@@ -142,21 +142,94 @@ public static int IndexOf<T>(this IEnumerable<T> s, IReadOnlyList<T> t, int star
142142 return - 1 ;
143143 }
144144
145+ internal static IEnumerable < int > EnumerateIndexes < T > ( this IEnumerable < T > s , IReadOnlyList < T > t , int startIndex , IEqualityComparer < T > comparer )
146+ where T : IEquatable < T >
147+ {
148+ var table = TableBuilder . BuildTable ( t , comparer ) ;
149+ var i = 0 ;
150+ var offset = startIndex + 1 ;
151+ 152+ using ( var enumerator = s . GetEnumerator ( ) )
153+ {
154+ while ( Skip ( enumerator , offset ) != null )
155+ {
156+ if ( comparer . Equals ( t [ i ] , enumerator . Current ) )
157+ {
158+ if ( i == t . Count - 1 )
159+ {
160+ yield return startIndex ;
161+ 162+ startIndex ++ ;
163+ offset = 1 ;
164+ i = 0 ;
165+ }
166+ else
167+ {
168+ i ++ ;
169+ }
170+ }
171+ else
172+ {
173+ // We will extract this as a method GetOffset() in future version
174+ // for upcoming APIs:
175+ // 1. IndexOfAny(IReadOnlyList{T}, IEnumerable{IReadOnlyList{T}})
176+ // 2. IndexesOfAll(IReadOnlyList{T}, IEnumerable{IReadOnlyList{T}}).
177+ if ( table [ i ] > - 1 )
178+ {
179+ startIndex += i ;
180+ offset = i ;
181+ i = table [ i ] ;
182+ }
183+ else
184+ {
185+ startIndex ++ ;
186+ offset = 1 ;
187+ i = 0 ;
188+ }
189+ }
190+ }
191+ }
192+ }
193+ 145194 #endregion
146195
147196 #region Others
148197
149198 internal static int IndexOf < T > ( this IEnumerable < T > s , T t , int startIndex , IEqualityComparer < T > comparer )
150199 where T : IEquatable < T >
151200 {
152- foreach ( var e in s )
201+ var offset = startIndex + 1 ;
202+ 203+ using ( var enumerator = s . GetEnumerator ( ) )
153204 {
154- if ( comparer . Equals ( e , t ) ) return startIndex ;
155- startIndex ++ ;
205+ while ( Skip ( enumerator , offset ) != null )
206+ {
207+ if ( comparer . Equals ( t , enumerator . Current ) ) return startIndex ;
208+ 209+ startIndex ++ ;
210+ offset = 1 ;
211+ }
156212 }
157213 return - 1 ;
158214 }
159215
216+ internal static IEnumerable < int > EnumerateIndexes < T > ( this IEnumerable < T > s , T t , int startIndex , IEqualityComparer < T > comparer )
217+ where T : IEquatable < T >
218+ {
219+ var offset = startIndex + 1 ;
220+ 221+ using ( var enumerator = s . GetEnumerator ( ) )
222+ {
223+ while ( Skip ( enumerator , offset ) != null )
224+ {
225+ if ( comparer . Equals ( t , enumerator . Current ) ) yield return startIndex ;
226+ 227+ startIndex ++ ;
228+ offset = 1 ;
229+ }
230+ }
231+ }
232+ 160233 internal static IEnumerator < T > Skip < T > ( IEnumerator < T > enumerator , int count )
161234 {
162235 var i = 0 ;
0 commit comments