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AK: Avoid allocations in ByteBuffer

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Creating a ByteBuffer involves two allocations:

-One for the ByteBufferImpl object
-Another one for the actual byte buffer

This changes the ByteBuffer and ByteBufferImpl classes
so only one allocation is necessary.
This commit is contained in:
Gunnar Beutner 2021-05-14 12:00:57 +02:00 committed by Andreas Kling
parent fccfc33dfb
commit a8e6cdc0d8
1 changed files with 18 additions and 50 deletions
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68
AK/ByteBuffer.h
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@ -21,17 +21,13 @@ public:
static NonnullRefPtr<ByteBufferImpl> create_zeroed(size_t);
static NonnullRefPtr<ByteBufferImpl> copy(const void*, size_t);
ByteBufferImpl() = delete;
~ByteBufferImpl() { clear(); }
void clear()
void operator delete(void* ptr)
{
if (!m_data)
return;
kfree(m_data);
m_data = nullptr;
kfree(ptr);
}
ByteBufferImpl() = delete;
u8& operator[](size_t i)
{
VERIFY(i < m_size);
@ -67,16 +63,13 @@ public:
m_size = size;
}
void grow(size_t size);
void zero_fill();
private:
explicit ByteBufferImpl(size_t);
ByteBufferImpl(const void*, size_t);
u8* m_data { nullptr };
size_t m_size { 0 };
u8 m_data[];
};
class ByteBuffer {
@ -205,10 +198,12 @@ public:
void grow(size_t size)
{
if (!m_impl)
m_impl = ByteBufferImpl::create_uninitialized(size);
else
m_impl->grow(size);
if (m_impl && size < m_impl->size())
return;
auto new_impl = ByteBufferImpl::create_uninitialized(size);
if (m_impl)
__builtin_memcpy(new_impl->data(), m_impl->data(), m_impl->size());
m_impl = new_impl;
}
void append(const void* data, size_t data_size)
@ -253,37 +248,6 @@ private:
inline ByteBufferImpl::ByteBufferImpl(size_t size)
: m_size(size)
{
if (size != 0)
m_data = static_cast<u8*>(kmalloc(size));
}
inline ByteBufferImpl::ByteBufferImpl(const void* data, size_t size)
: m_size(size)
{
if (size != 0) {
m_data = static_cast<u8*>(kmalloc(size));
__builtin_memcpy(m_data, data, size);
}
}
inline void ByteBufferImpl::grow(size_t size)
{
VERIFY(size > m_size);
if (size == 0) {
if (m_data)
kfree(m_data);
m_data = nullptr;
m_size = 0;
return;
}
u8* new_data = static_cast<u8*>(kmalloc(size));
if (m_data)
__builtin_memcpy(new_data, m_data, m_size);
u8* old_data = m_data;
m_data = new_data;
m_size = size;
if (old_data)
kfree(old_data);
}
inline void ByteBufferImpl::zero_fill()
@ -293,12 +257,14 @@ inline void ByteBufferImpl::zero_fill()
inline NonnullRefPtr<ByteBufferImpl> ByteBufferImpl::create_uninitialized(size_t size)
{
return ::adopt_ref(*new ByteBufferImpl(size));
auto* buffer = kmalloc(sizeof(ByteBufferImpl) + size);
VERIFY(buffer);
return ::adopt_ref(*new (buffer) ByteBufferImpl(size));
}
inline NonnullRefPtr<ByteBufferImpl> ByteBufferImpl::create_zeroed(size_t size)
{
auto buffer = ::adopt_ref(*new ByteBufferImpl(size));
auto buffer = create_uninitialized(size);
if (size != 0)
__builtin_memset(buffer->data(), 0, size);
return buffer;
@ -306,7 +272,9 @@ inline NonnullRefPtr<ByteBufferImpl> ByteBufferImpl::create_zeroed(size_t size)
inline NonnullRefPtr<ByteBufferImpl> ByteBufferImpl::copy(const void* data, size_t size)
{
return ::adopt_ref(*new ByteBufferImpl(data, size));
auto buffer = create_uninitialized(size);
__builtin_memcpy(buffer->data(), data, size);
return buffer;
}
}