IF: pack size of bitset #57
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… it will be the size of the underlying storage
greg7mdp
reviewed
Apr 22, 2024
Comment on lines
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598
| 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] );
greg7mdp
reviewed
Apr 22, 2024
Comment on lines
594
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| auto add_extra = [&]() { | ||
| bool extra_needed = (size % (sizeof(T) * CHAR_BIT)) != 0; | ||
| return static_cast<size_t>(extra_needed); // bool => 0,1 | ||
| }; | ||
| size_t num_blocks = size / (sizeof(T) * CHAR_BIT) + add_extra(); |
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or could be the more usual:
Suggested change
| auto add_extra = [&]() { | |
| bool extra_needed = (size % (sizeof(T) * CHAR_BIT)) != 0; | |
| return static_cast<size_t>(extra_needed); // bool => 0,1 | |
| }; | |
| size_t num_blocks = size / (sizeof(T) * CHAR_BIT) + add_extra(); | |
| constexpr size_t word_size = sizeof(T) * CHAR_BIT; | |
| size_t num_blocks = (size + word_size - 1) / word_size; |
greg7mdp
approved these changes
Apr 22, 2024
linh2931
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Apr 22, 2024
greg7mdp
approved these changes
Apr 23, 2024
linh2931
approved these changes
Apr 23, 2024
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Change the
pack/unpackscheme forboost::dynamic_bitsetused byquorum_certificate.Before this PR the number of blocks of the underlying storage was packed. On
unpackthe size of the dynamic bitset was the size of the number of bits in the underlying blocks.With this PR, the size of the bitset is pack/unpack so that the bitset can be restored to its original size.
Included in this PR is the introduction of
fc::dynamic_bitsetdefined to beboost::dynamic_bitset<uint8_t>. Usinguint8_tminimizes space used for packed format and provides a more expected packed format where only the bytes that are needed are packed/unpacked.fc::dynamic_bitsetis used for votes inquorum_certificatewhich is included in most blocks.