/* coalesce free blocks */
static void *coalesce(void *bp){
size_t prevAllocBit = getPrevAlloc(getHeader(bp));
size_t nextAllocBit = getAlloc(getHeader(nextBlock(bp)));
size_t size = getSize(getHeader(bp));
size_t index;
size_t prevPAlloc;
/* both the previous and next block allocated */
if (prevAllocBit && nextAllocBit) {
setPrevFree(getHeader(nextBlock(bp)));
}
/* Only previous block is free */
else if (!prevAllocBit && nextAllocBit) {
size += getSize(getHeader(prevBlock(bp)));
prevPAlloc = getPrevAlloc(getHeader(prevBlock(bp)));
deleteListNode(prevBlock(bp));
put(getFooter(bp), size);
bp = prevBlock(bp);
put(getHeader(bp), pack(size, prevPAlloc, 0));
setPrevFree(getHeader(nextBlock(bp)));
}
/* Only next block is free */
else if (prevAllocBit && !nextAllocBit) {
size += getSize(getHeader(nextBlock(bp)));
deleteListNode(nextBlock(bp));
put(getHeader(bp), pack(size, prevAllocBit, 0));
put(getFooter(bp), size);
}
/* Both previous and next block are free */
else {
size += getSize(getHeader(prevBlock(bp))) +
getSize(getFooter(nextBlock(bp)));
prevPAlloc = getPrevAlloc(getHeader(prevBlock(bp)));
deleteListNode(nextBlock(bp));
deleteListNode(prevBlock(bp));
put(getHeader(prevBlock(bp)), pack(size, prevPAlloc, 0));
put(getFooter(nextBlock(bp)), size);
bp = prevBlock(bp);
}
index = getIndex(size);
insertListNode(bp, index);
return bp;
}
void free(void * ptr)
{
char * charPtr = static_cast<char *>(ptr);
Block & prev = prevBlock(charPtr);
Block & next = nextBlock(charPtr);
Block & block = blocks.at(charPtr);
assert(block.free == false);
assert(prev.ptr == NULL || prev.ptr + prev.size == block.ptr);
assert(next.ptr == NULL || block.ptr + block.size == next.ptr);
/* prev is busy and next is busy */
/* just mark current block as free */
if(!prev.free && !next.free)
{
markBlockFree(block);
}
/* prev is free and next is busy */
/* concat prev and curr block into one free block */
else if(prev.free && !next.free)
{
resizeBlock(prev, prev.size + block.size);
removeBlock(block);
}
/* prev is busy and next is free */
/* concat curr and next block into one free block */
else if(!prev.free && next.free)
{
resizeBlock(block, block.size + next.size);
removeBlock(next);
markBlockFree(block);
}
/* concat all three blocks into one block*/
else if(prev.free && next.free)
{
resizeBlock(prev, prev.size + block.size + next.size);
removeBlock(block);
removeBlock(next);
}
#ifdef SELFTEST
selfTest();
#endif
}
