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AK: Fix all quadratic-time append-loops over ByteBuffer
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@ -289,6 +289,12 @@ private:
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NEVER_INLINE ErrorOr<void> try_ensure_capacity_slowpath(size_t new_capacity)
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NEVER_INLINE ErrorOr<void> try_ensure_capacity_slowpath(size_t new_capacity)
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{
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{
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// When we are asked to raise the capacity by very small amounts,
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// the caller is perhaps appending very little data in many calls.
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// To avoid copying the entire ByteBuffer every single time,
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// we raise the capacity exponentially, by a factor of roughly 1.5.
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// This is most noticable in Lagom, where kmalloc_good_size is just a no-op.
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new_capacity = max(new_capacity, (capacity() * 3) / 2);
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new_capacity = kmalloc_good_size(new_capacity);
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new_capacity = kmalloc_good_size(new_capacity);
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auto* new_buffer = (u8*)kmalloc(new_capacity);
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auto* new_buffer = (u8*)kmalloc(new_capacity);
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if (!new_buffer)
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if (!new_buffer)
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@ -33,6 +33,14 @@ TEST_CASE(equality_operator)
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EXPECT_EQ(d == d, true);
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EXPECT_EQ(d == d, true);
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}
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}
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BENCHMARK_CASE(append)
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{
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ByteBuffer bb;
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for (size_t i = 0; i < 1000000; ++i) {
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bb.append(static_cast<u8>(i));
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}
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}
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/*
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/*
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* FIXME: These `negative_*` tests should cause precisely one compilation error
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* FIXME: These `negative_*` tests should cause precisely one compilation error
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* each, and always for the specified reason. Currently we do not have a harness
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* each, and always for the specified reason. Currently we do not have a harness
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