updated kavl to support bidirectional iteration

diff --git a/kavl.h b/kavl.h
index f3520fd79d55c390f6c7da4c85d85334d8b7e444..e0a8e1ba4384ce915328f161040f64b7ffd9cbfd 100644 (file)
--- a/kavl.h
+++ b/kavl.h
@@ -92,6 +92,19 @@ int main(void) {
                } \
                if (cnt_) *cnt_ = cnt; \
                return (__type*)p; \
+       } \
+       __scope __type *kavl_interval_##suf(const __type *root, const __type *x, __type **lower, __type **upper) { \
+               const __type *p = root, *l = 0, *u = 0; \
+               while (p != 0) { \
+                       int cmp; \
+                       cmp = __cmp(x, p); \
+                       if (cmp < 0) u = p, p = p->__head.p[0]; \
+                       else if (cmp > 0) l = p, p = p->__head.p[1]; \
+                       else { l = u = p; break; } \
+               } \
+               if (lower) *lower = (__type*)l; \
+               if (upper) *upper = (__type*)u; \
+               return (__type*)p; \
        }
 
 #define __KAVL_ROTATE(suf, __type, __head) \
@@ -271,43 +284,42 @@ int main(void) {
 
 #define __KAVL_ITR(suf, __scope, __type, __head, __cmp) \
        struct kavl_itr_##suf { \
-               const __type *stack[KAVL_MAX_DEPTH], **top, *right; /* _right_ points to the right child of *top */ \
+               const __type *stack[KAVL_MAX_DEPTH], **top; \
        }; \
        __scope void kavl_itr_first_##suf(const __type *root, struct kavl_itr_##suf *itr) { \
                const __type *p; \
                for (itr->top = itr->stack - 1, p = root; p; p = p->__head.p[0]) \
                        *++itr->top = p; \
-               itr->right = (*itr->top)->__head.p[1]; \
        } \
        __scope int kavl_itr_find_##suf(const __type *root, const __type *x, struct kavl_itr_##suf *itr) { \
                const __type *p = root; \
                itr->top = itr->stack - 1; \
                while (p != 0) { \
                        int cmp; \
+                       *++itr->top = p; \
                        cmp = __cmp(x, p); \
-                       if (cmp < 0) *++itr->top = p, p = p->__head.p[0]; \
+                       if (cmp < 0) p = p->__head.p[0]; \
                        else if (cmp > 0) p = p->__head.p[1]; \
                        else break; \
                } \
-               if (p) { \
-                       *++itr->top = p; \
-                       itr->right = p->__head.p[1]; \
-                       return 1; \
-               } else if (itr->top >= itr->stack) { \
-                       itr->right = (*itr->top)->__head.p[1]; \
-                       return 0; \
-               } else return 0; \
+               return p? 1 : 0; \
        } \
-       __scope int kavl_itr_next_##suf(struct kavl_itr_##suf *itr) { \
-               for (;;) { \
-                       const __type *p; \
-                       for (p = itr->right, --itr->top; p; p = p->__head.p[0]) \
+       __scope int kavl_itr_next_bidir_##suf(struct kavl_itr_##suf *itr, int dir) { \
+               const __type *p; \
+               if (itr->top < itr->stack) return 0; \
+               dir = !!dir; \
+               p = (*itr->top)->__head.p[dir]; \
+               if (p) { /* go down */ \
+                       for (; p; p = p->__head.p[!dir]) \
                                *++itr->top = p; \
-                       if (itr->top < itr->stack) return 0; \
-                       itr->right = (*itr->top)->__head.p[1]; \
                        return 1; \
+               } else { /* go up */ \
+                       do { \
+                               p = *itr->top--; \
+                       } while (itr->top >= itr->stack && p == (*itr->top)->__head.p[dir]); \
+                       return itr->top < itr->stack? 0 : 1; \
                } \
-       }
+       } \
 
 /**
  * Insert a node to the tree
@@ -332,6 +344,7 @@ int main(void) {
  * @return node equal to _x_ if present, or NULL if absent
  */
 #define kavl_find(suf, root, x, cnt) kavl_find_##suf(root, x, cnt)
+#define kavl_interval(suf, root, x, lower, upper) kavl_interval_##suf(root, x, lower, upper)
 
 /**
  * Delete a node from the tree
@@ -376,7 +389,8 @@ int main(void) {
  *
  * @return 1 if there is a next object; 0 otherwise
  */
-#define kavl_itr_next(suf, itr) kavl_itr_next_##suf(itr)
+#define kavl_itr_next(suf, itr) kavl_itr_next_bidir_##suf(itr, 1)
+#define kavl_itr_prev(suf, itr) kavl_itr_next_bidir_##suf(itr, 0)
 
 /**
  * Return the pointer at the iterator