Add reverse iterators to CFX String classes.

Reverse iteration with signed lengths and indices is kinda icky
without this abstraction, and STL provides this pretty much "for
free" given the existing forward iterator.

Change-Id: I97c36c8bd23c0aa48195bc17da7c672292b4cde2
Reviewed-on: https://pdfium-review.googlesource.com/13770
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/core/fxcrt/cfx_string_c_template.h b/core/fxcrt/cfx_string_c_template.h
index b0e17a1222..9123fc234b 100644
--- a/core/fxcrt/cfx_string_c_template.h
+++ b/core/fxcrt/cfx_string_c_template.h
@@ -8,6 +8,7 @@
 #define CORE_FXCRT_CFX_STRING_C_TEMPLATE_H_
 
 #include <algorithm>
+#include <iterator>
 #include <type_traits>
 #include <utility>
 #include <vector>
@@ -26,6 +27,7 @@ class CFX_StringCTemplate {
   using CharType = T;
   using UnsignedType = typename std::make_unsigned<CharType>::type;
   using const_iterator = const CharType*;
+  using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
   CFX_StringCTemplate() : m_Ptr(nullptr), m_Length(0) {}
 
@@ -84,6 +86,13 @@ class CFX_StringCTemplate {
                  : nullptr;
   }
 
+  const_reverse_iterator rbegin() const {
+    return const_reverse_iterator(end());
+  }
+  const_reverse_iterator rend() const {
+    return const_reverse_iterator(begin());
+  }
+
   bool operator==(const CharType* ptr) const {
     return FXSYS_len(ptr) == m_Length &&
            FXSYS_cmp(ptr, reinterpret_cast<const CharType*>(m_Ptr.Get()),