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mem_pool.c
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mem_pool.c
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#include <stdlib.h>
#include <assert.h>
#include <stdio.h> // for perror()
#include "mem_pool.h"
/*************/
/* */
/* Constants */
/* */
/*************/
static const float MEM_FILL_FACTOR = 0.75;
static const unsigned MEM_EXPAND_FACTOR = 2;
static const unsigned MEM_POOL_STORE_INIT_CAPACITY = 20;
static const float MEM_POOL_STORE_FILL_FACTOR = 0.75;
static const unsigned MEM_POOL_STORE_EXPAND_FACTOR = 2;
static const unsigned MEM_NODE_HEAP_INIT_CAPACITY = 40;
static const float MEM_NODE_HEAP_FILL_FACTOR = 0.75;
static const unsigned MEM_NODE_HEAP_EXPAND_FACTOR = 2;
static const unsigned MEM_GAP_IX_INIT_CAPACITY = 40;
static const float MEM_GAP_IX_FILL_FACTOR = 0.75;
static const unsigned MEM_GAP_IX_EXPAND_FACTOR = 2;
/*********************/
/* */
/* Type declarations */
/* */
/*********************/
typedef struct _node {
alloc_t alloc_record;
unsigned used;
unsigned allocated;
struct _node *next, *prev; // doubly-linked list for gap deletion
} node_t, *node_pt;
typedef struct _gap {
size_t size;
node_pt node;
} gap_t, *gap_pt;
typedef struct _pool_mgr {
pool_t pool;
node_pt node_heap;
unsigned total_nodes;
unsigned used_nodes;
gap_pt gap_ix;
unsigned gap_ix_capacity;
} pool_mgr_t, *pool_mgr_pt;
/***************************/
/* */
/* Static global variables */
/* */
/***************************/
static pool_mgr_pt *pool_store = NULL; // an array of pointers, only expand
static unsigned pool_store_size = 0;
static unsigned pool_store_capacity = 0;
/********************************************/
/* */
/* Forward declarations of static functions */
/* */
/********************************************/
static alloc_status _mem_resize_pool_store();
static alloc_status _mem_resize_node_heap(pool_mgr_pt pool_mgr);
static alloc_status _mem_resize_gap_ix(pool_mgr_pt pool_mgr);
static alloc_status
_mem_add_to_gap_ix(pool_mgr_pt pool_mgr,
size_t size,
node_pt node);
static alloc_status
_mem_remove_from_gap_ix(pool_mgr_pt pool_mgr,
size_t size,
node_pt node);
static alloc_status _mem_sort_gap_ix(pool_mgr_pt pool_mgr);
/****************************************/
/* */
/* Definitions of user-facing functions */
/* */
/****************************************/
alloc_status mem_init() {
//verify that mem_init() is only called once for every mem_fee()
if(pool_store != NULL){
return ALLOC_CALLED_AGAIN;
};
// allocate the pool store with initial capacity
pool_store = calloc(MEM_POOL_STORE_INIT_CAPACITY, sizeof(pool_mgr_pt));
pool_store_capacity = MEM_POOL_STORE_INIT_CAPACITY;
return ALLOC_OK;
}
alloc_status mem_free() {
// verify that mem_free() is called only once for each mem_init()
if(pool_store == NULL){
return ALLOC_CALLED_AGAIN;
};
// verify all pool managers have been deallocated
for(int i=0;i<pool_store_size;i++){
if(pool_store[i] != NULL){
mem_pool_close((pool_pt) pool_store[i]);
};
}
// free pool store and static variables
free(pool_store);
pool_store = NULL;
pool_store_size = 0;
pool_store_capacity = 0;
return ALLOC_OK;
}
pool_pt mem_pool_open(size_t size, alloc_policy policy) {
// verify that the pool store is allocated
