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
13namespace leveldb {
14
15void 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
23Status BlockHandle::DecodeFrom(Slice* input) {
24  if (GetVarint64(input, &offset_) &&
25      GetVarint64(input, &size_)) {
26    return Status::OK();
27  } else {
28    return Status::Corruption("bad block handle");
29  }
30}
31
32void Footer::EncodeTo(std::string* dst) const {
33#ifndef NDEBUG
34  const size_t original_size = dst->size();
35#endif
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);
42}
43
44Status 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::InvalidArgument("not an sstable (bad magic number)");
52  }
53
54  Status result = metaindex_handle_.DecodeFrom(input);
55  if (result.ok()) {
56    result = index_handle_.DecodeFrom(input);
57  }
58  if (result.ok()) {
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);
62  }
63  return result;
64}
65
66Status 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;
73
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];
78  Slice contents;
79  Status s = file->Read(handle.offset(), n + kBlockTrailerSize, &contents, buf);
80  if (!s.ok()) {
81    delete[] buf;
82    return s;
83  }
84  if (contents.size() != n + kBlockTrailerSize) {
85    delete[] buf;
86    return Status::Corruption("truncated block read");
87  }
88
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);
94    if (actual != crc) {
95      delete[] buf;
96      s = Status::Corruption("block checksum mismatch");
97      return s;
98    }
99  }
100
101  switch (data[n]) {
102    case kNoCompression:
103      if (data != buf) {
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.
107        delete[] buf;
108        result->data = Slice(data, n);
109        result->heap_allocated = false;
110        result->cachable = false;  // Do not double-cache
111      } else {
112        result->data = Slice(buf, n);
113        result->heap_allocated = true;
114        result->cachable = true;
115      }
116
117      // Ok
118      break;
119    case kSnappyCompression: {
120      size_t ulength = 0;
121      if (!port::Snappy_GetUncompressedLength(data, n, &ulength)) {
122        delete[] buf;
123        return Status::Corruption("corrupted compressed block contents");
124      }
125      char* ubuf = new char[ulength];
126      if (!port::Snappy_Uncompress(data, n, ubuf)) {
127        delete[] buf;
128        delete[] ubuf;
129        return Status::Corruption("corrupted compressed block contents");
130      }
131      delete[] buf;
132      result->data = Slice(ubuf, ulength);
133      result->heap_allocated = true;
134      result->cachable = true;
135      break;
136    }
137    default:
138      delete[] buf;
139      return Status::Corruption("bad block type");
140  }
141
142  return Status::OK();
143}
144
145}  // namespace leveldb
146