/**
* Ensures that a big array can contain the given number of entries, preserving just a part of the
* big array.
*
* <p><strong>Warning:</strong> the returned array might use part of the segments of the original
* array, which must be considered read-only after calling this method.
*
* @param array a big array.
* @param length the new minimum length for this big array.
* @param preserve the number of elements of the big array that must be preserved in case a new
* allocation is necessary.
* @return <code>array</code>, if it can contain <code>length</code> entries or more; otherwise, a
* big array with <code>length</code> entries whose first <code>preserve</code> entries are
* the same as those of <code>array</code>.
*/
public static boolean[][] ensureCapacity(
final boolean[][] array, final long length, final long preserve) {
final long oldLength = length(array);
if (length > oldLength) {
final int valid =
array.length
- (array.length == 0
|| array.length > 0 && array[array.length - 1].length == SEGMENT_SIZE
? 0
: 1);
final int baseLength = (int) ((length + SEGMENT_MASK) / SEGMENT_SIZE);
final boolean[][] base = Arrays.copyOf(array, baseLength);
final int residual = (int) (length & SEGMENT_MASK);
if (residual != 0) {
for (int i = valid; i < baseLength - 1; i++) base[i] = new boolean[SEGMENT_SIZE];
base[baseLength - 1] = new boolean[residual];
} else for (int i = valid; i < baseLength; i++) base[i] = new boolean[SEGMENT_SIZE];
if (preserve - (valid * (long) SEGMENT_SIZE) > 0)
copy(
array,
valid * (long) SEGMENT_SIZE,
base,
valid * (long) SEGMENT_SIZE,
preserve - (valid * (long) SEGMENT_SIZE));
return base;
}
return array;
}
/**
* Returns a copy of a portion of a big array.
*
* @param array a big array.
* @param offset the first element to copy.
* @param length the number of elements to copy.
* @return a new big array containing <code>length</code> elements of <code>array</code> starting
* at <code>offset</code>.
*/
public static boolean[][] copy(final boolean[][] array, final long offset, final long length) {
ensureOffsetLength(array, offset, length);
final boolean[][] a = newBigArray(length);
copy(array, offset, a, 0, length);
return a;
}