OLD | NEW |
| (Empty) |
1 // Copyright 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 #ifndef SYNC_INTERNAL_API_PUBLIC_BASE_NODE_ORDINAL_H_ | |
6 #define SYNC_INTERNAL_API_PUBLIC_BASE_NODE_ORDINAL_H_ | |
7 | |
8 #include <stddef.h> | |
9 #include <stdint.h> | |
10 | |
11 #include "sync/base/sync_export.h" | |
12 #include "sync/internal_api/public/base/ordinal.h" | |
13 | |
14 namespace syncer { | |
15 | |
16 // A NodeOrdinal is an Ordinal whose internal value comes from the | |
17 // ordinal_in_parent field of SyncEntity (see sync.proto). It uses | |
18 // the entire uint8_t range for backwards compatibility with the old | |
19 // int64_t-based positioning. | |
20 | |
21 struct NodeOrdinalTraits { | |
22 static const uint8_t kZeroDigit = 0; | |
23 static const uint8_t kMaxDigit = UINT8_MAX; | |
24 static const size_t kMinLength = 8; | |
25 }; | |
26 | |
27 typedef Ordinal<NodeOrdinalTraits> NodeOrdinal; | |
28 | |
29 static_assert(static_cast<char>(NodeOrdinal::kZeroDigit) == '\x00', | |
30 "NodeOrdinal has incorrect zero digit"); | |
31 static_assert(static_cast<char>(NodeOrdinal::kOneDigit) == '\x01', | |
32 "NodeOrdinal has incorrect one digit"); | |
33 static_assert(static_cast<char>(NodeOrdinal::kMidDigit) == '\x80', | |
34 "NodeOrdinal has incorrect mid digit"); | |
35 static_assert(static_cast<char>(NodeOrdinal::kMaxDigit) == '\xff', | |
36 "NodeOrdinal has incorrect max digit"); | |
37 static_assert(NodeOrdinal::kMidDigitValue == 128, | |
38 "NodeOrdinal has incorrect mid digit value"); | |
39 static_assert(NodeOrdinal::kMaxDigitValue == 255, | |
40 "NodeOrdinal has incorrect max digit value"); | |
41 static_assert(NodeOrdinal::kRadix == 256, | |
42 "NodeOrdinal has incorrect radix"); | |
43 | |
44 // Converts an int64_t position (usually from the position_in_parent | |
45 // field of SyncEntity) to a NodeOrdinal. This transformation | |
46 // preserves the ordering relation: a < b under integer ordering if | |
47 // and only if Int64ToNodeOrdinal(a) < Int64ToNodeOrdinal(b). | |
48 SYNC_EXPORT NodeOrdinal Int64ToNodeOrdinal(int64_t x); | |
49 | |
50 // The inverse of Int64ToNodeOrdinal. This conversion is, in general, | |
51 // lossy: NodeOrdinals can have arbitrary fidelity, while numeric | |
52 // positions contain only 64 bits of information (in fact, this is the | |
53 // reason we've moved away from them). | |
54 SYNC_EXPORT int64_t NodeOrdinalToInt64(const NodeOrdinal& ordinal); | |
55 | |
56 } // namespace syncer | |
57 | |
58 #endif // SYNC_INTERNAL_API_PUBLIC_BASE_NODE_ORDINAL_H_ | |
OLD | NEW |