracting data from non-volatile packets.

auto&& rx = the_twelite.receiver.read();
char fourchars[5]{}; 
uint8_t u8DI_BM_remote = 0xff;
uint16_t au16AI_remote[5];

uint8_t *p = rx.get_payload().begin();
fourchars[0] = p[0];
fourchars[1] = p[1];
fourchars[2] = p[2];
fourchars[3] = p[3];
fourchars[4] = 0;
p += 4;

u8DI_BM_remote = (p[0] << 8) + p[1]; p+=2;
au16AI_remote[0] = (p[0] << 8) + p[1]; p+=2;
...

The above is the simplest description, but it can be read from a byte array using Byte array utils as follows

auto&& rx = the_twelite.receiver.read();
char fourchars[5]{}; 
uint8_t u8DI_BM_remote = 0xff;
uint16_t au16AI_remote[5];

uint8_t *p = rx.get_payload().begin();
fourchars[0] = G_BYTE(p);
fourchars[1] = G_BYTE(p);
fourchars[2] = G_BYTE(p);
fourchars[3] = G_BYTE(p);
fourchars[4] = 0;

u8DI_BM_remote = G_WORD(p);
au16AI_remote[0] = G_WORD(p);
...