cmStringAlgorithms: Add cmCatViews and cmStrCat functions

Source/CMakeLists.txt

@@ -404,6 +404,7 @@ set(SRCS
   cmStateSnapshot.cxx
   cmStateSnapshot.h
   cmStateTypes.h
+  cmStringAlgorithms.cxx
   cmStringAlgorithms.h
   cmSystemTools.cxx
   cmSystemTools.h

Source/cmStringAlgorithms.cxx

+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#include "cmStringAlgorithms.h"
+
+#include <algorithm>
+#include <cstdio>
+
+namespace {
+template <std::size_t N, typename T>
+inline void MakeDigits(cm::string_view& view, char (&digits)[N],
+                       const char* pattern, T value)
+{
+  int res = std::snprintf(digits, N, pattern, value);
+  if (res > 0 && res < static_cast<int>(N)) {
+    view = cm::string_view(digits, static_cast<std::size_t>(res));
+  }
+}
+} // unnamed namespace
+
+cmAlphaNum::cmAlphaNum(int val)
+{
+  MakeDigits(View_, Digits_, "%i", val);
+}
+
+cmAlphaNum::cmAlphaNum(unsigned int val)
+{
+  MakeDigits(View_, Digits_, "%u", val);
+}
+
+cmAlphaNum::cmAlphaNum(long int val)
+{
+  MakeDigits(View_, Digits_, "%li", val);
+}
+
+cmAlphaNum::cmAlphaNum(unsigned long int val)
+{
+  MakeDigits(View_, Digits_, "%lu", val);
+}
+
+cmAlphaNum::cmAlphaNum(long long int val)
+{
+  MakeDigits(View_, Digits_, "%lli", val);
+}
+
+cmAlphaNum::cmAlphaNum(unsigned long long int val)
+{
+  MakeDigits(View_, Digits_, "%llu", val);
+}
+
+cmAlphaNum::cmAlphaNum(float val)
+{
+  MakeDigits(View_, Digits_, "%g", static_cast<double>(val));
+}
+
+cmAlphaNum::cmAlphaNum(double val)
+{
+  MakeDigits(View_, Digits_, "%g", val);
+}
+
+std::string cmCatViews(std::initializer_list<cm::string_view> views)
+{
+  std::size_t total_size = 0;
+  for (cm::string_view const& view : views) {
+    total_size += view.size();
+  }
+
+  std::string result(total_size, '\0');
+  std::string::iterator sit = result.begin();
+  for (cm::string_view const& view : views) {
+    sit = std::copy_n(view.data(), view.size(), sit);
+  }
+  return result;
+}

Source/cmStringAlgorithms.h

@@ -7,6 +7,7 @@
 
 #include "cmRange.h"
 #include "cm_string_view.hxx"
+#include <initializer_list>
 #include <sstream>
 #include <string.h>
 #include <string>
@@ -48,6 +49,55 @@ std::string cmJoin(Range const& rng, cm::string_view separator)
   return os.str();
 }
 
+/** Concatenate string pieces into a single string.  */
+std::string cmCatViews(std::initializer_list<cm::string_view> views);
+
+/** Utility class for cmStrCat.  */
+class cmAlphaNum
+{
+public:
+  cmAlphaNum(cm::string_view view)
+    : View_(view)
+  {
+  }
+  cmAlphaNum(std::string const& str)
+    : View_(str)
+  {
+  }
+  cmAlphaNum(const char* str)
+    : View_(str)
+  {
+  }
+  cmAlphaNum(char ch)
+    : View_(Digits_, 1)
+  {
+    Digits_[0] = ch;
+  }
+  cmAlphaNum(int val);
+  cmAlphaNum(unsigned int val);
+  cmAlphaNum(long int val);
+  cmAlphaNum(unsigned long int val);
+  cmAlphaNum(long long int val);
+  cmAlphaNum(unsigned long long int val);
+  cmAlphaNum(float val);
+  cmAlphaNum(double val);
+
+  cm::string_view View() const { return View_; }
+
+private:
+  cm::string_view View_;
+  char Digits_[32];
+};
+
+/** Concatenate string pieces and numbers into a single string.  */
+template <typename... AV>
+inline std::string cmStrCat(cmAlphaNum const& a, cmAlphaNum const& b,
+                            AV const&... args)
+{
+  return cmCatViews(
+    { a.View(), b.View(), static_cast<cmAlphaNum const&>(args).View()... });
+}
+
 template <typename Range>
 std::string cmWrap(std::string const& prefix, Range const& r,
                    std::string const& suffix, std::string const& sep)

bootstrap

@@ -422,6 +422,7 @@ CMAKE_CXX_SOURCES="\
   cmState \
   cmStateDirectory \
   cmStateSnapshot \
+  cmStringAlgorithms \
   cmStringReplaceHelper \
   cmStringCommand \
   cmSubdirCommand \