--- /dev/null
+/*
+ * test-treap.c: code to exercise the svn importer's treap structure
+ */
+
+#include "cache.h"
+#include "vcs-svn/obj_pool.h"
+#include "vcs-svn/trp.h"
+
+struct int_node {
+ uintmax_t n;
+ struct trp_node children;
+};
+
+obj_pool_gen(node, struct int_node, 3)
+
+static int node_cmp(struct int_node *a, struct int_node *b)
+{
+ return (a->n > b->n) - (a->n < b->n);
+}
+
+trp_gen(static, treap_, struct int_node, children, node, node_cmp)
+
+static void strtonode(struct int_node *item, const char *s)
+{
+ char *end;
+ item->n = strtoumax(s, &end, 10);
+ if (*s == '\0' || (*end != '\n' && *end != '\0'))
+ die("invalid integer: %s", s);
+}
+
+int main(int argc, char *argv[])
+{
+ struct strbuf sb = STRBUF_INIT;
+ struct trp_root root = { ~0 };
+ uint32_t item;
+
+ if (argc != 1)
+ usage("test-treap < ints");
+
+ while (strbuf_getline(&sb, stdin, '\n') != EOF) {
+ item = node_alloc(1);
+ strtonode(node_pointer(item), sb.buf);
+ treap_insert(&root, node_pointer(item));
+ }
+
+ item = node_offset(treap_first(&root));
+ while (~item) {
+ uint32_t next;
+ struct int_node *tmp = node_pointer(node_alloc(1));
+
+ tmp->n = node_pointer(item)->n;
+ next = node_offset(treap_next(&root, node_pointer(item)));
+
+ treap_remove(&root, node_pointer(item));
+ item = node_offset(treap_nsearch(&root, tmp));
+
+ if (item != next && (!~item || node_pointer(item)->n != tmp->n))
+ die("found %"PRIuMAX" in place of %"PRIuMAX"",
+ ~item ? node_pointer(item)->n : ~(uintmax_t) 0,
+ ~next ? node_pointer(next)->n : ~(uintmax_t) 0);
+ printf("%"PRIuMAX"\n", tmp->n);
+ }
+ node_reset();
+ return 0;
+}
--- /dev/null
+/*
+ * C macro implementation of treaps.
+ *
+ * Usage:
+ * #include <stdint.h>
+ * #include "trp.h"
+ * trp_gen(...)
+ *
+ * Licensed under a two-clause BSD-style license.
+ * See LICENSE for details.
+ */
+
+#ifndef TRP_H_
+#define TRP_H_
+
+#define MAYBE_UNUSED __attribute__((__unused__))
+
+/* Node structure. */
+struct trp_node {
+ uint32_t trpn_left;
+ uint32_t trpn_right;
+};
+
+/* Root structure. */
+struct trp_root {
+ uint32_t trp_root;
+};
+
+/* Pointer/Offset conversion. */
+#define trpn_pointer(a_base, a_offset) (a_base##_pointer(a_offset))
+#define trpn_offset(a_base, a_pointer) (a_base##_offset(a_pointer))
+#define trpn_modify(a_base, a_offset) \
+ do { \
+ if ((a_offset) < a_base##_pool.committed) { \
+ uint32_t old_offset = (a_offset);\
+ (a_offset) = a_base##_alloc(1); \
+ *trpn_pointer(a_base, a_offset) = \
+ *trpn_pointer(a_base, old_offset); \
+ } \
+ } while (0);
+
+/* Left accessors. */
+#define trp_left_get(a_base, a_field, a_node) \
+ (trpn_pointer(a_base, a_node)->a_field.trpn_left)
+#define trp_left_set(a_base, a_field, a_node, a_left) \
+ do { \
+ trpn_modify(a_base, a_node); \
+ trp_left_get(a_base, a_field, a_node) = (a_left); \
+ } while(0)
+
+/* Right accessors. */
+#define trp_right_get(a_base, a_field, a_node) \
+ (trpn_pointer(a_base, a_node)->a_field.trpn_right)
+#define trp_right_set(a_base, a_field, a_node, a_right) \
+ do { \
+ trpn_modify(a_base, a_node); \
+ trp_right_get(a_base, a_field, a_node) = (a_right); \
+ } while(0)
+
+/*
+ * Fibonacci hash function.
