I Space distributor

One . Space allocator

Allocate memory ：

• When a container needs space to hold elements , Space configurator required （ That is, the distributor ） Allocate memory , When the allocated memory is greater than 128 Bytes , Call the first level configurator , call malloc Allocate memory for it , When the allocated memory is less than 128 Bytes , Call the second level configurator , Check the corresponding free-list Is there a block available on , If any , Use directly , If not, call rfill.

• rfill Workflow ：

• If I found free list After there are no available blocks in , From the memory pool （ adopt chunk_alloc） To get new blocks .

• chunk_alloc Workflow ：

1. With end_free - start_free To determine whether there is memory , If there's enough memory , Then get 20 New nodes （ New area block ）, When memory pool space is insufficient 20 individual , But satisfy one , Get less 20 Number of nodes , When memory pool No node can be assigned , Call the first level configurator from malloc Recapture a chunk of memory .

2. At the end of time ,system heap There's not enough space （ Now the computer memory is very large , This rarely happens ）, He has out-of-memory Processing mechanism （ similar new_handler Mechanism ）, Free up memory elsewhere , Assign in turn , Call again malloc, If you can, you will succeed , If it fails, send out bad_alloc abnormal .

Reclaim memory ：

• First, determine the memory size , If memory is greater than 128 Bytes , Call free Reclaiming memory , If memory is less than 128 Bytes , Find out the corresponding free-list Reclaim blocks .

Be careful ：malloc and free from os From there

First level configurator ：

1. allocate() Use it directly malloc（）,deallocate（） Use it directly free（）.
2. simulation c ++ Of set_new_handler() To handle out of memory conditions .

Second level configurator ：

1. maintain 16 A free list （free list）.

   • be responsible for 16 Configuration capability of small blocks .
   • Memory pool （memory） With malloc( ) From configuration . If there is not enough memory , Call the first level configurator （ There is memory processing ）.

2. If the demand block is greater than 128bytes, Then call the first level configurator .

3. If the demand block is greater than 128bytes, Then call the first level configurator .