[PATCH] D126159: [ADT] Add edit_distance_insensitive to StringRef

[Nathan James via Phabricator via llvm-commits]

njames93 created this revision.
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In some instances its advantageous to calculate edit distances without worrying about casing.
Currently to achieve this both strings need to be converted to the same case first, then edit distance can be calculated.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D126159

Files:
  llvm/include/llvm/ADT/StringRef.h
  llvm/lib/Support/StringRef.cpp
  llvm/unittests/ADT/StringRefTest.cpp


Index: llvm/unittests/ADT/StringRefTest.cpp
===================================================================
--- llvm/unittests/ADT/StringRefTest.cpp
+++ llvm/unittests/ADT/StringRefTest.cpp
@@ -584,6 +584,15 @@
                                        "people soiled our green "));
 }
 
+TEST(StringRefTest, EditDistanceInsensitive) {
+  StringRef Hello("HELLO");
+  EXPECT_EQ(2U, Hello.edit_distance_insensitive("hill"));
+  EXPECT_EQ(0U, Hello.edit_distance_insensitive("hello"));
+
+  StringRef Industry("InDuStRy");
+  EXPECT_EQ(6U, Industry.edit_distance_insensitive("iNtErEsT"));
+}
+
 TEST(StringRefTest, Misc) {
   std::string Storage;
   raw_string_ostream OS(Storage);
Index: llvm/lib/Support/StringRef.cpp
===================================================================
--- llvm/lib/Support/StringRef.cpp
+++ llvm/lib/Support/StringRef.cpp
@@ -98,6 +98,52 @@
       AllowReplacements, MaxEditDistance);
 }
 
+unsigned llvm::StringRef::edit_distance_insensitive(
+    StringRef Other, bool AllowReplacements, unsigned MaxEditDistance) const {
+  size_t Size = size();
+  size_t OtherSize = Other.size();
+  constexpr unsigned SmallBufferSize = 64;
+  unsigned SmallBuffer[SmallBufferSize];
+  std::unique_ptr<unsigned[]> Allocated;
+  unsigned *Row = SmallBuffer;
+  if (OtherSize + 1 > SmallBufferSize) {
+    Row = new unsigned[OtherSize + 1];
+    Allocated.reset(Row);
+  }
+
+  for (unsigned i = 1; i <= OtherSize; ++i)
+    Row[i] = i;
+
+  for (size_t y = 1; y <= Size; ++y) {
+    Row[0] = y;
+    unsigned BestThisRow = Row[0];
+
+    unsigned Previous = y - 1;
+    for (size_t x = 1; x <= OtherSize; ++x) {
+      int OldRow = Row[x];
+      if (AllowReplacements) {
+        Row[x] = std::min(
+            Previous +
+                (toLower(data()[y - 1]) == toLower(Other[x - 1]) ? 0u : 1u),
+            std::min(Row[x - 1], Row[x]) + 1);
+      } else {
+        if (toLower(data()[y - 1]) == toLower(Other[x - 1]))
+          Row[x] = Previous;
+        else
+          Row[x] = std::min(Row[x - 1], Row[x]) + 1;
+      }
+      Previous = OldRow;
+      BestThisRow = std::min(BestThisRow, Row[x]);
+    }
+
+    if (MaxEditDistance && BestThisRow > MaxEditDistance)
+      return MaxEditDistance + 1;
+  }
+
+  unsigned Result = Row[OtherSize];
+  return Result;
+}
+
 //===----------------------------------------------------------------------===//
 // String Operations
 //===----------------------------------------------------------------------===//
Index: llvm/include/llvm/ADT/StringRef.h
===================================================================
--- llvm/include/llvm/ADT/StringRef.h
+++ llvm/include/llvm/ADT/StringRef.h
@@ -240,6 +240,10 @@
     unsigned edit_distance(StringRef Other, bool AllowReplacements = true,
                            unsigned MaxEditDistance = 0) const;
 
+    LLVM_NODISCARD unsigned
+    edit_distance_insensitive(StringRef Other, bool AllowReplacements = true,
+                              unsigned MaxEditDistance = 0) const;
+
     /// str - Get the contents as an std::string.
     LLVM_NODISCARD
     std::string str() const {


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