Add copy of opus library in deps/third_party.

opus/celt/cwrs.c

+/* Copyright (c) 2007-2008 CSIRO
+   Copyright (c) 2007-2009 Xiph.Org Foundation
+   Copyright (c) 2007-2009 Timothy B. Terriberry
+   Written by Timothy B. Terriberry and Jean-Marc Valin */
+/*
+   Redistribution and use in source and binary forms, with or without
+   modification, are permitted provided that the following conditions
+   are met:
+
+   - Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+
+   - 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.
+
+   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+   ``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 COPYRIGHT OWNER
+   OR CONTRIBUTORS 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.
+*/
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "os_support.h"
+#include "cwrs.h"
+#include "mathops.h"
+#include "arch.h"
+
+#ifdef CUSTOM_MODES
+
+/*Guaranteed to return a conservatively large estimate of the binary logarithm
+   with frac bits of fractional precision.
+  Tested for all possible 32-bit inputs with frac=4, where the maximum
+   overestimation is 0.06254243 bits.*/
+int log2_frac(opus_uint32 val, int frac)
+{
+  int l;
+  l=EC_ILOG(val);
+  if(val&(val-1)){
+    /*This is (val>>l-16), but guaranteed to round up, even if adding a bias
+       before the shift would cause overflow (e.g., for 0xFFFFxxxx).
+       Doesn't work for val=0, but that case fails the test above.*/
+    if(l>16)val=((val-1)>>(l-16))+1;
+    else val<<=16-l;
+    l=(l-1)<<frac;
+    /*Note that we always need one iteration, since the rounding up above means
+       that we might need to adjust the integer part of the logarithm.*/
+    do{
+      int b;
+      b=(int)(val>>16);
+      l+=b<<frac;
+      val=(val+b)>>b;
+      val=(val*val+0x7FFF)>>15;
+    }
+    while(frac-->0);
+    /*If val is not exactly 0x8000, then we have to round up the remainder.*/
+    return l+(val>0x8000);
+  }
+  /*Exact powers of two require no rounding.*/
+  else return (l-1)<<frac;
+}
+#endif
+
+#ifndef SMALL_FOOTPRINT
+
+#define MASK32 (0xFFFFFFFF)
+
+/*INV_TABLE[i] holds the multiplicative inverse of (2*i+1) mod 2**32.*/
+static const opus_uint32 INV_TABLE[53]={
+  0x00000001,0xAAAAAAAB,0xCCCCCCCD,0xB6DB6DB7,
+  0x38E38E39,0xBA2E8BA3,0xC4EC4EC5,0xEEEEEEEF,
+  0xF0F0F0F1,0x286BCA1B,0x3CF3CF3D,0xE9BD37A7,
+  0xC28F5C29,0x684BDA13,0x4F72C235,0xBDEF7BDF,
+  0x3E0F83E1,0x8AF8AF8B,0x914C1BAD,0x96F96F97,
+  0xC18F9C19,0x2FA0BE83,0xA4FA4FA5,0x677D46CF,
+  0x1A1F58D1,0xFAFAFAFB,0x8C13521D,0x586FB587,
+  0xB823EE09,0xA08AD8F3,0xC10C9715,0xBEFBEFBF,
+  0xC0FC0FC1,0x07A44C6B,0xA33F128D,0xE327A977,
+  0xC7E3F1F9,0x962FC963,0x3F2B3885,0x613716AF,
+  0x781948B1,0x2B2E43DB,0xFCFCFCFD,0x6FD0EB67,
+  0xFA3F47E9,0xD2FD2FD3,0x3F4FD3F5,0xD4E25B9F,
+  0x5F02A3A1,0xBF5A814B,0x7C32B16D,0xD3431B57,
+  0xD8FD8FD9,
+};
+
+/*Computes (_a*_b-_c)/(2*_d+1) when the quotient is known to be exact.
+  _a, _b, _c, and _d may be arbitrary so long as the arbitrary precision result
+   fits in 32 bits, but currently the table for multiplicative inverses is only
+   valid for _d<=52.*/
+static inline opus_uint32 imusdiv32odd(opus_uint32 _a,opus_uint32 _b,
+ opus_uint32 _c,int _d){
+  celt_assert(_d<=52);
+  return (_a*_b-_c)*INV_TABLE[_d]&MASK32;
+}
+
+/*Computes (_a*_b-_c)/_d when the quotient is known to be exact.
