tmk_core/tool/mbed/mbed-sdk/libraries/dsp/cmsis_dsp/SupportFunctions/arm_q15_to_q7.c

   1 /* ----------------------------------------------------------------------------
   2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
   3 *
   4 * $Date:        17. January 2013
   5 * $Revision:    V1.4.1
   6 *
   7 * Project:          CMSIS DSP Library
   8 * Title:                arm_q15_to_q7.c
   9 *
  10 * Description:  Converts the elements of the Q15 vector to Q7 vector.
  11 *
  12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
  13 *
  14 * Redistribution and use in source and binary forms, with or without
  15 * modification, are permitted provided that the following conditions
  16 * are met:
  17 *   - Redistributions of source code must retain the above copyright
  18 *     notice, this list of conditions and the following disclaimer.
  19 *   - Redistributions in binary form must reproduce the above copyright
  20 *     notice, this list of conditions and the following disclaimer in
  21 *     the documentation and/or other materials provided with the
  22 *     distribution.
  23 *   - Neither the name of ARM LIMITED nor the names of its contributors
  24 *     may be used to endorse or promote products derived from this
  25 *     software without specific prior written permission.
  26 *
  27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  38 * POSSIBILITY OF SUCH DAMAGE.
  39 * ---------------------------------------------------------------------------- */
  40
  41 #include "arm_math.h"
  42
  43 /**
  44  * @ingroup groupSupport
  45  */
  46
  47 /**
  48  * @addtogroup q15_to_x
  49  * @{
  50  */
  51
  52
  53 /**
  54  * @brief Converts the elements of the Q15 vector to Q7 vector.
  55  * @param[in]       *pSrc points to the Q15 input vector
  56  * @param[out]      *pDst points to the Q7 output vector
  57  * @param[in]       blockSize length of the input vector
  58  * @return none.
  59  *
  60  * \par Description:
  61  *
  62  * The equation used for the conversion process is:
  63  *
  64  * <pre>
  65  *      pDst[n] = (q7_t) pSrc[n] >> 8;   0 <= n < blockSize.
  66  * </pre>
  67  *
  68  */
  69
  70
  71 void arm_q15_to_q7(
  72   q15_t * pSrc,
  73   q7_t * pDst,
  74   uint32_t blockSize)
  75 {
  76   q15_t *pIn = pSrc;                             /* Src pointer */
  77   uint32_t blkCnt;                               /* loop counter */
  78
  79 #ifndef ARM_MATH_CM0_FAMILY
  80
  81   /* Run the below code for Cortex-M4 and Cortex-M3 */
  82   q31_t in1, in2;
  83   q31_t out1, out2;
  84
  85   /*loop Unrolling */
  86   blkCnt = blockSize >> 2u;
  87
  88   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
  89    ** a second loop below computes the remaining 1 to 3 samples. */
  90   while(blkCnt > 0u)
  91   {
  92     /* C = (q7_t) A >> 8 */
  93     /* convert from q15 to q7 and then store the results in the destination buffer */
  94     in1 = *__SIMD32(pIn)++;
  95     in2 = *__SIMD32(pIn)++;
  96
  97 #ifndef ARM_MATH_BIG_ENDIAN
  98
  99     out1 = __PKHTB(in2, in1, 16);
 100     out2 = __PKHBT(in2, in1, 16);
 101
 102 #else
 103
 104     out1 = __PKHTB(in1, in2, 16);
 105     out2 = __PKHBT(in1, in2, 16);
 106
 107 #endif //      #ifndef ARM_MATH_BIG_ENDIAN
 108
 109     /* rotate packed value by 24 */
 110     out2 = ((uint32_t) out2 << 8) | ((uint32_t) out2 >> 24);
 111
 112     /* anding with 0xff00ff00 to get two 8 bit values */
 113     out1 = out1 & 0xFF00FF00;
 114     /* anding with 0x00ff00ff to get two 8 bit values */
 115     out2 = out2 & 0x00FF00FF;
 116
 117     /* oring two values(contains two 8 bit values) to get four packed 8 bit values */
 118     out1 = out1 | out2;
 119
 120     /* store 4 samples at a time to destiantion buffer */
 121     *__SIMD32(pDst)++ = out1;
 122
 123     /* Decrement the loop counter */
 124     blkCnt--;
 125   }
 126
 127   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
 128    ** No loop unrolling is used. */
 129   blkCnt = blockSize % 0x4u;
 130
 131 #else
 132
 133   /* Run the below code for Cortex-M0 */
 134
 135   /* Loop over blockSize number of values */
 136   blkCnt = blockSize;
 137
 138 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
 139
 140   while(blkCnt > 0u)
 141   {
 142     /* C = (q7_t) A >> 8 */
 143     /* convert from q15 to q7 and then store the results in the destination buffer */
 144     *pDst++ = (q7_t) (*pIn++ >> 8);
 145
 146     /* Decrement the loop counter */
 147     blkCnt--;
 148   }
 149
 150 }
 151
 152 /**
 153  * @} end of q15_to_x group
 154  */