if(pool_store == NULL){
return NULL;
};
// resize the pool store if nessisary
_mem_resize_pool_store();
// allocate a new mem pool mgr
pool_mgr_t *pool_manager;
pool_manager = calloc(1,sizeof(pool_mgr_t));
// ccheck if pool mgr was allocated properly
if(pool_manager == NULL){
return NULL;
};
// allocate a new memory pool
pool_manager->pool.mem = malloc(size);
// check if pool was allocated properly, if not, deallocate pool mgr
if(pool_manager->pool.mem == NULL){
free(pool_manager);
return NULL;
};
// allocate a new node heap
pool_manager->node_heap = calloc(MEM_NODE_HEAP_INIT_CAPACITY, sizeof(node_t));
pool_manager->total_nodes = MEM_NODE_HEAP_INIT_CAPACITY;
// check if node heap was allocated properly, if not, deallocate pool mgr and pool
if(pool_manager->node_heap == NULL){
free(pool_manager->pool.mem);
free(pool_manager);
return NULL;
};
// allocate a new gap index
pool_manager->gap_ix = calloc(MEM_GAP_IX_INIT_CAPACITY,sizeof(gap_t));
pool_manager->gap_ix_capacity = MEM_GAP_IX_INIT_CAPACITY;
// check if gap index was allocated properly, if not, deallocate pool mgr, node heap, and pool
if(pool_manager->gap_ix == NULL){
free(pool_manager->pool.mem);
free(pool_manager->node_heap);
free(pool_manager);
return NULL;
};
//initialize the pool
pool_manager->pool.total_size = size;
pool_manager->pool.alloc_size = 0;
pool_manager->pool.policy = policy;
pool_manager->pool.num_gaps = 1;
pool_manager->pool.num_allocs = 0;
// initialize top node of node heap
pool_manager->node_heap[0].next = NULL;
pool_manager->node_heap[0].prev = NULL;
pool_manager->node_heap[0].allocated = 0;
pool_manager->node_heap[0].used = 1;
pool_manager->node_heap[0].alloc_record.size = pool_manager->pool.total_size;
pool_manager->node_heap[0].alloc_record.mem = pool_manager->pool.mem;
pool_manager->used_nodes = 1;
// initialize top node of gap index
pool_manager->gap_ix[0].node = &pool_manager->node_heap[0];
// assign pool manager to the pool store array index
pool_store[pool_store_size] = pool_manager;
pool_store_size++;
// return the address of the mgr, cast to (pool_pt)
return (pool_pt) pool_manager;
}
alloc_status mem_pool_close(pool_pt pool) {
// get mgr from pool by casting the pointer to (pool_mgr_pt)
pool_mgr_pt pool_mgr = (pool_mgr_pt) pool;
// verify that the pool is allocated
if(pool_mgr->pool.mem == NULL){
// not allocated
};
// verify if the pool has one gap
if(pool_mgr->gap_ix->size == 1){
// only one gap
}
// verify that the pool has more than zero allocations
if(pool_mgr->pool.num_allocs != 0){
return ALLOC_NOT_FREED;
// no allocations
}
// free memory pool
free(pool_mgr->pool.mem);
// free node heap
free(pool_mgr->node_heap);
// free gap index
free(pool_mgr->gap_ix);
// locate pool mgr in pool store array and set to null
for(int i = 0;i<pool_store_capacity - 1;i++){
if(pool_store[i] == pool_mgr){
pool_store[i] = NULL;
};
};
// free pool manager
free(pool_mgr);
return ALLOC_OK;
}
alloc_pt mem_new_alloc(pool_pt pool, size_t size) {
// get mgr from pool by casting the pointer to (pool_mgr_pt)
pool_mgr_pt pool_mgr = (pool_mgr_pt) pool;
// verify if there are any gaps in the pool
if (pool_mgr->pool.num_gaps == 0) {
return NULL;
};
// resize node heap if nessisary
_mem_resize_node_heap(pool_mgr);
// check if used nodes are greater than total nodes
