void umm_free( void *ptr ) {
unsigned short int c;
/* If we're being asked to free a NULL pointer, well that's just silly! */
if( (void *)0 == ptr ) {
DBGLOG_DEBUG( "free a null pointer -> do nothing\n" );
return;
}
/*
* FIXME: At some point it might be a good idea to add a check to make sure
* that the pointer we're being asked to free up is actually within
* the umm_heap!
*
* NOTE: See the new umm_info() function that you can use to see if a ptr is
* on the free list!
*/
/* Protect the critical section... */
UMM_CRITICAL_ENTRY();
/* Figure out which block we're in. Note the use of truncated division... */
c = (((char *)ptr)-(char *)(&(umm_heap[0])))/sizeof(umm_block);
DBGLOG_DEBUG( "Freeing block %6i\n", c );
/* Now let's assimilate this block with the next one if possible. */
umm_assimilate_up( c );
/* Then assimilate with the previous block if possible */
if( UMM_NBLOCK(UMM_PBLOCK(c)) & UMM_FREELIST_MASK ) {
DBGLOG_DEBUG( "Assimilate down to next block, which is FREE\n" );
c = umm_assimilate_down(c, UMM_FREELIST_MASK);
} else {
/*
* The previous block is not a free block, so add this one to the head
* of the free list
*/
DBGLOG_DEBUG( "Just add to head of free list\n" );
UMM_PFREE(UMM_NFREE(0)) = c;
UMM_NFREE(c) = UMM_NFREE(0);
UMM_PFREE(c) = 0;
UMM_NFREE(0) = c;
UMM_NBLOCK(c) |= UMM_FREELIST_MASK;
}
/* Release the critical section... */
UMM_CRITICAL_EXIT();
}
void umm_free( void *ptr ) {
unsigned short int c;
// If we're being asked to free a NULL pointer, well that's just silly!
if( (void *)0 == ptr ) {
DBG_LOG_DEBUG( "free a null pointer -> do nothing\n" );
return;
}
// FIXME: At some point it might be a good idea to add a check to make sure
// that the pointer we're being asked to free up is actually within
// the umm_heap!
//
// NOTE: See the new umm_info() function that you can use to see if a ptr is
// on the free list!
// Protect the critical section...
//
UMM_CRITICAL_ENTRY();
// Figure out which block we're in. Note the use of truncated division...
c = (ptr-(void *)(&(umm_heap[0])))/sizeof(umm_block);
DBG_LOG_DEBUG( "Freeing block %6d\n", c );
// Now let's assimilate this block with the next one if possible.
umm_assimilate_up( c );
// Then assimilate with the previous block if possible
if( UMM_NBLOCK(UMM_PBLOCK(c)) & UMM_FREELIST_MASK ) {
DBG_LOG_DEBUG( "Assimilate down to next block, which is FREE\n" );
c = umm_assimilate_down(c, UMM_FREELIST_MASK);
} else {
// The previous block is not a free block, so add this one to the head
// of the free list
DBG_LOG_DEBUG( "Just add to head of free list\n" );
UMM_PFREE(UMM_NFREE(0)) = c;
UMM_NFREE(c) = UMM_NFREE(0);
UMM_PFREE(c) = 0;
UMM_NFREE(0) = c;
UMM_NBLOCK(c) |= UMM_FREELIST_MASK;
}
#if(0)
// The following is experimental code that checks to see if the block we just
// freed can be assimilated with the very last block - it's pretty convoluted in
// terms of block index manipulation, and has absolutely no effect on heap
// fragmentation. I'm not sure that it's worth including but I've left it
// here for posterity.
if( 0 == UMM_NBLOCK(UMM_NBLOCK(c) & UMM_BLOCKNO_MASK ) ) {
if( UMM_PBLOCK(UMM_NBLOCK(c) & UMM_BLOCKNO_MASK) != UMM_PFREE(UMM_NBLOCK(c) & UMM_BLOCKNO_MASK) ) {
UMM_NFREE(UMM_PFREE(UMM_NBLOCK(c) & UMM_BLOCKNO_MASK)) = c;
UMM_NFREE(UMM_PFREE(c)) = UMM_NFREE(c);
UMM_PFREE(UMM_NFREE(c)) = UMM_PFREE(c);
UMM_PFREE(c) = UMM_PFREE(UMM_NBLOCK(c) & UMM_BLOCKNO_MASK);
}
UMM_NFREE(c) = 0;
UMM_NBLOCK(c) = 0;
}
#endif
// Release the critical section...
//
UMM_CRITICAL_EXIT();
}
void *umm_realloc( void *ptr, size_t size ) {
unsigned short int blocks;
unsigned short int blockSize;
unsigned short int c;
size_t curSize;
// This code looks after the case of a NULL value for ptr. The ANSI C
// standard says that if ptr is NULL and size is non-zero, then we've
// got to work the same a malloc(). If size is also 0, then our version
// of malloc() returns a NULL pointer, which is OK as far as the ANSI C
// standard is concerned.
if( ((void *)NULL == ptr) ) {
DBG_LOG_DEBUG( "realloc the NULL pointer - call malloc()\n" );
return( umm_malloc(size) );
}
// Now we're sure that we have a non_NULL ptr, but we're not sure what
// we should do with it. If the size is 0, then the ANSI C standard says that
// we should operate the same as free.
if( 0 == size ) {
DBG_LOG_DEBUG( "realloc to 0 size, just free the block\n" );
umm_free( ptr );
return( (void *)NULL );
}
// Protect the critical section...
