/* -*- mode: C; c-basic-offset: 4 -*- */
#ident "Copyright (c) 2010 Tokutek Inc.  All rights reserved."
#ident "The technology is licensed by the Massachusetts Institute of Technology, Rutgers State University of New Jersey, and the Research Foundation of State University of New York at Stony Brook under United States of America Serial No. 11/760379 and to the patents and/or patent applications resulting from it."

#include "includes.h"
#include "le-cursor.h"

// A LE_CURSOR is a special type of BRT_CURSOR that retrieves all of the leaf entries in a BRT.
// It caches the key that is was last positioned over to speed up key comparisions.

struct le_cursor {
    BRT_CURSOR brt_cursor;
    DBT key;
    BOOL neg_infinity, pos_infinity;
};

int 
le_cursor_create(LE_CURSOR *le_cursor_result, BRT brt, TOKUTXN txn) {
    int result = 0;
    LE_CURSOR le_cursor = (LE_CURSOR) toku_malloc(sizeof (struct le_cursor));
    if (le_cursor == NULL)
        result = errno;
    else {
        result = toku_brt_cursor(brt, &le_cursor->brt_cursor, txn, FALSE);
        if (result == 0) {
            toku_brt_cursor_set_leaf_mode(le_cursor->brt_cursor);
            toku_init_dbt(&le_cursor->key); le_cursor->key.flags = DB_DBT_REALLOC;
            le_cursor->neg_infinity = TRUE;
            le_cursor->pos_infinity = FALSE;
        }
    }

    if (result == 0)
        *le_cursor_result = le_cursor;
    else
        toku_free(le_cursor);

    return result;
}

int 
le_cursor_close(LE_CURSOR le_cursor) {
    int result = 0;
    result = toku_brt_cursor_close(le_cursor->brt_cursor);
    toku_destroy_dbt(&le_cursor->key);
    toku_free(le_cursor);
    return result;
}

struct le_cursor_callback_arg {
    DBT *key, *val;
};

static int
le_cursor_callback(ITEMLEN keylen, bytevec key, ITEMLEN vallen, bytevec val, void *v) {
    struct le_cursor_callback_arg *arg = (struct le_cursor_callback_arg *) v;
    toku_dbt_set(keylen, key, arg->key, NULL);
    toku_dbt_set(vallen, val, arg->val, NULL);
    return 0;
}

int 
le_cursor_next(LE_CURSOR le_cursor, DBT *key, DBT *val) {
    le_cursor->neg_infinity = FALSE;
    struct le_cursor_callback_arg arg = { &le_cursor->key, val };
    int error = toku_brt_cursor_get(le_cursor->brt_cursor, NULL, le_cursor_callback, &arg, DB_NEXT);
    if (error == 0 && key != NULL)
        toku_dbt_set(le_cursor->key.size, le_cursor->key.data, key, NULL);
    else if (error == DB_NOTFOUND)
        le_cursor->pos_infinity = TRUE;
    return error;
}

int
is_key_right_of_le_cursor(LE_CURSOR le_cursor, const DBT *key, int (*keycompare)(DB *, const DBT *, const DBT *), DB *db) {
    int result;
    if (le_cursor->neg_infinity)
        result = TRUE;
    else if (le_cursor->pos_infinity)
        return FALSE;
    else {
        int r = keycompare(db, &le_cursor->key, key);
        if (r < 0)
            result = TRUE;
        else
            result = FALSE;
    }
    return result;
}