fix: minor formatting

ds_*ll_insert -> ds_*ll_append to better reflect what it does and there
is now ds_*ll_add to add data anywhere in the ll.

.gitignore

@@ -1 +1,3 @@
 test
+.cache
+compile_commands.json

README.md

@@ -8,8 +8,8 @@ Example of working with a singly linked list (sll):
 char *a = "one";
 char *b = "two";
 ds_sll_t *ll = ds_sll_init();
-ds_sll_insert(ll, a); // [ "one" ]
+ds_sll_append(ll, a); // [ "one" ]
-ds_sll_insert(ll, b); // [ "one", "two" ]
+ds_sll_append(ll, b); // [ "one", "two" ]
 ds_ll_foreach(ds_sll_t, ll) {
     puts(cur->data);
     // one
@@ -45,6 +45,20 @@ ds_hmp_free(&hmp, NULL);
 free(b);
 ```
 
+## Stack
+```c
+char *a = "a";
+char *b = "b";
+
+ds_stack_t *stack = ds_stack_init();
+ds_stack_push(stack, a); // [ "a" ]
+ds_stack_push(stack, b); // [ "b", "a" ]
+ds_stack_peek(stack, 0); // "b"
+ds_stack_pop(stack); // "b"
+ds_stack_pop(stack); // "a"
+free(stack);
+```
+
 # TODO
 - [ ] more data structures
 - [x] tests

ds.c

@@ -40,7 +40,67 @@ ds_dll_t
 }
 
 int
-ds_sll_insert(ds_sll_t *ll, void *data)
+ds_sll_add(ds_sll_t **ll, void *data, unsigned x)
+{
+  int i;
+  ds_sll_t *cur, *prev, *new;
+  if (!ll || !data) {
+    return -1;
+  }
+
+  for (i = 0, cur = *ll; cur; prev = cur, cur = cur->next, i++) {
+    if (i == x) {
+      if (!cur->data) {
+        cur->data = data;
+        return 0;
+      }
+      new = ds_sll_new_node(data);
+      new->next = cur;
+      if (i == 0) {
+        *ll = new;
+      } else {
+        prev->next = new;
+      }
+      return 0;
+    }
+  }
+
+  return -1;
+}
+
+int
+ds_dll_add(ds_dll_t **ll, void *data, unsigned x)
+{
+  int i;
+  ds_dll_t *cur, *new;
+  if (!ll || !data) {
+    return -1;
+  }
+
+  for (i = 0, cur = *ll; cur; cur = cur->next, i++) {
+    if (i == x) {
+      if (!cur->data) {
+        cur->data = data;
+        return 0;
+      }
+      new = ds_dll_new_node(data);
+      new->next = cur;
+      new->prev = cur->prev;
+      cur->prev = new;
+      if (i == 0) {
+        *ll = new;
+      } else {
+        cur->prev->next = new;
+      }
+      return 0;
+    }
+  }
+
+  return -1;
+}
+
+int
+ds_sll_append(ds_sll_t *ll, void *data)
 {
   if (!ll || !data) {
     return -1;
@@ -60,7 +120,7 @@ ds_sll_insert(ds_sll_t *ll, void *data)
 }
 
 int
-ds_dll_insert(ds_dll_t *ll, void *data)
+ds_dll_append(ds_dll_t *ll, void *data)
 {
   if (!ll || !data) {
     return -1;
@@ -241,7 +301,7 @@ ds_hmp_insert(ds_hmp_t *hmp, char *key, void *data)
 
   /* get the ll and put the data into it */
   ll = hmp->data[hash_pos];
-	if (ds_sll_insert(ll, kv) != 0) {
+  if (ds_sll_append(ll, kv) != 0) {
     return -1;
   }
 
@@ -307,3 +367,56 @@ void
 
   return NULL;
 }
+
+ds_stack_t
+*ds_stack_init(void)
+{
+  ds_stack_t *stack = malloc(sizeof(ds_stack_t));
+  stack->n = 0;
+
+  return stack;
+}
+
+int
+ds_stack_push(ds_stack_t *stack, void *data)
+{
+  if (stack->n == 0) {
+    stack->items = ds_sll_new_node(data);
+    stack->n++;
+    return 0;
+  }
+  int r = ds_sll_add(&stack->items, data, 0);
+  if (!r) {
+    stack->n++;
+  }
+  return r;
+}
+
+void
+*ds_stack_pop(ds_stack_t *stack)
+{
+  void *r = ds_sll_remove(&stack->items, 0);
+  if (r != NULL) {
+    stack->n--;
+  }
+  return r;
+}
+
+void
+*ds_stack_peek(ds_stack_t *stack, unsigned x)
+{
+  int i;
+  ds_sll_t *cur;
+
+  if (x > stack->n) {
+    return NULL;
+  }
+
+  for (cur = stack->items, i = 0; cur; cur = cur->next, i++) {
+    if (i == x) {
+      return cur->data;
+    }
+  }
+
+  return NULL;
+}

ds.h

@@ -22,6 +22,11 @@ typedef struct {
   void *val;
 } _ds_hmp_kv_t;
 
+typedef struct {
+  unsigned  n;
+  ds_sll_t *items;
+} ds_stack_t;
+
 #define ds_ll_foreach(t, ll) for (t *cur = ll; cur; cur = cur->next)
 
 /**
@@ -55,24 +60,46 @@ ds_sll_t *ds_sll_new_node(void *data);
 ds_dll_t *ds_dll_new_node(void *data);
 
 /**
- * @brief data to insert into a singly linked list. This will use
+ * @brief data to add at x of a singly linked list. This will use
  * ds_sll_new_node to create the node for you.
  *
  * @param ll singly linked list
  * @param data data you want to add
+ * @param x the position to add it at
  * @return 0 on success
  */
-int ds_sll_insert(ds_sll_t *ll, void *data);
+int ds_sll_add(ds_sll_t **ll, void *data, unsigned x);
 
 /**
- * @brief data to insert into a doubly linked list. This will use
+ * @brief data to add at x of a doubly linked list. This will use
- * ds_sll_new_node to create the node for you.
