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/*
* Copyright (c) 2006 The Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the
* distribution.
* - Neither the name of the University of California nor the names of
* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
* THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
/**
* An LRU cache that stores integer values, where an insert operation
* indicates "use". Inserting an element not in the cache will replace
* the oldest, and inserting an element already in the cache will refresh
* its age.
*
* @author Rodrigo Fonseca
* @author Philip Levis
*/
generic module LruIntCacheP(typedef cache_key_t @integer(), uint8_t size) {
provides {
interface Init;
interface Cache<cache_key_t>;
}
}
implementation {
cache_key_t cache[size];
uint8_t first;
uint8_t count;
command error_t Init.init() {
first = 0;
count = 0;
return SUCCESS;
}
void printCache() {
#ifdef TOSSIM
int i;
dbg("Cache","Cache:");
for (i = 0; i < count; i++) {
dbg_clear("Cache", " %08x", cache[i]);
if (i == first)
dbg_clear("Cache","*");
}
dbg_clear("Cache","\n");
#endif
}
/* if key is in cache returns the index (offset by first), otherwise returns count */
uint8_t lookup(cache_key_t key) {
uint8_t i;
cache_key_t k;
for (i = 0; i < count; i++) {
k = cache[(i + first) % size];
if (k == key)
break;
}
return i;
}
/* remove the entry with index i (relative to first) */
void remove(uint8_t i) {
uint8_t j;
if (i >= count)
return;
if (i == 0) {
//shift all by moving first
first = (first + 1) % size;
} else {
//shift everyone down
for (j = i; j < count; j++) {
cache[(j + first) % size] = cache[(j + first + 1) % size];
}
}
count--;
}
command void Cache.insert(cache_key_t key) {
uint8_t i;
if (count == size ) {
//remove someone. If item not in
//cache, remove the first item.
//otherwise remove the item temporarily for
//reinsertion. This moves the item up in the
//LRU stack.
i = lookup(key);
remove(i % count);
}
//now count < size
cache[(first + count) % size] = key;
count++;
}
command bool Cache.lookup(cache_key_t key) {
return (lookup(key) < count);
}
command void Cache.flush() {
call Init.init();
}
}
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