# Vector ShiftBasic Math Functions

## 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.

The functions support in-place computation allowing the source and destination pointers to reference the same memory buffer.

## 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 __PKHBT, __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.