Add simple static arena allocator

src/sarena.c

@@ -0,0 +1,30 @@
+#include <assert.h>
+#include "ucore/sarena.h"
+
+void *uc_sar_alloc(UCSArena *a, size_t sz)
+{
+    if (a->curr + sz > a->end) {
+        return NULL;
+    }
+    void *start = a->curr;
+    a->curr += sz;
+    return start;
+}
+
+void *uc_sar_alloc_aligned(UCSArena *a, size_t sz, unsigned int align)
+{
+    assert(align != 0);
+    assert((align & (align - 1)) == 0); //power of 2
+
+    uintptr_t curr = (uintptr_t)a->curr;
+    uintptr_t aligned = (curr + (align - (uintptr_t)1)) & ~(align - (uintptr_t)1);
+    char *start = (char *)aligned;
+
+     if (start + sz > a->end) {
+        return NULL;
+     }
+
+     a->curr = start + sz;
+
+     return start;
+}