Vous ne pouvez pas sélectionner plus de 25 sujets
Les noms de sujets doivent commencer par une lettre ou un nombre, peuvent contenir des tirets ('-') et peuvent comporter jusqu'à 35 caractères.
176 lignes
4.9 KiB
176 lignes
4.9 KiB
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style license that can be
|
|
// found in the LICENSE file. See the AUTHORS file for names of contributors.
|
|
|
|
#include "db/log_reader.h"
|
|
|
|
#include <stdint.h>
|
|
#include "leveldb/env.h"
|
|
#include "util/coding.h"
|
|
#include "util/crc32c.h"
|
|
|
|
namespace leveldb {
|
|
namespace log {
|
|
|
|
Reader::Reporter::~Reporter() {
|
|
}
|
|
|
|
Reader::Reader(SequentialFile* file, Reporter* reporter, bool checksum)
|
|
: file_(file),
|
|
reporter_(reporter),
|
|
checksum_(checksum),
|
|
backing_store_(new char[kBlockSize]),
|
|
buffer_(),
|
|
eof_(false) {
|
|
}
|
|
|
|
Reader::~Reader() {
|
|
delete[] backing_store_;
|
|
}
|
|
|
|
bool Reader::ReadRecord(Slice* record, std::string* scratch) {
|
|
scratch->clear();
|
|
record->clear();
|
|
bool in_fragmented_record = false;
|
|
|
|
Slice fragment;
|
|
while (true) {
|
|
switch (ReadPhysicalRecord(&fragment)) {
|
|
case kFullType:
|
|
if (in_fragmented_record) {
|
|
ReportDrop(scratch->size(), "partial record without end");
|
|
}
|
|
scratch->clear();
|
|
*record = fragment;
|
|
return true;
|
|
|
|
case kFirstType:
|
|
if (in_fragmented_record) {
|
|
ReportDrop(scratch->size(), "partial record without end");
|
|
}
|
|
scratch->assign(fragment.data(), fragment.size());
|
|
in_fragmented_record = true;
|
|
break;
|
|
|
|
case kMiddleType:
|
|
if (!in_fragmented_record) {
|
|
ReportDrop(fragment.size(), "missing start of fragmented record");
|
|
} else {
|
|
scratch->append(fragment.data(), fragment.size());
|
|
}
|
|
break;
|
|
|
|
case kLastType:
|
|
if (!in_fragmented_record) {
|
|
ReportDrop(fragment.size(), "missing start of fragmented record");
|
|
} else {
|
|
scratch->append(fragment.data(), fragment.size());
|
|
*record = Slice(*scratch);
|
|
return true;
|
|
}
|
|
break;
|
|
|
|
case kEof:
|
|
if (in_fragmented_record) {
|
|
ReportDrop(scratch->size(), "partial record without end");
|
|
scratch->clear();
|
|
}
|
|
return false;
|
|
|
|
case kBadRecord:
|
|
if (in_fragmented_record) {
|
|
ReportDrop(scratch->size(), "error in middle of record");
|
|
in_fragmented_record = false;
|
|
scratch->clear();
|
|
}
|
|
break;
|
|
|
|
default:
|
|
ReportDrop(
|
|
(fragment.size() + (in_fragmented_record ? scratch->size() : 0)),
|
|
"unknown record type");
|
|
in_fragmented_record = false;
|
|
scratch->clear();
|
|
break;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
void Reader::ReportDrop(size_t bytes, const char* reason) {
|
|
if (reporter_ != NULL) {
|
|
reporter_->Corruption(bytes, Status::Corruption(reason));
|
|
}
|
|
}
|
|
|
|
unsigned int Reader::ReadPhysicalRecord(Slice* result) {
|
|
while (true) {
|
|
if (buffer_.size() < kHeaderSize) {
|
|
if (!eof_) {
|
|
// Last read was a full read, so this is a trailer to skip
|
|
buffer_.clear();
|
|
Status status = file_->Read(kBlockSize, &buffer_, backing_store_);
|
|
if (!status.ok()) {
|
|
if (reporter_ != NULL) {
|
|
reporter_->Corruption(kBlockSize, status);
|
|
}
|
|
buffer_.clear();
|
|
eof_ = true;
|
|
return kEof;
|
|
} else if (buffer_.size() < kBlockSize) {
|
|
eof_ = true;
|
|
}
|
|
continue;
|
|
} else if (buffer_.size() == 0) {
|
|
// End of file
|
|
return kEof;
|
|
} else {
|
|
ReportDrop(buffer_.size(), "truncated record at end of file");
|
|
buffer_.clear();
|
|
return kEof;
|
|
}
|
|
}
|
|
|
|
// Parse the header
|
|
const char* header = buffer_.data();
|
|
const uint32_t a = static_cast<uint32_t>(header[4]) & 0xff;
|
|
const uint32_t b = static_cast<uint32_t>(header[5]) & 0xff;
|
|
const unsigned int type = header[6];
|
|
const uint32_t length = a | (b << 8);
|
|
if (kHeaderSize + length > buffer_.size()) {
|
|
ReportDrop(buffer_.size(), "bad record length");
|
|
buffer_.clear();
|
|
return kBadRecord;
|
|
}
|
|
|
|
// Check crc
|
|
if (checksum_) {
|
|
if (type == kZeroType && length == 0) {
|
|
// Skip zero length record without reporting any drops since
|
|
// such records are produced by the mmap based writing code in
|
|
// env_posix.cc that preallocates file regions.
|
|
buffer_.clear();
|
|
return kBadRecord;
|
|
}
|
|
|
|
uint32_t expected_crc = crc32c::Unmask(DecodeFixed32(header));
|
|
uint32_t actual_crc = crc32c::Value(header + 6, 1 + length);
|
|
if (actual_crc != expected_crc) {
|
|
// Drop the rest of the buffer since "length" itself may have
|
|
// been corrupted and if we trust it, we could find some
|
|
// fragment of a real log record that just happens to look
|
|
// like a valid log record.
|
|
ReportDrop(buffer_.size(), "checksum mismatch");
|
|
buffer_.clear();
|
|
return kBadRecord;
|
|
}
|
|
}
|
|
|
|
buffer_.remove_prefix(kHeaderSize + length);
|
|
*result = Slice(header + kHeaderSize, length);
|
|
return type;
|
|
}
|
|
}
|
|
|
|
}
|
|
}
|