Ignore empty collation elements in EndsWith

We should ignore empty collaction elements at the end of the string
when doing our EndsWith checks.  This means the match ICU finds might
not span to the end of string, but the only elements after the match
before the end are completely ignorable.

U+00AD (SOFT HYPHEN) is one such case where the codepoint is completely
ignorable.

Fixes dotnet/corefx#3467

1 files changed, 41 insertions, 29 deletions

diff --git a/src/corefx/System.Globalization.Native/collation.cpp b/src/corefx/System.Globalization.Native/collation.cpp
index f1ec6f4051..6039a9ef39 100644
--- a/src/corefx/System.Globalization.Native/collation.cpp
+++ b/src/corefx/System.Globalization.Native/collation.cpp
@@ -295,6 +295,40 @@ UCollator* CloneCollatorWithOptions(const UCollator* pCollator, int32_t options,
     return pClonedCollator;
 }
 
+// Returns TRUE if all the collation elements in str are completely ignorable
+bool CanIgnoreAllCollationElements(const UCollator* pColl, const UChar* lpStr, int32_t length)
+{
+    bool result = FALSE;
+    UErrorCode err = U_ZERO_ERROR;
+    UCollationElements* pCollElem = ucol_openElements(pColl, lpStr, length, &err);
+
+    if (U_SUCCESS(err))
+    {
+        int32_t curCollElem = UCOL_NULLORDER;
+
+        result = TRUE;
+
+        while ((curCollElem = ucol_next(pCollElem, &err)) != UCOL_NULLORDER)
+        {
+            if (curCollElem != 0)
+            {
+                result = FALSE;
+                break;
+            }
+        }
+
+        if (U_FAILURE(err))
+        {
+            result = FALSE;
+        }
+
+        ucol_closeElements(pCollElem);
+    }
+
+    return result;
+
+}
+
 extern "C" SortHandle* GlobalizationNative_GetSortHandle(const char* lpLocaleName)
 {
     SortHandle* pSortHandle = new SortHandle();
@@ -551,32 +585,7 @@ extern "C" int32_t GlobalizationNative_StartsWith(
                 }
                 else
                 {
-                    UCollationElements* pCollElem = ucol_openElements(pColl, lpSource, idx, &err);
-
-                    if (U_SUCCESS(err))
-                    {
-                        int32_t curCollElem = UCOL_NULLORDER;
-
-                        result = TRUE;
-
-                        while ((curCollElem = ucol_next(pCollElem, &err)) != UCOL_NULLORDER)
-                        {
-                            if (curCollElem != 0)
-                            {
-                                // Non ignorable collation element found between start of the
-                                // string and the first match for lpTarget.
-                                result = FALSE;
-                                break;
-                            }
-                        }
-
-                        if (U_FAILURE(err))
-                        {
-                            result = FALSE;
-                        }
-
-                        ucol_closeElements(pCollElem);
-                    }
+                    result = CanIgnoreAllCollationElements(pColl, lpSource, idx);
                 }
             }
 
@@ -617,10 +626,13 @@ extern "C" int32_t GlobalizationNative_EndsWith(
                 {
                     result = TRUE;
                 }
+                else
+                {
+                    int32_t matchEnd = idx + usearch_getMatchedLength(pSearch);
+                    int32_t remainingStringLength = cwSourceLength - matchEnd;
 
-                // TODO (dotnet/corefx#3467): We should do something similar to what
-                // StartsWith does where we can ignore
-                // some collation elements at the end of the string if they are zero.
+                    result = CanIgnoreAllCollationElements(pColl, lpSource + matchEnd, remainingStringLength);
+                }
             }
 
             usearch_close(pSearch);