add utils::trim() function to remove leading and trailing whitespace from string

src/utils.cpp

@@ -348,6 +348,19 @@ tagint utils::tnumeric(const char *file, int line, const char *str,
   return ATOTAGINT(str);
 }
 
+/* ----------------------------------------------------------------------
+   Return string without leading or trailing whitespace
+------------------------------------------------------------------------- */
+
+std::string utils::trim(const std::string & line) {
+  int beg = re_match(line.c_str(),"\\S+");
+  int end = re_match(line.c_str(),"\\s+$");
+  if (beg < 0) beg = 0;
+  if (end < 0) end = line.size();
+
+  return line.substr(beg,end-beg);
+}
+
 /* ----------------------------------------------------------------------
    Return string without trailing # comment
 ------------------------------------------------------------------------- */

src/utils.h

@@ -143,6 +143,13 @@ namespace LAMMPS_NS {
     tagint tnumeric(const char *file, int line, const char *str,
                     bool do_abort, LAMMPS *lmp);
 
+    /**
+     * \brief Trim leading and trailing whitespace. Like TRIM() in Fortran.
+     * \param line string that should be trimmed
+     * \return new string without whitespace (string)
+     */
+    std::string trim(const std::string &line);
+
     /**
      * \brief Trim anything from '#' onward
      * \param line string that should be trimmed

unittest/utils/test_utils.cpp

@@ -25,6 +25,24 @@ using ::testing::EndsWith;
 using ::testing::Eq;
 using ::testing::StrEq;
 
+TEST(Utils, trim)
+{
+    auto trimmed = utils::trim("\t some text");
+    ASSERT_THAT(trimmed, StrEq("some text"));
+
+    trimmed = utils::trim("some text \r\n");
+    ASSERT_THAT(trimmed, StrEq("some text"));
+
+    trimmed = utils::trim("\v some text \f");
+    ASSERT_THAT(trimmed, StrEq("some text"));
+
+    trimmed = utils::trim("   some\t text    ");
+    ASSERT_THAT(trimmed, StrEq("some\t text"));
+
+    trimmed = utils::trim("  \t\n   ");
+    ASSERT_THAT(trimmed, StrEq(""));
+}
+
 TEST(Utils, trim_comment)
 {
     auto trimmed = utils::trim_comment("some text # comment");