CMSIS-DSP: Vector Shift

| CMSIS-DSP Version 1.4.7 CMSIS DSP Software Library

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Vector Shift
Basic 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 __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.