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libinn_tst(3) InterNetNews Documentation libinn_tst(3)

NAME

tst - Ternary search trie functions

SYNOPSIS

    #include <inn/tst.h>
    enum tst_constants {
        TST_OK,
        TST_NULL_KEY,
        TST_NULL_DATA,
        TST_DUPLICATE_KEY,
        TST_REPLACE
    };
    struct tst;
    struct tst *tst_init(int node_line_width);
    void tst_cleanup(struct tst *tst);
    int tst_insert(struct tst *tst, const unsigned char *key,
                   void *data, int option, void **exist_ptr);
    void *tst_search(struct tst *tst, const unsigned char *key);
    void *tst_delete(struct tst *tst, const unsigned char *key);

DESCRIPTION

tst_init allocates memory for members of struct tst, and allocates the first node_line_width nodes. A NULL pointer is returned by tst_init if any part of the memory allocation fails. On success, a pointer to a struct tst is returned.

The value for node_line_width must be chosen very carefully. One node is required for every character in the tree. If you choose a value that is too small, your application will spend too much time calling malloc(3) and your node space will be too spread out. Too large a value is just a waste of space.

tst_cleanup frees all memory allocated to nodes, internal structures, as well as tst itself.

tst_insert inserts the string key into the tree. Behavior when a duplicate key is inserted is controlled by option. If key is already in the tree, then "TST_DUPLICATE_KEY" is returned, and the data pointer for the existing key is placed in exist_ptr. If option is set to "TST_REPLACE", then the existing data pointer for the existing key is replaced by data. Note that the old data pointer will still be placed in exist_ptr.

If a duplicate key is encountered and option is not set to "TST_REPLACE", then "TST_DUPLICATE_KEY" is returned. If key is zero length, then "TST_NULL_KEY" is returned. A successful insert or replace returns "TST_OK". A return value of "TST_ERROR" indicates that a memory allocation error occurred while trying to grow the node free.

Note that the data argument must never be "NULL". If it is, then calls to tst_search will fail for a key that exists because the data value was set to "NULL", which is what tst_search returns. If you just want a simple existence tree, use the tst pointer as the data pointer.

tst_search finds the string key in the tree if it exists and returns the data pointer associated with that key.

If key is not found then "NULL" is returned, otherwise the data pointer associated with key is returned.

tst_delete deletes the string key from the tree if it exists and returns the data pointer associated with that key.

If key is not found, then "NULL" is returned, otherwise the data pointer associated with key is returned.

HISTORY

Converted to POD from Peter A. Friend's ternary search trie documentation by Alex Kiernan <alex.kiernan@thus.net> for InterNetNews 2.4.0.

SEE ALSO

libinn(3).

2023-01-22 INN 2.7.1