use std::string_view in string_utils

src/util/string_utils.cpp

@@ -18,26 +18,27 @@ Author: Daniel Poetzl
 /// in the middle of the string is left unchanged
 /// \param s: the string to strip
 /// \return The stripped string
-std::string strip_string(const std::string &s)
+std::string strip_string(const std::string_view &s)
 {
   auto pred=[](char c){ return std::isspace(c); };
 
-  std::string::const_iterator left
-    =std::find_if_not(s.begin(), s.end(), pred);
+  std::string_view::const_iterator left =
+    std::find_if_not(s.begin(), s.end(), pred);
   if(left==s.end())
     return "";
 
-  std::string::size_type i=std::distance(s.begin(), left);
+  std::string_view::size_type i = std::distance(s.begin(), left);
 
-  std::string::const_reverse_iterator right
-    =std::find_if_not(s.rbegin(), s.rend(), pred);
+  std::string_view::const_reverse_iterator right =
+    std::find_if_not(s.rbegin(), s.rend(), pred);
   std::string::size_type j=std::distance(right, s.rend())-1;
 
-  return s.substr(i, (j-i+1));
+  // copy happens here; this could return a view in the future
+  return std::string{s.substr(i, (j - i + 1))};
 }
 
 void split_string(
-  const std::string &s,
+  const std::string_view &s,
   char delim,
   std::vector<std::string> &result,
   bool strip,
@@ -64,7 +65,8 @@ void split_string(
   {
     if(s[i]==delim)
     {
-      std::string new_s=s.substr(start, i-start);
+      // this is a copy, and should become a view
+      std::string new_s = std::string{s.substr(start, i - start)};
 
       if(strip)
         new_s=strip_string(new_s);
@@ -76,7 +78,8 @@ void split_string(
     }
   }
 
-  std::string new_s=s.substr(start, n-start);
+  // this is a copy, and should become a view
+  std::string new_s = std::string{s.substr(start, n - start)};
 
   if(strip)
     new_s=strip_string(new_s);
@@ -89,7 +92,7 @@ void split_string(
 }
 
 void split_string(
-  const std::string &s,
+  const std::string_view &s,
   char delim,
   std::string &left,
   std::string &right,
@@ -102,19 +105,19 @@ void split_string(
 
   if(result.size() != 2)
   {
-    throw deserialization_exceptiont{"expected string '" + s +
-                                     "' to contain two substrings "
-                                     "delimited by " +
-                                     delim + " but has " +
-                                     std::to_string(result.size())};
+    throw deserialization_exceptiont{
+      "expected string '" + std::string{s} +
+      "' to contain two substrings "
+      "delimited by " +
+      delim + " but has " + std::to_string(result.size())};
   }
 
   left=result[0];
   right=result[1];
 }
 
 std::vector<std::string> split_string(
-  const std::string &s,
+  const std::string_view &s,
   char delim,
   bool strip,
   bool remove_empty)
@@ -124,9 +127,8 @@ std::vector<std::string> split_string(
   return result;
 }
 
-std::string trim_from_last_delimiter(
-  const std::string &s,
-  const char delim)
+std::string
+trim_from_last_delimiter(const std::string_view &s, const char delim)
 {
   std::string result;
   const size_t index=s.find_last_of(delim);
@@ -135,7 +137,7 @@ std::string trim_from_last_delimiter(
   return result;
 }
 
-std::string escape(const std::string &s)
+std::string escape(const std::string_view &s)
 {
   std::string result;
 
@@ -150,7 +152,7 @@ std::string escape(const std::string &s)
   return result;
 }
 
-std::string escape_non_alnum(const std::string &to_escape)
+std::string escape_non_alnum(const std::string_view &to_escape)
 {
   std::ostringstream escaped;
   for(auto &ch : to_escape)
@@ -172,11 +174,12 @@ std::string escape_non_alnum(const std::string &to_escape)
   }
   return escaped.str();
 }
-std::string capitalize(const std::string &str)
+
+std::string capitalize(const std::string_view &str)
 {
   if(str.empty())
-    return str;
-  std::string capitalized = str;
+    return std::string{};
+  std::string capitalized = std::string{str}; // copy
   capitalized[0] = toupper(capitalized[0]);
   return capitalized;
 }

src/util/string_utils.h

@@ -11,14 +11,15 @@ Author: Daniel Poetzl
 #define CPROVER_UTIL_STRING_UTILS_H
 
 #include <string>
+#include <string_view>
 #include <vector>
 
-std::string strip_string(const std::string &s);
+std::string strip_string(const std::string_view &);
 
-std::string capitalize(const std::string &str);
+std::string capitalize(const std::string_view &);
 
 void split_string(
-  const std::string &s,
+  const std::string_view &s,
   char delim,
   std::string &left,
   std::string &right,
@@ -34,14 +35,13 @@ void split_string(
 ///   This is applied after strip so whitespace only elements will be removed if
 ///   both are set to true.
 std::vector<std::string> split_string(
-  const std::string &s,
+  const std::string_view &s,
   char delim,
   bool strip = false,
   bool remove_empty = false);
 
-std::string trim_from_last_delimiter(
-  const std::string &s,
-  const char delim);
+std::string
+trim_from_last_delimiter(const std::string_view &s, const char delim);
 
 /// Prints items to an stream, separated by a constant delimiter
 /// \tparam It: An iterator type
@@ -97,13 +97,13 @@ join_strings(Stream &&os, const It b, const It e, const Delimiter &delimiter)
 
 /// Generic escaping of strings; this is not meant to be a particular
 /// programming language.
-std::string escape(const std::string &);
+std::string escape(const std::string_view &);
 
 /// Replace non-alphanumeric characters with `_xx` escapes, where xx are hex
 /// digits. Underscores are replaced by `__`.
 /// \param to_escape: string to escape
 /// \return string with non-alphanumeric characters escaped
-std::string escape_non_alnum(const std::string &to_escape);
+std::string escape_non_alnum(const std::string_view &to_escape);
 
 /// Wrap line at spaces to not extend past the right margin, and include given
 /// padding with spaces to the left