steal a linked list implementation

Makefile

@@ -1,5 +1,8 @@
 .DEFAULT_GOAL := purge 
 
+llist.o:
+	cc -c engine/llist.c -o llist.o
+
 todo.o:
 	cc -c engine/todo.c -o todo.o
 
@@ -10,5 +13,5 @@ purge:
 	rm -f *.o
 	make all
 
-all: todo.o main.o
-	cc todo.o main.o -o todd
+all: todo.o main.o llist.o
+	cc todo.o main.o llist.o -o todd

README.md

@@ -10,3 +10,6 @@ Just run: `./build.sh` and run `./todd` after that.
 - [ ] Save todos to disk
 - [ ] Smarter way to organize todos (instead of global array)
 - [ ] Add a TUI
+
+# Attributions
+- https://gist.github.com/meylingtaing/11018042

engine/llist.c

@@ -0,0 +1,99 @@
+/* llist.c
+ * Generic Linked List implementation
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include "llist.h"
+
+llist *llist_create(TodoItem *new_item)
+{
+    TodoItemNode *new_node;
+
+    llist *new_list = (llist *)malloc(sizeof (llist));
+    *new_list = (TodoItemNode *)malloc(sizeof (TodoItemNode));
+    
+    new_node = *new_list;
+    new_node->item = new_item;
+    new_node->next = NULL;
+    return new_list;
+}
+
+void llist_free(llist *list)
+{
+    TodoItemNode *curr = *list;
+    TodoItemNode *next;
+
+    while (curr != NULL) {
+        next = curr->next;
+        free(curr);
+        curr = next;
+    }
+
+    free(list);
+}
+
+void llist_push(llist *list, TodoItem *item)
+{
+    TodoItemNode *head;
+    TodoItemNode *new_node;
+    if (list == NULL || *list == NULL) {
+        fprintf(stderr, "llist_add_inorder: list is null\n");
+    }
+
+    head = *list;
+    
+    // Head is empty node
+    if (head->item == NULL)
+        head->item = item;
+
+    // Head is not empty, add new node to front
+    else {
+        new_node = malloc(sizeof (TodoItemNode));
+        new_node->item = item;
+        new_node->next = head;
+        *list = new_node;
+    }
+}
+
+TodoItem *llist_pop(llist *list)
+{
+    TodoItem *popped_item;
+    TodoItemNode *head = *list;
+
+    if (list == NULL || head->item == NULL)
+        return NULL;
+    
+    popped_item = head->item;
+    *list = head->next;
+
+    free(head);
+
+    return popped_item;
+}
+
+void llist_print(llist *list, void (*print)(TodoItem *))
+{
+    TodoItemNode *curr = *list;
+    while (curr != NULL) {
+        print(curr->item);
+        printf(" ");
+        curr = curr->next;
+    }
+    putchar('\n');
+}
+
+unsigned int llist_length(llist *list) {
+  if (list == NULL) {
+    return 0;
+  }
+
+  TodoItemNode *curr = *list;
+  unsigned int length = 0;
+  while (curr != NULL) {
+    length++;
+    curr = curr->next;
+  }
+
+  return length;
+}

engine/llist.h

@@ -0,0 +1,21 @@
+#ifndef LLIST_H
+#define LLIST_H
+#include "todo.h"
+/* llist.h
+ * Generic Linked List
+ */
+
+typedef struct Node {
+    TodoItem *item;
+    struct Node *next;
+} TodoItemNode;
+
+typedef TodoItemNode *llist;
+
+llist *llist_create(TodoItem *item);
+void llist_free(llist *list);
+void llist_push(llist *list, TodoItem *item);
+TodoItem *llist_pop(llist *list);
+void llist_print(llist *list, void (*print)(TodoItem *item));
+unsigned int llist_length(llist *list);
+#endif

main.c

@@ -2,6 +2,7 @@
 #include <string.h>
 #include <stdlib.h>
 #include "engine/todo.h"
+#include "engine/llist.h"
 
 #define MAX_TODOS 10
 #define SAVE_FILE "todos.todd"
@@ -13,11 +14,11 @@ enum Command {
   REMOVE = 'r',
   QUIT = 'q',
 
-  SERIALIZE = 's'
+  WRITE_TO_FILE = 'w',
+  LOAD_FROM_FILE = 'l',
 };
 
