//===----------------------------------------------------------------------===//
#include "llvm/ADT/StringRef.h"
+
using namespace llvm;
// MSVC emits references to this into the translation units which reference it.
return Length < RHS.Length ? -1 : 1;
}
+// Compute the edit distance between the two given strings.
+unsigned StringRef::edit_distance(llvm::StringRef Other,
+ bool AllowReplacements) {
+ // 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];
+ unsigned *Allocated = 0;
+ unsigned *previous = SmallBuffer;
+ if (2*(n + 1) > SmallBufferSize)
+ Allocated = previous = new unsigned [2*(n+1)];
+ 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;
+ 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;
+ }
+ }
+
+ unsigned *tmp = current;
+ current = previous;
+ previous = tmp;
+ }
+
+ unsigned Result = previous[n];
+ delete [] Allocated;
+
+ return Result;
+}
+
//===----------------------------------------------------------------------===//
// String Searching
//===----------------------------------------------------------------------===//