format.cc raw
1 // Copyright (c) 2011 The LevelDB 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. See the AUTHORS file for names of contributors.
4
5 #include "table/format.h"
6
7 #include "leveldb/env.h"
8 #include "port/port.h"
9 #include "table/block.h"
10 #include "util/coding.h"
11 #include "util/crc32c.h"
12
13 namespace leveldb {
14
15 void BlockHandle::EncodeTo(std::string* dst) const {
16 // Sanity check that all fields have been set
17 assert(offset_ != ~static_cast<uint64_t>(0));
18 assert(size_ != ~static_cast<uint64_t>(0));
19 PutVarint64(dst, offset_);
20 PutVarint64(dst, size_);
21 }
22
23 Status BlockHandle::DecodeFrom(Slice* input) {
24 if (GetVarint64(input, &offset_) && GetVarint64(input, &size_)) {
25 return Status::OK();
26 } else {
27 return Status::Corruption("bad block handle");
28 }
29 }
30
31 void Footer::EncodeTo(std::string* dst) const {
32 const size_t original_size = dst->size();
33 metaindex_handle_.EncodeTo(dst);
34 index_handle_.EncodeTo(dst);
35 dst->resize(2 * BlockHandle::kMaxEncodedLength); // Padding
36 PutFixed32(dst, static_cast<uint32_t>(kTableMagicNumber & 0xffffffffu));
37 PutFixed32(dst, static_cast<uint32_t>(kTableMagicNumber >> 32));
38 assert(dst->size() == original_size + kEncodedLength);
39 (void)original_size; // Disable unused variable warning.
40 }
41
42 Status Footer::DecodeFrom(Slice* input) {
43 const char* magic_ptr = input->data() + kEncodedLength - 8;
44 const uint32_t magic_lo = DecodeFixed32(magic_ptr);
45 const uint32_t magic_hi = DecodeFixed32(magic_ptr + 4);
46 const uint64_t magic = ((static_cast<uint64_t>(magic_hi) << 32) |
47 (static_cast<uint64_t>(magic_lo)));
48 if (magic != kTableMagicNumber) {
49 return Status::Corruption("not an sstable (bad magic number)");
50 }
51
52 Status result = metaindex_handle_.DecodeFrom(input);
53 if (result.ok()) {
54 result = index_handle_.DecodeFrom(input);
55 }
56 if (result.ok()) {
57 // We skip over any leftover data (just padding for now) in "input"
58 const char* end = magic_ptr + 8;
59 *input = Slice(end, input->data() + input->size() - end);
60 }
61 return result;
62 }
63
64 Status ReadBlock(RandomAccessFile* file, const ReadOptions& options,
65 const BlockHandle& handle, BlockContents* result) {
66 result->data = Slice();
67 result->cachable = false;
68 result->heap_allocated = false;
69
70 // Read the block contents as well as the type/crc footer.
71 // See table_builder.cc for the code that built this structure.
72 size_t n = static_cast<size_t>(handle.size());
73 char* buf = new char[n + kBlockTrailerSize];
74 Slice contents;
75 Status s = file->Read(handle.offset(), n + kBlockTrailerSize, &contents, buf);
76 if (!s.ok()) {
77 delete[] buf;
78 return s;
79 }
80 if (contents.size() != n + kBlockTrailerSize) {
81 delete[] buf;
82 return Status::Corruption("truncated block read", file->GetName());
83 }
84
85 // Check the crc of the type and the block contents
86 const char* data = contents.data(); // Pointer to where Read put the data
87 if (options.verify_checksums) {
88 const uint32_t crc = crc32c::Unmask(DecodeFixed32(data + n + 1));
89 const uint32_t actual = crc32c::Value(data, n + 1);
90 if (actual != crc) {
91 delete[] buf;
92 s = Status::Corruption("block checksum mismatch", file->GetName());
93 return s;
94 }
95 }
96
97 switch (data[n]) {
98 case kNoCompression:
99 if (data != buf) {
100 // File implementation gave us pointer to some other data.
101 // Use it directly under the assumption that it will be live
102 // while the file is open.
103 delete[] buf;
104 result->data = Slice(data, n);
105 result->heap_allocated = false;
106 result->cachable = false; // Do not double-cache
107 } else {
108 result->data = Slice(buf, n);
109 result->heap_allocated = true;
110 result->cachable = true;
111 }
112
113 // Ok
114 break;
115 case kSnappyCompression: {
116 size_t ulength = 0;
117 if (!port::Snappy_GetUncompressedLength(data, n, &ulength)) {
118 delete[] buf;
119 return Status::Corruption("corrupted compressed block contents", file->GetName());
120 }
121 char* ubuf = new char[ulength];
122 if (!port::Snappy_Uncompress(data, n, ubuf)) {
123 delete[] buf;
124 delete[] ubuf;
125 return Status::Corruption("corrupted compressed block contents", file->GetName());
126 }
127 delete[] buf;
128 result->data = Slice(ubuf, ulength);
129 result->heap_allocated = true;
130 result->cachable = true;
131 break;
132 }
133 default:
134 delete[] buf;
135 return Status::Corruption("bad block type", file->GetName());
136 }
137
138 return Status::OK();
139 }
140
141 } // namespace leveldb
142