+ * The multiplier is the nearest prime to (2^32 times (√5 - 1)/2).
+ * See Knuth §6.4: volume 3, 3rd ed, p518.
+ */
+#define trpn_hash(a_node) (uint32_t) (2654435761u * (a_node))
+
+/* Priority accessors. */
+#define trp_prio_get(a_node) trpn_hash(a_node)
+
+/* Node initializer. */
+#define trp_node_new(a_base, a_field, a_node) \
+ do { \
+ trp_left_set(a_base, a_field, (a_node), ~0); \
+ trp_right_set(a_base, a_field, (a_node), ~0); \
+ } while(0)
+
+/* Internal utility macros. */
+#define trpn_first(a_base, a_field, a_root, r_node) \
+ do { \
+ (r_node) = (a_root); \
+ if ((r_node) == ~0) \
+ return NULL; \
+ while (~trp_left_get(a_base, a_field, (r_node))) \
+ (r_node) = trp_left_get(a_base, a_field, (r_node)); \
+ } while (0)
+
+#define trpn_rotate_left(a_base, a_field, a_node, r_node) \
+ do { \
+ (r_node) = trp_right_get(a_base, a_field, (a_node)); \
+ trp_right_set(a_base, a_field, (a_node), \
+ trp_left_get(a_base, a_field, (r_node))); \
+ trp_left_set(a_base, a_field, (r_node), (a_node)); \
+ } while(0)
+
+#define trpn_rotate_right(a_base, a_field, a_node, r_node) \
+ do { \
+ (r_node) = trp_left_get(a_base, a_field, (a_node)); \
+ trp_left_set(a_base, a_field, (a_node), \
+ trp_right_get(a_base, a_field, (r_node))); \
+ trp_right_set(a_base, a_field, (r_node), (a_node)); \
+ } while(0)
+
+#define trp_gen(a_attr, a_pre, a_type, a_field, a_base, a_cmp) \
+a_attr a_type MAYBE_UNUSED *a_pre##first(struct trp_root *treap) \
+{ \
+ uint32_t ret; \
+ trpn_first(a_base, a_field, treap->trp_root, ret); \
+ return trpn_pointer(a_base, ret); \
+} \
+a_attr a_type MAYBE_UNUSED *a_pre##next(struct trp_root *treap, a_type *node) \
+{ \
+ uint32_t ret; \
+ uint32_t offset = trpn_offset(a_base, node); \
+ if (~trp_right_get(a_base, a_field, offset)) { \
+ trpn_first(a_base, a_field, \
+ trp_right_get(a_base, a_field, offset), ret); \
+ } else { \
+ uint32_t tnode = treap->trp_root; \
+ ret = ~0; \
+ while (1) { \
+ int cmp = (a_cmp)(trpn_pointer(a_base, offset), \
+ trpn_pointer(a_base, tnode)); \
+ if (cmp < 0) { \
+ ret = tnode; \
+ tnode = trp_left_get(a_base, a_field, tnode); \
+ } else if (cmp > 0) { \
+ tnode = trp_right_get(a_base, a_field, tnode); \
+ } else { \
+ break; \
+ } \
+ } \
+ } \
+ return trpn_pointer(a_base, ret); \
+} \
+a_attr a_type MAYBE_UNUSED *a_pre##search(struct trp_root *treap, a_type *key) \
+{ \
+ int cmp; \
+ uint32_t ret = treap->trp_root; \
+ while (~ret && (cmp = (a_cmp)(key, trpn_pointer(a_base,ret)))) { \
+ if (cmp < 0) { \
+ ret = trp_left_get(a_base, a_field, ret); \
+ } else { \
+ ret = trp_right_get(a_base, a_field, ret); \
+ } \
+ } \
+ return trpn_pointer(a_base, ret); \
+} \
+a_attr a_type MAYBE_UNUSED *a_pre##nsearch(struct trp_root *treap, a_type *key) \
+{ \
+ int cmp; \
+ uint32_t ret = treap->trp_root; \
+ while (~ret && (cmp = (a_cmp)(key, trpn_pointer(a_base,ret)))) { \
+ if (cmp < 0) { \
