/*
* lca_lookup
*
* Perform the constant time LCA computation, finding the least
* common ancestor of x and y.
*
* Parameters: lca - an LCA_STRUCT structure
* x - a suffix tree node
* y - another suffix tree node
*
* Returns: the suffix tree node which is the LCA of x and y
*/
STREE_NODE lca_lookup(LCA_STRUCT *lca, STREE_NODE x, STREE_NODE y)
{
assert(lca && lca->tree && lca->type == LCA_LINEAR && x && y);
SUFFIX_TREE tree = lca->tree;
unsigned int *I = lca->I;
unsigned int *A = lca->A;
STREE_NODE *L = lca->L;
// Shift idents so that they go from 1..num_nodes.
unsigned int xid = (unsigned int)stree_get_ident(tree, x) + 1;
unsigned int yid = (unsigned int)stree_get_ident(tree, y) + 1;
/*
* Steps 1 and 2.
*
* Step 1 here differs from the book in that it returns the most
* significant bit counting from the right (and starting the count
* with 0), and then simply OR's the k+1..32 bits of I[xid] and the
* number 2^k.
*/
//printf("xid=%3d, I[xid]=%3d\n", xid, I[xid]);
// printf("yid=%3d, I[yid]=%3d\n", yid, I[yid]);
unsigned int k = MSB(I[xid] ^ I[yid]);
unsigned int b = (I[xid] & HIGH_BITS(k+1)) | (1 << k);
unsigned int j = h( (A[xid] & A[yid]) & HIGH_BITS(h(b)) );
// printf("k=%d, b=%d, j =%d\n", k, b, j);
IF_STATS(lca->num_compares++);
// Step 3.
unsigned int l = h(A[xid]);
STREE_NODE xbar, ybar;
if (l == j) {
xbar = x;
} else {
k = MSB(A[xid] & ~HIGH_BITS(j));
xbar = stree_get_parent(tree, L[(I[xid] & HIGH_BITS(k+1)) | (1 << k)]);
}
IF_STATS(lca->num_compares++);
// Step 4.
l = h(A[yid]);
if (l == j) {
ybar = y;
} else {
k = MSB(A[yid] & ~HIGH_BITS(j));
ybar = stree_get_parent(tree, L[(I[yid] & HIGH_BITS(k+1)) | (1 << k)]);
}
IF_STATS(lca->num_compares++);
// Step 5.
IF_STATS(lca->num_compares++);
return (stree_get_ident(tree, xbar) < stree_get_ident(tree, ybar)) ? xbar : ybar;
}
int posix_fadvise(int fd, off_t offset, off_t len, int advise)
{
INTERNAL_SYSCALL_DECL (err);
int ret = INTERNAL_SYSCALL (arm_fadvise64_64, err, 6, fd, advise,
__LONG_LONG_PAIR (HIGH_BITS(offset), (long)offset),
__LONG_LONG_PAIR (HIGH_BITS(len), (long)len));
if (INTERNAL_SYSCALL_ERROR_P (ret, err))
return INTERNAL_SYSCALL_ERRNO (ret, err);
return 0;
}
