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+/*
+ * crit-bit tree implementation, does no allocations internally
+ * For more information on crit-bit trees: https://cr.yp.to/critbit.html
+ * Based on Adam Langley's adaptation of Dan Bernstein's public domain code
+ * git clone https://github.com/agl/critbit.git
+ *
+ * This is adapted to store arbitrary data (not just NUL-terminated C strings
+ * and allocates no memory internally. The user needs to allocate
+ * "struct cb_node" and fill cb_node.k[] with arbitrary match data
+ * for memcmp.
+ * If "klen" is variable, then it should be embedded into "c_node.k[]"
+ * Recursion is bound by the maximum value of "klen" used.
+ */
+#ifndef CBTREE_H
+#define CBTREE_H
+
+#include "git-compat-util.h"
+
+struct cb_node;
+struct cb_node {
+ struct cb_node *child[2];
+ /*
+ * n.b. uint32_t for `byte' is excessive for OIDs,
+ * we may consider shorter variants if nothing else gets stored.
+ */
+ uint32_t byte;
+ uint8_t otherbits;
+ uint8_t k[FLEX_ARRAY]; /* arbitrary data, unaligned */
+};
+
+struct cb_tree {
+ struct cb_node *root;
+};
+
+enum cb_next {
+ CB_CONTINUE = 0,
+ CB_BREAK = 1
+};
+
+#define CBTREE_INIT { 0 }
+
+static inline void cb_init(struct cb_tree *t)
+{
+ struct cb_tree blank = CBTREE_INIT;
+ memcpy(t, &blank, sizeof(*t));
+}
+
+struct cb_node *cb_lookup(struct cb_tree *, const uint8_t *k, size_t klen);
+struct cb_node *cb_insert(struct cb_tree *, struct cb_node *, size_t klen);
+
+typedef enum cb_next (*cb_iter)(struct cb_node *, void *arg);
+
+void cb_each(struct cb_tree *, const uint8_t *kpfx, size_t klen,
+ cb_iter, void *arg);
+
+#endif /* CBTREE_H */