if (pool_mgr->used_nodes >= pool_mgr->total_nodes) {
return NULL;
};
// if FIRST_FIT, then find the first unallocated node with appropriate size in the node heap
node_pt alloc_node;
if (pool_mgr->pool.policy == FIRST_FIT) {
for (int i = 0; i < pool_mgr->total_nodes; i++) {
if (pool_mgr->node_heap[i].alloc_record.size >= size && pool_mgr->node_heap[i].allocated == 0) {
alloc_node = &pool_mgr->node_heap[i];
break;
}else{
alloc_node = NULL;
};
}
};
// if BEST_FIT, then find the first gap node with appropriate size in the gap index
if(pool_mgr->pool.policy == BEST_FIT){
for (int i = 0; i < pool_mgr->pool.num_gaps; i++) {
if (pool_mgr->gap_ix[i].node->alloc_record.size >= size && pool_mgr->gap_ix[i].node->allocated == 0) {
alloc_node = pool_mgr->gap_ix[i].node;
break;
}else{
alloc_node = NULL;
};
}
};
// check if node found
if (alloc_node == NULL) {
return NULL;
};
// incriment num_allocs and add the size of the new allocation to alloc_size
pool->num_allocs++;
pool->alloc_size += size;
// calculate the size of the remaining gap
size_t gap_remain;
gap_remain = alloc_node->alloc_record.size - size;
// remove node from gap index
_mem_remove_from_gap_ix(pool_mgr, size, alloc_node);
// update the variables of the new allocated node
alloc_node->allocated = 1;
alloc_node->alloc_record.size = size;
//use new node to handle remaining gap
node_pt gap_node;
// locate an unused node in the node heap
if(gap_remain != 0) {
for (int i = 0; i < pool_mgr->total_nodes; i++) {
if (pool_mgr->node_heap[i].used == 0) {
gap_node = &pool_mgr->node_heap[i];
break;
}
}
// verify that the node we found exists
if (gap_node == NULL) {
//gap not found!
}
// initialize the gap node by adding the appropriate values
gap_node->alloc_record.size = gap_remain;
gap_node->alloc_record.mem = alloc_node->alloc_record.mem + size;
gap_node->used = 1;
gap_node->allocated = 0;
// incriment the used nodes of the pool manager
pool_mgr->used_nodes++;
// set new allocated node to point next to the remaining gap node
if (alloc_node->next == NULL) {
alloc_node->next = gap_node;
gap_node->next = NULL;
gap_node->prev = alloc_node;
}
else {
gap_node->next = alloc_node->next;
alloc_node->next->prev = gap_node;
alloc_node->next = gap_node;
gap_node->prev = alloc_node;
};
// add to gap index
_mem_add_to_gap_ix(pool_mgr, gap_remain, gap_node);
}
// verify that the new allocated node was created succesfully
if(alloc_node == NULL){
return NULL;
};
// return allocation record by casting the node to (alloc_pt)
return (alloc_pt) alloc_node;
}
alloc_status mem_del_alloc(pool_pt pool, alloc_pt alloc) {
// get mgr from pool by casting the pointer to (pool_mgr_pt)
pool_mgr_pt pool_mgr = (pool_mgr_pt) pool;
// get node from alloc by casting the pointer to (node_pt)
node_pt node = (node_pt) alloc;
node_pt node_delete;
// locate the node in the node heap
for(int i=0;i < pool_mgr->total_nodes; i++){
if(pool_mgr->node_heap[i].alloc_record.mem == node->alloc_record.mem){
node_delete = &pool_mgr->node_heap[i];
break;
};
};
// verify that node is not null
if(node_delete == NULL){
return ALLOC_NOT_FREED;
};
// set node to gap
node_delete->allocated = 0;
// update pool manager variables
pool_mgr->pool.num_allocs--;
pool_mgr->pool.alloc_size = pool_mgr->pool.alloc_size - node_delete->alloc_record.size;
