1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
|
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2009, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id: ListBuffer.scala 14378 2008-03-13 11:39:05Z dragos $
package scalax.collection.mutable
import generic.SequenceForwarder
import immutable.List
import collection.immutable.{List, Nil, ::}
/** A Buffer implementation back up by a list. It provides constant time
* prepend and append. Most other operations are linear.
*
* @author Matthias Zenger
* @author Martin Odersky
* @version 2.8
*/
@serializable
final class ListBuffer[A]
extends Buffer[A]
with Builder[List, A]
with SequenceForwarder[A]
{
private var start: List[A] = Nil
private var last0: ::[A] = _
private var exported: Boolean = false
protected def underlying: Sequence[A] = start
// Implementations of abstract methods in Buffer
/** Replaces element at index <code>n</code> with the new element
* <code>newelem</code>. Takes time linear in the buffer size. (except the first
* element, which is updated in constant time).
*
* @param n the index of the element to replace.
* @param x the new element.
* @throws Predef.IndexOutOfBoundsException if <code>n</code> is out of bounds.
*/
def update(n: Int, x: A) {
try {
if (exported) copy()
if (n == 0) {
val newElem = new :: (x, start.tail);
if (last0 eq start) last0 = newElem
start = newElem
} else {
var cursor = start
var i = 1
while (i < n) {
cursor = cursor.tail
i += 1
}
val newElem = new :: (x, cursor.tail.tail)
if (last0 eq cursor.tail) last0 = newElem
cursor.asInstanceOf[::[A]].tl = newElem
}
} catch {
case ex: Exception => throw new IndexOutOfBoundsException(n.toString())
}
}
/** Appends a single element to this buffer. This operation takes constant time.
*
* @param x the element to append.
*/
def += (x: A) {
if (exported) copy()
if (start.isEmpty) {
last0 = new :: (x, Nil)
start = last0
} else {
val last1 = last0
last0 = new :: (x, Nil)
last1.tl = last0
}
}
/** Clears the buffer contents.
*/
def clear() {
start = Nil
exported = false
}
/** Prepends a single element to this buffer. This operation takes constant
* time.
*
* @param x the element to prepend.
* @return this buffer.
*/
def +: (x: A): this.type = {
if (exported) copy()
val newElem = new :: (x, start)
if (start.isEmpty) last0 = newElem
start = newElem
this
}
/** Inserts new elements at the index <code>n</code>. Opposed to method
* <code>update</code>, this method will not replace an element with a new
* one. Instead, it will insert a new element at index <code>n</code>.
*
* @param n the index where a new element will be inserted.
* @param iter the iterable object providing all elements to insert.
* @throws Predef.IndexOutOfBoundsException if <code>n</code> is out of bounds.
*/
def insertAll(n: Int, iter: Iterable[A]) {
try {
if (exported) copy()
var elems = iter.elements.toList.reverse
if (n == 0) {
while (!elems.isEmpty) {
val newElem = new :: (elems.head, start)
if (start.isEmpty) last0 = newElem
start = newElem
elems = elems.tail
}
} else {
var cursor = start
var i = 1
while (i < n) {
cursor = cursor.tail
i += 1
}
while (!elems.isEmpty) {
val newElem = new :: (elems.head, cursor.tail)
if (cursor.tail.isEmpty) last0 = newElem
cursor.asInstanceOf[::[A]].tl = newElem
elems = elems.tail
}
}
} catch {
case ex: Exception =>
throw new IndexOutOfBoundsException(n.toString())
}
}
/** Removes the element on a given index position. This operation takes time linear in
* the buffer size.
*
* @param n the index which refers to the element to delete.
* @return the updated array buffer.
* @throws Predef.IndexOutOfBoundsException if <code>n</code> is out of bounds.
*/
def remove(n: Int, count: Int) {
try {
if (exported) copy()
var old = start.head;
if (n == 0) {
var c = count
while (c > 0) {
start = start.tail
c -= 1
}
} else {
var cursor = start
var i = 1
while (i < n) {
cursor = cursor.tail
i += 1
}
var c = count
while (c > 0) {
if (last0 eq cursor.tail) last0 = cursor.asInstanceOf[::[A]]
cursor.asInstanceOf[::[A]].tl = cursor.tail.tail
c -= 1
}
}
old
} catch {
case ex: Exception =>
throw new IndexOutOfBoundsException(n.toString())
}
}
// Implementation of abstract method in Builder
def result = toList
/** Converts this buffer to a list. Takes constant time. The buffer is
* copied lazily, the first time it is mutated.
*/
override def toList: List[A] = {
exported = !start.isEmpty
start
}
// New methods in ListBuffer
/** Prepends the elements of this buffer to a given list
*
* @param xs the list to which elements are prepended
*/
def prependToList(xs: List[A]): List[A] =
if (start.isEmpty) xs
else { last0.tl = xs; toList }
// Overrides of methods in Buffer
/** Removes the element on a given index position. Takes time linear in
* the buffer size (except for the first element, which is removed in constant
* time).
*
* @param n the index which refers to the element to delete.
* @return n the element that was formerly at position <code>n</code>.
* @pre an element exists at position <code>n</code>
* @throws Predef.IndexOutOfBoundsException if <code>n</code> is out of bounds.
*/
override def remove(n: Int): A = try {
if (exported) copy()
var old = start.head;
if (n == 0) {
start = start.tail
} else {
var cursor = start
var i = 1
while (i < n) {
cursor = cursor.tail
i += 1
}
old = cursor.tail.head
if (last0 eq cursor.tail) last0 = cursor.asInstanceOf[::[A]]
cursor.asInstanceOf[::[A]].tl = cursor.tail.tail
}
old
} catch {
case ex: Exception =>
throw new IndexOutOfBoundsException(n.toString())
}
/** Remove a single element from this buffer. This operation takes linear time
* (except removing the first element, which is done in constant time).
*
* @param x the element to remove.
*/
override def -= (x: A) {
if (exported) copy()
if (start.isEmpty) {}
else if (start.head == x) start = start.tail
else {
var cursor = start
while (!cursor.tail.isEmpty && cursor.tail.head != x) { cursor = cursor.tail }
if (!cursor.tail.isEmpty) {
val z = cursor.asInstanceOf[::[A]]
if (z.tl == last0)
last0 = z
z.tl = cursor.tail.tail
}
}
}
/** expose the underlying list but do not mark it as exported */
override def readOnly : List[A] = start
// Private methods
/** Copy contents of this buffer */
private def copy() {
var cursor = start
val limit = last0.tail
clear
while (cursor ne limit) {
this += cursor.head
cursor = cursor.tail
}
}
/** Returns a clone of this buffer.
*
* @return a <code>ListBuffer</code> with the same elements.
*/
override def clone(): Buffer[A] = (new ListBuffer[A]) ++ this
/** Defines the prefix of the string representation.
*
* @return the string representation of this buffer.
*/
override def stringPrefix: String = "ListBuffer"
}
|
