1 /* Copyright 2015 The TensorFlow Authors. All Rights Reserved.
2
3 Licensed under the Apache License, Version 2.0 (the "License");
4 you may not use this file except in compliance with the License.
5 You may obtain a copy of the License at
6
7 http://www.apache.org/licenses/LICENSE-2.0
8
9 Unless required by applicable law or agreed to in writing, software
10 distributed under the License is distributed on an "AS IS" BASIS,
11 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 See the License for the specific language governing permissions and
13 limitations under the License.
14 ==============================================================================*/
15
16 #include "tensorflow/core/lib/io/table.h"
17
18 #include "tensorflow/core/lib/core/coding.h"
19 #include "tensorflow/core/lib/core/errors.h"
20 #include "tensorflow/core/lib/io/block.h"
21 #include "tensorflow/core/lib/io/format.h"
22 #include "tensorflow/core/lib/io/table_options.h"
23 #include "tensorflow/core/lib/io/two_level_iterator.h"
24 #include "tensorflow/core/platform/env.h"
25
26 namespace tensorflow {
27 namespace table {
28
29 struct Table::Rep {
~Reptensorflow::table::Table::Rep30 ~Rep() { delete index_block; }
31
32 Options options;
33 Status status;
34 RandomAccessFile* file;
35 // XXX uint64 cache_id;
36
37 BlockHandle metaindex_handle; // Handle to metaindex_block: saved from footer
38 Block* index_block;
39 };
40
Open(const Options & options,RandomAccessFile * file,uint64 size,Table ** table)41 Status Table::Open(const Options& options, RandomAccessFile* file, uint64 size,
42 Table** table) {
43 *table = nullptr;
44 if (size < Footer::kEncodedLength) {
45 return errors::DataLoss("file is too short to be an sstable");
46 }
47
48 char footer_space[Footer::kEncodedLength];
49 StringPiece footer_input;
50 Status s = file->Read(size - Footer::kEncodedLength, Footer::kEncodedLength,
51 &footer_input, footer_space);
52 if (!s.ok()) return s;
53
54 Footer footer;
55 s = footer.DecodeFrom(&footer_input);
56 if (!s.ok()) return s;
57
58 // Read the index block
59 BlockContents contents;
60 Block* index_block = nullptr;
61 if (s.ok()) {
62 s = ReadBlock(file, footer.index_handle(), &contents);
63 if (s.ok()) {
64 index_block = new Block(contents);
65 }
66 }
67
68 if (s.ok()) {
69 // We've successfully read the footer and the index block: we're
70 // ready to serve requests.
71 Rep* rep = new Table::Rep;
72 rep->options = options;
73 rep->file = file;
74 rep->metaindex_handle = footer.metaindex_handle();
75 rep->index_block = index_block;
76 // XXX rep->cache_id = (options.block_cache ?
77 // options.block_cache->NewId() : 0);
78 *table = new Table(rep);
79 } else {
80 if (index_block) delete index_block;
81 }
82
83 return s;
84 }
85
~Table()86 Table::~Table() { delete rep_; }
87
DeleteBlock(void * arg,void * ignored)88 static void DeleteBlock(void* arg, void* ignored) {
89 delete reinterpret_cast<Block*>(arg);
90 }
91
92 // Convert an index iterator value (i.e., an encoded BlockHandle)
93 // into an iterator over the contents of the corresponding block.
BlockReader(void * arg,const StringPiece & index_value)94 Iterator* Table::BlockReader(void* arg, const StringPiece& index_value) {
95 Table* table = reinterpret_cast<Table*>(arg);
96 // Cache* block_cache = table->rep_->options.block_cache;
97 Block* block = nullptr;
98 // Cache::Handle* cache_handle = NULL;
99
100 BlockHandle handle;
101 StringPiece input = index_value;
102 Status s = handle.DecodeFrom(&input);
103 // We intentionally allow extra stuff in index_value so that we
104 // can add more features in the future.
105
106 if (s.ok()) {
107 BlockContents contents;
108 s = ReadBlock(table->rep_->file, handle, &contents);
109 if (s.ok()) {
110 block = new Block(contents);
111 }
112 }
113
114 Iterator* iter;
115 if (block != nullptr) {
116 iter = block->NewIterator();
117 iter->RegisterCleanup(&DeleteBlock, block, nullptr);
118 } else {
119 iter = NewErrorIterator(s);
120 }
121 return iter;
122 }
123
NewIterator() const124 Iterator* Table::NewIterator() const {
125 return NewTwoLevelIterator(rep_->index_block->NewIterator(),
126 &Table::BlockReader, const_cast<Table*>(this));
127 }
128
InternalGet(const StringPiece & k,void * arg,void (* saver)(void *,const StringPiece &,const StringPiece &))129 Status Table::InternalGet(const StringPiece& k, void* arg,
130 void (*saver)(void*, const StringPiece&,
131 const StringPiece&)) {
132 Status s;
133 Iterator* iiter = rep_->index_block->NewIterator();
134 iiter->Seek(k);
135 if (iiter->Valid()) {
136 Iterator* block_iter = BlockReader(this, iiter->value());
137 block_iter->Seek(k);
138 if (block_iter->Valid()) {
139 (*saver)(arg, block_iter->key(), block_iter->value());
140 }
141 s = block_iter->status();
142 delete block_iter;
143 }
144 if (s.ok()) {
145 s = iiter->status();
146 }
147 delete iiter;
148 return s;
149 }
150
ApproximateOffsetOf(const StringPiece & key) const151 uint64 Table::ApproximateOffsetOf(const StringPiece& key) const {
152 Iterator* index_iter = rep_->index_block->NewIterator();
153 index_iter->Seek(key);
154 uint64 result;
155 if (index_iter->Valid()) {
156 BlockHandle handle;
157 StringPiece input = index_iter->value();
158 Status s = handle.DecodeFrom(&input);
159 if (s.ok()) {
160 result = handle.offset();
161 } else {
162 // Strange: we can't decode the block handle in the index block.
163 // We'll just return the offset of the metaindex block, which is
164 // close to the whole file size for this case.
165 result = rep_->metaindex_handle.offset();
166 }
167 } else {
168 // key is past the last key in the file. Approximate the offset
169 // by returning the offset of the metaindex block (which is
170 // right near the end of the file).
171 result = rep_->metaindex_handle.offset();
172 }
173 delete index_iter;
174 return result;
175 }
176
177 } // namespace table
178 } // namespace tensorflow
179