Working linked memory structure on linux.

kernel/linked_list.c

@@ -0,0 +1,164 @@
+#ifndef LINKED_LIST_C
+#define LINKED_LIST_C
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct ll_node {
+    void *data;
+    int size;
+    bool used;
+
+    struct ll_node *previous;
+    struct ll_node *next;
+} ll_node;
+
+ll_node *__new_node() {
+    ll_node *new_node = malloc(sizeof(ll_node));
+    new_node->data = NULL;
+    new_node->size = 0;
+    new_node->used = false;
+
+    new_node->previous = NULL;
+    new_node->next = NULL;
+    return new_node;
+}
+
+ll_node *__search_ll_node(ll_node *heap_head, void *data) {
+    ll_node *curr_node = heap_head;
+    while (!curr_node->used || curr_node->data != data) {
+        curr_node = curr_node->next;
+    }
+    return curr_node;
+}
+
+void *__alloc(ll_node *ll_head, int size) {
+    ll_node *curr_node = ll_head;
+    ll_node *new_node = __new_node();
+    new_node->used = true;
+    new_node->size = size;
+
+    while (curr_node->next != NULL) {
+        curr_node = curr_node->next;
+
+        if (!curr_node->used && curr_node->size >= size) {
+            curr_node->size -= size;
+
+            // xxx -> <new_node> -> empty block -> yyy
+
+            // link new_node to xxx
+            curr_node->previous->next = new_node;
+            new_node->previous = curr_node->previous;
+
+            // link new_node to empty_block or yyy
+            if (curr_node->size == 0) {
+                new_node->next = curr_node->next;
+                curr_node->next->previous = new_node;
+                free(curr_node);
+            } else {
+                new_node->next = curr_node;
+                curr_node->previous = new_node;
+            }
+
+            void *data = new_node->previous->data + new_node->previous->size;
+            new_node->data = data;
+            return new_node->data;
+        }
+    }
+    new_node->previous = curr_node;
+    curr_node->next = new_node;
+
+    void *data = new_node->previous->data + new_node->previous->size;
+    new_node->data = data;
+    return new_node->data;
+}
+
+void __free(ll_node *ll_head, void *data) {
+    // Search the corresponding block of memory
+    // TODO This can be held in a table for quicker lookup
+    ll_node *empty_node = __search_ll_node(ll_head, data);
+    empty_node->used = false;
+
+    // Free the node
+    if (!empty_node->previous->used) {
+        empty_node->size += empty_node->previous->size;
+
+        empty_node->previous->previous->next = empty_node;
+
+        ll_node* previous = empty_node->previous;
+        empty_node->previous = empty_node->previous->previous;
+
+        free(previous);
+    }
+
+    if (!empty_node->next->used) {
+        empty_node->size += empty_node->next->size;
+
+        empty_node->next->next->previous = empty_node;
+
+        ll_node* next = empty_node->next;
+        empty_node->next = empty_node->next->next;
+
+        free(next);
+    }
+}
+
+void print(ll_node *ll_head) {
+    printf("==== MEM DUMP ====\n");
+    ll_node *curr_node = ll_head;
+    while (curr_node != NULL) {
+        if (!curr_node->used) {
+            printf("empty");
+        } else {
+            printf("%p", curr_node->data);
+        }
+        printf(" (%d)\n", curr_node->size);
+
+        curr_node = curr_node->next;
+    }
+    printf("-------------------\n\n");
+}
+
+void test_allocs(){
+    ll_node *ll_head = __new_node();
+    ll_head->data = malloc(sizeof(size_t) * 1000);
+    ll_head->used = true;
+    ll_head->size = 1;
+    void* ptr0 = __alloc(ll_head, 5);
+    void* ptr1 = __alloc(ll_head, 5);
+    void* ptr4 = __alloc(ll_head, 5);
+    print(ll_head);
+
+    printf("Free nr 3\n");
+    __free(ll_head, ptr1);
+    print(ll_head);
+
+    printf("Alloc 3 bytes\n");
+    void* ptr2 = __alloc(ll_head, 3);
+    print(ll_head);
+
+    printf("Alloc 3 bytes\n");
+    __alloc(ll_head, 3);
+    print(ll_head);
+
+    printf("Alloc 2 bytes\n");
+    void* ptr3 = __alloc(ll_head, 2);
+    print(ll_head);
+
+    __free(ll_head, ptr2);
+    print(ll_head);
+    __free(ll_head, ptr4);
+    print(ll_head);
+    __free(ll_head, ptr3);
+    print(ll_head);
+
+    __free(ll_head, ptr0);
+    print(ll_head);
+}
+
+int main() {
+    test_allocs();
+}
+
+#endif // LINKED_LIST_C