tlsf: update calculation of fl index max

The calculation of fl index max is changed to always be the smallest
number that includes the size of the registered memory.

The control_construct() function now checks for minimum size as the control structure
parameters are calculated.

There is no longer a minimum configuration for fl index max so the tlsf_config
enum is striped down to remove unecessary compile time values.

the tlsf_size() function will fail if no tlsf pointer is passed as parameter since there
is no way to calculate a default tlsf size anymore.

tlsf.c

@@ -584,16 +584,19 @@ static inline __attribute__((always_inline)) void* block_prepare_used(control_t*
 }
 
 /* Clear structure and point all empty lists at the null block. */
-static void control_construct(control_t* control, size_t bytes)
+static control_t* control_construct(control_t* control, size_t bytes)
 {
-	int i, j;
-
-	control->block_null.next_free = &control->block_null;
-	control->block_null.prev_free = &control->block_null;
+	// check that the requested size can at least hold the control_t. This will allow us 
+	// to fill in the field of control_t necessary to determine the final size of 
+	// the metadata overhead and check that the requested size can hold
+	// this data and at least a block of minimum size
+	if (bytes < sizeof(control_t))
+	{
+		return NULL;
+	}
 
 	/* Find the closest power of two for first layer */
-	i = (bytes - 1) / (16 * 1024);
-	control->fl_index_max = FL_INDEX_MAX_MIN + sizeof(i) * 8 - __builtin_clz(i);
+	control->fl_index_max = 32 - __builtin_clz(bytes);
 
 	/* Adapt second layer to the pool */
 	if (bytes <= 16 * 1024) control->sl_index_count_log2 = 3;
@@ -604,11 +607,26 @@ static void control_construct(control_t* control, size_t bytes)
 	control->sl_index_count = 1 << control->sl_index_count_log2;
 	control->fl_index_count = control->fl_index_max - control->fl_index_shift + 1;
 	control->small_block_size = 1 << control->fl_index_shift;
+	
+	// the total size fo the metadata overhead is the size of the control_t
+	// added to the size of the sl_bitmaps and the size of blocks
+	control->size = sizeof(control_t) + (sizeof(*control->sl_bitmap) * control->fl_index_count) +
+										(sizeof(*control->blocks) * (control->fl_index_count * control->sl_index_count));
+
+	// check that the requested size can hold the whole control structure and
+	// a small block at least
+	if (bytes < control->size + block_size_min)
+	{
+		return NULL;
+	}
+
+	control->block_null.next_free = &control->block_null;
+	control->block_null.prev_free = &control->block_null;
 
 	control->fl_bitmap = 0;
 	control->sl_bitmap = align_ptr(control + 1, sizeof(*control->sl_bitmap));
 	control->blocks = align_ptr(control->sl_bitmap + control->fl_index_count, sizeof(*control->blocks));
-	control->size = (void*) (control->blocks + control->sl_index_count * control->fl_index_count) - (void*) control;
+
 
 	/* SL_INDEX_COUNT must be <= number of bits in sl_bitmap's storage type. */
 	tlsf_assert(sizeof(unsigned int) * CHAR_BIT >= control->sl_index_count); //CHAR_BIT less than sl_index_count");
@@ -616,14 +634,16 @@ static void control_construct(control_t* control, size_t bytes)
 	/* Ensure we've properly tuned our sizes. */
 	tlsf_assert(ALIGN_SIZE == control->small_block_size / control->sl_index_count); //ALIGN_SIZE does not match");
 
-	for (i = 0; i < control->fl_index_count; ++i)
+	for (int i = 0; i < control->fl_index_count; ++i)
 	{
 		control->sl_bitmap[i] = 0;
-		for (j = 0; j < control->sl_index_count; ++j)
+		for (int j = 0; j < control->sl_index_count; ++j)
 		{
 			control->blocks[i * control->sl_index_count + j] = &control->block_null;
 		}
 	}
+
+	return control;
 }
 