//
UMM_CRITICAL_ENTRY();
// Otherwise we need to actually do a reallocation. A naiive approach
// would be to malloc() a new block of the correct size, copy the old data
// to the new block, and then free the old block.
//
// While this will work, we end up doing a lot of possibly unnecessary
// copying. So first, let's figure out how many blocks we'll need.
blocks = umm_blocks( size );
// Figure out which block we're in. Note the use of truncated division...
c = (ptr-(void *)(&(umm_heap[0])))/sizeof(umm_block);
// Figure out how big this block is...
blockSize = (UMM_NBLOCK(c) - c);
// Figure out how many bytes are in this block
curSize = (blockSize*sizeof(umm_block))-(sizeof(((umm_block *)0)->header));
// Ok, now that we're here, we know the block number of the original chunk
// of memory, and we know how much new memory we want, and we know the original
// block size...
if( blockSize == blocks ) {
// This space intentionally left blank - return the original pointer!
DBG_LOG_DEBUG( "realloc the same size block - %d, do nothing\n", blocks );
// Release the critical section...
//
UMM_CRITICAL_EXIT();
return( ptr );
}
// Now we have a block size that could be bigger or smaller. Either
// way, try to assimilate up to the next block before doing anything...
//
// If it's still too small, we have to free it anyways and it will save the
// assimilation step later in free :-)
umm_assimilate_up( c );
// Now check if it might help to assimilate down, but don't actually
// do the downward assimilation unless the resulting block will hold the
// new request! If this block of code runs, then the new block will
// either fit the request exactly, or be larger than the request.
if( (UMM_NBLOCK(UMM_PBLOCK(c)) & UMM_FREELIST_MASK) &&
(blocks <= (UMM_NBLOCK(c)-UMM_PBLOCK(c))) ) {
// Check if the resulting block would be big enough...
DBG_LOG_DEBUG( "realloc() could assimilate down %d blocks - fits!\n\r", c-UMM_PBLOCK(c) );
// Disconnect the previous block from the FREE list
umm_disconnect_from_free_list( UMM_PBLOCK(c) );
// Connect the previous block to the next block ... and then
// realign the current block pointer
c = umm_assimilate_down(c, 0);
// Move the bytes down to the new block we just created, but be sure to move
// only the original bytes.
memmove( (void *)&UMM_DATA(c), ptr, curSize );
// And don't forget to adjust the pointer to the new block location!
ptr = (void *)&UMM_DATA(c);
}
// Now calculate the block size again...and we'll have three cases
blockSize = (UMM_NBLOCK(c) - c);
if( blockSize == blocks ) {
// This space intentionally left blank - return the original pointer!
DBG_LOG_DEBUG( "realloc the same size block - %d, do nothing\n", blocks );
} else if (blockSize > blocks ) {
// New block is smaller than the old block, so just make a new block
// at the end of this one and put it up on the free list...
DBG_LOG_DEBUG( "realloc %d to a smaller block %d, shrink and free the leftover bits\n", blockSize, blocks );
umm_make_new_block( c, blocks, 0 );
umm_free( (void *)&UMM_DATA(c+blocks) );
} else {
// New block is bigger than the old block...
void *oldptr = ptr;
DBG_LOG_DEBUG( "realloc %d to a bigger block %d, make new, copy, and free the old\n", blockSize, blocks );
// Now umm_malloc() a new/ one, copy the old data to the new block, and
// free up the old block, but only if the malloc was sucessful!
if( (ptr = umm_malloc( size )) ) {
memcpy( ptr, oldptr, curSize );
}
umm_free( oldptr );
}
// Release the critical section...
//
UMM_CRITICAL_EXIT();
return( ptr );
}
void *umm_realloc( void *ptr, size_t size ) {
unsigned short int blocks;
unsigned short int blockSize;
unsigned short int prevBlockSize = 0;
unsigned short int nextBlockSize = 0;
unsigned short int c;
size_t curSize;
if (umm_heap == NULL) {
umm_init();
}
/*
* This code looks after the case of a NULL value for ptr. The ANSI C
* standard says that if ptr is NULL and size is non-zero, then we've
* got to work the same a malloc(). If size is also 0, then our version
* of malloc() returns a NULL pointer, which is OK as far as the ANSI C
* standard is concerned.
*/
if( ((void *)NULL == ptr) ) {
DBGLOG_DEBUG( "realloc the NULL pointer - call malloc()\n" );
return( umm_malloc(size) );
}
/*
* Now we're sure that we have a non_NULL ptr, but we're not sure what
* we should do with it. If the size is 0, then the ANSI C standard says that
* we should operate the same as free.
