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Merge pull request #16408 from Chocobo1/vararray

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Use QVarLengthArray whenever applicable
This commit is contained in:
Chocobo1
2022-02-10 12:44:41 +08:00
committed by GitHub
parent 4a7f1116ac f12ce78b5c
commit 2668a42f0c
4 changed files with 18 additions and 20 deletions
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32
src/base/bittorrent/ltqbitarray.cpp
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@@ -28,18 +28,27 @@
#include "ltqbitarray.h"
#include <memory>
#include <libtorrent/bitfield.hpp>
#include <QBitArray>
#include <QVarLengthArray>
namespace
{
unsigned char reverseByte(const unsigned char byte)
{
// https://graphics.stanford.edu/~seander/bithacks.html#ReverseByteWith64Bits
return (((byte * 0x80200802ULL) & 0x0884422110ULL) * 0x0101010101ULL) >> 32;
// https://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
static const unsigned char table[] =
{
#define R2(n) n, (n + (2 * 64)), (n + 64), (n + (3 * 64))
#define R4(n) R2(n), R2(n + (2 * 16)), R2(n + 16), R2(n + (3 * 16))
#define R6(n) R4(n), R4(n + (2 * 4)), R4(n + 4), R4(n + (3 * 4))
R6(0), R6(2), R6(1), R6(3)
#undef R6
#undef R4
#undef R2
};
return table[byte];
}
}
@@ -52,21 +61,10 @@ namespace BitTorrent::LT
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);
QVarLengthArray<char, STACK_ALLOC_SIZE> tmp(dataLength);
for (int i = 0; i < dataLength; ++i)
tmp[i] = reverseByte(bitsData[i]);
return QBitArray::fromBits(tmp.get(), bits.size());
return QBitArray::fromBits(tmp.data(), tmp.size());
}
}