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发表于 2019-10-8 16:40:40
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本帖最后由 ilawp 于 2019-10-8 17:10 编辑
我理解错了，按字节或者4b翻转我是知道的，但库里貌似不是硬件指令，cortex m3指令集里有对应指令。
按位翻转没有库，也不知道用啥指令
我说的按位翻转是指：
0b10000000 变成0b00000001
源自cmsis_armclang.h：
**
\brief Reverse byte order (32 bit)
\details Reverses the byte order in unsigned integer value. For example, 0x12345678 becomes 0x78563412.
\param [in] value Value to reverse
\return Reversed value
*/
#define __REV(value) __builtin_bswap32(value)
/**
\brief Reverse byte order (16 bit)
\details Reverses the byte order within each halfword of a word. For example, 0x12345678 becomes 0x34127856.
\param [in] value Value to reverse
\return Reversed value
*/
#define __REV16(value) __ROR(__REV(value), 16)
/**
\brief Reverse byte order (16 bit)
\details Reverses the byte order in a 16-bit value and returns the signed 16-bit result. For example, 0x0080 becomes 0x8000.
\param [in] value Value to reverse
\return Reversed value
*/
#define __REVSH(value) (int16_t)__builtin_bswap16(value)
/**
\brief Rotate Right in unsigned value (32 bit)
\details Rotate Right (immediate) provides the value of the contents of a register rotated by a variable number of bits.
\param [in] op1 Value to rotate
\param [in] op2 Number of Bits to rotate
\return Rotated value
*/
__STATIC_FORCEINLINE uint32_t __ROR(uint32_t op1, uint32_t op2)
{
op2 %= 32U;
if (op2 == 0U)
{
return op1;
}
return (op1 >> op2) | (op1 << (32U - op2));
}
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