Detailed Description

The ByteSwap operator lets the user re-position bytes from the default input to default output.

Depending on the type size, the ByteSwap has up to 8 numbered 'BytePosition' properties. Each 'BytePosition' property can be assigned a value which indicates where that byte should be positioned in the output. The special BytePosition value '-1' means 'Skip processing of this byte'.

The following table describes the byte-positions in an 8-byte (uint64_t, int64_t, double) signal, and how they relate to Least Significant Byte (LSB) and the Most Significant Byte (MSB):

Example

To reverse the order of bytes in an 8-byte type, the following 'BytePosition' property values could be set

...resulting in a value that is re-mapped to the byte positions shown in this table:

Arguments

For example: Assume an Input='1' CDPSignal<uint64_t> with a ByteSwap<uint64_t>. If configured with the above BytePositions, a Value of 0x0011223344556677 would yield an InternalValue of 0x7766554433221100.

For signals with less bytes, the scheme is the same, but you only have 4 or 2 BytePosition properties to configure.

When operator is used inside a signal its default input is automatically tied to signal's InternalValue or previous operator's output. Its default output is automatically tied to next operator's input or to signal's Value. See also CDP Operator Usage In CDP Signals.

Actual Processing Code of the ByteSwap

unsigned int ByteSwap<T>::Process()
{
  const T input = static_cast<T>(m_input);
  T output = 0;
  const unsigned char* inputPtr = reinterpret_cast<const unsigned char*>(&input);
  unsigned char* outputPtr = reinterpret_cast<unsigned char*>(&output);

  for(std::size_t i=0;i<sizeof(T);++i)
    if((int)m_bytePosition[i]!=-1)
      outputPtr[m_bytePosition[i]] = inputPtr[i];

  m_output = output;
  return STATUS_OK;
}