//if the next node is also a gap, merge to one gap
node_pt merge_node;
if(node_delete->next != NULL && node_delete->next->allocated == 0 && node_delete->next->used == 1){
merge_node = node_delete->next;
// remove the next node from the gap index
_mem_remove_from_gap_ix(pool_mgr,merge_node->alloc_record.size,merge_node);
// add size to the gap node
node_delete->alloc_record.size = node_delete->alloc_record.size + node_delete->next->alloc_record.size;
// set merged node used variable to zero
merge_node->used = 0;
// deincriment used nodes
pool_mgr->used_nodes--;
// set the merge node next prev pointer to
//node delete and node delete next to the merge node next
// or set it to null if the merged next is null
if (merge_node->next) {
merge_node->next->prev = node_delete;
node_delete->next = merge_node->next;
} else {
node_delete->next = NULL;
}
merge_node->next = NULL;
merge_node->prev = NULL;
merge_node->alloc_record.size = 0;
merge_node->alloc_record.mem = NULL;
};
// add the node delete to the gap index
_mem_add_to_gap_ix(pool_mgr,node_delete->alloc_record.size,node_delete);
//if the node previous to the node to delete is a gap, merge the node
node_pt prev_node;
if (node_delete->prev != NULL && node_delete->prev->used == 1 && node_delete->prev->allocated == 0) {
prev_node = node_delete->prev;
// remove the previous node and node to delete from the gap index
_mem_remove_from_gap_ix(pool_mgr, prev_node->alloc_record.size, prev_node);
_mem_remove_from_gap_ix(pool_mgr, node_delete->alloc_record.size,node_delete);
// add the node to delete to the previous node
prev_node->alloc_record.size = node_delete->alloc_record.size + node_delete->prev->alloc_record.size;
// clear the metadata from the node to delete
node_delete->alloc_record.size = 0;
node_delete->alloc_record.mem = NULL;
node_delete->used = 0;
node_delete->allocated = 0;
// deincrement used nodes
pool_mgr->used_nodes--;
// set the prev node next pointer to node delete next
// and the prev pointer from the node delete next to prev node
if (node_delete->next) {
prev_node->next = node_delete->next;
node_delete->next->prev = prev_node;
} else {
prev_node->next = NULL;
}
node_delete->next = NULL;
node_delete->prev = NULL;
// add the previous node to the gap index
_mem_add_to_gap_ix(pool_mgr,prev_node->alloc_record.size,prev_node);
};
return ALLOC_OK;
}
void mem_inspect_pool(pool_pt pool,
pool_segment_pt *segments,
unsigned *num_segments) {
// get the mgr from the pool
pool_mgr_pt pool_mgr = (pool_mgr_pt) pool;
// allocate the segments array with number of elements as the
//number of used nodes
pool_segment_pt segs;
segs = calloc(pool_mgr->used_nodes, sizeof(pool_segment_t));
if(segments == NULL){
return;
}
// set each segment size and allocation to the corresponding
//node size and allocation
int j = 0;
node_pt node_loop;
node_loop = &pool_mgr->node_heap[0];
while(node_loop){
segs[j].allocated = node_loop->allocated;
segs[j].size = node_loop->alloc_record.size;
node_loop = node_loop->next;
j++;
}
*segments = segs;
*num_segments = pool_mgr->used_nodes;
return;
}
/***********************************/
/* */
/* Definitions of static functions */
/* */
/***********************************/
static alloc_status _mem_resize_pool_store() {
