DataStream
General
A DataStream is a binary stream of encoded information which is 100% independent of the host computers’ operating system, CPU or byte order. For example, a DataStream that is written by a e.g. ARM microcontroller can be read by a PC under e.g. Windows or Ubuntu.
You can also use a DataStream to read or write raw unencoded binary data.
The DataStream class implements the serialization of C++’s basic data types, like int8_t … int32_t, uint8_t … uint32_t, bool, float, double.
In the following example we assume you want to send data from a microcontroller through amy communication hardware to a computer.
Microcontroller as transmitter
For using a DataStrem object, you need a working buffer for data handling.
// Size of the buffer to transmit
const size_t dataStreamBufferSize = 16;
// Buffer to transmit later
uint8_t dataStreamBuffer[dataStreamBufferSize] = {0};
// Data stream object initialized with the transmit buffer
semf::DataStream dataStream(dataStreamBuffer, dataStreamBufferSize);
Now we create the data to transceive later.
uint8_t byte = 0x10; // Example byte
int16_t shortint = 0x1234; // Example short int
const size_t arraySize = 10; // Size of binary array
// Binary array (will not be shifted by DataStream class, you have to take care about)
uint8_t array[arraySize] = {0};
for (uint8_t i = 0; i < arraySize; i++)
array[i] = i; // Fill binary array
By the following lines, the transmit buffer will be filled.
// resets the pointer for write operation to the // first element of the dataStreamBuffer. dataStream.resetWrite(); dataStream << byte; // write byte to the buffer dataStream << shortint; // write short int to the buffer dataStream.writeRawData(array, arraySize); // write raw byte array to the buffer // ... // write data via any communication hardware you prefer // ...
Computer as receiver
For using a DataStrem object, you need a working buffer for data handling.
// Size of the buffer to read int
const size_t dataStreamBufferSize = 16;
// Buffer to read into
uint8_t dataStreamBuffer[dataStreamBufferSize] = {0};
// Data stream object initialized with the read buffer
semf::DataStream dataStream(dataStreamBuffer, dataStreamBufferSize);
// ...
uint8_t byte;
int16_t shortint;
const size_t arraySize = 10;
uint8_t array[arraySize] = {0};
The following function is called, by estimated data has read by the computer.
void onDataAvailable()
{
// resets the pointer for read operation to the
// first element of the dataStreamBuffer
dataStream.resetRead();
// read byte from the buffer
dataStream >> byte;
// read short int from the buffer
dataStream >> shortint;
// write raw byte array to the buffer
dataStream.readRawData(array, arraySize);
printf("%02X\n", byte);
printf("%04X\n", shortint);
for (uint8_t i=0; i < arraySize; i++)
printf("%02X\n", array[i]);
}
Output
0x10 0x1234 00 01 02 03 04 05 06 07 08 09