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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
//
// 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_writer.h"
#include <stdint.h>
#include "file/writable_file_writer.h"
#include "rocksdb/env.h"
#include "util/coding.h"
#include "util/crc32c.h"
namespace ROCKSDB_NAMESPACE {
namespace log {
Writer::Writer(std::unique_ptr<WritableFileWriter>&& dest, uint64_t log_number,
bool recycle_log_files, bool manual_flush)
: dest_(std::move(dest)),
block_offset_(0),
log_number_(log_number),
recycle_log_files_(recycle_log_files),
manual_flush_(manual_flush) {
for (int i = 0; i <= kMaxRecordType; i++) {
char t = static_cast<char>(i);
type_crc_[i] = crc32c::Value(&t, 1);
}
}
Writer::~Writer() {
if (dest_) {
WriteBuffer();
}
}
Status Writer::WriteBuffer() { return dest_->Flush(); }
Status Writer::Close() {
Status s;
if (dest_) {
s = dest_->Close();
dest_.reset();
}
return s;
}
Status Writer::AddRecord(const Slice& slice) {
const char* ptr = slice.data();
size_t left = slice.size();
// Header size varies depending on whether we are recycling or not.
const int header_size =
recycle_log_files_ ? kRecyclableHeaderSize : kHeaderSize;
// Fragment the record if necessary and emit it. Note that if slice
// is empty, we still want to iterate once to emit a single
// zero-length record
Status s;
bool begin = true;
do {
const int64_t leftover = kBlockSize - block_offset_;
assert(leftover >= 0);
if (leftover < header_size) {
// Switch to a new block
if (leftover > 0) {
// Fill the trailer (literal below relies on kHeaderSize and
// kRecyclableHeaderSize being <= 11)
assert(header_size <= 11);
s = dest_->Append(Slice("\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00",
static_cast<size_t>(leftover)));
if (!s.ok()) {
break;
}
}
block_offset_ = 0;
}
// Invariant: we never leave < header_size bytes in a block.
assert(static_cast<int64_t>(kBlockSize - block_offset_) >= header_size);
const size_t avail = kBlockSize - block_offset_ - header_size;
const size_t fragment_length = (left < avail) ? left : avail;
RecordType type;
const bool end = (left == fragment_length);
if (begin && end) {
type = recycle_log_files_ ? kRecyclableFullType : kFullType;
} else if (begin) {
type = recycle_log_files_ ? kRecyclableFirstType : kFirstType;
} else if (end) {
type = recycle_log_files_ ? kRecyclableLastType : kLastType;
} else {
type = recycle_log_files_ ? kRecyclableMiddleType : kMiddleType;
}
s = EmitPhysicalRecord(type, ptr, fragment_length);
ptr += fragment_length;
left -= fragment_length;
begin = false;
} while (s.ok() && left > 0);
if (s.ok()) {
if (!manual_flush_) {
s = dest_->Flush();
}
}
return s;
}
bool Writer::TEST_BufferIsEmpty() { return dest_->TEST_BufferIsEmpty(); }
Status Writer::EmitPhysicalRecord(RecordType t, const char* ptr, size_t n) {
assert(n <= 0xffff); // Must fit in two bytes
size_t header_size;
char buf[kRecyclableHeaderSize];
// Format the header
buf[4] = static_cast<char>(n & 0xff);
buf[5] = static_cast<char>(n >> 8);
buf[6] = static_cast<char>(t);
uint32_t crc = type_crc_[t];
if (t < kRecyclableFullType) {
// Legacy record format
assert(block_offset_ + kHeaderSize + n <= kBlockSize);
header_size = kHeaderSize;
} else {
// Recyclable record format
assert(block_offset_ + kRecyclableHeaderSize + n <= kBlockSize);
header_size = kRecyclableHeaderSize;
// Only encode low 32-bits of the 64-bit log number. This means
// we will fail to detect an old record if we recycled a log from
// ~4 billion logs ago, but that is effectively impossible, and
// even if it were we'dbe far more likely to see a false positive
// on the 32-bit CRC.
EncodeFixed32(buf + 7, static_cast<uint32_t>(log_number_));
crc = crc32c::Extend(crc, buf + 7, 4);
}
// Compute the crc of the record type and the payload.
crc = crc32c::Extend(crc, ptr, n);
crc = crc32c::Mask(crc); // Adjust for storage
EncodeFixed32(buf, crc);
// Write the header and the payload
Status s = dest_->Append(Slice(buf, header_size));
if (s.ok()) {
s = dest_->Append(Slice(ptr, n));
}
block_offset_ += header_size + n;
return s;
}
} // namespace log
} // namespace ROCKSDB_NAMESPACE
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