1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
|
/*************************************************************************************************
* Example for serious use cases of the hash database
*
* Copyright 2020 Google LLC
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of the License at
* https://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software distributed under the
* License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
* either express or implied. See the License for the specific language governing permissions
* and limitations under the License.
*************************************************************************************************/
#include "tkrzw_cmd_util.h"
#include "tkrzw_dbm_hash.h"
// Main routine.
int main(int argc, char** argv) {
// All symbols of Tkrzw are under the namespace "tkrzw".
using namespace tkrzw;
// Creates the database manager.
HashDBM dbm;
// Tuning parameters.
// The update mode is in-place writing.
// Using a 4-byte integer for addressing.
// Using 3-bit = 8 byte unit alignment.
// Using 7 buckets for the hash table.
HashDBM::TuningParameters tuning_params;
tuning_params.update_mode = HashDBM::UPDATE_IN_PLACE;
tuning_params.offset_width = 4;
tuning_params.align_pow = 3;
tuning_params.num_buckets = 7;
// Opens a new database, OPEN_TRUNCATE means to clear the file content.
// The result is returned as a Status object.
Status status = dbm.OpenAdvanced(
"casket.tkh", true, File::OPEN_TRUNCATE, tuning_params);
if (status != Status::SUCCESS) {
// Failure of the Open operation is critical so we stop.
Die("Open failed: ", status);
}
// Stores records.
// Bit-or assignment to the status updates the status if the original
// state is SUCCESS and the new state is an error.
status |= dbm.Set("foo", "hop");
status |= dbm.Set("bar", "step");
status |= dbm.Set("baz", "jump");
if (status != Status::SUCCESS) {
// The Set operation shouldn't fail. So we stop if it happens.
Die("Set failed: ", status);
}
// Closes the database.
status = dbm.Close();
if (status != Status::SUCCESS) {
// The Close operation shouldn't fail. So we stop if it happens.
Die("Close failed: ", status);
}
// Opens the existing database as a reader mode.
status = dbm.Open("casket.tkh", false);
if (status != Status::SUCCESS) {
// Failure of the Open operation is critical so we stop.
Die("Open failed: ", status);
}
// Retrieves records.
// If there was no record, NOT_FOUND_ERROR would be returned.
std::string value;
status = dbm.Get("foo", &value);
if (status == Status::SUCCESS) {
std::cout << value << std::endl;
} else {
std::cerr << "missing: " << status << std::endl;
}
// Traverses records.
std::unique_ptr<DBM::Iterator> iter = dbm.MakeIterator();
if (iter->First() != Status::SUCCESS) {
// Failure of the First operation is critical so we stop.
Die("First failed: ", status);
}
while (true) {
// Retrieves the current record data.
std::string iter_key, iter_value;
status = iter->Get(&iter_key, &iter_value);
if (status == Status::SUCCESS) {
std::cout << iter_key << ":" << iter_value << std::endl;
} else {
// This happens at the end of iteration.
if (status != Status::NOT_FOUND_ERROR) {
// Error types other than NOT_FOUND_ERROR are critical.
Die("Iterator::Get failed: ", status);
}
break;
}
// Moves the iterator to the next record.
status = iter->Next();
if (status != Status::SUCCESS) {
// This could happen if another thread removed the current record.
if (status != Status::NOT_FOUND_ERROR) {
// Error types other than NOT_FOUND_ERROR are critical.
Die("Iterator::Get failed: ", status);
}
std::cerr << "missing: " << status << std::endl;
break;
}
}
// Closes the database.
// Even if you forgot to close it, the destructor would close it.
// However, checking the status is a good manner.
status = dbm.Close();
if (status != Status::SUCCESS) {
// The Close operation shouldn't fail. So we stop if it happens.
Die("Close failed: ", status);
}
return 0;
}
// END OF FILE
|