// resize pool store and capacity if ratio is less than fill factor
if (((float) pool_store_size / pool_store_capacity)
> MEM_POOL_STORE_FILL_FACTOR) {
if((pool_store = realloc(pool_store,
pool_store_capacity * MEM_POOL_STORE_EXPAND_FACTOR *
sizeof(pool_mgr_pt)))){
pool_store_capacity *= MEM_POOL_STORE_EXPAND_FACTOR;
return ALLOC_OK;
};
};
return ALLOC_FAIL;
}
static alloc_status _mem_resize_node_heap(pool_mgr_pt pool_mgr) {
// resize node heap and capacity if ratio is less than fill factor
if (((float) pool_mgr->node_heap->used / pool_mgr->node_heap->alloc_record.size) > MEM_NODE_HEAP_FILL_FACTOR){
if((pool_mgr->node_heap = realloc(pool_mgr->node_heap,
MEM_NODE_HEAP_EXPAND_FACTOR * MEM_NODE_HEAP_INIT_CAPACITY * sizeof(node_t)))){
pool_mgr->node_heap->alloc_record.size *= MEM_NODE_HEAP_EXPAND_FACTOR;
return ALLOC_OK;
};
};
return ALLOC_FAIL;
}
static alloc_status _mem_resize_gap_ix(pool_mgr_pt pool_mgr) {
// resize gap index and capacity if ratio is less than fill factor
if(((float)pool_mgr->pool.num_gaps / pool_mgr->gap_ix_capacity) > MEM_GAP_IX_FILL_FACTOR){
if((pool_mgr->gap_ix = realloc(pool_mgr->gap_ix,
MEM_GAP_IX_EXPAND_FACTOR * MEM_GAP_IX_INIT_CAPACITY * sizeof(gap_t)))){
pool_mgr->gap_ix_capacity *= MEM_GAP_IX_EXPAND_FACTOR;
return ALLOC_OK;
};
};
return ALLOC_FAIL;
}
static alloc_status _mem_add_to_gap_ix(pool_mgr_pt pool_mgr,
size_t size,
node_pt node) {
// expand the gap index
_mem_resize_gap_ix(pool_mgr);
// add the entry at the last slot (total number of gaps)
pool_mgr->gap_ix[pool_mgr->pool.num_gaps].node = node;
pool_mgr->gap_ix[pool_mgr->pool.num_gaps].size = size;
// increment number of gaps
pool_mgr->pool.num_gaps++;
// check if the gap sort is successful, return ok
if(_mem_sort_gap_ix(pool_mgr) == ALLOC_OK){
return ALLOC_OK;
};
return ALLOC_FAIL;
}
static alloc_status _mem_remove_from_gap_ix(pool_mgr_pt pool_mgr,
size_t size,
node_pt node) {
// locate the position of the node in the gap index
int position;
for(int i=0; i < pool_mgr->pool.num_gaps - 1; i++){
if(pool_mgr->gap_ix[i].node->alloc_record.mem == node->alloc_record.mem && pool_mgr->gap_ix[i].size == size){
position = i;
}
}
// loop from the position to the end of the number of gaps
//set each gap from the slot above to the slot previous
for(int i=position; i<pool_mgr->pool.num_gaps - 1; i++){
pool_mgr->gap_ix[i] = pool_mgr->gap_ix[i+1];
}
// deincriment the number of gaps
pool_mgr->pool.num_gaps--;
//clear the metadata from the position gap
pool_mgr->gap_ix[pool_mgr->pool.num_gaps].size = 0;
pool_mgr->gap_ix[pool_mgr->pool.num_gaps].node = NULL;
return ALLOC_OK;
}
static alloc_status _mem_sort_gap_ix(pool_mgr_pt pool_mgr) {
// loop from num_gaps - 1 to 1
// if the size of the current gap is less than the previous gap, swap them
for(int i= pool_mgr->pool.num_gaps-1;i > 0; i--){
if(pool_mgr->gap_ix[i].node->alloc_record.size < pool_mgr->gap_ix[i - 1].node->alloc_record.size
|| pool_mgr->gap_ix[i].node->alloc_record.mem < pool_mgr->gap_ix[i - 1].node->alloc_record.mem
&& pool_mgr->gap_ix[i].node->alloc_record.size == pool_mgr->gap_ix[i - 1].node->alloc_record.size){
struct _gap temp_gap;
temp_gap = pool_mgr->gap_ix[i - 1];
pool_mgr->gap_ix[i - 1] = pool_mgr->gap_ix[i];
pool_mgr->gap_ix[i] = temp_gap;
};
};
return ALLOC_OK;
}