From 37758a01761331f534768a95f1948637cb7149c6 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Tue, 20 Apr 2021 10:40:37 +0200
Subject: Optimize getenv() for const char* name

---
 libbutl/utility.cxx | 12 ++++++------
 libbutl/utility.mxx |  8 +++++++-
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/libbutl/utility.cxx b/libbutl/utility.cxx
index 0a8ba1e..a891fc2 100644
--- a/libbutl/utility.cxx
+++ b/libbutl/utility.cxx
@@ -16,7 +16,7 @@
 #include <cstddef>
 #include <utility>
 
-#include <cstring>      // strncmp()
+#include <cstring>      // strncmp(), strlen()
 #include <ostream>
 #include <type_traits>  // enable_if, is_base_of
 #include <system_error>
@@ -349,11 +349,11 @@ namespace butl
 #endif
 
   optional<std::string>
-  getenv (const std::string& name)
+  getenv (const char* name)
   {
     if (const char* const* vs = thread_env_)
     {
-      size_t n (name.size ());
+      size_t n (strlen (name));
 
       for (; *vs != nullptr; ++vs)
       {
@@ -362,9 +362,9 @@ namespace butl
         // Note that on Windows variable names are case-insensitive.
         //
 #ifdef _WIN32
-        if (icasecmp (name.c_str (), v, n) == 0)
+        if (icasecmp (name, v, n) == 0)
 #else
-        if (strncmp (name.c_str (), v, n) == 0)
+        if (strncmp (name, v, n) == 0)
 #endif
         {
           switch (v[n])
@@ -376,7 +376,7 @@ namespace butl
       }
     }
 
-    if (const char* r = ::getenv (name.c_str ()))
+    if (const char* r = ::getenv (name))
       return std::string (r);
 
     return nullopt;
diff --git a/libbutl/utility.mxx b/libbutl/utility.mxx
index 6965be4..bd24ffd 100644
--- a/libbutl/utility.mxx
+++ b/libbutl/utility.mxx
@@ -322,7 +322,13 @@ LIBBUTL_MODEXPORT namespace butl
   // overrides (thread_env).
   //
   LIBBUTL_SYMEXPORT optional<std::string>
-  getenv (const std::string&);
+  getenv (const char*);
+
+  inline optional<std::string>
+  getenv (const std::string& n)
+  {
+    return getenv (n.c_str ());
+  }
 
   // Set the process environment variable. Best done before starting any
   // threads (see thread_env). Throw system_error on failure.
-- 
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