RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-07-26 12:17:35 +00:00
Code Issues Activity Actions

AK: Optimize BitStream refilling a bit further

Browse source 
This tries to optimize the refill code by making it easier to digest for
the branch predictor. This includes not looping as much across function
calls and marking our EOF case to be unlikely.

Co-Authored-By: Lucas Chollet <lucas.chollet@free.fr>
This commit is contained in:
Tim Schumacher 2023-11-28 13:06:19 +01:00 • committed by Andreas Kling
parent 197331c922
commit e9e89d7e4e
1 changed files with 20 additions and 19 deletions
Download patch file Download diff file Expand all files Collapse all files

27
AK/BitStream.h
View file

@ -215,15 +215,8 @@ public:
template<Unsigned T = u64>
ErrorOr<T> peek_bits(size_t count)
{
while (count > m_bit_count) {
if (TRY(refill_buffer_from_stream()))
continue;
if (m_unsatisfiable_read_behavior == UnsatisfiableReadBehavior::Reject)
return Error::from_string_literal("Reached end-of-stream without collecting the required number of bits");
break;
}
if (count > m_bit_count)
TRY(refill_buffer_from_stream(count));
return m_bit_buffer & lsb_mask<T>(min(count, m_bit_count));
}
@ -254,10 +247,17 @@ public:
}
private:
ErrorOr<bool> refill_buffer_from_stream()
ErrorOr<void> refill_buffer_from_stream(size_t requested_bit_count)
{
if (m_stream->is_eof())
return false;
while (requested_bit_count > m_bit_count) [[likely]] {
if (m_stream->is_eof()) [[unlikely]] {
if (m_unsatisfiable_read_behavior == UnsatisfiableReadBehavior::FillWithZero) {
m_bit_count = requested_bit_count;
return {};
}
return Error::from_string_literal("Reached end-of-stream without collecting the required number of bits");
}
size_t bits_to_read = bit_buffer_size - m_bit_count;
size_t bytes_to_read = bits_to_read / bits_per_byte;
@ -267,8 +267,9 @@ private:
m_bit_buffer |= (buffer << m_bit_count);
m_bit_count += bytes.size() * bits_per_byte;
}
return true;
return {};
}
UnsatisfiableReadBehavior m_unsatisfiable_read_behavior;