commit 1c77602280a0079f998e093a19d9160f60454c6e
author William A. Kennington III <wak@google.com> Wed Jan 05 14:12:16 2022 -0800
committer William A. Kennington III <wak@google.com> Wed Jan 05 14:14:52 2022 -0800
tree 8cb8c6a3ee1c8391e86907e57acc1368bb949b6f
parent da0b1d4627d7b71fe24e962b383401b4ed63c5c9

util: fromString: Reduce string allocations

Change-Id: Ie6f7fa5dcc958081e7d7e2b880c17fe3548955a7
Signed-off-by: William A. Kennington III <wak@google.com>

src/util.cpp

diff --git a/src/util.cpp b/src/util.cpp
index 094e4bf..c331463 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -5,6 +5,8 @@
 
 #include <arpa/inet.h>
 #include <dirent.h>
+#include <fmt/compile.h>
+#include <fmt/format.h>
 #include <net/if.h>
 #include <sys/wait.h>
 
@@ -633,31 +635,27 @@
     return fromString(std::get<std::string>(value));
 }
 
-ether_addr fromString(std::string_view str)
+ether_addr fromString(const char* str)
 {
-    std::string mac_str{};
-    ether_addr mac{};
-
-    auto mac_c_str = str.data();
+    std::string genstr;
 
     // MAC address without colons
-    if (str.size() == 12 && str.find(":") == std::string::npos)
+    std::string_view strv = str;
+    if (strv.size() == 12 && strv.find(":") == strv.npos)
     {
-        mac_str = std::string(str.substr(0, 2)) + ":" +
-                  std::string(str.substr(2, 2)) + ":" +
-                  std::string(str.substr(4, 2)) + ":" +
-                  std::string(str.substr(6, 2)) + ":" +
-                  std::string(str.substr(8, 2)) + ":" +
-                  std::string(str.substr(10, 2));
-        mac_c_str = mac_str.c_str();
+        genstr =
+            fmt::format(FMT_COMPILE("{}:{}:{}:{}:{}:{}"), strv.substr(0, 2),
+                        strv.substr(2, 2), strv.substr(4, 2), strv.substr(6, 2),
+                        strv.substr(8, 2), strv.substr(10, 2));
+        str = genstr.c_str();
     }
 
-    if (ether_aton_r(mac_c_str, &mac) != nullptr)
+    ether_addr addr;
+    if (ether_aton_r(str, &addr) == nullptr)
     {
-        return mac;
+        throw std::invalid_argument("Invalid MAC Address");
     }
-
-    throw std::invalid_argument("Invalid MAC Address");
+    return addr;
 }
 
 std::string toString(const ether_addr& mac)

src/util.hpp

diff --git a/src/util.hpp b/src/util.hpp
index b1d27c4..804d492 100644
--- a/src/util.hpp
+++ b/src/util.hpp
@@ -44,7 +44,11 @@
  *  @returns A mac address in network byte order
  *  @throws std::runtime_error for bad mac
  */
-ether_addr fromString(std::string_view str);
+ether_addr fromString(const char* str);
+inline ether_addr fromString(const std::string& str)
+{
+    return fromString(str.c_str());
+}
 
 /** @brief Converts the given mac address bytes into a string
  *  @param[in] mac - The mac address