github.com/moontrade/nogc@v0.1.7/collections/tree/art.h

#ifndef ART_H
#define ART_H

#include "lock.h"

#ifdef __cplusplus
extern "C" {
#endif

#include <stdint.h>

#define NODE4   1
#define NODE16  2
#define NODE48  3
#define NODE256 4

#define MAX_PREFIX_LEN 10

#if defined(__GNUC__) && !defined(__clang__)
# if __STDC_VERSION__ >= 199901L && 402 == (__GNUC__ * 100 + __GNUC_MINOR__)
/*
 * GCC 4.2.2's C99 inline keyword support is pretty broken; avoid. Introduced in
 * GCC 4.2.something, fixed in 4.3.0. So checking for specific major.minor of
 * 4.2 is fine.
 */
#  define BROKEN_GCC_C99_INLINE
# endif
#endif

struct art_lock_api;
extern const struct art_lock_api art_lock_api_unfair;
extern const struct art_lock_api art_lock_api_fair;

typedef struct art_value {
    union {
	    void* value;
	    uint64_t uvalue;
	};
} art_value;

typedef struct art_search_result {
    art_value value;
    size_t found;
} art_search_result;

static const art_value ART_NULL_VALUE = {
    .value=0
};

static const art_search_result ART_NOT_FOUND = {
    .found=0
};

//#define ART_NULL_VALUE {.file=0,.offset=0,.value=NULL}

typedef int(*art_callback)(void *data, const unsigned char *key, uint32_t key_len, art_value value);

/**
 * This struct is included as part
 * of all the various node sizes
 */
typedef struct {
    uint32_t partial_len;
    uint8_t type;
    uint8_t num_children;
    unsigned char partial[MAX_PREFIX_LEN];
} art_node;

/**
 * Small node with only 4 children
 */
typedef struct {
    art_node n;
    unsigned char keys[4];
    art_node *children[4];
} art_node4;

/**
 * Node with 16 children
 */
typedef struct {
    art_node n;
    unsigned char keys[16];
    art_node *children[16];
} art_node16;

/**
 * Node with 48 children, but
 * a full 256 byte field.
 */
typedef struct {
    art_node n;
    unsigned char keys[256];
    art_node *children[48];
} art_node48;

/**
 * Full node with 256 children
 */
typedef struct {
    art_node n;
    art_node *children[256];
} art_node256;

/**
 * Represents a leaf. These are
 * of arbitrary size, as they include the key.
 */
typedef struct {
    art_value value;
    uint32_t key_len;
    unsigned char key[0];
} art_leaf;

/**
 * Main struct, points to root.
 */
typedef struct art_tree {
    art_node *root;
    uint64_t size;
    uint64_t memory;
    int32_t free;
    int32_t fair;
    int32_t calc_memory;
    uint32_t lock_;
    void* lock;
} art_tree;

/**
 * Initializes an ART tree
 * @return 0 on success.
 */
int art_tree_init(art_tree *t);

/**
 * Initializes a lock for an ART tree.
 * Access to the tree will become thread-safe.
 */
void art_tree_init_lock(art_tree *t);

/**
 * Destroys an ART tree
 * @return 0 on success.
 */
int art_tree_destroy(art_tree *t);

/**
 * Returns the size of the ART tree.
 */
#ifdef BROKEN_GCC_C99_INLINE
# define art_size(t) ((t)->size)
#else
inline uint64_t art_size(art_tree *t) {
    return t->size;
}
#endif

void art_sleep(uint64_t nanos);

/**
 * inserts a new value into the art tree
 * @arg t the tree
 * @arg key the key
 * @arg key_len the length of the key
 * @arg value opaque value.
 * @return null if the item was newly inserted, otherwise
 * the old value pointer is returned.
 */
art_value art_insert(art_tree *t, const unsigned char *key, int key_len, art_value value);

art_search_result art_insert_value(art_tree *t, const unsigned char *key, int key_len, art_value value);

/**
 * inserts a new value into the art tree (not replacing)
 * @arg t the tree
 * @arg key the key
 * @arg key_len the length of the key
 * @arg value opaque value.
 * @return null if the item was newly inserted, otherwise
 * the old value pointer is returned.
 */
art_value art_insert_no_replace(art_tree *t, const unsigned char *key, int key_len, art_value value);

art_search_result art_insert_no_replace_value(art_tree *t, const unsigned char *key, int key_len, art_value value);

/**
 * Deletes a value from the ART tree
 * @arg t The tree
 * @arg key The key
 * @arg key_len The length of the key
 * @return NULL if the item was not found, otherwise
 * the value pointer is returned.
 */
art_value art_delete(art_tree *t, const unsigned char *key, int key_len);

art_search_result art_delete_value(art_tree *t, const unsigned char *key, int key_len);

/**
 * Searches for a value in the ART tree
 * @arg t The tree
 * @arg key The key
 * @arg key_len The length of the key
 * @return NULL if the item was not found, otherwise
 * the value pointer is returned.
 */
art_search_result art_search(const art_tree *t, const unsigned char *key, int key_len);

/**
 * Returns the minimum valued leaf
 * @return The minimum leaf or NULL
 */
art_leaf* art_minimum(art_tree *t);

/**
 * Returns the maximum valued leaf
 * @return The maximum leaf or NULL
 */
art_leaf* art_maximum(art_tree *t);

/**
 * Iterates through the entries pairs in the map,
 * invoking a callback for each. The call back gets a
 * key, value for each and returns an integer stop value.
 * If the callback returns non-zero, then the iteration stops.
 * @arg t The tree to iterate over
 * @arg cb The callback function to invoke
 * @arg data Opaque handle passed to the callback
 * @return 0 on success, or the return of the callback.
 */
int art_iter(art_tree *t, art_callback cb, void *data);

/**
 * Iterates through the entries pairs in the map,
 * invoking a callback for each that matches a given prefix.
 * The call back gets a key, value for each and returns an integer stop value.
 * If the callback returns non-zero, then the iteration stops.
 * @arg t The tree to iterate over
 * @arg prefix The prefix of keys to read
 * @arg prefix_len The length of the prefix
 * @arg cb The callback function to invoke
 * @arg data Opaque handle passed to the callback
 * @return 0 on success, or the return of the callback.
 */
int art_iter_prefix(art_tree *t, const unsigned char *prefix, int prefix_len, art_callback cb, void *data);

#ifdef __cplusplus
}
#endif

#endif