Adding gem5 source to svn.
git-svn-id: https://www4.informatik.uni-erlangen.de/i4svn/danceos/trunk/devel/fail@1819 8c4709b5-6ec9-48aa-a5cd-a96041d1645a
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friemel
360
simulators/gem5/src/base/trie.hh
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360
simulators/gem5/src/base/trie.hh
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/*
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* Copyright (c) 2012 Google
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Authors: Gabe Black
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*/
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#ifndef __BASE_TRIE_HH__
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#define __BASE_TRIE_HH__
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#include <cassert>
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#include "base/cprintf.hh"
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#include "base/misc.hh"
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#include "base/types.hh"
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// Key has to be an integral type.
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template <class Key, class Value>
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class Trie
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{
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protected:
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struct Node
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{
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Key key;
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Key mask;
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bool
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matches(Key test)
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{
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return (test & mask) == key;
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}
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Value *value;
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Node *parent;
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Node *kids[2];
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Node(Key _key, Key _mask, Value *_val) :
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key(_key & _mask), mask(_mask), value(_val),
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parent(NULL)
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{
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kids[0] = NULL;
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kids[1] = NULL;
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}
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void
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clear()
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{
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if (kids[1]) {
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kids[1]->clear();
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delete kids[1];
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kids[1] = NULL;
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}
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if (kids[0]) {
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kids[0]->clear();
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delete kids[0];
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kids[0] = NULL;
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}
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}
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void
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dump(int level)
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{
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for (int i = 1; i < level; i++) {
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cprintf("|");
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}
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if (level == 0)
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cprintf("Root ");
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else
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cprintf("+ ");
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cprintf("(%p, %p, %#X, %#X, %p)\n", parent, this, key, mask, value);
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if (kids[0])
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kids[0]->dump(level + 1);
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if (kids[1])
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kids[1]->dump(level + 1);
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}
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};
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protected:
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Node head;
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public:
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typedef Node *Handle;
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Trie() : head(0, 0, NULL)
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{}
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static const unsigned MaxBits = sizeof(Key) * 8;
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private:
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/**
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* A utility method which checks whether the key being looked up lies
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* beyond the Node being examined. If so, it returns true and advances the
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* node being examined.
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* @param parent The node we're currently "at", which can be updated.
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* @param kid The node we may want to move to.
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* @param key The key we're looking for.
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* @param new_mask The mask to use when matching against the key.
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* @return Whether the current Node was advanced.
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*/
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bool
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goesAfter(Node **parent, Node *kid, Key key, Key new_mask)
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{
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if (kid && kid->matches(key) && (kid->mask & new_mask) == kid->mask) {
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*parent = kid;
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return true;
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} else {
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return false;
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}
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}
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/**
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* A utility method which extends a mask value one more bit towards the
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* lsb. This is almost just a signed right shift, except that the shifted
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* in bits are technically undefined. This is also slightly complicated by
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* the zero case.
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* @param orig The original mask to extend.
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* @return The extended mask.
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*/
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Key
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extendMask(Key orig)
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{
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// Just in case orig was 0.
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const Key msb = ULL(1) << (MaxBits - 1);
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return orig | (orig >> 1) | msb;
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}
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/**
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* Method which looks up the Handle corresponding to a particular key. This
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* is useful if you want to delete the Handle corresponding to a key since
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* the "remove" function takes a Handle as its argument.
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* @param key The key to look up.
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* @return The first Handle matching this key, or NULL if none was found.
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*/
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Handle
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lookupHandle(Key key)
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{
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Node *node = &head;
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while (node) {
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if (node->value)
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return node;
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if (node->kids[0] && node->kids[0]->matches(key))
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node = node->kids[0];
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else if (node->kids[1] && node->kids[1]->matches(key))
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node = node->kids[1];
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else
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node = NULL;
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}
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return NULL;
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}
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public:
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/**
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* Method which inserts a key/value pair into the trie.
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* @param key The key which can later be used to look up this value.
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* @param width How many bits of the key (from msb) should be used.
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* @param val A pointer to the value to store in the trie.
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* @return A Handle corresponding to this value.
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*/
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Handle
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insert(Key key, unsigned width, Value *val)
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{
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// Build a mask which masks off all the bits we don't care about.
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Key new_mask = ~(Key)0;
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if (width < MaxBits)
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new_mask <<= (MaxBits - width);
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// Use it to tidy up the key.
