1 files changed, 199 insertions, 0 deletions
diff --git a/kit/allocator.c b/kit/allocator.c
new file mode 100644
index 0000000..9fd7bad
--- /dev/null
+++ b/kit/allocator.c
@@ -0,0 +1,199 @@
+#include "allocator.h"
+
+#include <assert.h>
+#include <string.h>
+
+#ifndef KIT_DISABLE_SYSTEM_MALLOC
+#  include <stdlib.h>
+#endif
+
+static void *kit_allocate_default_(i32 request, i64 size,
+                                   i64 previous_size, void *pointer) {
+#ifndef KIT_DISABLE_SYSTEM_MALLOC
+  switch (request) {
+    case KIT_ALLOCATE:
+    case KIT_ALLOCATE_ZERO: {
+      assert(size >= 0);
+      assert(previous_size == 0);
+      assert(pointer == NULL);
+
+      if (size <= 0)
+        return NULL;
+
+      void *p = malloc(size);
+
+      if (p != NULL && request == KIT_ALLOCATE_ZERO)
+        memset(p, 0, size);
+
+      return p;
+    }
+
+    case KIT_REALLOCATE:
+    case KIT_REALLOCATE_ZERO: {
+      assert(size >= 0);
+      assert(previous_size != 0 || pointer == NULL);
+      assert(previous_size == 0 || pointer != NULL);
+
+      if (previous_size == 0 && pointer != NULL)
+        return NULL;
+      if (previous_size != 0 && pointer == NULL)
+        return NULL;
+      if (size == previous_size)
+        return pointer;
+
+      u8 *p = NULL;
+
+      if (size > 0) {
+        p = (u8 *) malloc(size);
+
+        if (p != NULL) {
+          if (size > 0 && previous_size > 0)
+            memcpy(p, pointer,
+                   size < previous_size ? size : previous_size);
+          if (request == KIT_REALLOCATE_ZERO && size > previous_size)
+            memset(p + previous_size, 0, size - previous_size);
+        }
+      }
+
+      free(pointer);
+
+      return p;
+    }
+
+    case KIT_DEALLOCATE:
+      assert(size == 0);
+      assert(pointer != NULL);
+      if (pointer != NULL)
+        free(pointer);
+      return NULL;
+
+    case KIT_DEALLOCATE_ALL:
+      //  Do nothing.
+      //
+      return NULL;
+
+    default:;
+  }
+#endif
+
+  assert(0);
+  return NULL;
+}
+
+static void *kit_allocate_from_buffer_(kit_allocator_t *alloc,
+                                       i32 request, i64 size,
+                                       i64   previous_size,
+                                       void *pointer) {
+  assert(alloc != NULL);
+  assert(pointer == NULL || pointer < alloc->data);
+
+  if (alloc == NULL)
+    return NULL;
+
+  switch (request) {
+    case KIT_ALLOCATE:
+    case KIT_ALLOCATE_ZERO: {
+      assert(size >= 0);
+      assert(previous_size == 0);
+      assert(pointer == NULL);
+
+      if (size <= 0)
+        return NULL;
+
+      if (alloc->size < size)
+        return NULL;
+
+      void *p = alloc->data;
+      alloc->bytes += size;
+      alloc->size -= size;
+
+      if (request == KIT_ALLOCATE_ZERO)
+        memset(p, 0, size);
+
+      return p;
+    }
+
+    case KIT_REALLOCATE:
+    case KIT_REALLOCATE_ZERO: {
+      assert(size >= 0);
+      assert(previous_size != 0 || pointer == NULL);
+      assert(previous_size == 0 || pointer != NULL);
+
+      if (size <= 0)
+        return NULL;
+      if (size <= previous_size)
+        return pointer;
+      if (previous_size == 0 && pointer != NULL)
+        return NULL;
+      if (previous_size != 0 && pointer == NULL)
+        return NULL;
+
+      if ((u8 *) pointer + previous_size == alloc->data) {
+        if (alloc->size < size - previous_size)
+          return NULL;
+        alloc->bytes += size - previous_size;
+        alloc->size -= size - previous_size;
+        return pointer;
+      }
+
+      if (alloc->size < size)
+        return NULL;
+
+      u8 *p = alloc->bytes;
+      alloc->bytes += size;
+      alloc->size -= size;
+
+      if (previous_size > 0)
+        memcpy(p, pointer, previous_size);
+      if (request == KIT_REALLOCATE_ZERO)
+        memset(p + previous_size, 0, size - previous_size);
+
+      return p;
+    }
+
+    case KIT_DEALLOCATE:
+    case KIT_DEALLOCATE_ALL: return NULL;
+
+    default:;
+  }
+
+  assert(0);
+  return NULL;
+}
+
+#ifndef KIT_ENABLE_CUSTOM_ALLOC_DISPATCH
+void *kit_alloc_dispatch(kit_allocator_t *alloc, i32 request,
+                         i64 size, i64 previous_size, void *pointer) {
+  if (alloc == NULL)
+    return kit_allocate_default_(request, size, previous_size,
+                                 pointer);
+
+  switch (alloc->type) {
+    case KIT_ALLOC_TYPE_DEFAULT:
+      return kit_allocate_default_(request, size, previous_size,
+                                   pointer);
+
+    case KIT_ALLOC_TYPE_BUFFER:
+      return kit_allocate_from_buffer_(alloc, request,
+                                       //  alignment
+                                       ((size + 7) / 8) * 8,
+                                       previous_size, pointer);
+
+    default:;
+  }
+
+  return NULL;
+}
+#endif
+
+kit_allocator_t kit_alloc_default(void) {
+  return (kit_allocator_t) { .type = KIT_ALLOC_TYPE_DEFAULT,
+                             .size = 0,
+                             .data = NULL };
+}
+
+kit_allocator_t kit_alloc_buffer(i64 size, void *buffer) {
+  return (kit_allocator_t) { .type = KIT_ALLOC_TYPE_BUFFER,
+                             .size = size,
+                             .data = buffer };
+}