+  _d does not actually have to be even, but imusdiv32odd will be faster when
+   it's odd, so you should use that instead.
+  _a and _d are assumed to be small (e.g., _a*_d fits in 32 bits; currently the
+   table for multiplicative inverses is only valid for _d<=54).
+  _b and _c may be arbitrary so long as the arbitrary precision reuslt fits in
+   32 bits.*/
+static inline opus_uint32 imusdiv32even(opus_uint32 _a,opus_uint32 _b,
+ opus_uint32 _c,int _d){
+  opus_uint32 inv;
+  int           mask;
+  int           shift;
+  int           one;
+  celt_assert(_d>0);
+  celt_assert(_d<=54);
+  shift=EC_ILOG(_d^(_d-1));
+  inv=INV_TABLE[(_d-1)>>shift];
+  shift--;
+  one=1<<shift;
+  mask=one-1;
+  return (_a*(_b>>shift)-(_c>>shift)+
+   ((_a*(_b&mask)+one-(_c&mask))>>shift)-1)*inv&MASK32;
+}
+
+#endif /* SMALL_FOOTPRINT */
+
+/*Although derived separately, the pulse vector coding scheme is equivalent to
+   a Pyramid Vector Quantizer \cite{Fis86}.
+  Some additional notes about an early version appear at
+   http://people.xiph.org/~tterribe/notes/cwrs.html, but the codebook ordering
+   and the definitions of some terms have evolved since that was written.
+
+  The conversion from a pulse vector to an integer index (encoding) and back
+   (decoding) is governed by two related functions, V(N,K) and U(N,K).
+
+  V(N,K) = the number of combinations, with replacement, of N items, taken K
+   at a time, when a sign bit is added to each item taken at least once (i.e.,
+   the number of N-dimensional unit pulse vectors with K pulses).
+  One way to compute this is via
+    V(N,K) = K>0 ? sum(k=1...K,2**k*choose(N,k)*choose(K-1,k-1)) : 1,
+   where choose() is the binomial function.
+  A table of values for N<10 and K<10 looks like:
+  V[10][10] = {
+    {1,  0,   0,    0,    0,     0,     0,      0,      0,       0},
+    {1,  2,   2,    2,    2,     2,     2,      2,      2,       2},
+    {1,  4,   8,   12,   16,    20,    24,     28,     32,      36},
+    {1,  6,  18,   38,   66,   102,   146,    198,    258,     326},
+    {1,  8,  32,   88,  192,   360,   608,    952,   1408,    1992},
+    {1, 10,  50,  170,  450,  1002,  1970,   3530,   5890,    9290},
+    {1, 12,  72,  292,  912,  2364,  5336,  10836,  20256,   35436},
+    {1, 14,  98,  462, 1666,  4942, 12642,  28814,  59906,  115598},
+    {1, 16, 128,  688, 2816,  9424, 27008,  68464, 157184,  332688},
+    {1, 18, 162,  978, 4482, 16722, 53154, 148626, 374274,  864146}
+  };
+
+  U(N,K) = the number of such combinations wherein N-1 objects are taken at
+   most K-1 at a time.
+  This is given by
+    U(N,K) = sum(k=0...K-1,V(N-1,k))
+           = K>0 ? (V(N-1,K-1) + V(N,K-1))/2 : 0.
+  The latter expression also makes clear that U(N,K) is half the number of such
+   combinations wherein the first object is taken at least once.
+  Although it may not be clear from either of these definitions, U(N,K) is the
+   natural function to work with when enumerating the pulse vector codebooks,
+   not V(N,K).
+  U(N,K) is not well-defined for N=0, but with the extension
+    U(0,K) = K>0 ? 0 : 1,
+   the function becomes symmetric: U(N,K) = U(K,N), with a similar table:
+  U[10][10] = {
+    {1, 0,  0,   0,    0,    0,     0,     0,      0,      0},
+    {0, 1,  1,   1,    1,    1,     1,     1,      1,      1},
+    {0, 1,  3,   5,    7,    9,    11,    13,     15,     17},
+    {0, 1,  5,  13,   25,   41,    61,    85,    113,    145},
+    {0, 1,  7,  25,   63,  129,   231,   377,    575,    833},
+    {0, 1,  9,  41,  129,  321,   681,  1289,   2241,   3649},
+    {0, 1, 11,  61,  231,  681,  1683,  3653,   7183,  13073},
+    {0, 1, 13,  85,  377, 1289,  3653,  8989,  19825,  40081},
+    {0, 1, 15, 113,  575, 2241,  7183, 19825,  48639, 108545},
+    {0, 1, 17, 145,  833, 3649, 13073, 40081, 108545, 265729}
+  };
+
+  With this extension, V(N,K) may be written in terms of U(N,K):
+    V(N,K) = U(N,K) + U(N,K+1)
+   for all N>=0, K>=0.