*/
if( 0 == size ) {
DBGLOG_DEBUG( "realloc to 0 size, just free the block\n" );
umm_free( ptr );
return( (void *)NULL );
}
/*
* Otherwise we need to actually do a reallocation. A naiive approach
* would be to malloc() a new block of the correct size, copy the old data
* to the new block, and then free the old block.
*
* While this will work, we end up doing a lot of possibly unnecessary
* copying. So first, let's figure out how many blocks we'll need.
*/
blocks = umm_blocks( size );
/* Figure out which block we're in. Note the use of truncated division... */
c = (((char *)ptr)-(char *)(&(umm_heap[0])))/sizeof(umm_block);
/* Figure out how big this block is ... the free bit is not set :-) */
blockSize = (UMM_NBLOCK(c) - c);
/* Figure out how many bytes are in this block */
curSize = (blockSize*sizeof(umm_block))-(sizeof(((umm_block *)0)->header));
/* Protect the critical section... */
UMM_CRITICAL_ENTRY();
/* Now figure out if the previous and/or next blocks are free as well as
* their sizes - this will help us to minimize special code later when we
* decide if it's possible to use the adjacent blocks.
*
* We set prevBlockSize and nextBlockSize to non-zero values ONLY if they
* are free!
*/
if ((UMM_NBLOCK(UMM_NBLOCK(c)) & UMM_FREELIST_MASK)) {
nextBlockSize = (UMM_NBLOCK(UMM_NBLOCK(c)) & UMM_BLOCKNO_MASK) - UMM_NBLOCK(c);
}
if ((UMM_NBLOCK(UMM_PBLOCK(c)) & UMM_FREELIST_MASK)) {
prevBlockSize = (c - UMM_PBLOCK(c));
}
DBGLOG_DEBUG( "realloc blocks %i blockSize %i nextBlockSize %i prevBlockSize %i\n", blocks, blockSize, nextBlockSize, prevBlockSize );
/*
* Ok, now that we're here we know how many blocks we want and the current
* blockSize. The prevBlockSize and nextBlockSize are set and we can figure
* out the best strategy for the new allocation as follows:
*
* 1. If the new block is the same size or smaller than the current block do
* nothing.
* 2. If the next block is free and adding it to the current block gives us
* enough memory, assimilate the next block.
* 3. If the prev block is free and adding it to the current block gives us
* enough memory, remove the previous block from the free list, assimilate
* it, copy to the new block.
* 4. If the prev and next blocks are free and adding them to the current
* block gives us enough memory, assimilate the next block, remove the
* previous block from the free list, assimilate it, copy to the new block.
* 5. Otherwise try to allocate an entirely new block of memory. If the
* allocation works free the old block and return the new pointer. If
* the allocation fails, return NULL and leave the old block intact.
*
* All that's left to do is decide if the fit was exact or not. If the fit
* was not exact, then split the memory block so that we use only the requested
* number of blocks and add what's left to the free list.
*/
if (blockSize >= blocks) {
DBGLOG_DEBUG( "realloc the same or smaller size block - %i, do nothing\n", blocks );
/* This space intentionally left blank */
} else if ((blockSize + nextBlockSize) >= blocks) {
DBGLOG_DEBUG( "realloc using next block - %i\n", blocks );
umm_assimilate_up( c );
blockSize += nextBlockSize;
} else if ((prevBlockSize + blockSize) >= blocks) {
DBGLOG_DEBUG( "realloc using prev block - %i\n", blocks );
umm_disconnect_from_free_list( UMM_PBLOCK(c) );
c = umm_assimilate_down(c, 0);
memmove( (void *)&UMM_DATA(c), ptr, curSize );
ptr = (void *)&UMM_DATA(c);
blockSize += prevBlockSize;
} else if ((prevBlockSize + blockSize + nextBlockSize) >= blocks) {
DBGLOG_DEBUG( "realloc using prev and next block - %i\n", blocks );
umm_assimilate_up( c );
umm_disconnect_from_free_list( UMM_PBLOCK(c) );
c = umm_assimilate_down(c, 0);
memmove( (void *)&UMM_DATA(c), ptr, curSize );
ptr = (void *)&UMM_DATA(c);
blockSize += (prevBlockSize + nextBlockSize);
} else {
DBGLOG_DEBUG( "realloc a completely new block %i\n", blocks );
void *oldptr = ptr;
if( (ptr = umm_malloc( size )) ) {
DBGLOG_DEBUG( "realloc %i to a bigger block %i, copy, and free the old\n", blockSize, blocks );
memcpy( ptr, oldptr, curSize );
umm_free( oldptr );
} else {
DBGLOG_DEBUG( "realloc %i to a bigger block %i failed - return NULL and leave the old block!\n", blockSize, blocks );
/* This space intentionally left blnk */
}
blockSize = blocks;
}
/* Now all we need to do is figure out if the block fit exactly or if we
* need to split and free ...
*/
if (blockSize > blocks ) {
DBGLOG_DEBUG( "split and free %i blocks from %i\n", blocks, blockSize );
umm_split_block( c, blocks, 0 );
umm_free( (void *)&UMM_DATA(c+blocks) );
}
/* Release the critical section... */
UMM_CRITICAL_EXIT();
return( ptr );
}