-TodoItem todos[MAX_TODOS];
-int todos_count = 0;
+llist *todos;
 
 void add_command_handler() {
   char title[TODO_MAX_TITLE_LENGTH];
@@ -27,28 +28,55 @@ void add_command_handler() {
   title[strlen(title) - 1] = '\0';
 
   TodoItem item = todo_create_item(title);
-  todos[todos_count] = item;
-  todos_count++;
+  if (llist_length(todos) == 0) {
+    todos = llist_create(&item);
+  } else {
+    llist_push(todos, &item);
+  }
 }
 
-void print_all_todos() {
-  for (int i = 0; i < todos_count; i++) {
-    todo_print_item(&todos[i]);
-  }
+void mark_command_handler() {
+  int op_index = -1;
+  do {
+    printf("Enter todo index: ");
+    op_index = getc(stdin) - '0';
+    getc(stdin); // remove the newline character from the buffer
+  } while (op_index < 0 || op_index >= llist_length(todos));
+
+  todo_mark_item(todos[op_index]->item, !todos[op_index]->item->completed);
+}
+
+void print_command_handler() {
+  llist_print(todos, todo_print_item);
 }
 
 void remove_todo_at_index(int index) {
-  for (int i = index; i < todos_count - 1; i++) {
-    todos[i] = todos[i + 1];
+  // TODO!: Implement this
+  /* for (int i = index; i < todos_count - 1; i++) { */
+  /*   todos[i] = todos[i + 1]; */
+  /* } */
+  /* todos_count--; */
+}
+
+void write_to_file_handler() {
+  FILE *file = fopen(SAVE_FILE, "wb");
+  int todos_count = llist_length(todos);
+  int bs = 0;
+  // write a magic value "TODD" to the file
+  fwrite("TODD", sizeof(char), 4, file);
+  // write the number of todos to the file
+  fwrite(&todos_count, sizeof(int), 1, file);
+  // write each todo to the file
+  for (int i = 0; i < todos_count; i++) {
+    char *buffer = todo_item_serialize(todos[i]->item, &bs);
+    fwrite(buffer, sizeof(char), bs, file);
+    free(buffer);
   }
-  todos_count--;
+  fclose(file);
 }
 
 int main(int argc, char **argv) {
   char cmd;
-  int op_index = -1;
-  int bs;
-  FILE *file;
 
   do {
     printf("Enter command: ");
@@ -57,43 +85,22 @@ int main(int argc, char **argv) {
 
     switch (cmd) {
       case ADD:
-        if (todos_count + 1 > MAX_TODOS) {
+        if (llist_length(todos) + 1 > MAX_TODOS) {
           printf("No more space for new todos\n");
           break;
         }
         add_command_handler();
         break;
       case MARK:
-        do {
-          printf("Enter todo index: ");
-          op_index = getc(stdin) - '0';
-          getc(stdin); // remove the newline character from the buffer
-        } while (op_index < 0 || op_index >= todos_count);
-        todo_mark_item(&todos[op_index], !todos[op_index].completed);
+        mark_command_handler();
         break;
       case PRINT:
-        print_all_todos();
+        print_command_handler();
         break;
       case REMOVE:
-        do {
-          printf("Enter todo index: ");
-          op_index = getc(stdin) - '0';
-          getc(stdin); // remove the newline character from the buffer
-        } while (op_index < 0 || op_index >= todos_count);
-        remove_todo_at_index(op_index);
-      case SERIALIZE:
-        file = fopen(SAVE_FILE, "wb");
-        // write a magic value "TODD" to the file
-        fwrite("TODD", sizeof(char), 4, file);
-        // write the number of todos to the file
-        fwrite(&todos_count, sizeof(int), 1, file);
-        // write each todo to the file
-        for (int i = 0; i < todos_count; i++) {
-          char *buffer = todo_item_serialize(&todos[i], &bs);
-          fwrite(buffer, sizeof(char), bs, file);
-          free(buffer);
-        }
-        fclose(file);
+        break;
+      case WRITE_TO_FILE:
+        write_to_file_handler();
         break;
       case QUIT:
         break;
@@ -104,7 +111,11 @@ int main(int argc, char **argv) {
 
   } while (cmd != QUIT);
 
+  // free all the todos
+  int todos_count = llist_length(todos);
+
   for (int i = 0; i < todos_count; i++) {
-    todo_free_item(&todos[i]);
+    todo_free_item(todos[i]->item);
+    llist_pop(todos);
   }
 }