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/**
* @memo Macros for examining and changing the path to a vdsNode.
* @name Manipulating vdsNodePath structures.
*
* These preprocessor macros manipulate vdsNodePath, the bit
* vector that encapsulates the path from the root of a vertex
* tree to a node.<p><dl>
*
* <dd>Details: For a binary tree, each bit represents a branch. For an 8-way
* tree, 3 bits represent a branch. And so on. The least
* significant bit(s) represent the branch from the root node to
* the level-1 node, the next least significant bit(s) represent
* the next branch, and so on; the most significant meaningful
* bit(s) represent the final branch to the leaf node. The root
* node has a depth of 0 and none of the bits mean anything (but
* all must be set to zero, see below).<p>
* <dd>Note 1: Defining VDS_64_BITS enforces 64-bit paths. This enables much
* larger vertex trees but may be slower on some architectures.<p>
* <dd>Note 2: For convenience, the depth of the node (and thus the node path
* length) is currently stored separately, and all unused bits
* must be set to zero (this eases path comparisons).</dl>
*
* @see path.h
*/
/*@{*/
/** Copy one vdsNodePath structure into another.
* Copies the vdsNodePath <b>src</b> into <b>dst</b>.
*/
#define PATH_COPY(dst,src) ((dst) = (src))
/** Look up a particular branch within a vdsNodePath.
* Given a vdsNodePath P and a depth D, returns a branch number
* indicating which child of the node at depth D is an ancestor
* of the node represented by P.
*/
#define PATH_BRANCH(P,D) (((P)>>((D)*VDS_NUMBITS))&VDS_BITMASK)
/** Set a particular branch within a vdsNodePath.
* Takes a vdsNodePath P representing node N, a depth D,
* and a branch number B. If node A is the ancestor of N at
* depth D, sets P to indicate that A->children[B] is the
* ancestor of N at depth D+1.<p>
* Note: B is assumed to be <= VDS_MAXDEGREE; no checking is done
*/
#define PATH_SET_BRANCH(P,D,B) (P |= ((vdsNodePath)(B)<<((D)*VDS_NUMBITS)))
/*@}*/
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