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.
5 #include "table/format.h"
7 #include "leveldb/env.h"
9 #include "table/block.h"
10 #include "util/coding.h"
11 #include "util/crc32c.h"
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_);
23 Status BlockHandle::DecodeFrom(Slice* input) {
24 if (GetVarint64(input, &offset_) &&
25 GetVarint64(input, &size_)) {
28 return Status::Corruption("bad block handle");
32 void Footer::EncodeTo(std::string* dst) const {
34 const size_t original_size = dst->size();
36 metaindex_handle_.EncodeTo(dst);
37 index_handle_.EncodeTo(dst);
38 dst->resize(2 * BlockHandle::kMaxEncodedLength); // Padding
39 PutFixed32(dst, static_cast<uint32_t>(kTableMagicNumber & 0xffffffffu));
40 PutFixed32(dst, static_cast<uint32_t>(kTableMagicNumber >> 32));
41 assert(dst->size() == original_size + kEncodedLength);
44 Status Footer::DecodeFrom(Slice* input) {
45 const char* magic_ptr = input->data() + kEncodedLength - 8;
46 const uint32_t magic_lo = DecodeFixed32(magic_ptr);
47 const uint32_t magic_hi = DecodeFixed32(magic_ptr + 4);
48 const uint64_t magic = ((static_cast<uint64_t>(magic_hi) << 32) |
49 (static_cast<uint64_t>(magic_lo)));
50 if (magic != kTableMagicNumber) {
51 return Status::Corruption("not an sstable (bad magic number)");
54 Status result = metaindex_handle_.DecodeFrom(input);
56 result = index_handle_.DecodeFrom(input);
59 // We skip over any leftover data (just padding for now) in "input"
60 const char* end = magic_ptr + 8;
61 *input = Slice(end, input->data() + input->size() - end);
66 Status ReadBlock(RandomAccessFile* file,
67 const ReadOptions& options,
68 const BlockHandle& handle,
69 BlockContents* result) {
70 result->data = Slice();
71 result->cachable = false;
72 result->heap_allocated = false;
74 // Read the block contents as well as the type/crc footer.
75 // See table_builder.cc for the code that built this structure.
76 size_t n = static_cast<size_t>(handle.size());
77 char* buf = new char[n + kBlockTrailerSize];
79 Status s = file->Read(handle.offset(), n + kBlockTrailerSize, &contents, buf);
84 if (contents.size() != n + kBlockTrailerSize) {
86 return Status::Corruption("truncated block read");
89 // Check the crc of the type and the block contents
90 const char* data = contents.data(); // Pointer to where Read put the data
91 if (options.verify_checksums) {
92 const uint32_t crc = crc32c::Unmask(DecodeFixed32(data + n + 1));
93 const uint32_t actual = crc32c::Value(data, n + 1);
96 s = Status::Corruption("block checksum mismatch");
104 // File implementation gave us pointer to some other data.
105 // Use it directly under the assumption that it will be live
106 // while the file is open.
108 result->data = Slice(data, n);
109 result->heap_allocated = false;
110 result->cachable = false; // Do not double-cache
112 result->data = Slice(buf, n);
113 result->heap_allocated = true;
114 result->cachable = true;
119 case kSnappyCompression: {
121 if (!port::Snappy_GetUncompressedLength(data, n, &ulength)) {
123 return Status::Corruption("corrupted compressed block contents");
125 char* ubuf = new char[ulength];
126 if (!port::Snappy_Uncompress(data, n, ubuf)) {
129 return Status::Corruption("corrupted compressed block contents");
132 result->data = Slice(ubuf, ulength);
133 result->heap_allocated = true;
134 result->cachable = true;
139 return Status::Corruption("bad block type");
145 } // namespace leveldb