+ if (!~trp_left_get(a_base, a_field, ret)) \
+ break; \
+ ret = trp_left_get(a_base, a_field, ret); \
+ } else { \
+ ret = trp_right_get(a_base, a_field, ret); \
+ } \
+ } \
+ return trpn_pointer(a_base, ret); \
+} \
+a_attr uint32_t MAYBE_UNUSED a_pre##insert_recurse(uint32_t cur_node, uint32_t ins_node) \
+{ \
+ if (cur_node == ~0) { \
+ return (ins_node); \
+ } else { \
+ uint32_t ret; \
+ int cmp = (a_cmp)(trpn_pointer(a_base, ins_node), \
+ trpn_pointer(a_base, cur_node)); \
+ if (cmp < 0) { \
+ uint32_t left = a_pre##insert_recurse( \
+ trp_left_get(a_base, a_field, cur_node), ins_node); \
+ trp_left_set(a_base, a_field, cur_node, left); \
+ if (trp_prio_get(left) < trp_prio_get(cur_node)) \
+ trpn_rotate_right(a_base, a_field, cur_node, ret); \
+ else \
+ ret = cur_node; \
+ } else { \
+ uint32_t right = a_pre##insert_recurse( \
+ trp_right_get(a_base, a_field, cur_node), ins_node); \
+ trp_right_set(a_base, a_field, cur_node, right); \
+ if (trp_prio_get(right) < trp_prio_get(cur_node)) \
+ trpn_rotate_left(a_base, a_field, cur_node, ret); \
+ else \
+ ret = cur_node; \
+ } \
+ return (ret); \
+ } \
+} \
+a_attr void MAYBE_UNUSED a_pre##insert(struct trp_root *treap, a_type *node) \
+{ \
+ uint32_t offset = trpn_offset(a_base, node); \
+ trp_node_new(a_base, a_field, offset); \
+ treap->trp_root = a_pre##insert_recurse(treap->trp_root, offset); \
+} \
+a_attr uint32_t MAYBE_UNUSED a_pre##remove_recurse(uint32_t cur_node, uint32_t rem_node) \
+{ \
+ int cmp = a_cmp(trpn_pointer(a_base, rem_node), \
+ trpn_pointer(a_base, cur_node)); \
+ if (cmp == 0) { \
+ uint32_t ret; \
+ uint32_t left = trp_left_get(a_base, a_field, cur_node); \
+ uint32_t right = trp_right_get(a_base, a_field, cur_node); \
+ if (left == ~0) { \
+ if (right == ~0) \
+ return (~0); \
+ } else if (right == ~0 || trp_prio_get(left) < trp_prio_get(right)) { \
+ trpn_rotate_right(a_base, a_field, cur_node, ret); \
+ right = a_pre##remove_recurse(cur_node, rem_node); \
+ trp_right_set(a_base, a_field, ret, right); \
+ return (ret); \
+ } \
+ trpn_rotate_left(a_base, a_field, cur_node, ret); \
+ left = a_pre##remove_recurse(cur_node, rem_node); \
+ trp_left_set(a_base, a_field, ret, left); \
+ return (ret); \
+ } else if (cmp < 0) { \
+ uint32_t left = a_pre##remove_recurse( \
+ trp_left_get(a_base, a_field, cur_node), rem_node); \
+ trp_left_set(a_base, a_field, cur_node, left); \
+ return (cur_node); \
+ } else { \
+ uint32_t right = a_pre##remove_recurse( \
+ trp_right_get(a_base, a_field, cur_node), rem_node); \
+ trp_right_set(a_base, a_field, cur_node, right); \
+ return (cur_node); \
+ } \
+} \
+a_attr void MAYBE_UNUSED a_pre##remove(struct trp_root *treap, a_type *node) \
+{ \
+ treap->trp_root = a_pre##remove_recurse(treap->trp_root, \
+ trpn_offset(a_base, node)); \
+} \
+
+#endif
--- /dev/null
+Motivation
+==========
+
+Treaps provide a memory-efficient binary search tree structure.
