From d394e4fa3411d8827255532cc83399f3dc3401ad Mon Sep 17 00:00:00 2001
From: Ivar Fatland <fatland99@hotmail.com>
Date: Mon, 6 Oct 2025 19:52:20 +0200
Subject: [PATCH] complete buffer allocator

---
 buffer_allocator.c      | 17 +++++++++++------
 test_buffer_allocator.c | 39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 6 deletions(-)
 create mode 100644 test_buffer_allocator.c

diff --git a/buffer_allocator.c b/buffer_allocator.c
index daaca94..088fb54 100644
--- a/buffer_allocator.c
+++ b/buffer_allocator.c
@@ -11,12 +11,16 @@ void *buffer_allocator_alloc(buffer_allocator_t *this, size_t bytes) {
 }
 
 void *buffer_allocator_resize(buffer_allocator_t *this, void *old_ptr, size_t bytes) {
-    // TODO: check if the pointer is even in the buffer?
     void *new_ptr = buffer_allocator_alloc(this, bytes);
     if (new_ptr == NULL) {
         return NULL;
     }
-    // TODO: copy over data
+    for (size_t i = 0; i < bytes; i++) {
+        unsigned char *new_ptr_b = (unsigned char *)new_ptr;
+        unsigned char *old_ptr_b = (unsigned char *)old_ptr;
+        new_ptr_b[i] = old_ptr_b[i];
+    }
+    return new_ptr;
 }
 
 void buffer_allocator_reset(buffer_allocator_t *this) {
@@ -30,12 +34,9 @@ static void *buffer_alloc(void *this, size_t bytes, const char *file, int line)
 }
 
 static void *buffer_resize(void *this, void *old_ptr, size_t bytes, const char *file, int line) {
-    (void)old_ptr;
     (void)file;
     (void)line;
-
-    // TODO: do the concrete implementation first!
-    void *new_ptr = buffer_allocator_alloc((buffer_allocator_t *)this, bytes);
+    return buffer_allocator_resize(this, old_ptr, bytes);
 }
 
 static void buffer_free(void *this, void *ptr, const char *file, int line) {
@@ -52,4 +53,8 @@ static const allocator_vtbl_t buffer_vtbl = {
 };
 
 allocator_t buffer_allocator_interface(buffer_allocator_t *this) {
+    return (allocator_t) {
+        .this=this,
+        .vtbl=&buffer_vtbl,
+    };
 }
diff --git a/test_buffer_allocator.c b/test_buffer_allocator.c
new file mode 100644
index 0000000..8ea700d
--- /dev/null
+++ b/test_buffer_allocator.c
@@ -0,0 +1,39 @@
+#include <criterion/criterion.h>
+#include "allocator.h"
+
+static void test_buffer_alloc(buffer_allocator_t impl) {
+    allocator_t inter = buffer_allocator_interface(&impl);
+    const int n_ints = 100;
+    int *ints = allocator_alloc(inter, sizeof(int) * n_ints);
+    for (int i = 0; i < n_ints; i++) {
+        ints[i] = i;
+    }
+    for (int i = 0; i < n_ints; i++) {
+        cr_assert_eq(ints[i], i);
+    }
+    cr_assert_eq(impl.size, sizeof(int)*n_ints);
+    ints = allocator_alloc(inter, sizeof(int) * n_ints);
+    for (int i = 0; i < n_ints; i++) {
+        ints[i] = i;
+    }
+    for (int i = 0; i < n_ints; i++) {
+        cr_assert_eq(ints[i], i);
+    }
+    cr_assert_eq(impl.size, sizeof(int)*2*n_ints);
+    allocator_free(inter, ints);
+    size_t remaining_bytes = impl.capacity - impl.size;
+    size_t double_remaining_bytes = 2 * remaining_bytes;
+    void *should_be_null = allocator_resize(inter, ints, double_remaining_bytes);
+    cr_assert_eq(should_be_null, NULL);
+    size_t double_ints = ((size_t) n_ints) * 2;
+    void *should_be_addr = allocator_resize(inter, ints, double_ints);
+    cr_assert_neq(should_be_addr, NULL);
+    buffer_allocator_reset(&impl);
+}
+
+Test(buffer_allocator, test) {
+    buffer_allocator_t impl = buffer_allocator_create(MB);
+    test_buffer_alloc(impl);
+    cr_assert_eq(impl.size, 0);
+    test_buffer_alloc(impl);
+}