 /*
@@ -791,16 +811,12 @@ size_t tlsf_fit_size(tlsf_t tlsf, size_t size)
 */
 size_t tlsf_size(tlsf_t tlsf)
 {
-	if (tlsf) 
+	if (tlsf == NULL)
 	{
-		control_t* control = tlsf_cast(control_t*, tlsf);
-		return control->size;
-	}   
-
-	/* no tlsf, we'll just return a min size */
-	return  sizeof(control_t) + 
-			sizeof(int) * SL_INDEX_COUNT_MIN + 
-			sizeof(block_header_t*) * SL_INDEX_COUNT_MIN * FL_INDEX_COUNT_MIN;
+		return 0;
+	}
+	control_t* control = tlsf_cast(control_t*, tlsf);
+	return control->size;
 }
 
 size_t tlsf_align_size(void)
@@ -946,15 +962,17 @@ tlsf_t tlsf_create(void* mem, size_t max_bytes)
 		return 0;
 	}
 
-	control_construct(tlsf_cast(control_t*, mem), max_bytes);
-
-	return tlsf_cast(tlsf_t, mem);
+	control_t* control_ptr = control_construct(tlsf_cast(control_t*, mem), max_bytes);
+	return tlsf_cast(tlsf_t, control_ptr);
 }
 
 tlsf_t tlsf_create_with_pool(void* mem, size_t pool_bytes, size_t max_bytes)
 {
 	tlsf_t tlsf = tlsf_create(mem, max_bytes ? max_bytes : pool_bytes);
-	tlsf_add_pool(tlsf, (char*)mem + tlsf_size(tlsf), pool_bytes - tlsf_size(tlsf));
+	if (tlsf != NULL)
+	{
+		tlsf_add_pool(tlsf, (char*)mem + tlsf_size(tlsf), pool_bytes - tlsf_size(tlsf));
+	}
 	return tlsf;
 }
 
@@ -1133,6 +1151,12 @@ void* tlsf_realloc(tlsf_t tlsf, void* ptr, size_t size)
 		const size_t combined = cursize + block_size(next) + block_header_overhead;
 		const size_t adjust = adjust_request_size(tlsf, size, ALIGN_SIZE);
 
+		// if adjust if equal to 0, the size is too big
+		if (adjust == 0)
+		{
+			return p;
+		}
+
 		tlsf_assert(!block_is_free(block) && "block already marked as free");
 
 		/*

tlsf_common.h

@@ -35,35 +35,9 @@ extern "C" {
 
 enum tlsf_config
 {
-	/* log2 of number of linear subdivisions of block sizes. Larger
-	** values require more memory in the control structure. Values of
-	** 4 or 5 are typical, 3 is for very small pools.
-	*/
-	SL_INDEX_COUNT_LOG2_MIN  = 3,
-
 	/* All allocation sizes and addresses are aligned to 4 bytes. */
 	ALIGN_SIZE_LOG2 = 2,
 	ALIGN_SIZE = (1 << ALIGN_SIZE_LOG2),
-
-	/*
-	** We support allocations of sizes up to (1 << FL_INDEX_MAX) bits.
-	** However, because we linearly subdivide the second-level lists, and
-	** our minimum size granularity is 4 bytes, it doesn't make sense to
-	** create first-level lists for sizes smaller than SL_INDEX_COUNT * 4,
-	** or (1 << (SL_INDEX_COUNT_LOG2 + 2)) bytes, as there we will be
-	** trying to split size ranges into more slots than we have available.
-	** Instead, we calculate the minimum threshold size, and place all
-	** blocks below that size into the 0th first-level list.
-	** Values below are the absolute minimum to accept a pool addition.    
-	*/
-
-	/* Tunning the first level, we can reduce TLSF pool overhead
-	 * in exchange of manage a pool smaller than 4GB
-	 */
-	FL_INDEX_MAX_MIN = 14,
-	SL_INDEX_COUNT_MIN = (1 << SL_INDEX_COUNT_LOG2_MIN),
-	FL_INDEX_SHIFT_MIN = (SL_INDEX_COUNT_LOG2_MIN + ALIGN_SIZE_LOG2),
-	FL_INDEX_COUNT_MIN = (FL_INDEX_MAX_MIN - FL_INDEX_SHIFT_MIN + 1),
 };
 
 /*
@@ -112,7 +86,6 @@ static const size_t block_start_offset =
 */
 static const size_t block_size_min = 
 	sizeof(block_header_t) - sizeof(block_header_t*);
-static const size_t block_size_max = tlsf_cast(size_t, 1) << FL_INDEX_MAX_MIN;
 
 /* The TLSF control structure. */
 typedef struct control_t