+ * ds_dll_new_node to create the node for you.
  *
  * @param ll doubly linked list
  * @param data data you want to add
+ * @param x the position to add it at
  * @return 0 on success
  */
-int ds_dll_insert(ds_dll_t *ll, void *data);
+int ds_dll_add(ds_dll_t **ll, void *data, unsigned x);
+
+/**
+ * @brief data to append to the end of a singly linked list. This will use
+ * ds_sll_new_node to create the node for you.
+ *
+ * @param ll singly linked list
+ * @param data data you want to append
+ * @return 0 on success
+ */
+int ds_sll_append(ds_sll_t *ll, void *data);
+
+/**
+ * @brief data to append to the end of a doubly linked list. This will use
+ * ds_dll_new_node to create the node for you.
+ *
+ * @param ll doubly linked list
+ * @param data data you want to append
+ * @return 0 on success
+ */
+int ds_dll_append(ds_dll_t *ll, void *data);
 
 /**
  * @brief remove an index from a singly linked list
@@ -146,4 +173,37 @@ void *ds_hmp_get(ds_hmp_t *hmp, char *key);
  */
 void *ds_hmp_remove(ds_hmp_t *hmp, char *key);
 
+/**
+ * @brief initialize a new stack
+ *
+ * @return the stack
+ */
+ds_stack_t *ds_stack_init(void);
+
+/**
+ * @brief push new data onto the stack
+ *
+ * @param stack the stack
+ * @param data the data
+ * @return 0 on success
+ */
+int ds_stack_push(ds_stack_t *stack, void *data);
+
+/**
+ * @brief pop the data off the top of the stack
+ *
+ * @param stack the stack
+ * @return the data
+ */
+void *ds_stack_pop(ds_stack_t *stack);
+
+/**
+ * @brief peek forward x items
+ *
+ * @param stack the stack
+ * @param x how many items to look ahead
+ * @return the data or NULL if out of range
+ */
+void *ds_stack_peek(ds_stack_t *stack, unsigned x);
+
 #endif

test.c

@@ -1,3 +1,4 @@
+#include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -16,7 +17,8 @@
 #define it(message, test) do {                                                 \
   _tests++;                                                                    \
   if (!(test)) {                                                               \
-		printf("%s %s FAILED\n", _test_name, message);	\
+    printf("%s %s FAILED @ %s:%d\n", _test_name, message, __FILE__, __LINE__); \
+    printf(" -> test condition: (%s)\n", #test);                               \
     _tests_passed--;                                                           \
   }                                                                            \
 } while (0)
@@ -30,29 +32,35 @@ int
 main(int argc, char *argv[])
 {
   test("sll",
-		char *a = "one";
+    char *a = "a";
+    char *b = "b";
 
     ds_sll_t *tmp;
-		it("ensures creates a new linked list", tmp = ds_sll_init());
+    it("creates a new linked list", tmp = ds_sll_init());
     free(tmp);
 
     ds_sll_t *ll = ds_sll_new_node(a);
-		it("inserts an invalid item", ds_sll_insert(ll, NULL) == -1);
+    it("appends an invalid item", ds_sll_append(ll, NULL) == -1);
     it("removes an invalid index", ds_sll_remove(&ll, 1234) == NULL);
-		it("removes an item", a == ds_sll_remove(&ll, 0));
+    it("adds an item to the beginning", ds_sll_add(&ll, b, 0) == 0);
+    it("removes an item", b == ds_sll_remove(&ll, 0));
+    ds_sll_remove(&ll, 0);
   );
 
   test("dll",
-		char *a = "one";
+    char *a = "a";
+    char *b = "b";
 
     ds_dll_t *tmp;
-		it("ensures creates a new linked list", tmp = ds_dll_init());
+    it("creates a new linked list", tmp = ds_dll_init());
     free(tmp);
 
     ds_dll_t *ll = ds_dll_new_node(a);
-		it("inserts an invalid item", ds_dll_insert(ll, NULL) == -1);
+    it("appends an invalid item", ds_dll_append(ll, NULL) == -1);
     it("removes an invalid index", ds_dll_remove(&ll, 1234) == NULL);
-		it("removes an item", a == ds_dll_remove(&ll, 0));
+    it("adds an item to the beginning", ds_dll_add(&ll, b, 0) == 0);
+    it("removes an item", b == ds_dll_remove(&ll, 0));
+    ds_dll_remove(&ll, 0);
   );
 
   test("hmp",
@@ -70,4 +78,25 @@ main(int argc, char *argv[])
 
     free(a);
   );
+
+  test("stack",
+    char *a = "a";
+    char *b = "b";
+    char *c = "c";
+
+    ds_stack_t *stack = ds_stack_init();
+    it("pushes an item", ds_stack_push(stack, a) == 0);
+    it("pops an item", ds_stack_pop(stack) == a);
+
+    ds_stack_push(stack, b);
+    ds_stack_push(stack, c);
+
+    it("peeks ahead", ds_stack_peek(stack, 0) == c);
+    it("peeks past the stack", ds_stack_peek(stack, INT_MAX) == NULL);
+
+    ds_stack_pop(stack);
+    ds_stack_pop(stack);
+
+    free(stack);
+  );
 }