util: Add a MacAddr population function

This one is pretty trivial since there is only one size of mac
address, but we want to be sure we validate the buffer.

Tested:
    Built and runs through unit tests. Works when integrated into
    neighbor parsing code.

Change-Id: Iaf58fc398b51a3bcbbf70968cbe353beeb7b9f54
Signed-off-by: William A. Kennington III <wak@google.com>

3 files changed, 29 insertions, 0 deletions

diff --git a/test/test_util.cpp b/test/test_util.cpp
index 0e58081..4e39821 100644
--- a/test/test_util.cpp
+++ b/test/test_util.cpp
@@ -31,6 +31,19 @@ TEST_F(TestUtil, ToHex)
     EXPECT_EQ('4', mac_address::internal::toHex(std::byte(4)));
 }
 
+TEST_F(TestUtil, MacFromBuf)
+{
+    std::string tooSmall(1, 'a');
+    std::string tooLarge(24, 'a');
+    std::string buf{'\x00', '\xde', '\xad', '\x00', '\xbe', '\xef'};
+
+    MacAddr mac = mac_address::fromBuf(buf);
+    EXPECT_EQ(0, memcmp(buf.data(), mac.data(), buf.size()));
+
+    EXPECT_THROW(mac_address::fromBuf(tooSmall), std::runtime_error);
+    EXPECT_THROW(mac_address::fromBuf(tooLarge), std::runtime_error);
+}
+
 TEST_F(TestUtil, MacToString)
 {
     MacAddr mac1{
diff --git a/util.cpp b/util.cpp
index b1300fb..d1bcc71 100644
--- a/util.cpp
+++ b/util.cpp
@@ -603,6 +603,17 @@ std::string getfromInventory(sdbusplus::bus::bus& bus)
     return sdbusplus::message::variant_ns::get<std::string>(value);
 }
 
+MacAddr fromBuf(std::string_view buf)
+{
+    MacAddr ret;
+    if (buf.size() != ret.size())
+    {
+        throw std::runtime_error("Invalid MacAddr size");
+    }
+    memcpy(ret.data(), buf.data(), ret.size());
+    return ret;
+}
+
 std::string toString(const MacAddr& mac)
 {
     std::string str;
diff --git a/util.hpp b/util.hpp
index a07fa49..9531d4f 100644
--- a/util.hpp
+++ b/util.hpp
@@ -49,6 +49,11 @@ inline bool validate(const std::string& value)
  */
 std::string getfromInventory(sdbusplus::bus::bus& bus);
 
+/* @brief Marshalls the bytes for a mac address into a MacAddr.
+ * @param[in] buf - The network byte order address
+ */
+MacAddr fromBuf(std::string_view buf);
+
 /** @brief Converts the given mac address bytes into a string
  *  @param[in] bytes - The mac address
  *  @returns A valid mac address string