cmcldeps: replace inefficient std::string::substr usage

1 files changed, 24 insertions, 26 deletions

diff --git a/Source/cmcldeps.cxx b/Source/cmcldeps.cxx
index fd2dd3334f..5c27ac1034 100644
--- a/Source/cmcldeps.cxx
+++ b/Source/cmcldeps.cxx
@@ -64,7 +64,7 @@ static void usage(const char* msg)
         msg);
 }
 
-static std::string trimLeadingSpace(const std::string& cmdline)
+static cm::string_view trimLeadingSpace(cm::string_view cmdline)
 {
   int i = 0;
   for (; cmdline[i] == ' '; ++i)
@@ -86,25 +86,26 @@ static void replaceAll(std::string& str, const std::string& search,
 // are removed from the argument if there were any.
 static std::string getArg(std::string& cmdline)
 {
-  std::string ret;
   bool in_quoted = false;
   unsigned int i = 0;
 
-  cmdline = trimLeadingSpace(cmdline);
+  cm::string_view cmdview = trimLeadingSpace(cmdline);
+  size_t spaceCnt = cmdline.size() - cmdview.size();
 
   for (;; ++i) {
-    if (i >= cmdline.size())
+    if (i >= cmdview.size())
       usage("Couldn't parse arguments.");
-    if (!in_quoted && cmdline[i] == ' ')
+    if (!in_quoted && cmdview[i] == ' ')
       break; // "a b" "x y"
-    if (cmdline[i] == '"')
+    if (cmdview[i] == '"')
       in_quoted = !in_quoted;
   }
 
-  ret = cmdline.substr(0, i);
-  if (ret[0] == '"' && ret[i - 1] == '"')
-    ret = ret.substr(1, ret.size() - 2);
-  cmdline = cmdline.substr(i);
+  cmdview = cmdview.substr(0, i);
+  if (cmdview[0] == '"' && cmdview[i - 1] == '"')
+    cmdview = cmdview.substr(1, i - 2);
+  std::string ret(cmdview);
+  cmdline.erase(0, spaceCnt + i);
   return ret;
 }
 
@@ -123,7 +124,7 @@ static void parseCommandLine(LPWSTR wincmdline, std::string& lang,
   prefix = getArg(cmdline);
   clpath = getArg(cmdline);
   binpath = getArg(cmdline);
-  rest = trimLeadingSpace(cmdline);
+  rest = std::string(trimLeadingSpace(cmdline));
 }
 
 // Not all backslashes need to be escaped in a depfile, but it's easier that
@@ -166,7 +167,7 @@ static void outputDepFile(const std::string& dfile, const std::string& objfile,
     // backward slashes and relativize the path to the build directory.
     replaceAll(tmp, "/", "\\");
     if (cmHasPrefix(tmp, cwd))
-      tmp = tmp.substr(cwd.size());
+      tmp.erase(0, cwd.size());
     escapePath(tmp);
     fprintf(out, "%s \\\n", tmp.c_str());
   }
@@ -190,7 +191,7 @@ std::string replace(const std::string& str, const std::string& what,
   return replaced.replace(pos, what.size(), replacement);
 }
 
-static int process(const std::string& srcfilename, const std::string& dfile,
+static int process(cm::string_view srcfilename, const std::string& dfile,
                    const std::string& objfile, const std::string& prefix,
                    const std::string& cmd, const std::string& dir = "",
                    bool quiet = false)
@@ -217,13 +218,14 @@ static int process(const std::string& srcfilename, const std::string& dfile,
   std::vector<std::string> includes;
   bool isFirstLine = true; // cl prints always first the source filename
   while (std::getline(ss, line)) {
-    if (cmHasPrefix(line, prefix)) {
-      std::string inc = trimLeadingSpace(line.substr(prefix.size()).c_str());
+    cm::string_view inc(line);
+    if (cmHasPrefix(inc, prefix)) {
+      inc = trimLeadingSpace(inc.substr(prefix.size()));
       if (inc.back() == '\r') // blech, stupid \r\n
         inc = inc.substr(0, inc.size() - 1);
-      includes.push_back(inc);
+      includes.emplace_back(std::string(inc));
     } else {
-      if (!isFirstLine || !cmHasPrefix(line, srcfilename)) {
+      if (!isFirstLine || !cmHasPrefix(inc, srcfilename)) {
         if (!quiet || exit_code != 0) {
           fprintf(stdout, "%s\n", line.c_str());
         }
@@ -254,14 +256,10 @@ int main()
                    cl, binpath, rest);
 
   // needed to suppress filename output of msvc tools
-  std::string srcfilename;
-  {
-    std::string::size_type pos = srcfile.rfind('\\');
-    if (pos == std::string::npos) {
-      srcfilename = srcfile;
-    } else {
-      srcfilename = srcfile.substr(pos + 1);
-    }
+  cm::string_view srcfilename(srcfile);
+  std::string::size_type pos = srcfile.rfind('\\');
+  if (pos != std::string::npos) {
+    srcfilename = srcfilename.substr(pos + 1);
   }
 
   std::string nol = " /nologo ";
@@ -282,7 +280,7 @@ int main()
     // call cl in object dir so the .i is generated there
     std::string objdir;
     {
-      std::string::size_type pos = objfile.rfind("\\");
+      pos = objfile.rfind("\\");
       if (pos != std::string::npos) {
         objdir = objfile.substr(0, pos);
       }