Adds endian_swap to fapi2

Change-Id: Ie076098cd05ea0ae768d8da142df1b933ab7eb07
Reviewed-on: http://rchgit01.rchland.ibm.com/gerrit1/65525
Dev-Ready: STEPHEN GLANCY <sglancy@us.ibm.com>
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: HWSV CI <hwsv-ci+hostboot@us.ibm.com>
Tested-by: PPE CI <ppe-ci+hostboot@us.ibm.com>
Tested-by: Hostboot CI <hostboot-ci+hostboot@us.ibm.com>
Reviewed-by: Louis Stermole <stermole@us.ibm.com>
Reviewed-by: ANDRE A. MARIN <aamarin@us.ibm.com>
Reviewed-by: Matt K. Light <mklight@us.ibm.com>
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>
Reviewed-by: Jennifer A. Stofer <stofer@us.ibm.com>
Reviewed-on: http://rchgit01.rchland.ibm.com/gerrit1/65527
Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com>
Reviewed-by: Sachin Gupta <sgupta2m@in.ibm.com>

src/import/hwpf/fapi2/include/utils.H

@@ -38,6 +38,33 @@
 
 namespace fapi2
 {
+
+///
+/// @brief Endian swapping
+/// @tparam T input type
+/// @param[in,out] io_input integral input
+/// @note https://stackoverflow.com/questions/105252/how-do-i-convert-between-big-endian-and-little-endian-values-in-c
+/// This function does not take into account the system's endianness, but just does the endian swap
+///
+template < typename T >
+void endian_swap(T& io_input)
+{
+    constexpr size_t MIN_BYTES = 2;
+    static_assert(sizeof(T) >= MIN_BYTES, "Byte swapping requires at least 2 bytes of data");
+
+    uint8_t* l_varArray = reinterpret_cast<uint8_t*>(&io_input);
+
+    for(size_t i = 0; i < sizeof(io_input) / 2; i++)
+    {
+        const size_t BYTE_SWAP_INDEX = sizeof(io_input) - 1 - i;
+
+        // Rolling our own swap as certain downstream libraries do not have std::swap enabled
+        const auto l_temp = l_varArray[BYTE_SWAP_INDEX];
+        l_varArray[BYTE_SWAP_INDEX] = l_varArray[i];
+        l_varArray[i] = l_temp;
+    }
+}
+
 #ifndef __PPE__
 ///
 /// @brief Enable/Disable special wakeup on processor chip core(s)