Add function for computing the edit distance of two arrays.
Accomplished by moving the body of StringRef::edit_distance into
a separate function that accepts two ArrayRefs, and making
StringRef::edit_distance a wrapper around the new function.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150621 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/StringRef.cpp b/lib/Support/StringRef.cpp
index e73c6e3..4d20903 100644
--- a/lib/Support/StringRef.cpp
+++ b/lib/Support/StringRef.cpp
@@ -10,6 +10,7 @@
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/OwningPtr.h"
+#include "llvm/ADT/edit_distance.h"
#include <bitset>
using namespace llvm;
@@ -84,57 +85,10 @@
unsigned StringRef::edit_distance(llvm::StringRef Other,
bool AllowReplacements,
unsigned MaxEditDistance) {
- // The algorithm implemented below is the "classic"
- // dynamic-programming algorithm for computing the Levenshtein
- // distance, which is described here:
- //
- // http://en.wikipedia.org/wiki/Levenshtein_distance
- //
- // Although the algorithm is typically described using an m x n
- // array, only two rows are used at a time, so this implemenation
- // just keeps two separate vectors for those two rows.
- size_type m = size();
- size_type n = Other.size();
-
- const unsigned SmallBufferSize = 64;
- unsigned SmallBuffer[SmallBufferSize];
- llvm::OwningArrayPtr<unsigned> Allocated;
- unsigned *previous = SmallBuffer;
- if (2*(n + 1) > SmallBufferSize) {
- previous = new unsigned [2*(n+1)];
- Allocated.reset(previous);
- }
- unsigned *current = previous + (n + 1);
-
- for (unsigned i = 0; i <= n; ++i)
- previous[i] = i;
-
- for (size_type y = 1; y <= m; ++y) {
- current[0] = y;
- unsigned BestThisRow = current[0];
-
- for (size_type x = 1; x <= n; ++x) {
- if (AllowReplacements) {
- current[x] = min(previous[x-1] + ((*this)[y-1] == Other[x-1]? 0u:1u),
- min(current[x-1], previous[x])+1);
- }
- else {
- if ((*this)[y-1] == Other[x-1]) current[x] = previous[x-1];
- else current[x] = min(current[x-1], previous[x]) + 1;
- }
- BestThisRow = min(BestThisRow, current[x]);
- }
-
- if (MaxEditDistance && BestThisRow > MaxEditDistance)
- return MaxEditDistance + 1;
-
- unsigned *tmp = current;
- current = previous;
- previous = tmp;
- }
-
- unsigned Result = previous[n];
- return Result;
+ return llvm::ComputeEditDistance(
+ llvm::ArrayRef<char>(data(), size()),
+ llvm::ArrayRef<char>(Other.data(), Other.size()),
+ AllowReplacements, MaxEditDistance);
}
//===----------------------------------------------------------------------===//