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Misc. CRC32 cleaning #189

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merged 3 commits into from
Dec 28, 2023
Merged

Misc. CRC32 cleaning #189

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83a710b
use the C++11 alignof operator instead of compiler specific code
robUx4 Dec 28, 2023
b4b56a6
don't export the CRC32 table
robUx4 Dec 28, 2023
1f43ee3
crc32: rename m_tab to s_tab as it's a static local table
robUx4 Dec 28, 2023
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9 changes: 1 addition & 8 deletions ebml/EbmlCrc32.h
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Original file line number Diff line number Diff line change
Expand Up @@ -61,7 +61,6 @@ DECLARE_EBML_BINARY(EbmlCrc32)
void ResetCRC();
void UpdateByte(binary b);

static const std::array<std::uint32_t, 256> m_tab;
std::uint32_t m_crc;
std::uint32_t m_crc_final{0};

Expand All @@ -71,13 +70,7 @@ DECLARE_EBML_BINARY(EbmlCrc32)
template <class T>
inline unsigned int GetAlignment(T * /* dummy */=nullptr) // VC60 workaround
{
#if defined(_MSC_VER) && (_MSC_VER >= 1300)
return __alignof(T);
#elif defined(__GNUC__)
return __alignof__(T);
#else
return sizeof(T);
#endif
return alignof(T);
}

template <class T>
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40 changes: 20 additions & 20 deletions src/EbmlCrc32.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,7 @@ namespace libebml {

DEFINE_EBML_CLASS_GLOBAL(EbmlCrc32, 0xBF, 1, "EBMLCrc32\0ratamadabapa")

constexpr std::array<std::uint32_t, 256> EbmlCrc32::m_tab {
static constexpr std::array<std::uint32_t, 256> s_tab {
#ifdef WORDS_BIGENDIAN
0x00000000L, 0x96300777L, 0x2c610eeeL, 0xba510999L, 0x19c46d07L,
0x8ff46a70L, 0x35a563e9L, 0xa395649eL, 0x3288db0eL, 0xa4b8dc79L,
Expand Down Expand Up @@ -154,7 +154,7 @@ void EbmlCrc32::ResetCRC()

void EbmlCrc32::UpdateByte(binary b)
{
m_crc = m_tab.at(CRC32_INDEX(m_crc) ^ b) ^ CRC32_SHIFTED(m_crc);
m_crc = s_tab.at(CRC32_INDEX(m_crc) ^ b) ^ CRC32_SHIFTED(m_crc);
}

void EbmlCrc32::AddElementCRC32(EbmlElement &ElementToCRC)
Expand Down Expand Up @@ -228,20 +228,20 @@ bool EbmlCrc32::CheckCRC(std::uint32_t inputCRC, const binary *input, std::uint3
std::uint32_t crc = CRC32_NEGL;

for(; !IsAligned<std::uint32_t>(input) && length > 0; length--)
crc = m_tab.at(CRC32_INDEX(crc) ^ *input++) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc) ^ *input++) ^ CRC32_SHIFTED(crc);

while (length >= 4) {
crc ^= *reinterpret_cast<const std::uint32_t *>(input);
crc = m_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = m_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = m_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = m_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
length -= 4;
input += 4;
}

while (length--)
crc = m_tab.at(CRC32_INDEX(crc) ^ *input++) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc) ^ *input++) ^ CRC32_SHIFTED(crc);

//Now we finalize the CRC32
crc ^= CRC32_NEGL;
Expand All @@ -258,21 +258,21 @@ void EbmlCrc32::FillCRC32(const binary *input, std::uint32_t length)
/*std::uint32_t crc = CRC32_NEGL;

for(; !IsAligned<std::uint32_t>(s) && n > 0; n--)
crc = m_tab.at(CRC32_INDEX(crc) ^ *s++) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc) ^ *s++) ^ CRC32_SHIFTED(crc);

while (n >= 4)
{
crc ^= *(const std::uint32_t *)s;
crc = m_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = m_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = m_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = m_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
n -= 4;
s += 4;
}

while (n--)
crc = m_tab.at(CRC32_INDEX(crc) ^ *s++) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc) ^ *s++) ^ CRC32_SHIFTED(crc);

m_crc = crc;

Expand All @@ -288,20 +288,20 @@ void EbmlCrc32::Update(const binary *input, std::uint32_t length)
std::uint32_t crc = m_crc;

for(; !IsAligned<std::uint32_t>(input) && length > 0; length--)
crc = m_tab.at(CRC32_INDEX(crc) ^ *input++) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc) ^ *input++) ^ CRC32_SHIFTED(crc);

while (length >= 4) {
crc ^= *reinterpret_cast<const std::uint32_t *>(input);
crc = m_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = m_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = m_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = m_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc)) ^ CRC32_SHIFTED(crc);
length -= 4;
input += 4;
}

while (length--)
crc = m_tab.at(CRC32_INDEX(crc) ^ *input++) ^ CRC32_SHIFTED(crc);
crc = s_tab.at(CRC32_INDEX(crc) ^ *input++) ^ CRC32_SHIFTED(crc);

m_crc = crc;
}
Expand Down