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Comment default block size logic, round up default_block_start

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Ion Gaztañaga
2025-09-24 23:05:11 +02:00
parent df4af0989c
commit 8470abf32d
1 changed files with 19 additions and 12 deletions
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31
include/boost/container/deque.hpp
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@@ -75,20 +75,27 @@ template<class T, std::size_t BlockBytes, std::size_t BlockSize, class StoredSiz
struct deque_block_traits
{
BOOST_CONTAINER_STATIC_ASSERT_MSG(!(BlockBytes && BlockSize), "BlockBytes and BlockSize can't be specified at the same time");
//Calculate default block size
BOOST_STATIC_CONSTEXPR std::size_t default_block_bytes = sizeof(void*)*128u;
BOOST_STATIC_CONSTEXPR std::size_t default_block_start = default_block_bytes/sizeof(T);
BOOST_STATIC_CONSTEXPR std::size_t default_min_block_size = 16u;
BOOST_STATIC_CONSTEXPR std::size_t default_block_size_initial = default_block_start < default_min_block_size
? default_min_block_size
: dtl::upper_power_of_2_ct<std::size_t, default_block_start>::value;
BOOST_STATIC_CONSTEXPR std::size_t max_stored_size_block_size = std::size_t(1u) << (sizeof(StoredSizeType)*CHAR_BIT - 4u);
BOOST_STATIC_CONSTEXPR std::size_t default_block_size = default_block_size_initial > max_stored_size_block_size
? max_stored_size_block_size
: default_block_size_initial;
BOOST_STATIC_CONSTEXPR std::size_t default_block_start = (default_block_bytes - 1u)/sizeof(T) + 1u;
//Round to the next power of two
BOOST_STATIC_CONSTEXPR std::size_t default_block_size_upp_pow2 = dtl::upper_power_of_2_ct<std::size_t, default_block_start>::value;
BOOST_STATIC_CONSTEXPR std::size_t value = BlockSize ? BlockSize
: BlockBytes ? (BlockBytes-1u)/sizeof(T) + 1u
: default_block_size
//Check minimal size
BOOST_STATIC_CONSTEXPR std::size_t default_min_block_size_pow = 3u;
BOOST_STATIC_CONSTEXPR std::size_t default_min_block_size = 8u;
BOOST_STATIC_CONSTEXPR std::size_t default_block_size_initial = default_block_size_upp_pow2 < default_min_block_size
? default_min_block_size
: default_block_size_upp_pow2;
//Limit by stored size max value
BOOST_STATIC_CONSTEXPR std::size_t max_stored_size_block_size = std::size_t(1u) << (sizeof(StoredSizeType)*CHAR_BIT - default_min_block_size_pow);
BOOST_STATIC_CONSTEXPR std::size_t default_block_size = default_block_size_initial > max_stored_size_block_size
? max_stored_size_block_size
: default_block_size_initial;
//Now select between the default or the specified by the user
BOOST_STATIC_CONSTEXPR std::size_t value = BlockSize ? BlockSize
: BlockBytes ? (BlockBytes-1u)/sizeof(T) + 1u : default_block_size
;
BOOST_CONTAINER_STATIC_ASSERT_MSG(value <= max_stored_size_block_size, "BlockSize or BlockBytes is too big for the stored_size_type");