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key &= new_mask;
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// Walk past all the nodes this new node will be inserted after. They
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// can be ignored for the purposes of this function.
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Node *node = &head;
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while (goesAfter(&node, node->kids[0], key, new_mask) ||
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goesAfter(&node, node->kids[1], key, new_mask))
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{}
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assert(node);
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Key cur_mask = node->mask;
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// If we're already where the value needs to be...
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if (cur_mask == new_mask) {
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assert(!node->value);
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node->value = val;
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return node;
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}
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for (unsigned int i = 0; i < 2; i++) {
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Node *&kid = node->kids[i];
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Node *new_node;
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if (!kid) {
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// No kid. Add a new one.
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new_node = new Node(key, new_mask, val);
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new_node->parent = node;
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kid = new_node;
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return new_node;
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}
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// Walk down the leg until something doesn't match or we run out
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// of bits.
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Key last_mask;
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bool done;
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do {
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last_mask = cur_mask;
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cur_mask = extendMask(cur_mask);
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done = ((key & cur_mask) != (kid->key & cur_mask)) ||
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last_mask == new_mask;
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} while (!done);
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cur_mask = last_mask;
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// If this isn't the right leg to go down at all, skip it.
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if (cur_mask == node->mask)
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continue;
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// At the point we walked to above, add a new node.
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new_node = new Node(key, cur_mask, NULL);
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new_node->parent = node;
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kid->parent = new_node;
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new_node->kids[0] = kid;
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kid = new_node;
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// If we ran out of bits, the value goes right here.
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if (cur_mask == new_mask) {
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new_node->value = val;
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return new_node;
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}
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// Still more bits to deal with, so add a new node for that path.
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new_node = new Node(key, new_mask, val);
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new_node->parent = kid;
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kid->kids[1] = new_node;
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return new_node;
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}
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panic("Reached the end of the Trie insert function!\n");
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return NULL;
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}
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/**
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* Method which looks up the Value corresponding to a particular key.
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* @param key The key to look up.
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* @return The first Value matching this key, or NULL if none was found.
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*/
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Value *
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lookup(Key key)
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{
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Node *node = lookupHandle(key);
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if (node)
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return node->value;
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else
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return NULL;
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}
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/**
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* Method to delete a value from the trie.
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* @param node A Handle to remove.
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* @return The Value pointer from the removed entry.
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*/
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Value *
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remove(Handle handle)
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{
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Node *node = handle;
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Value *val = node->value;
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if (node->kids[1]) {
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assert(node->value);
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node->value = NULL;
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return val;
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}
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if (!node->parent)
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panic("Trie: Can't remove root node.\n");
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Node *parent = node->parent;
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// If there's a kid, fix up it's parent pointer.
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if (node->kids[0])
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node->kids[0]->parent = parent;
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// Figure out which kid we are, and update our parent's pointers.
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if (parent->kids[0] == node)
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parent->kids[0] = node->kids[0];
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else if (parent->kids[1] == node)
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parent->kids[1] = node->kids[0];
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else
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panic("Trie: Inconsistent parent/kid relationship.\n");
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// Make sure if the parent only has one kid, it's kid[0].
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if (parent->kids[1] && !parent->kids[0]) {
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parent->kids[0] = parent->kids[1];
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parent->kids[1] = NULL;
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}
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// If the parent has less than two kids and no cargo and isn't the
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// root, delete it too.
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if (!parent->kids[1] && !parent->value && parent->parent)
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remove(parent);
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delete node;
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return val;
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}
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/**
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* Method to lookup a value from the trie and then delete it.
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* @param key The key to look up and then remove.
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* @return The Value pointer from the removed entry, if any.
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*/
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Value *
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remove(Key key)
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{
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Handle handle = lookupHandle(key);
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if (!handle)
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return NULL;
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return remove(handle);
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}
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/**
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* A method which removes all key/value pairs from the trie. This is more
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* efficient than trying to remove elements individually.
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*/
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void
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clear()
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{
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head.clear();
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}
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/**
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* A debugging method which prints the contents of this trie.
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* @param title An identifying title to put in the dump header.
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*/
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void
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dump(const char *title)
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{
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cprintf("**************************************************\n");
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cprintf("*** Start of Trie: %s\n", title);
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cprintf("*** (parent, me, key, mask, value pointer)\n");
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cprintf("**************************************************\n");
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head.dump(0);
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}
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};
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#endif
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