feat: update structure

cs2106/labs/lab4/linkedlist/wf/mymalloc.c

@@ -0,0 +1,103 @@
+#include "mymalloc.h"
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/_types/_null.h>
+
+#include "llist.h"
+
+char _heap[MEMSIZE] = {0};
+TNode *_memlist = NULL; // To maintain information about length
+
+// Do not change this. Used by the test harness.
+// You may however use this function in your code if necessary.
+long get_index(void *ptr) {
+  if (ptr == NULL)
+    return -1;
+  else
+    return (long)((char *)ptr - &_heap[0]);
+}
+
+// Allocates size bytes of memory and returns a pointer
+// to the first byte.
+void *mymalloc(size_t size) {
+  if (_memlist == NULL) {
+    TData *data = malloc(sizeof(TData));
+    data->occupied = false;
+    data->size = MEMSIZE;
+    _memlist = make_node(0, data);
+  }
+
+  // loop through the list to find a free block
+  // if found, split the block and return the pointer
+  // if not found, return NULL
+  TNode *curr = _memlist;
+  TNode *best = NULL;
+  while (curr != NULL) {
+    if (curr->pdata->occupied == true) {
+      curr = curr->next;
+      continue;
+    }
+    if (curr->pdata->size < size) {
+      curr = curr->next;
+      continue;
+    }
+    if (best == NULL) {
+      best = curr;
+      curr = curr->next;
+      continue;
+    }
+    if (best->pdata->size < curr->pdata->size) {
+      best = curr;
+      curr = curr->next;
+      continue;
+    }
+    curr = curr->next;
+  }
+  if (best == NULL)
+    return NULL;
+  best->pdata->occupied = true;
+  if (best->pdata->size > size) {
+    // 	Create a new node with the leftover space
+    TData *newData = malloc(sizeof(TData));
+    newData->occupied = false;
+    newData->size = best->pdata->size - size;
+    TNode *newNode = make_node(best->key + size, newData);
+    // insert new node after the current one in the list.
+    insert_node(&_memlist, newNode, 0);
+    // change the size of the current node.
+    best->pdata->size = size;
+  }
+  return &_heap[best->key];
+}
+
+// Frees memory pointer to by ptr.
+void myfree(void *ptr) {
+  if (ptr == NULL)
+    return;
+  long index = get_index(ptr);
+  TNode *node = find_node(_memlist, index);
+  if (node == NULL)
+    return;
+  node->pdata->occupied = false;
+  // merge with the next node if it is free
+  while (node->next != NULL && node->next->pdata->occupied == false) {
+    node->pdata->size += node->next->pdata->size;
+    merge_node(_memlist, node, 1);
+  }
+
+  while (node->prev != NULL && node->prev->pdata->occupied == false) {
+    TNode *prev = node->prev;
+    prev->pdata->size += node->pdata->size;
+    merge_node(_memlist, node, 0);
+  }
+}
+
+void print_node(TNode *node) {
+  printf("Status: %s Start index: %d Length: %zu\n",
+         node->pdata->occupied ? "ALLOCATED" : "FREE", node->key,
+         node->pdata->size);
+}
+
+void print_memlist() { process_list(_memlist, print_node); }