stream_helper

stream_helper is a helper object that grants the mwx::stream interface. It creates a helper object that references a data class and performs data input/output via the helper object.

The following creates a helper object bs from an array b of smplbufs and inputs data using the mwx::stream::operator <<() operator.

smplbuf_u8<32> b;
auto&& bs = b.get_stream_helper(); // helper object

// Data String Generation
uint8_t FOURCHARS[]={'A', 'B', 'C', 'D'};
bs << FOURCHARS;
bs << ';';
bs << uint32_t(0x30313233); // "0123"
bs << format(";%d", 99);

Serial << b << crlf; // Output to Serial via smplbuf_u8<32> class

//result: ABCD;0123;99

Overview

stream_helper behaves as if the data array were a stream.

Internally, it holds read/write positions in the data array. It behaves as follows.

• After the last data is read or written, it moves to the next read/write position.

• After the last data is read or data is appended to the end, the read/write position becomes the end.

• If the read/write position is the end of the line, then

  • available() becomes false.

  • Read cannot be performed.

  • Writing is appended if it is within the writable range.

generating stream_helper

stream_helper is a data class (smplbuf, EEPROM) member functions.

auto&& obj_helper = obj.get_stream_helper()
// obj is an object of data class, obj_helper type is accepted by auto&& because it is long.

methods

rewind()

void rewind()

Moves the read/write position to the beginning.

seek()

int seek(int offset, int whence = MWX_SEEK_SET)

Set the read/write position.

whence	Set the location
MWX_SEEK_SET	set from the leading position. If offset is 0, it means the same as rewind().
MWX_SEEK_CUR	Move by offset with respect to the current position.
MWX_SEEK_END	end position. Setting offset to 0 sets the end position. If -1 is set, it moves to the last character.

tell()

int tell()

Returns the read/write position. Returns -1 for the end position.

available()

int available()

Returns 0 if the read/write position is the end. If it is not the end, it returns any other value.