src/paimon/common/memory/memory_slice.h

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#include <cassert>
#include <cstdint>
#include <cstring>
#include <memory>
#include <type_traits>

#include "paimon/common/memory/memory_segment.h"
#include "paimon/memory/bytes.h"
#include "paimon/result.h"
#include "paimon/visibility.h"
namespace paimon {
class MemoryPool;
class MemorySliceInput;

/// Slice of a MemorySegment.
///
/// Represents a sub-range [offset_, offset_ + length_) of a MemorySegment.
/// The MemorySegment may be owning (with shared_ptr<Bytes>) or non-owning (view).
class PAIMON_EXPORT MemorySlice {
 public:
    static MemorySlice Wrap(const std::shared_ptr<Bytes>& bytes);
    static MemorySlice Wrap(const MemorySegment& segment);

    using SliceComparator = std::function<Result<int32_t>(const MemorySlice&, const MemorySlice&)>;

 public:
    /// Construct a slice over a segment with given offset and length.
    MemorySlice(const MemorySegment& segment, int32_t offset, int32_t length);

    MemorySlice Slice(int32_t index, int32_t length) const;

    int32_t Length() const;
    int32_t Offset() const;
    std::shared_ptr<Bytes> GetOrCreateHeapMemory(MemoryPool* pool) const;
    const MemorySegment& GetSegment() const;

    /// Returns a raw pointer to the start of this slice's data.
    inline const char* Data() const {
        return segment_.Data() + offset_;
    }

    int8_t ReadByte(int32_t position) const;
    int32_t ReadInt(int32_t position) const;
    int16_t ReadShort(int32_t position) const;
    int64_t ReadLong(int32_t position) const;
    std::string_view ReadStringView() const;

    std::shared_ptr<Bytes> CopyBytes(MemoryPool* pool) const;

    MemorySliceInput ToInput() const;

 private:
    MemorySegment segment_;
    int32_t offset_;
    int32_t length_;
};

}  // namespace paimon