+  Thus U(N,K+1) represents the number of combinations where the first element
+   is positive or zero, and U(N,K) represents the number of combinations where
+   it is negative.
+  With a large enough table of U(N,K) values, we could write O(N) encoding
+   and O(min(N*log(K),N+K)) decoding routines, but such a table would be
+   prohibitively large for small embedded devices (K may be as large as 32767
+   for small N, and N may be as large as 200).
+
+  Both functions obey the same recurrence relation:
+    V(N,K) = V(N-1,K) + V(N,K-1) + V(N-1,K-1),
+    U(N,K) = U(N-1,K) + U(N,K-1) + U(N-1,K-1),
+   for all N>0, K>0, with different initial conditions at N=0 or K=0.
+  This allows us to construct a row of one of the tables above given the
+   previous row or the next row.
+  Thus we can derive O(NK) encoding and decoding routines with O(K) memory
+   using only addition and subtraction.
+
+  When encoding, we build up from the U(2,K) row and work our way forwards.
+  When decoding, we need to start at the U(N,K) row and work our way backwards,
+   which requires a means of computing U(N,K).
+  U(N,K) may be computed from two previous values with the same N:
+    U(N,K) = ((2*N-1)*U(N,K-1) - U(N,K-2))/(K-1) + U(N,K-2)
+   for all N>1, and since U(N,K) is symmetric, a similar relation holds for two
+   previous values with the same K:
+    U(N,K>1) = ((2*K-1)*U(N-1,K) - U(N-2,K))/(N-1) + U(N-2,K)
+   for all K>1.
+  This allows us to construct an arbitrary row of the U(N,K) table by starting
+   with the first two values, which are constants.
+  This saves roughly 2/3 the work in our O(NK) decoding routine, but costs O(K)
+   multiplications.
+  Similar relations can be derived for V(N,K), but are not used here.
+
+  For N>0 and K>0, U(N,K) and V(N,K) take on the form of an (N-1)-degree
+   polynomial for fixed N.
+  The first few are
+    U(1,K) = 1,
+    U(2,K) = 2*K-1,
+    U(3,K) = (2*K-2)*K+1,
+    U(4,K) = (((4*K-6)*K+8)*K-3)/3,
+    U(5,K) = ((((2*K-4)*K+10)*K-8)*K+3)/3,
+   and
+    V(1,K) = 2,
+    V(2,K) = 4*K,
+    V(3,K) = 4*K*K+2,
+    V(4,K) = 8*(K*K+2)*K/3,
+    V(5,K) = ((4*K*K+20)*K*K+6)/3,
+   for all K>0.
+  This allows us to derive O(N) encoding and O(N*log(K)) decoding routines for
+   small N (and indeed decoding is also O(N) for N<3).
+
+  @ARTICLE{Fis86,
+    author="Thomas R. Fischer",
+    title="A Pyramid Vector Quantizer",
+    journal="IEEE Transactions on Information Theory",
+    volume="IT-32",
+    number=4,
+    pages="568--583",
+    month=Jul,
+    year=1986
+  }*/
+
+#ifndef SMALL_FOOTPRINT
+/*Compute U(2,_k).
+  Note that this may be called with _k=32768 (maxK[2]+1).*/
+static inline unsigned ucwrs2(unsigned _k){
+  celt_assert(_k>0);
+  return _k+(_k-1);
+}
+
+/*Compute V(2,_k).*/
+static inline opus_uint32 ncwrs2(int _k){
+  celt_assert(_k>0);
+  return 4*(opus_uint32)_k;
+}
+
+/*Compute U(3,_k).
