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IF: pack size of bitset #57

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merged 6 commits into from
Apr 23, 2024
Merged

IF: pack size of bitset #57

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c6ae7c6
pack the size of the bitset so it can be resized on unpack, otherwise…
heifner Apr 19, 2024
b24b8b6
Pack the size of the bitset instead of the size of blocks in the bitset.
heifner Apr 22, 2024
ee8c1bd
Fix num_blocks logic and avoid extra copy of T
heifner Apr 22, 2024
7bc7725
Simplify implementation
heifner Apr 22, 2024
9115a1b
Merge remote-tracking branch 'spring/savanna' into bitset-pack-size
heifner Apr 23, 2024
ddcbbce
Standardize on use of boost::dynamic_bitset<uint8_t> for more expecte…
heifner Apr 23, 2024
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23 changes: 15 additions & 8 deletions libraries/libfc/include/fc/io/raw.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -567,30 +567,37 @@ namespace fc {

template<typename Stream, typename T>
inline void pack( Stream& s, const boost::dynamic_bitset<T>& value ) {
// pack the size of the bitset, not the number of blocks
const auto num_blocks = value.num_blocks();
FC_ASSERT( num_blocks <= MAX_NUM_ARRAY_ELEMENTS );
fc::raw::pack( s, unsigned_int((uint32_t)num_blocks) );

fc::raw::pack( s, unsigned_int(value.size()) );
// 8 bits per byte
assert(num_blocks == value.size() / (sizeof(T) * CHAR_BIT) + (value.size() % (sizeof(T) * CHAR_BIT)));
// convert bitset to a vector of blocks
std::vector<T> blocks;
blocks.resize(num_blocks);
boost::to_block_range(value, blocks.begin());

// pack the blocks
for (const auto& b: blocks) {
fc::raw::pack( s, b );
fc::raw::pack( s, b );
}
}

template<typename Stream, typename T>
inline void unpack( Stream& s, boost::dynamic_bitset<T>& value ) {
// the packed size is the number of bits in the set, not the number of blocks
unsigned_int size; fc::raw::unpack( s, size );
FC_ASSERT( size.value <= MAX_NUM_ARRAY_ELEMENTS );
std::vector<T> blocks((size_t)size.value);
for( uint64_t i = 0; i < size.value; ++i ) {
fc::raw::unpack( s, blocks[i] );
size_t num_blocks = size / (sizeof(T) * CHAR_BIT) + (value.size() % (sizeof(T) * CHAR_BIT));
FC_ASSERT( num_blocks <= MAX_NUM_ARRAY_ELEMENTS );
std::vector<T> blocks;
blocks.reserve(num_blocks);
for( size_t i = 0; i < size.value; ++i ) {
T tmp;
fc::raw::unpack( s, tmp );
blocks.emplace_back( std::move(tmp) );
}
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Why this change? It is arguably less efficient since it does an extra copy.

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Not exactly sure what you mean by this. The vector unpack expects the size of the vector which is not there in this case. Are you talking about something else?

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Yes, I mean using this code instead:

      std::vector<T> blocks(num_blocks);
      for( size_t i = 0; i < num_blocks; ++i ) {
        fc::raw::unpack( s, blocks[i] );

value = { blocks.cbegin(), blocks.cend() };
value.resize(size.value);
}

template<typename Stream, typename T>
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23 changes: 22 additions & 1 deletion libraries/libfc/test/io/test_raw.cpp
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Expand Up @@ -14,7 +14,7 @@ BOOST_AUTO_TEST_CASE(dynamic_bitset_test)
constexpr uint8_t bits = 0b00011110;
boost::dynamic_bitset<uint8_t> bs1(8, bits); // bit set size 8

char buff[4];
char buff[32];
datastream<char*> ds(buff, sizeof(buff));

fc::raw::pack( ds, bs1 );
Expand All @@ -35,4 +35,25 @@ BOOST_AUTO_TEST_CASE(dynamic_bitset_test)
BOOST_CHECK(!bs2.test(7));
}

BOOST_AUTO_TEST_CASE(dynamic_bitset_large_test)
{
boost::dynamic_bitset<uint32_t> bs1;
bs1.resize(12345);

bs1.set(42);
bs1.set(23);
bs1.set(12000);

auto packed = fc::raw::pack(bs1);
auto unpacked = fc::raw::unpack<boost::dynamic_bitset<uint32_t>>(packed);

BOOST_TEST(unpacked.at(42));
BOOST_TEST(unpacked.at(23));
BOOST_TEST(unpacked.at(12000));
unpacked.flip(42);
unpacked.flip(23);
unpacked.flip(1200);
BOOST_TEST(unpacked.none());
}

BOOST_AUTO_TEST_SUITE_END()
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