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, 134 insertions, 0 deletions

diff --git a/core/fxcrt/cfx_bytestring_unittest.cpp b/core/fxcrt/cfx_bytestring_unittest.cpp
index a4c5187c11..6bbe305268 100644
--- a/core/fxcrt/cfx_bytestring_unittest.cpp
+++ b/core/fxcrt/cfx_bytestring_unittest.cpp
@@ -833,6 +833,73 @@ TEST(fxcrt, ByteStringReleaseBuffer) {
   }
 }
 
+TEST(fxcrt, ByteStringEmptyReverseIterator) {
+  CFX_ByteString empty;
+  auto iter = empty.rbegin();
+  EXPECT_TRUE(iter == empty.rend());
+  EXPECT_FALSE(iter != empty.rend());
+  EXPECT_FALSE(iter < empty.rend());
+}
+
+TEST(fxcrt, ByteStringOneCharReverseIterator) {
+  CFX_ByteString one_str("a");
+  auto iter = one_str.rbegin();
+  EXPECT_FALSE(iter == one_str.rend());
+  EXPECT_TRUE(iter != one_str.rend());
+  EXPECT_TRUE(iter < one_str.rend());
+
+  char ch = *iter++;
+  EXPECT_EQ('a', ch);
+  EXPECT_TRUE(iter == one_str.rend());
+  EXPECT_FALSE(iter != one_str.rend());
+  EXPECT_FALSE(iter < one_str.rend());
+}
+
+TEST(fxcrt, ByteStringMultiCharReverseIterator) {
+  CFX_ByteString multi_str("abcd");
+  auto iter = multi_str.rbegin();
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  char ch = *iter++;
+  EXPECT_EQ('d', ch);
+  EXPECT_EQ('c', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *(++iter);
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('b', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter++;
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('a', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter++;
+  EXPECT_EQ('a', ch);
+  EXPECT_TRUE(iter == multi_str.rend());
+
+  ch = *(--iter);
+  EXPECT_EQ('a', ch);
+  EXPECT_EQ('a', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter--;
+  EXPECT_EQ('a', ch);
+  EXPECT_EQ('b', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter--;
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('c', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *(--iter);
+  EXPECT_EQ('d', ch);
+  EXPECT_EQ('d', *iter);
+  EXPECT_TRUE(iter == multi_str.rbegin());
+}
+
 TEST(fxcrt, ByteStringCNotNull) {
   CFX_ByteStringC string3("abc");
   CFX_ByteStringC string6("abcdef");
@@ -1200,6 +1267,73 @@ TEST(fxcrt, ByteStringCMultiCharIterator) {
   EXPECT_EQ('a' + 'b' + 'c', sum);
 }
 
+TEST(fxcrt, ByteStringCEmptyReverseIterator) {
+  CFX_ByteStringC empty;
+  auto iter = empty.rbegin();
+  EXPECT_TRUE(iter == empty.rend());
+  EXPECT_FALSE(iter != empty.rend());
+  EXPECT_FALSE(iter < empty.rend());
+}
+
+TEST(fxcrt, ByteStringCOneCharReverseIterator) {
+  CFX_ByteStringC one_str("a");
+  auto iter = one_str.rbegin();
+  EXPECT_FALSE(iter == one_str.rend());
+  EXPECT_TRUE(iter != one_str.rend());
+  EXPECT_TRUE(iter < one_str.rend());
+
+  char ch = *iter++;
+  EXPECT_EQ('a', ch);
+  EXPECT_TRUE(iter == one_str.rend());
+  EXPECT_FALSE(iter != one_str.rend());
+  EXPECT_FALSE(iter < one_str.rend());
+}
+
+TEST(fxcrt, ByteStringCMultiCharReverseIterator) {
+  CFX_ByteStringC multi_str("abcd");
+  auto iter = multi_str.rbegin();
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  char ch = *iter++;
+  EXPECT_EQ('d', ch);
+  EXPECT_EQ('c', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *(++iter);
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('b', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter++;
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('a', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter++;
+  EXPECT_EQ('a', ch);
+  EXPECT_TRUE(iter == multi_str.rend());
+
+  ch = *(--iter);
+  EXPECT_EQ('a', ch);
+  EXPECT_EQ('a', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter--;
+  EXPECT_EQ('a', ch);
+  EXPECT_EQ('b', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter--;
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('c', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *(--iter);
+  EXPECT_EQ('d', ch);
+  EXPECT_EQ('d', *iter);
+  EXPECT_TRUE(iter == multi_str.rbegin());
+}
+
 TEST(fxcrt, ByteStringCAnyAllNoneOf) {
   CFX_ByteStringC str("aaaaaaaaaaaaaaaaab");
   EXPECT_FALSE(std::all_of(str.begin(), str.end(),