mariadb/locktree/wfg.cc

/* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
// vim: ft=cpp:expandtab:ts=8:sw=4:softtabstop=4:
#ident "$Id$"
#ident "Copyright (c) 2007-2012 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 <db.h>
#include <toku_assert.h>
#include <memory.h>
#include <string.h>

#include "txnid_set.h"
#include "wfg.h"

namespace toku {

// Create a lock request graph
void wfg::create(void) {
    m_nodes.create();
}

// Destroy the internals of the lock request graph
void wfg::destroy(void) {
    size_t n_nodes = m_nodes.size();
    for (size_t i = 0; i < n_nodes; i++) {
        node *n;
        int r = m_nodes.fetch(i, &n); 
        invariant_zero(r);
        invariant_notnull(n);
        node::free(n);
    }
    m_nodes.destroy();
}

// Add an edge (a_id, b_id) to the graph
void wfg::add_edge(TXNID a_txnid, TXNID b_txnid) {
    node *a_node = find_create_node(a_txnid);
    node *b_node = find_create_node(b_txnid);
    a_node->edges.add(b_node->txnid);
}

// Return true if a node with the given transaction id exists in the graph.
// Return false otherwise.
bool wfg::node_exists(TXNID txnid) {
    node *n = find_node(txnid);
    return n != NULL;
}

bool wfg::cycle_exists_from_node(node *target, node *head) {
    bool cycle_found = false;
    head->visited = true;
    size_t n_edges = head->edges.size();
    for (size_t i = 0; i < n_edges && !cycle_found; i++) {
        TXNID edge_id = head->edges.get(i);
        if (target->txnid == edge_id) { 
            cycle_found = true;
        } else {
            node *new_head = find_node(edge_id);
            if (new_head && !new_head->visited) {
                cycle_found = cycle_exists_from_node(target, new_head);
            }
        }
    }
    head->visited = false;
    return cycle_found;
}

// Return true if there exists a cycle from a given transaction id in the graph.
// Return false otherwise.
bool wfg::cycle_exists_from_txnid(TXNID txnid) {
    node *a_node = find_node(txnid);
    bool cycles_found = false;
    if (a_node) {
        cycles_found = cycle_exists_from_node(a_node, a_node);
    }
    return cycles_found;
}

// Apply a given function f to all of the nodes in the graph.  The apply function
// returns when the function f is called for all of the nodes in the graph, or the 
// function f returns non-zero.
void wfg::apply_nodes(int (*fn)(TXNID id, void *extra), void *extra) {
    int r = 0;
    size_t n_nodes = m_nodes.size();
    for (size_t i = 0; i < n_nodes && r == 0; i++) {
        node *n;
        r = m_nodes.fetch(i, &n);
        invariant_zero(r);
        r = fn(n->txnid, extra);
    }
}

// Apply a given function f to all of the edges whose origin is a given node id. 
// The apply function returns when the function f is called for all edges in the
// graph rooted at node id, or the function f returns non-zero.
void wfg::apply_edges(TXNID txnid,
        int (*fn)(TXNID txnid, TXNID edge_txnid, void *extra), void *extra) {
    node *n = find_node(txnid);
    if (n) {
        int r = 0;
        size_t n_edges = n->edges.size();
        for (size_t i = 0; i < n_edges && r == 0; i++) {
            r = fn(txnid, n->edges.get(i), extra);
        }
    }
}

// find node by id
wfg::node *wfg::find_node(TXNID txnid) {
    node *n = nullptr;
    int r = m_nodes.find_zero<TXNID, find_by_txnid>(txnid, &n, nullptr);
    invariant(r == 0 || r == DB_NOTFOUND);
    return n;
}

// this is the omt comparison function
// nodes are compared by their txnid.
int wfg::find_by_txnid(node *const &node_a, const TXNID &txnid_b) {
    TXNID txnid_a = node_a->txnid;
    if (txnid_a < txnid_b) {
        return -1;
    } else if (txnid_a == txnid_b) {
        return 0;
    } else {
        return 1;
    }
}

// insert a new node
wfg::node *wfg::find_create_node(TXNID txnid) {
    node *n;
    uint32_t idx;
    int r = m_nodes.find_zero<TXNID, find_by_txnid>(txnid, &n, &idx);
    if (r == DB_NOTFOUND) {
        n = node::alloc(txnid);
        r = m_nodes.insert_at(n, idx);
        invariant_zero(r);
    }
    invariant_notnull(n);
    return n;
}

wfg::node *wfg::node::alloc(TXNID txnid) {
    node *XCALLOC(n);
    n->txnid = txnid;
    n->visited = false;
    n->edges.create();
    return n;
}

void wfg::node::free(wfg::node *n) {
    n->edges.destroy();
    toku_free(n);
}

} /* namespace toku */