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realm / realm-core / jorgen.edelbo_338

03 Jul 2024 03:00PM UTC coverage: 90.856% (-0.008%) from 90.864%
jorgen.edelbo_338

Pull #7803

Evergreen

nicola-cab
Merge branch 'next-major' into feature/string-compression
Pull Request #7803: Feature/string compression

103028 of 180606 branches covered (57.05%)

1144 of 1267 new or added lines in 33 files covered. (90.29%)

155 existing lines in 24 files now uncovered.

218583 of 240583 relevant lines covered (90.86%)

7959624.7 hits per line

Source File
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79.03
/src/realm/alloc.cpp
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/*************************************************************************
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 *
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 * Copyright 2016 Realm Inc.
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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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 **************************************************************************/
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#include <cerrno>
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#include <cstdlib>
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#include <stdexcept>
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#include <algorithm>
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#include <realm/array.hpp>
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#include <realm/alloc_slab.hpp>
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#include <realm/group.hpp>
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using namespace realm;
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namespace {
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/// For use with free-standing objects (objects that are not part of a
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/// Realm group)
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///
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/// Note that it is essential that this class is stateless as it may
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/// be used by multiple threads. Although it has m_replication, this
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/// is not a problem, as there is no way to modify it, so it will
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/// remain zero.
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class DefaultAllocator : public realm::Allocator {
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public:
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    DefaultAllocator()
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    {
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        m_baseline = 0;
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    }
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    MemRef do_alloc(const size_t size) override
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    {
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        char* addr = static_cast<char*>(::malloc(size));
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        if (REALM_UNLIKELY(REALM_COVER_NEVER(!addr))) {
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            // LCOV_EXCL_START
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            REALM_ASSERT_DEBUG(errno == ENOMEM);
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            throw std::bad_alloc();
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            // LCOV_EXCL_STOP
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        }
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#if REALM_ENABLE_ALLOC_SET_ZERO
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        std::fill(addr, addr + size, 0);
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#endif
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        return MemRef(addr, reinterpret_cast<size_t>(addr), *this);
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    }
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    MemRef do_realloc(ref_type, char* addr, size_t old_size, size_t new_size) override
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    {
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        char* new_addr = static_cast<char*>(::realloc(const_cast<char*>(addr), new_size));
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        if (REALM_UNLIKELY(REALM_COVER_NEVER(!new_addr))) {
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            // LCOV_EXCL_START
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            REALM_ASSERT_DEBUG(errno == ENOMEM);
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            throw std::bad_alloc();
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            // LCOV_EXCL_STOP
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        }
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#if REALM_ENABLE_ALLOC_SET_ZERO
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        std::fill(new_addr + old_size, new_addr + new_size, 0);
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#else
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        static_cast<void>(old_size);
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#endif
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        return MemRef(new_addr, reinterpret_cast<size_t>(new_addr), *this);
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    }
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    void do_free(ref_type, char* addr) override
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    {
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        ::free(addr);
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    }
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    char* do_translate(ref_type ref) const noexcept override
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    {
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        return reinterpret_cast<char*>(ref);
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    }
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    void verify() const override {}
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    void get_or_add_xover_mapping(RefTranslation&, size_t, size_t, size_t) override
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    {
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        REALM_ASSERT(false);
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    }
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};
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// This variable is declared such that get_default() can return it. It could be a static local variable, but
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// Valgrind/Helgrind gives a false error report because it doesn't recognize gcc's static variable initialization
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// mutex
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DefaultAllocator default_alloc;
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} // anonymous namespace
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namespace realm {
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Allocator& Allocator::get_default() noexcept
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{
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    return default_alloc;
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}
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// This function is called to handle translation of a ref which is above the limit for its
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// memory mapping. This requires one of three:
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// * bumping the limit of the mapping. (if the entire array is inside the mapping)
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// * adding a cross-over mapping. (if the array crosses a mapping boundary)
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// * using an already established cross-over mapping. (ditto)
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// this can proceed concurrently with other calls to translate()
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char* Allocator::translate_less_critical(RefTranslation* ref_translation_ptr, ref_type ref,
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                                         bool known_in_slab) const noexcept
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{
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    size_t idx = get_section_index(ref);
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    RefTranslation& txl = ref_translation_ptr[idx];
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    size_t offset = ref - get_section_base(idx);
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    char* addr = txl.mapping_addr + offset;
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    util::encryption_read_barrier(addr, NodeHeader::header_size, txl.encrypted_mapping);
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    // if we know the translation is inside the slab area, we don't need to check
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    // for anything beyond the header, and we don't need to check if decryption is needed
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    auto size = known_in_slab ? 8 : NodeHeader::get_byte_size_from_header(addr);
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    bool crosses_mapping = offset + size > (1 << section_shift);
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    // Move the limit on use of the existing primary mapping.
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    // Take into account that another thread may attempt to change / have changed it concurrently,
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    size_t lowest_possible_xover_offset = txl.lowest_possible_xover_offset.load(std::memory_order_relaxed);
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    auto new_lowest_possible_xover_offset = offset + (crosses_mapping ? 0 : size);
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    while (new_lowest_possible_xover_offset > lowest_possible_xover_offset) {
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        if (txl.lowest_possible_xover_offset.compare_exchange_weak(
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                lowest_possible_xover_offset, new_lowest_possible_xover_offset, std::memory_order_relaxed))
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            break;
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    }
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    if (REALM_LIKELY(!crosses_mapping)) {
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        // Array fits inside primary mapping, no new mapping needed.
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        util::encryption_read_barrier(addr, size, txl.encrypted_mapping);
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        return addr;
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    }
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    // we need a cross-over mapping. If one is already established, use that.
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    auto xover_mapping_addr = txl.xover_mapping_addr.load(std::memory_order_acquire);
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    if (!xover_mapping_addr) {
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        // we need to establish a xover mapping - or wait for another thread to finish
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        // establishing one:
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        const_cast<Allocator*>(this)->get_or_add_xover_mapping(txl, idx, offset, size);
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        // reload (can be relaxed since the call above synchronizes on a mutex)
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        xover_mapping_addr = txl.xover_mapping_addr.load(std::memory_order_relaxed);
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UNCOV
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    }
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    // array is now known to be inside the established xover mapping:
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    addr = xover_mapping_addr + (offset - txl.xover_mapping_base);
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    util::encryption_read_barrier(addr, size, txl.xover_encrypted_mapping);
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    return addr;
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}
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} // namespace realm
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