This library provides routines for manipulating dynamic memory allocation. Dynamic memory allocation (also known as heap-based memory allocation) is the allocation of memory storage for use in a program during the runtime of that program.
Dynamically allocated memory exists until it is released. This is in contrast to static memory allocation, which has a fixed duration. It is said that an object so allocated has a dynamic lifetime.

The heap memory size can be configured in the Edit Project window. Also, user can override heap memory size in the code, by setting the HEAP_SIZE constant.

Library Routines

• MM_Init
• Malloc
• Free
• MM_LargestFreeMemBlock
• MM_TotalFreeMemSize

MM_Init

MM_Init();             // set Heap size

Malloc

int *pi;      // pointer to integer
int ai[100];  // array of integers

void main() {
  pi = (int *)Malloc(sizeof ai);  // pi will point to a memory block where the array is allocated
}

Free

int *pi;      // pointer to integer
int ai[100];  // array of integers

void main() {
  pi = (int *)Malloc(sizeof ai);  // pi will point to a memory block in the Heap where the array is allocated
  Free(pi, sizeof(pi));           // frees memory block from the Heap allocated by Malloc, pointed to by the pi pointer
}

MM_LargestFreeMemBlock

unsigned long block;      

void main() {
  block = MM_LargestFreeMemBlock();
}

MM_TotalFreeMemSize

unsigned long total;      

void main() {
  block = MM_TotalFreeMemSize();
}

Library Example

The example shows use how to use Memory Manager library.

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// Structure that describes Item object
typedef struct {
    long         id;     // Item number
    char *      name;    // Item name
} tItem;

// Allocate and initialize a new Item object and returns pointer to created Item
tItem * make_item(char *name) {
    tItem * item;

    item = (tItem*) malloc(sizeof(tItem)); // Allocate a block of memory for a new Item object
    if (item == 0)                         // If allocation failed return null
        return (tItem *)0;

    memset(item, 0, sizeof(tItem));        // Initialize the members of the new Item
    item->id =   -1;
    item->name = (char *)0;

    item->name = malloc(strlen(name) + 1); // Allocate a block of memory for a name in the Item
    if (item->name == 0) {                 // If allocation failed return null
        Free( (char*)item, sizeof(tItem));
        return (tItem *)0;
    }
    strcpy(item->name, name);              //Save a copy of the name in the new Item

    return item;                           // Return the created Item object
}

// Deallocate an Item object
void destroy_item(tItem *item) {

    if (item == 0)                         // Check for a null object pointer
        return;

    if (item->name != 0) {
        Free(item->name, strlen(item->name) + 1);// Deallocate the name string saved within the Item
        item->name = (char *)0;
    }

    Free((char*)item, sizeof(tItem));      // Deallocate the Item object itself
}

tItem *it[3];    // Array of pointers to Item objects
char txt[15];
long freeMemSize;
long largerstFreeBlock;

void main() {
  MM_Init();

  freeMemSize = MM_TotalFreeMemSize();          // Get free memory size before allocating
  largerstFreeBlock = MM_LargestFreeMemBlock(); // Get largest free memory block size before allocating

  it[0] = make_item("one");                     // Allocate object
  it[1] = make_item("two");
  it[2] = make_item("three");
  freeMemSize = MM_TotalFreeMemSize();          // Get free memory size
  largerstFreeBlock = MM_LargestFreeMemBlock(); // Get largest free memory block size
  strcpy(txt,it[0]->name);
  strcpy(txt,it[1]->name);
  strcpy(txt,it[2]->name);

  destroy_item(it[0]);                          // Deallocate the Item object
  it[0] = make_item("instead one");             // Make another Item object
  strcpy(txt,it[0]->name);
  strcpy(txt,it[1]->name);
  strcpy(txt,it[2]->name);

  destroy_item(it[1]);                          // Deallocate Items
  destroy_item(it[2]);
  freeMemSize = MM_TotalFreeMemSize();          // Get free memory size
}

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