Fix T70952: EXR files bigger than 2GB don't open on Windows

1 files changed, 5 insertions, 2 deletions

diff --git a/intern/guardedalloc/intern/mmap_win.c b/intern/guardedalloc/intern/mmap_win.c
index 5b0c4b6614a..3508ae4e1aa 100644
--- a/intern/guardedalloc/intern/mmap_win.c
+++ b/intern/guardedalloc/intern/mmap_win.c
@@ -125,8 +125,11 @@ void *mmap(void *UNUSED(start), size_t len, int prot, int flags, int fd, off_t o
     }
   }
 
-  /* note len is passed to a 32 bit DWORD, so can't be > 4 GB */
-  maphandle = CreateFileMapping(fhandle, NULL, prot_flags, 0, len, NULL);
+  /* Split 64 bit size into low and high bits. */
+  DWORD len_bits_high = len >> 32;
+  DWORD len_bits_low = len & 0xFFFFFFFF;
+
+  maphandle = CreateFileMapping(fhandle, NULL, prot_flags, len_bits_high, len_bits_low, NULL);
   if (maphandle == 0) {
     errno = EBADF;
     return MAP_FAILED;