+  Note that this may be called with _k=32768 (maxK[3]+1).*/
+static inline opus_uint32 ucwrs3(unsigned _k){
+  celt_assert(_k>0);
+  return (2*(opus_uint32)_k-2)*_k+1;
+}
+
+/*Compute V(3,_k).*/
+static inline opus_uint32 ncwrs3(int _k){
+  celt_assert(_k>0);
+  return 2*(2*(unsigned)_k*(opus_uint32)_k+1);
+}
+
+/*Compute U(4,_k).*/
+static inline opus_uint32 ucwrs4(int _k){
+  celt_assert(_k>0);
+  return imusdiv32odd(2*_k,(2*_k-3)*(opus_uint32)_k+4,3,1);
+}
+
+/*Compute V(4,_k).*/
+static inline opus_uint32 ncwrs4(int _k){
+  celt_assert(_k>0);
+  return ((_k*(opus_uint32)_k+2)*_k)/3<<3;
+}
+
+#endif /* SMALL_FOOTPRINT */
+
+/*Computes the next row/column of any recurrence that obeys the relation
+   u[i][j]=u[i-1][j]+u[i][j-1]+u[i-1][j-1].
+  _ui0 is the base case for the new row/column.*/
+static inline void unext(opus_uint32 *_ui,unsigned _len,opus_uint32 _ui0){
+  opus_uint32 ui1;
+  unsigned      j;
+  /*This do-while will overrun the array if we don't have storage for at least
+     2 values.*/
+  j=1; do {
+    ui1=UADD32(UADD32(_ui[j],_ui[j-1]),_ui0);
+    _ui[j-1]=_ui0;
+    _ui0=ui1;
+  } while (++j<_len);
+  _ui[j-1]=_ui0;
+}
+
+/*Computes the previous row/column of any recurrence that obeys the relation
+   u[i-1][j]=u[i][j]-u[i][j-1]-u[i-1][j-1].
+  _ui0 is the base case for the new row/column.*/
+static inline void uprev(opus_uint32 *_ui,unsigned _n,opus_uint32 _ui0){
+  opus_uint32 ui1;
+  unsigned      j;
+  /*This do-while will overrun the array if we don't have storage for at least
+     2 values.*/
+  j=1; do {
+    ui1=USUB32(USUB32(_ui[j],_ui[j-1]),_ui0);
+    _ui[j-1]=_ui0;
+    _ui0=ui1;
+  } while (++j<_n);
+  _ui[j-1]=_ui0;
+}
+
+/*Compute V(_n,_k), as well as U(_n,0..._k+1).
+  _u: On exit, _u[i] contains U(_n,i) for i in [0..._k+1].*/
+static opus_uint32 ncwrs_urow(unsigned _n,unsigned _k,opus_uint32 *_u){
+  opus_uint32 um2;
+  unsigned      len;
+  unsigned      k;
+  len=_k+2;
+  /*We require storage at least 3 values (e.g., _k>0).*/
+  celt_assert(len>=3);
+  _u[0]=0;
+  _u[1]=um2=1;
+#ifndef SMALL_FOOTPRINT
+  /*_k>52 doesn't work in the false branch due to the limits of INV_TABLE,
+    but _k isn't tested here because k<=52 for n=7*/
+  if(_n<=6)
+#endif
+ {
+    /*If _n==0, _u[0] should be 1 and the rest should be 0.*/
+    /*If _n==1, _u[i] should be 1 for i>1.*/
+    celt_assert(_n>=2);
+    /*If _k==0, the following do-while loop will overflow the buffer.*/
+    celt_assert(_k>0);
+    k=2;
+    do _u[k]=(k<<1)-1;
+    while(++k<len);
+    for(k=2;k<_n;k++)unext(_u+1,_k+1,1);
+  }
+#ifndef SMALL_FOOTPRINT
+  else{
+    opus_uint32 um1;
+    opus_uint32 n2m1;
+    _u[2]=n2m1=um1=(_n<<1)-1;
+    for(k=3;k<len;k++){
+      /*U(N,K) = ((2*N-1)*U(N,K-1)-U(N,K-2))/(K-1) + U(N,K-2)*/
+      _u[k]=um2=imusdiv32even(n2m1,um1,um2,k-1)+um2;
+      if(++k>=len)break;
+      _u[k]=um1=imusdiv32odd(n2m1,um2,um1,(k-1)>>1)+um1;
+    }
+  }
+#endif /* SMALL_FOOTPRINT */
+  return _u[_k]+_u[_k+1];
+}
+
+#ifndef SMALL_FOOTPRINT
+
+/*Returns the _i'th combination of _k elements (at most 32767) chosen from a
+   set of size 1 with associated sign bits.
+  _y: Returns the vector of pulses.*/
+static inline void cwrsi1(int _k,opus_uint32 _i,int *_y){
+  int s;
+  s=-(int)_i;
+  _y[0]=(_k+s)^s;
+}
+
+/*Returns the _i'th combination of _k elements (at most 32767) chosen from a
+   set of size 2 with associated sign bits.
