sync/internal_api/public/base/node_ordinal.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "sync/internal_api/public/base/node_ordinal.h"
   6
   7 #include <algorithm>
   8
   9 namespace syncer {
  10
  11 NodeOrdinal Int64ToNodeOrdinal(int64 x) {
  12   uint64 y = static_cast<uint64>(x);
  13   y ^= 0x8000000000000000ULL;
  14   std::string bytes(NodeOrdinal::kMinLength, '\x00');
  15   if (y == 0) {
  16     // 0 is a special case since |bytes| must not be all zeros.
  17     bytes.push_back('\x80');
  18   } else {
  19     for (int i = 7; i >= 0; --i) {
  20       bytes[i] = static_cast<uint8>(y);
  21       y >>= 8;
  22     }
  23   }
  24   NodeOrdinal ordinal(bytes);
  25   DCHECK(ordinal.IsValid());
  26   return ordinal;
  27 }
  28
  29 int64 NodeOrdinalToInt64(const NodeOrdinal& ordinal) {
  30   uint64 y = 0;
  31   const std::string& s = ordinal.ToInternalValue();
  32   size_t l = NodeOrdinal::kMinLength;
  33   if (s.length() < l) {
  34     NOTREACHED();
  35     l = s.length();
  36   }
  37   for (size_t i = 0; i < l; ++i) {
  38     const uint8 byte = s[l - i - 1];
  39     y |= static_cast<uint64>(byte) << (i * 8);
  40   }
  41   y ^= 0x8000000000000000ULL;
  42   // This is technically implementation-defined if y > INT64_MAX, so
  43   // we're assuming that we're on a twos-complement machine.
  44   return static_cast<int64>(y);
  45 }
  46
  47 }  // namespace syncer