feat(tlsf): Add a function to malloc at a given address

The function will find a suitable free block that can contain
the malloc size at the given address in the memory pool, split
the free block to create the block that will contain the allocated
memory, update the status of the newly created blocks (free / used)
and return the pointer to the memory allocated at the given address.

If no block is found (the status of the heap doesn't allow for an
allocation at the given address) the function will return NULL.

tlsf.c

@@ -1009,6 +1009,77 @@ void* tlsf_malloc(tlsf_t tlsf, size_t size)
 	return block_prepare_used(control, block, adjust);
 }
 
+/**
+ * @brief Allocate memory of at least `size` bytes at a given address in the pool.
+ *
+ * @param tlsf TLSF structure to allocate memory from.
+ * @param size Minimum size, in bytes, of the memory to allocate
+ * @param address address at which the allocation must be done
+ *
+ * @return pointer to free memory or NULL in case of incapacity to perform the malloc
+ */
+void* tlsf_malloc_addr(tlsf_t tlsf, size_t size, void *address)
+{
+	control_t* control = tlsf_cast(control_t*, tlsf);
+
+	/* adjust the address to be ALIGN_SIZE bytes aligned. */
+	const unsigned int addr_adjusted = align_down(tlsf_cast(unsigned int, address), ALIGN_SIZE);
+
+	/* adjust the size to be ALIGN_SIZE bytes aligned. Add to the size the difference
+	 * between the requested address and the address_adjusted. */
+	size_t size_adjusted = align_up(size + (tlsf_cast(unsigned int, address) - addr_adjusted), ALIGN_SIZE);
+
+	/* find the free block that starts before the address in the pool and is big enough
+	 * to support the size of allocation at the given address */
+	block_header_t* block = offset_to_block(tlsf_get_pool(tlsf), -(int)block_header_overhead);
+	
+	const char *alloc_start = tlsf_cast(char*, addr_adjusted);
+	const char *alloc_end = alloc_start + size_adjusted;
+	bool block_found = false;
+	do {
+		const char *block_start = tlsf_cast(char*, block_to_ptr(block));
+		const char *block_end = tlsf_cast(char*, block_to_ptr(block)) + block_size(block);
+		if (block_start <= alloc_start && block_end > alloc_start) {
+			/* A: block_end >= alloc_end. B: block is free */
+			if (block_end < alloc_end || !block_is_free(block)) {
+				/* not(A) || not(B)
+				 * We won't find another suitable block from this point on
+				 * so we can break and return NULL */
+				break;
+			} 
+			/* A && B
+			 * The block can fit the alloc and is located at a position allowing for the alloc
+			 * to be placed at the given address. We can return from the while */
+			block_found = true;
+		} else if (!block_is_last(block)) {
+			/* the block doesn't match the expected criteria, continue with the next block */
+			block = block_next(block);
+		}
+
+	} while (!block_is_last(block) && block_found == false);
+
+	if (!block_found) {
+		return NULL;
+	}
+	
+	/* remove block from the free list since a part of it will be used */
+	block_remove(control, block);
+
+	/* trim any leading space or add the leading space to the overall requested size
+	 * if the leading space is not big enough to store a block of minimum size */
+	const size_t space_before_addr_adjusted = addr_adjusted - tlsf_cast(unsigned int, block_to_ptr(block));
+	block_header_t *return_block = block;
+	if (space_before_addr_adjusted >= block_size_min) {
+		return_block = block_trim_free_leading(control, block, space_before_addr_adjusted);
+	}
+	else {
+		size_adjusted += space_before_addr_adjusted;
+	}
+
+	/* trim trailing space if any and return a pointer to the first usable byte allocated */
+	return  block_prepare_used(control, return_block, size_adjusted);
+}
+
 /**
  * @brief Allocate memory of at least `size` bytes where byte at `data_offset` will be aligned to `alignment`.
  *

tlsf.h

@@ -33,6 +33,7 @@ void tlsf_remove_pool(tlsf_t tlsf, pool_t pool);
 void* tlsf_malloc(tlsf_t tlsf, size_t size);
 void* tlsf_memalign(tlsf_t tlsf, size_t align, size_t size);
 void* tlsf_memalign_offs(tlsf_t tlsf, size_t align, size_t size, size_t offset);
+void* tlsf_malloc_addr(tlsf_t tlsf, size_t size, void *address);
 void* tlsf_realloc(tlsf_t tlsf, void* ptr, size_t size);
 void tlsf_free(tlsf_t tlsf, void* ptr);