+  _y: Returns the vector of pulses.*/
+static inline void cwrsi2(int _k,opus_uint32 _i,int *_y){
+  opus_uint32 p;
+  int           s;
+  int           yj;
+  p=ucwrs2(_k+1U);
+  s=-(_i>=p);
+  _i-=p&s;
+  yj=_k;
+  _k=(_i+1)>>1;
+  p=_k?ucwrs2(_k):0;
+  _i-=p;
+  yj-=_k;
+  _y[0]=(yj+s)^s;
+  cwrsi1(_k,_i,_y+1);
+}
+
+/*Returns the _i'th combination of _k elements (at most 32767) chosen from a
+   set of size 3 with associated sign bits.
+  _y: Returns the vector of pulses.*/
+static void cwrsi3(int _k,opus_uint32 _i,int *_y){
+  opus_uint32 p;
+  int           s;
+  int           yj;
+  p=ucwrs3(_k+1U);
+  s=-(_i>=p);
+  _i-=p&s;
+  yj=_k;
+  /*Finds the maximum _k such that ucwrs3(_k)<=_i (tested for all
+     _i<2147418113=U(3,32768)).*/
+  _k=_i>0?(isqrt32(2*_i-1)+1)>>1:0;
+  p=_k?ucwrs3(_k):0;
+  _i-=p;
+  yj-=_k;
+  _y[0]=(yj+s)^s;
+  cwrsi2(_k,_i,_y+1);
+}
+
+/*Returns the _i'th combination of _k elements (at most 1172) chosen from a set
+   of size 4 with associated sign bits.
+  _y: Returns the vector of pulses.*/
+static void cwrsi4(int _k,opus_uint32 _i,int *_y){
+  opus_uint32 p;
+  int           s;
+  int           yj;
+  int           kl;
+  int           kr;
+  p=ucwrs4(_k+1);
+  s=-(_i>=p);
+  _i-=p&s;
+  yj=_k;
+  /*We could solve a cubic for k here, but the form of the direct solution does
+     not lend itself well to exact integer arithmetic.
+    Instead we do a binary search on U(4,K).*/
+  kl=0;
+  kr=_k;
+  for(;;){
+    _k=(kl+kr)>>1;
+    p=_k?ucwrs4(_k):0;
+    if(p<_i){
+      if(_k>=kr)break;
+      kl=_k+1;
+    }
+    else if(p>_i)kr=_k-1;
+    else break;
+  }
+  _i-=p;
+  yj-=_k;
+  _y[0]=(yj+s)^s;
+  cwrsi3(_k,_i,_y+1);
+}
+
+#endif /* SMALL_FOOTPRINT */
+
+/*Returns the _i'th combination of _k elements chosen from a set of size _n
+   with associated sign bits.
+  _y: Returns the vector of pulses.
+  _u: Must contain entries [0..._k+1] of row _n of U() on input.
+      Its contents will be destructively modified.*/
+static void cwrsi(int _n,int _k,opus_uint32 _i,int *_y,opus_uint32 *_u){
+  int j;
+  celt_assert(_n>0);
+  j=0;
+  do{
+    opus_uint32 p;
+    int           s;
+    int           yj;
+    p=_u[_k+1];
+    s=-(_i>=p);
+    _i-=p&s;
+    yj=_k;
+    p=_u[_k];
+    while(p>_i)p=_u[--_k];
+    _i-=p;
+    yj-=_k;
+    _y[j]=(yj+s)^s;
+    uprev(_u,_k+2,0);
+  }
+  while(++j<_n);
+}
+
+/*Returns the index of the given combination of K elements chosen from a set
+   of size 1 with associated sign bits.
+  _y: The vector of pulses, whose sum of absolute values is K.
+  _k: Returns K.*/
+static inline opus_uint32 icwrs1(const int *_y,int *_k){
+  *_k=abs(_y[0]);
+  return _y[0]<0;
+}
+
+#ifndef SMALL_FOOTPRINT
+
+/*Returns the index of the given combination of K elements chosen from a set
+   of size 2 with associated sign bits.
+  _y: The vector of pulses, whose sum of absolute values is K.
