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Add 16-bit rev16 and rbit

pull/853/head
Jeffrey Walton 2019-05-28 02:50:58 -04:00
parent 623059f28c
commit a2e7c26f6c
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GPG Key ID: B36AB348921B1838
1 changed files with 11 additions and 3 deletions
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14
misc.h
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@ -2005,7 +2005,11 @@ inline byte ByteReverse(byte value)
/// performs a 8-bit rotate on the word16.
inline word16 ByteReverse(word16 value)
{
#if defined(CRYPTOPP_BYTESWAP_AVAILABLE)
#if defined(CRYPTOPP_ARM_BYTEREV_AVAILABLE)
word16 rvalue;
__asm__ ("rev16 %0, %1" : "=r" (rvalue) : "r" (value));
return rvalue;
#elif defined(CRYPTOPP_BYTESWAP_AVAILABLE)
return bswap_16(value);
#elif (_MSC_VER >= 1400) || (defined(_MSC_VER) && !defined(_DLL))
return _byteswap_ushort(value);
@ -2081,10 +2085,12 @@ inline byte BitReverse(byte value)
inline word16 BitReverse(word16 value)
{
#if defined(CRYPTOPP_ARM_BITREV_AVAILABLE)
// 4 instructions on ARM.
word32 rvalue;
__asm__ ("rbit %0, %1" : "=r" (rvalue) : "r" (word32(value)));
__asm__ ("rbit %0, %1" : "=r" (rvalue) : "r" (value));
return word16(rvalue >> 16);
#else
// 15 instructions on ARM.
value = word16((value & 0xAAAA) >> 1) | word16((value & 0x5555) << 1);
value = word16((value & 0xCCCC) >> 2) | word16((value & 0x3333) << 2);
value = word16((value & 0xF0F0) >> 4) | word16((value & 0x0F0F) << 4);
@ -2098,10 +2104,12 @@ inline word16 BitReverse(word16 value)
inline word32 BitReverse(word32 value)
{
#if defined(CRYPTOPP_ARM_BITREV_AVAILABLE)
// 2 instructions on ARM.
word32 rvalue;
__asm__ ("rbit %0, %1" : "=r" (rvalue) : "r" (value));
return rvalue;
#else
// 19 instructions on ARM.
value = word32((value & 0xAAAAAAAA) >> 1) | word32((value & 0x55555555) << 1);
value = word32((value & 0xCCCCCCCC) >> 2) | word32((value & 0x33333333) << 2);
value = word32((value & 0xF0F0F0F0) >> 4) | word32((value & 0x0F0F0F0F) << 4);
@ -2144,7 +2152,7 @@ inline T BitReverse(T value)
else
{
CRYPTOPP_ASSERT(0);
return 0;
return (T)BitReverse((word64)value);
}
}