115 lines
3.3 KiB
C
115 lines
3.3 KiB
C
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/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef FOLLY_IO_RECORDIO_H_
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#error This file may only be included from folly/io/RecordIO.h
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#endif
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#include <folly/detail/Iterators.h>
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#include <folly/hash/SpookyHashV2.h>
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namespace folly {
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class RecordIOReader::Iterator : public detail::IteratorFacade<
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RecordIOReader::Iterator,
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const std::pair<ByteRange, off_t>,
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std::forward_iterator_tag> {
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friend class detail::
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IteratorFacade<Iterator, value_type, std::forward_iterator_tag>;
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friend class RecordIOReader;
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public:
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Iterator() = default;
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private:
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Iterator(ByteRange range, uint32_t fileId, off_t pos);
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reference dereference() const {
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return recordAndPos_;
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}
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bool equal(const Iterator& other) const {
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return range_ == other.range_;
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}
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void increment() {
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size_t skip = recordio_helpers::headerSize() + recordAndPos_.first.size();
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recordAndPos_.second += off_t(skip);
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range_.advance(skip);
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advanceToValid();
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}
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void advanceToValid();
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ByteRange range_;
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uint32_t fileId_ = 0;
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// stored as a pair so we can return by reference in dereference()
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std::pair<ByteRange, off_t> recordAndPos_;
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};
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inline auto RecordIOReader::cbegin() const -> Iterator {
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return seek(0);
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}
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inline auto RecordIOReader::begin() const -> Iterator {
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return cbegin();
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}
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inline auto RecordIOReader::cend() const -> Iterator {
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return seek(off_t(-1));
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}
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inline auto RecordIOReader::end() const -> Iterator {
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return cend();
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}
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inline auto RecordIOReader::seek(off_t pos) const -> Iterator {
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return Iterator(map_.range(), fileId_, pos);
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}
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namespace recordio_helpers {
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namespace recordio_detail {
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FOLLY_PACK_PUSH
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struct Header {
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// First 4 bytes of SHA1("zuck"), big-endian
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// Any values will do, except that the sequence must not have a
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// repeated prefix (that is, if we see kMagic, we know that the next
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// occurrence must start at least 4 bytes later)
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static constexpr uint32_t kMagic = 0xeac313a1;
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uint32_t magic;
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uint8_t version; // backwards incompatible version, currently 0
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uint8_t hashFunction; // 0 = SpookyHashV2
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uint16_t flags; // reserved (must be 0)
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uint32_t fileId; // unique file ID
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uint32_t dataLength;
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std::size_t dataHash;
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uint32_t headerHash; // must be last
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} FOLLY_PACK_ATTR;
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FOLLY_PACK_POP
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static_assert(
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offsetof(Header, headerHash) + sizeof(Header::headerHash) == sizeof(Header),
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"invalid header layout");
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} // namespace recordio_detail
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constexpr size_t headerSize() {
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return sizeof(recordio_detail::Header);
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}
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inline RecordInfo findRecord(ByteRange range, uint32_t fileId) {
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return findRecord(range, range, fileId);
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}
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} // namespace recordio_helpers
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} // namespace folly
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