base::OffsetAdjuster: Refactor offset limiting logic into the base::OffsetAdjuster

base/strings/utf_offset_string_conversions.cc

Index: base/strings/utf_offset_string_conversions.cc
diff --git a/base/strings/utf_offset_string_conversions.cc b/base/strings/utf_offset_string_conversions.cc
index 79c00f03834ea80e58216787eee50dbfa47508b9..5cdbaf9de0b4b11097d8afb57543b23df36d5be5 100644
--- a/base/strings/utf_offset_string_conversions.cc
+++ b/base/strings/utf_offset_string_conversions.cc
@@ -15,6 +15,23 @@
 
 namespace base {
 
+namespace {
+
+// Limiting function callable by std::for_each which will replace any value
+// which is greater than |limit| with npos.
+struct LimitOffset {
+  explicit LimitOffset(size_t limit) : limit_(limit) {}
+
+  void operator()(size_t& offset) {
+    if (offset > limit_)
+      offset = string16::npos;
+  }
+
+  size_t limit_;
+};
+
+}  // namespace
+
 OffsetAdjuster::Adjustment::Adjustment(size_t original_offset,
                                        size_t original_length,
                                        size_t output_length)
@@ -24,19 +41,20 @@ OffsetAdjuster::Adjustment::Adjustment(size_t original_offset,
 }
 
 // static
-void OffsetAdjuster::AdjustOffsets(
-    const Adjustments& adjustments,
-    std::vector<size_t>* offsets_for_adjustment) {
-  if (!offsets_for_adjustment || adjustments.empty())
-    return;
+void OffsetAdjuster::AdjustOffsets(const Adjustments& adjustments,
+                                   std::vector<size_t>* offsets_for_adjustment,
+                                   size_t limit) {
+  DCHECK(offsets_for_adjustment);
   for (std::vector<size_t>::iterator i(offsets_for_adjustment->begin());
        i != offsets_for_adjustment->end(); ++i)
-    AdjustOffset(adjustments, &(*i));
+    AdjustOffset(adjustments, &(*i), limit);
 }
 
 // static
 void OffsetAdjuster::AdjustOffset(const Adjustments& adjustments,
-                                  size_t* offset) {
+                                  size_t* offset,
+                                  size_t limit) {
+  DCHECK(offset);
   if (*offset == string16::npos)
     return;
   int adjustment = 0;
@@ -51,6 +69,9 @@ void OffsetAdjuster::AdjustOffset(const Adjustments& adjustments,
     adjustment += static_cast<int>(i->original_length - i->output_length);
   }
   *offset -= adjustment;
+
+  if (*offset > limit)
+    *offset = string16::npos;
 }
 
 // static
@@ -236,9 +257,8 @@ string16 UTF8ToUTF16WithAdjustments(
 string16 UTF8ToUTF16AndAdjustOffsets(
     const base::StringPiece& utf8,
     std::vector<size_t>* offsets_for_adjustment) {
-  std::for_each(offsets_for_adjustment->begin(),
-                offsets_for_adjustment->end(),
-                LimitOffset<base::StringPiece>(utf8.length()));
+  std::for_each(offsets_for_adjustment->begin(), offsets_for_adjustment->end(),
+                LimitOffset(utf8.length()));
   OffsetAdjuster::Adjustments adjustments;
   string16 result = UTF8ToUTF16WithAdjustments(utf8, &adjustments);
   OffsetAdjuster::AdjustOffsets(adjustments, offsets_for_adjustment);
@@ -248,9 +268,8 @@ string16 UTF8ToUTF16AndAdjustOffsets(
 std::string UTF16ToUTF8AndAdjustOffsets(
     const base::StringPiece16& utf16,
     std::vector<size_t>* offsets_for_adjustment) {
-  std::for_each(offsets_for_adjustment->begin(),
-                offsets_for_adjustment->end(),
-                LimitOffset<base::StringPiece16>(utf16.length()));
+  std::for_each(offsets_for_adjustment->begin(), offsets_for_adjustment->end(),
+                LimitOffset(utf16.length()));
   std::string result;
   PrepareForUTF8Output(utf16.data(), utf16.length(), &result);
   OffsetAdjuster::Adjustments adjustments;