Initial import

third_party/dlmalloc/dlmalloc-usable.c

@@ -0,0 +1,10 @@
+#include "libc/mem/mem.h"
+#include "third_party/dlmalloc/dlmalloc.h"
+
+size_t dlmalloc_usable_size(const void* mem) {
+  if (mem != 0) {
+    mchunkptr p = mem2chunk(mem);
+    if (is_inuse(p)) return chunksize(p) - overhead_for(p);
+  }
+  return 0;
+}