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144 строки
4.5 KiB
144 строки
4.5 KiB
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#include "table/format.h"
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#include "leveldb/env.h"
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#include "port/port.h"
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#include "table/block.h"
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#include "util/coding.h"
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#include "util/crc32c.h"
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namespace leveldb {
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void BlockHandle::EncodeTo(std::string* dst) const {
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// Sanity check that all fields have been set
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assert(offset_ != ~static_cast<uint64_t>(0));
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assert(size_ != ~static_cast<uint64_t>(0));
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PutVarint64(dst, offset_);
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PutVarint64(dst, size_);
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}
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Status BlockHandle::DecodeFrom(Slice* input) {
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if (GetVarint64(input, &offset_) &&
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GetVarint64(input, &size_)) {
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return Status::OK();
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} else {
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return Status::Corruption("bad block handle");
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}
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}
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void Footer::EncodeTo(std::string* dst) const {
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const size_t original_size = dst->size();
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metaindex_handle_.EncodeTo(dst);
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index_handle_.EncodeTo(dst);
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dst->resize(2 * BlockHandle::kMaxEncodedLength); // Padding
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PutFixed32(dst, static_cast<uint32_t>(kTableMagicNumber & 0xffffffffu));
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PutFixed32(dst, static_cast<uint32_t>(kTableMagicNumber >> 32));
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assert(dst->size() == original_size + kEncodedLength);
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(void)original_size; // Disable unused variable warning.
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}
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Status Footer::DecodeFrom(Slice* input) {
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const char* magic_ptr = input->data() + kEncodedLength - 8;
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const uint32_t magic_lo = DecodeFixed32(magic_ptr);
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const uint32_t magic_hi = DecodeFixed32(magic_ptr + 4);
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const uint64_t magic = ((static_cast<uint64_t>(magic_hi) << 32) |
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(static_cast<uint64_t>(magic_lo)));
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if (magic != kTableMagicNumber) {
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return Status::Corruption("not an sstable (bad magic number)");
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}
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Status result = metaindex_handle_.DecodeFrom(input);
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if (result.ok()) {
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result = index_handle_.DecodeFrom(input);
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}
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if (result.ok()) {
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// We skip over any leftover data (just padding for now) in "input"
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const char* end = magic_ptr + 8;
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*input = Slice(end, input->data() + input->size() - end);
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}
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return result;
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}
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Status ReadBlock(RandomAccessFile* file,
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const ReadOptions& options,
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const BlockHandle& handle,
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BlockContents* result) {
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result->data = Slice();
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result->cachable = false;
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result->heap_allocated = false;
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// Read the block contents as well as the type/crc footer.
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// See table_builder.cc for the code that built this structure.
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size_t n = static_cast<size_t>(handle.size());
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char* buf = new char[n + kBlockTrailerSize];
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Slice contents;
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Status s = file->Read(handle.offset(), n + kBlockTrailerSize, &contents, buf);
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if (!s.ok()) {
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delete[] buf;
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return s;
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}
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if (contents.size() != n + kBlockTrailerSize) {
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delete[] buf;
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return Status::Corruption("truncated block read");
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}
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// Check the crc of the type and the block contents
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const char* data = contents.data(); // Pointer to where Read put the data
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if (options.verify_checksums) {
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const uint32_t crc = crc32c::Unmask(DecodeFixed32(data + n + 1));
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const uint32_t actual = crc32c::Value(data, n + 1);
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if (actual != crc) {
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delete[] buf;
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s = Status::Corruption("block checksum mismatch");
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return s;
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}
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}
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switch (data[n]) {
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case kNoCompression:
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if (data != buf) {
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// File implementation gave us pointer to some other data.
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// Use it directly under the assumption that it will be live
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// while the file is open.
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delete[] buf;
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result->data = Slice(data, n);
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result->heap_allocated = false;
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result->cachable = false; // Do not double-cache
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} else {
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result->data = Slice(buf, n);
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result->heap_allocated = true;
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result->cachable = true;
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}
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// Ok
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break;
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case kSnappyCompression: {
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size_t ulength = 0;
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if (!port::Snappy_GetUncompressedLength(data, n, &ulength)) {
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delete[] buf;
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return Status::Corruption("corrupted compressed block contents");
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}
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char* ubuf = new char[ulength];
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if (!port::Snappy_Uncompress(data, n, ubuf)) {
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delete[] buf;
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delete[] ubuf;
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return Status::Corruption("corrupted compressed block contents");
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}
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delete[] buf;
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result->data = Slice(ubuf, ulength);
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result->heap_allocated = true;
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result->cachable = true;
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break;
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}
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default:
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delete[] buf;
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return Status::Corruption("bad block type");
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}
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return Status::OK();
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}
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} // namespace leveldb
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