return old values when inserting or removing from hashmap

5 files changed, 84 insertions, 18 deletions

diff --git a/.vscode/settings.json b/.vscode/settings.json
new file mode 100644
index 0000000..420aa6e
--- /dev/null
+++ b/.vscode/settings.json
@@ -0,0 +1,13 @@
+{
+    "files.associations": {
+        "cstdio": "cpp",
+        "mpc.h": "c",
+        "stdio.h": "c",
+        "typeinfo": "c",
+        "template.h": "c",
+        "test.h": "c",
+        "stdlib.h": "c",
+        "list": "c",
+        "hashmap.h": "c"
+    }
+}
\ No newline at end of file
diff --git a/src/hashmap.c b/src/hashmap.c
index 6797475..f99ba4c 100644
--- a/src/hashmap.c
+++ b/src/hashmap.c
@@ -22,16 +22,18 @@ struct hashmap *hashmap_new() {
     return hm;
 }
 
-/* insert key-value into hashmap */
-void hashmap_insert(struct hashmap *hm, char *key, void *value) {
+/* Inserts a key-value pair into the map. Returns NULL if map did not have key, old value if it did. */
+void *hashmap_insert(struct hashmap *hm, char *key, void *value) {
     int pos = HASH(key);
     struct node *head = hm->buckets[pos];
     struct node *node = head;
+    void *old_value;
 
     while (node) {
         if (strcmp(node->key, key) == 0) {
+            old_value = node->value;
             node->value = value;
-            return;
+            return old_value;
         }
         node = node->next;
     }
@@ -41,9 +43,10 @@ void hashmap_insert(struct hashmap *hm, char *key, void *value) {
     node->value = value;
     node->next = head;
     hm->buckets[pos] = node;
+    return NULL;
 }
 
-/* retrieve value by key */
+/* Returns a pointer to the value corresponding to the key. */
 void *hashmap_get(struct hashmap *hm, char *key) {
     int pos = HASH(key);
     struct node *node = hm->buckets[pos];
@@ -58,7 +61,7 @@ void *hashmap_get(struct hashmap *hm, char *key) {
     return NULL;
 }
 
-/* retrieve value by key, handles dot notation for nested hashmaps */
+/* Retrieve pointer to value by key, handles dot notation for nested hashmaps */
 void *hashmap_resolve(struct hashmap *hm, char *key) {
     char tmp_key[64];
     int i = 0;
@@ -83,8 +86,30 @@ void *hashmap_resolve(struct hashmap *hm, char *key) {
     return hm;
 }
 
-void hashmap_remove(char *key) {
-    // TODO: Implement this
+/* Removes a key from the map, returning the value at the key if the key was previously in the map. */
+void *hashmap_remove(struct hashmap *hm, char *key) {
+    int pos = HASH(key);
+    struct node *node = hm->buckets[pos];
+    struct node *prev = NULL;
+    void *old_value;
+
+    while (node) {
+        if (strcmp(node->key, key) == 0) {
+            if (prev) {
+                prev->next = node->next;
+            } else {
+                hm->buckets[pos] = node->next;
+            }
+            old_value = node->value;
+            free(node);            
+            return old_value;
+        }
+
+        node = node->next;
+        prev = node;
+    }
+
+    return NULL;
 }
 
 /* free hashmap related memory */
diff --git a/src/hashmap.h b/src/hashmap.h
index 369f594..be2b80e 100644
--- a/src/hashmap.h
+++ b/src/hashmap.h
@@ -4,9 +4,9 @@ struct hashmap {
     struct node *buckets[HASHMAP_CAP];
 };
 
-void hashmap_insert(struct hashmap *hm, char *key, void *value);
-void *hashmap_get(struct hashmap *hm, char *key);
-void hashmap_remove(char *key);
 struct hashmap *hashmap_new();
-void hashmap_free(struct hashmap *hm);
-void *hashmap_resolve(struct hashmap *hm, char *key);
\ No newline at end of file
+void *hashmap_insert(struct hashmap *hm, char *key, void *value);
+void *hashmap_get(struct hashmap *hm, char *key);
+void *hashmap_resolve(struct hashmap *hm, char *key);
+void *hashmap_remove(struct hashmap *hm, char *key);
+void hashmap_free(struct hashmap *hm);
\ No newline at end of file
diff --git a/tests/test.h b/tests/test.h
index f860ee2..7a82d08 100644
--- a/tests/test.h
+++ b/tests/test.h
@@ -6,6 +6,8 @@
 #define START_TESTS int main() {
 #define END_TESTS }
 #define TEST(name) strcpy(current_test, #name);
+#define assert_null(actual) _assert(actual == NULL, __FILE__, __LINE__, "invalid value: expected NULL, got %s", actual)
+
 #define assert_str(actual, expected) _assert(actual != NULL && strcmp(actual, expected) == 0, __FILE__, __LINE__, "invalid string: expected %s, got %s", expected, actual)
 #define assert(assertion, format, ...) _assert(assertion, __FILE__, __LINE__, format, ##__VA_ARGS__)
 #define ARRAY_SIZE(arr) sizeof arr / sizeof arr[0]
diff --git a/tests/test_hashmap.c b/tests/test_hashmap.c
index 14ec552..82f340c 100644
--- a/tests/test_hashmap.c
+++ b/tests/test_hashmap.c
@@ -5,23 +5,49 @@ START_TESTS
 
 TEST(hashmap) {
     struct hashmap *hm = hashmap_new();
-    assert(hashmap_get(hm, "foo") == NULL, "expected NULL");
-    hashmap_insert(hm, "foo", "bar");
     char *value = hashmap_get(hm, "foo");
+    assert_null(value);
+    value = hashmap_insert(hm, "foo", "bar");
+    assert_null(value);
+    value = hashmap_get(hm, "foo");
     assert_str(value, "bar");
     hashmap_free(hm);
 } 
 
 TEST(dot_notation) {
+    void *val;
     struct hashmap *user = hashmap_new();
-    hashmap_insert(user, "name", "Danny");
+    val = hashmap_insert(user, "name", "Danny");
+    assert_null(val);
     struct hashmap *hm = hashmap_new();
-    hashmap_insert(hm, "user", user);
+    val = hashmap_insert(hm, "user", user);
+    assert_null(val);
     assert(hashmap_resolve(hm, "user") == user, "expected user hashmap, got something else");
-    char *value = (char *) hashmap_resolve(hm, "user.name");
-    assert_str(value, "Danny");
+    val = hashmap_resolve(hm, "user.name");
+    assert_str(val, "Danny");
     hashmap_free(user);
     hashmap_free(hm);
 } 
 
+TEST(hashmap_remove) {
+    struct hashmap *hm = hashmap_new();
+    hashmap_insert(hm, "foo", "bar");
+    char *value = hashmap_get(hm, "foo");
+    assert_str(value, "bar");
+
+    // remove once
+    value = hashmap_remove(hm, "foo");
+    assert_str(value, "bar");
+    value = hashmap_get(hm, "foo");
+    assert_null(value);
+
+    // remove again (should no-op)
+    value = hashmap_remove(hm, "foo");
+    assert_null(value);
+    value = hashmap_get(hm, "foo");
+    assert_null(value);
+
+    hashmap_free(hm);
+} 
+
 END_TESTS
\ No newline at end of file