text: /*
   * Copyright (c) 2012
   *      MIPS Technologies, Inc., California.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. Neither the name of the MIPS Technologies, Inc., nor the names of its
   *    contributors may be used to endorse or promote products derived from
   *    this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE MIPS TECHNOLOGIES, INC. ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE MIPS TECHNOLOGIES, INC. BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   * Author:  Nedeljko Babic (nbabic@mips.com)
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #ifndef AVUTIL_FIXED_DSP_H
  #define AVUTIL_FIXED_DSP_H
  
  #include <stdint.h>
  #include "attributes.h"
  #include "common.h"
  #include "libavcodec/mathops.h"
  
  typedef struct AVFixedDSPContext {
      /**
       * Overlap/add with window function.
       * Used primarily by MDCT-based audio codecs.
       * Source and destination vectors must overlap exactly or not at all.
       *
       * @param dst  result vector
       *             constraints: 16-byte aligned
       * @param src0 first source vector
       *             constraints: 16-byte aligned
       * @param src1 second source vector
       *             constraints: 16-byte aligned
       * @param win  half-window vector
       *             constraints: 16-byte aligned
       * @param len  length of vector
       *             constraints: multiple of 4
       * @param bits scaling parameter
       *
       */
      void (*vector_fmul_window_scaled)(int16_t *dst, const int32_t *src0, const int32_t *src1, const int32_t *win, int len, uint8_t bits);
  
      /**
       * Overlap/add with window function.
       * Used primarily by MDCT-based audio codecs.
       * Source and destination vectors must overlap exactly or not at all.
       *
       * @param dst  result vector
       *             constraints: 32-byte aligned
       * @param src0 first source vector
       *             constraints: 16-byte aligned
       * @param src1 second source vector
       *             constraints: 16-byte aligned
       * @param win  half-window vector
       *             constraints: 16-byte aligned
       * @param len  length of vector
       *             constraints: multiple of 4
       */
      void (*vector_fmul_window)(int32_t *dst, const int32_t *src0, const int32_t *src1, const int32_t *win, int len);
  
  } AVFixedDSPContext;
  
  /**
   * Allocate and initialize a fixed DSP context.
   * note: should be freed with a av_free call when no longer needed.
   *
   * @param strict  setting to non-zero avoids using functions which may not be IEEE-754 compliant
   */
  AVFixedDSPContext * avpriv_alloc_fixed_dsp(int strict);
  
  /**
   * Calculate the square root
   *
   * @param x    input fixed point number
   *
   * @param bits format of fixed point number (32 - bits).bits
   *
   * note: input is normalized to (0, 1) fixed point value
   */
  
  static av_always_inline int fixed_sqrt(int x, int bits)
  {
      int retval, bit_mask, guess, square, i;
      int64_t accu;
      int shift1 = 30 - bits;
      int shift2 = bits - 15;
  
      if (shift1 > 0) retval = ff_sqrt(x << shift1);
      else retval = ff_sqrt(x >> -shift1);
  
      if (shift2 > 0) {
          retval = retval << shift2;
          bit_mask = (1 << (shift2 - 1));
  
          for (i=0; i<shift2; i++){
              guess = retval + bit_mask;
              accu = (int64_t)guess * guess;
              square = (int)((accu + bit_mask) >> bits);
              if (x >= square)
                  retval += bit_mask;
              bit_mask >>= 1;
          }
  
      }
      else retval >>= (-shift2);
  
      return retval;
  }
  
  #endif /* AVUTIL_FIXED_DSP_H */
  