Add a Python-like join function to merge a list of strings with a

separator between each two elements.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189846 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 43 insertions, 0 deletions

diff --git a/include/llvm/ADT/StringExtras.h b/include/llvm/ADT/StringExtras.h
index d2887c5c2c..56dbb5b806 100644
--- a/include/llvm/ADT/StringExtras.h
+++ b/include/llvm/ADT/StringExtras.h
@@ -14,6 +14,7 @@
 #ifndef LLVM_ADT_STRINGEXTRAS_H
 #define LLVM_ADT_STRINGEXTRAS_H
 
+#include <iterator>
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/DataTypes.h"
 
@@ -159,6 +160,48 @@ static inline StringRef getOrdinalSuffix(unsigned Val) {
   }
 }
 
+template <typename IteratorT>
+inline std::string join_impl(IteratorT Begin, IteratorT End,
+                             StringRef Separator, std::input_iterator_tag) {
+  std::string S;
+  if (Begin == End)
+    return S;
+
+  S += (*Begin);
+  while (++Begin != End) {
+    S += Separator;
+    S += (*Begin);
+  }
+  return S;
+}
+
+template <typename IteratorT>
+inline std::string join_impl(IteratorT Begin, IteratorT End,
+                             StringRef Separator, std::forward_iterator_tag) {
+  std::string S;
+  if (Begin == End)
+    return S;
+
+  size_t Len = (std::distance(Begin, End) - 1) * Separator.size();
+  for (IteratorT I = Begin; I != End; ++I)
+    Len += (*Begin).size();
+  S.reserve(Len);
+  S += (*Begin);
+  while (++Begin != End) {
+    S += Separator;
+    S += (*Begin);
+  }
+  return S;
+}
+
+/// Joins the strings in the range [Begin, End), adding Separator between
+/// the elements.
+template <typename IteratorT>
+inline std::string join(IteratorT Begin, IteratorT End, StringRef Separator) {
+  typedef typename std::iterator_traits<IteratorT>::iterator_category tag;
+  return join_impl(Begin, End, Separator, tag());
+}
+
 } // End llvm namespace
 
 #endif