+Insertion/deletion/search are about as about as fast in the average
+case as red-black trees and the chances of worst-case behavior are
+vanishingly small, thanks to (pseudo-)randomness. The bad worst-case
+behavior is a small price to pay, given that treaps are much simpler
+to implement.
+
+API
+===
+
+The trp API generates a data structure and functions to handle a
+large growing set of objects stored in a pool.
+
+The caller:
+
+. Specifies parameters for the generated functions with the
+ trp_gen(static, foo_, ...) macro.
+
+. Allocates a `struct trp_root` variable and sets it to {~0}.
+
+. Adds new nodes to the set using `foo_insert`.
+
+. Can find a specific item in the set using `foo_search`.
+
+. Can iterate over items in the set using `foo_first` and `foo_next`.
+
+. Can remove an item from the set using `foo_remove`.
+
+Example:
+
+----
+struct ex_node {
+ const char *s;
+ struct trp_node ex_link;
+};
+static struct trp_root ex_base = {~0};
+obj_pool_gen(ex, struct ex_node, 4096);
+trp_gen(static, ex_, struct ex_node, ex_link, ex, strcmp)
+struct ex_node *item;
+
+item = ex_pointer(ex_alloc(1));
+item->s = "hello";
+ex_insert(&ex_base, item);
+item = ex_pointer(ex_alloc(1));
+item->s = "goodbye";
+ex_insert(&ex_base, item);
+for (item = ex_first(&ex_base); item; item = ex_next(&ex_base, item))
+ printf("%s\n", item->s);
+----
+
+Functions
+---------
+
+trp_gen(attr, foo_, node_type, link_field, pool, cmp)::
+
+ Generate a type-specific treap implementation.
++
+. The storage class for generated functions will be 'attr' (e.g., `static`).
+. Generated function names are prefixed with 'foo_' (e.g., `treap_`).
+. Treap nodes will be of type 'node_type' (e.g., `struct treap_node`).
+ This type must be a struct with at least one `struct trp_node` field
+ to point to its children.
+. The field used to access child nodes will be 'link_field'.
+. All treap nodes must lie in the 'pool' object pool.
+. Treap nodes must be totally ordered by the 'cmp' relation, with the
+ following prototype:
++
+int (*cmp)(node_type \*a, node_type \*b)
++
+and returning a value less than, equal to, or greater than zero
+according to the result of comparison.
+
+void foo_insert(struct trp_root *treap, node_type \*node)::
+
+ Insert node into treap. If inserted multiple times,
+ a node will appear in the treap multiple times.
+
+void foo_remove(struct trp_root *treap, node_type \*node)::
+
+ Remove node from treap. Caller must ensure node is
+ present in treap before using this function.
+
+node_type *foo_search(struct trp_root \*treap, node_type \*key)::
+
+ Search for a node that matches key. If no match is found,
+ result is NULL.
+
+node_type *foo_nsearch(struct trp_root \*treap, node_type \*key)::
+
+ Like `foo_search`, but if if the key is missing return what
+ would be key's successor, were key in treap (NULL if no
+ successor).
+
+node_type *foo_first(struct trp_root \*treap)::
+
+ Find the first item from the treap, in sorted order.
+
+node_type *foo_next(struct trp_root \*treap, node_type \*node)::
+
+ Find the next item.
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