From eea2fc997205899bb994c3389affcca7031933be Mon Sep 17 00:00:00 2001
From: Adam Paszke <adam.paszke@gmail.com>
Date: Mon, 18 Apr 2016 20:57:23 +0200
Subject: Add general methods for pointer serialization in sharedserialize

---
 sharedserialize.lua | 43 +++++++++++++++++++++++++++----------------
 1 file changed, 27 insertions(+), 16 deletions(-)

diff --git a/sharedserialize.lua b/sharedserialize.lua
index 9cd8ebf..17d18b6 100644
--- a/sharedserialize.lua
+++ b/sharedserialize.lua
@@ -1,23 +1,43 @@
 require 'torch'
+local ffi = require 'ffi'
 
 local serialize = {}
 local typenames = {}
 
+local function serializePointer(obj, f)
+   -- on 32-bit systems double can represent all possible
+   -- pointer values, but signed long can't
+   if ffi.sizeof('long') == 4 then
+      f:writeDouble(torch.pointer(obj))
+   -- on 64-bit systems, long can represent a larger
+   -- range of integers than double, so it's safer to use this
+   else
+      f:writeLong(torch.pointer(obj))
+   end
+end
+
+local function deserializePointer(f)
+   if ffi.sizeof('long') == 4 then
+      return f:readDouble()
+   else
+      return f:readLong()
+   end
+end
+
 -- tds support
 local _, tds = pcall(require, 'tds') -- for the free/retain functions
 if tds then
-   local ffi = require 'ffi'
 
    -- hash
    local mt = {}
    function mt.__factory(f)
-      local self = f:readLong()
+      local self = deserializePointer(f)
       self = ffi.cast('tds_hash&', self)
       ffi.gc(self, tds.C.tds_hash_free)
       return self
    end
    function mt.__write(self, f)
-      f:writeLong(torch.pointer(self))
+      serializePointer(self, f)
       tds.C.tds_hash_retain(self)
    end
    function mt.__read(self, f)
@@ -27,22 +47,13 @@ if tds then
    -- vec
    local mt = {}
    function mt.__factory(f)
-      local self
-      if ffi.sizeof('long') == 4 then
-         self = f:readDouble()
-      else
-         self = f:readLong()
-      end
+      local self = deserializePointer(f)
       self = ffi.cast('tds_vec&', self)
       ffi.gc(self, tds.C.tds_vec_free)
       return self
    end
    function mt.__write(self, f)
-      if ffi.sizeof('long') == 4 then
-         f:writeDouble(torch.pointer(self))
-      else
-         f:writeLong(torch.pointer(self))
-      end
+      serializePointer(self, f)
       tds.C.tds_vec_retain(self)
    end
    function mt.__read(self, f)
@@ -73,13 +84,13 @@ for _, typename in ipairs{
    local mt = {}
 
    function mt.__factory(f)
-      local self = f:readLong()
+      local self = deserializePointer(f)
       self = torch.pushudata(self, typename)
       return self
    end
 
    function mt.write(self, f)
-      f:writeLong(torch.pointer(self))
+      serializePointer(self, f)
       if typename ~= 'torch.Allocator' then
          self:retain()
       end
-- 
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