Vector Shift

Functions
void	arm_shift_q15 (q15_t *pSrc, int8_t shiftBits, q15_t *pDst, uint32_t blockSize)
	Shifts the elements of a Q15 vector a specified number of bits.
void	arm_shift_q31 (q31_t *pSrc, int8_t shiftBits, q31_t *pDst, uint32_t blockSize)
	Shifts the elements of a Q31 vector a specified number of bits.
void	arm_shift_q7 (q7_t *pSrc, int8_t shiftBits, q7_t *pDst, uint32_t blockSize)
	Shifts the elements of a Q7 vector a specified number of bits.

---

Description

Shifts the elements of a fixed-point vector by a specified number of bits. There are separate functions for Q7, Q15, and Q31 data types. The underlying algorithm used is:

        
     pDst[n] = pSrc[n] << shift,   0 <= n < blockSize.        
 

If shift is positive then the elements of the vector are shifted to the left. If shift is negative then the elements of the vector are shifted to the right.

---

Function Documentation

void arm_shift_q15	(	q15_t *	pSrc,
		int8_t	shiftBits,
		q15_t *	pDst,
		uint32_t	blockSize
	)

Parameters:

[in]	*pSrc	points to the input vector
[in]	shiftBits	number of bits to shift. A positive value shifts left; a negative value shifts right.
[out]	*pDst	points to the output vector
[in]	blockSize	number of samples in the vector

Returns:

none.

Scaling and Overflow Behavior:

The function uses saturating arithmetic. Results outside of the allowable Q15 range [0x8000 0x7FFF] will be saturated.

References __SIMD32, and blockSize.

Referenced by arm_dct4_q15().

void arm_shift_q31	(	q31_t *	pSrc,
		int8_t	shiftBits,
		q31_t *	pDst,
		uint32_t	blockSize
	)

Parameters:

[in]	*pSrc	points to the input vector
[in]	shiftBits	number of bits to shift. A positive value shifts left; a negative value shifts right.
[out]	*pDst	points to the output vector
[in]	blockSize	number of samples in the vector

Returns:

none.

Scaling and Overflow Behavior:

The function uses saturating arithmetic. Results outside of the allowable Q31 range [0x80000000 0x7FFFFFFF] will be saturated.

References blockSize, and clip_q63_to_q31().

Referenced by arm_dct4_q31().

void arm_shift_q7	(	q7_t *	pSrc,
		int8_t	shiftBits,
		q7_t *	pDst,
		uint32_t	blockSize
	)

Parameters:

[in]	*pSrc	points to the input vector
[in]	shiftBits	number of bits to shift. A positive value shifts left; a negative value shifts right.
[out]	*pDst	points to the output vector
[in]	blockSize	number of samples in the vector

Returns:

none.

Conditions for optimum performance

Input and output buffers should be aligned by 32-bit

Scaling and Overflow Behavior:

The function uses saturating arithmetic. Results outside of the allowable Q7 range [0x8 0x7F] will be saturated.

References __PACKq7, __SIMD32, and blockSize.