tomFlowee
c63519fa47
The leveldb and univalue 3rd party libraries are not installed and not needed by anyone outside of the Hub. So move them there, making it easier for 3rd party usage.
104 lines
2.8 KiB
C++
104 lines
2.8 KiB
C++
// 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 "db/log_writer.h"
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#include <stdint.h>
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#include "leveldb/env.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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namespace log {
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Writer::Writer(WritableFile* dest)
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: dest_(dest),
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block_offset_(0) {
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for (int i = 0; i <= kMaxRecordType; i++) {
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char t = static_cast<char>(i);
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type_crc_[i] = crc32c::Value(&t, 1);
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}
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}
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Writer::~Writer() {
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}
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Status Writer::AddRecord(const Slice& slice) {
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const char* ptr = slice.data();
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size_t left = slice.size();
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// Fragment the record if necessary and emit it. Note that if slice
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// is empty, we still want to iterate once to emit a single
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// zero-length record
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Status s;
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bool begin = true;
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do {
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const int leftover = kBlockSize - block_offset_;
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assert(leftover >= 0);
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if (leftover < kHeaderSize) {
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// Switch to a new block
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if (leftover > 0) {
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// Fill the trailer (literal below relies on kHeaderSize being 7)
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assert(kHeaderSize == 7);
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dest_->Append(Slice("\x00\x00\x00\x00\x00\x00", leftover));
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}
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block_offset_ = 0;
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}
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// Invariant: we never leave < kHeaderSize bytes in a block.
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assert(kBlockSize - block_offset_ - kHeaderSize >= 0);
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const size_t avail = kBlockSize - block_offset_ - kHeaderSize;
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const size_t fragment_length = (left < avail) ? left : avail;
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RecordType type;
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const bool end = (left == fragment_length);
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if (begin && end) {
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type = kFullType;
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} else if (begin) {
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type = kFirstType;
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} else if (end) {
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type = kLastType;
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} else {
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type = kMiddleType;
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}
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s = EmitPhysicalRecord(type, ptr, fragment_length);
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ptr += fragment_length;
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left -= fragment_length;
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begin = false;
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} while (s.ok() && left > 0);
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return s;
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}
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Status Writer::EmitPhysicalRecord(RecordType t, const char* ptr, size_t n) {
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assert(n <= 0xffff); // Must fit in two bytes
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assert(block_offset_ + kHeaderSize + n <= kBlockSize);
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// Format the header
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char buf[kHeaderSize];
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buf[4] = static_cast<char>(n & 0xff);
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buf[5] = static_cast<char>(n >> 8);
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buf[6] = static_cast<char>(t);
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// Compute the crc of the record type and the payload.
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uint32_t crc = crc32c::Extend(type_crc_[t], ptr, n);
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crc = crc32c::Mask(crc); // Adjust for storage
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EncodeFixed32(buf, crc);
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// Write the header and the payload
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Status s = dest_->Append(Slice(buf, kHeaderSize));
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if (s.ok()) {
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s = dest_->Append(Slice(ptr, n));
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if (s.ok()) {
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s = dest_->Flush();
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}
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}
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block_offset_ += kHeaderSize + n;
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return s;
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}
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} // namespace log
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} // namespace leveldb
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