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Allocate memory on stack whenever feasible

The fast path gives another 20% speed up than the slower path.
adaptive-webui-19844
Chocobo1 3 years ago
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commit
aafee60033
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GPG Key ID: 210D9C873253A68C
  1. 13
      src/base/bittorrent/ltqbitarray.cpp

13
src/base/bittorrent/ltqbitarray.cpp

@ -47,9 +47,22 @@ namespace BitTorrent::LT @@ -47,9 +47,22 @@ namespace BitTorrent::LT
{
QBitArray toQBitArray(const lt::bitfield &bits)
{
const int STACK_ALLOC_SIZE = 10 * 1024;
const char *bitsData = bits.data();
const int dataLength = (bits.size() + 7) / 8;
if (dataLength <= STACK_ALLOC_SIZE)
{
// fast path for small bitfields
char tmp[STACK_ALLOC_SIZE]; // uninitialized for faster allocation
for (int i = 0; i < dataLength; ++i)
tmp[i] = reverseByte(bitsData[i]);
return QBitArray::fromBits(tmp, bits.size());
}
// slow path for big bitfields
auto tmp = std::make_unique<char []>(dataLength);
for (int i = 0; i < dataLength; ++i)
tmp[i] = reverseByte(bitsData[i]);

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