+  _k: Returns K.*/
+static inline opus_uint32 icwrs2(const int *_y,int *_k){
+  opus_uint32 i;
+  int           k;
+  i=icwrs1(_y+1,&k);
+  i+=k?ucwrs2(k):0;
+  k+=abs(_y[0]);
+  if(_y[0]<0)i+=ucwrs2(k+1U);
+  *_k=k;
+  return i;
+}
+
+/*Returns the index of the given combination of K elements chosen from a set
+   of size 3 with associated sign bits.
+  _y: The vector of pulses, whose sum of absolute values is K.
+  _k: Returns K.*/
+static inline opus_uint32 icwrs3(const int *_y,int *_k){
+  opus_uint32 i;
+  int           k;
+  i=icwrs2(_y+1,&k);
+  i+=k?ucwrs3(k):0;
+  k+=abs(_y[0]);
+  if(_y[0]<0)i+=ucwrs3(k+1U);
+  *_k=k;
+  return i;
+}
+
+/*Returns the index of the given combination of K elements chosen from a set
+   of size 4 with associated sign bits.
+  _y: The vector of pulses, whose sum of absolute values is K.
+  _k: Returns K.*/
+static inline opus_uint32 icwrs4(const int *_y,int *_k){
+  opus_uint32 i;
+  int           k;
+  i=icwrs3(_y+1,&k);
+  i+=k?ucwrs4(k):0;
+  k+=abs(_y[0]);
+  if(_y[0]<0)i+=ucwrs4(k+1);
+  *_k=k;
+  return i;
+}
+
+#endif /* SMALL_FOOTPRINT */
+
+/*Returns the index of the given combination of K elements chosen from a set
+   of size _n with associated sign bits.
+  _y:  The vector of pulses, whose sum of absolute values must be _k.
+  _nc: Returns V(_n,_k).*/
+static inline opus_uint32 icwrs(int _n,int _k,opus_uint32 *_nc,const int *_y,
+ opus_uint32 *_u){
+  opus_uint32 i;
+  int           j;
+  int           k;
+  /*We can't unroll the first two iterations of the loop unless _n>=2.*/
+  celt_assert(_n>=2);
+  _u[0]=0;
+  for(k=1;k<=_k+1;k++)_u[k]=(k<<1)-1;
+  i=icwrs1(_y+_n-1,&k);
+  j=_n-2;
+  i+=_u[k];
+  k+=abs(_y[j]);
+  if(_y[j]<0)i+=_u[k+1];
+  while(j-->0){
+    unext(_u,_k+2,0);
+    i+=_u[k];
+    k+=abs(_y[j]);
+    if(_y[j]<0)i+=_u[k+1];
+  }
+  *_nc=_u[k]+_u[k+1];
+  return i;
+}
+
+#ifdef CUSTOM_MODES
+void get_required_bits(opus_int16 *_bits,int _n,int _maxk,int _frac){
+  int k;
+  /*_maxk==0 => there's nothing to do.*/
+  celt_assert(_maxk>0);
+  _bits[0]=0;
+  if (_n==1)
+  {
+    for (k=1;k<=_maxk;k++)
+      _bits[k] = 1<<_frac;
+  }
+  else {
+    VARDECL(opus_uint32,u);
+    SAVE_STACK;
+    ALLOC(u,_maxk+2U,opus_uint32);
+    ncwrs_urow(_n,_maxk,u);
+    for(k=1;k<=_maxk;k++)
+      _bits[k]=log2_frac(u[k]+u[k+1],_frac);
+    RESTORE_STACK;
+  }
+}
+#endif /* CUSTOM_MODES */
+
+void encode_pulses(const int *_y,int _n,int _k,ec_enc *_enc){
+  opus_uint32 i;
+  celt_assert(_k>0);
+#ifndef SMALL_FOOTPRINT
+  switch(_n){
+    case 2:{
+      i=icwrs2(_y,&_k);
+      ec_enc_uint(_enc,i,ncwrs2(_k));
+    }break;
+    case 3:{
+      i=icwrs3(_y,&_k);
+      ec_enc_uint(_enc,i,ncwrs3(_k));
+    }break;
+    case 4:{
+      i=icwrs4(_y,&_k);
+      ec_enc_uint(_enc,i,ncwrs4(_k));
+    }break;
+     default:
+    {
+#endif
+      VARDECL(opus_uint32,u);
+      opus_uint32 nc;
+      SAVE_STACK;
+      ALLOC(u,_k+2U,opus_uint32);
+      i=icwrs(_n,_k,&nc,_y,u);
+      ec_enc_uint(_enc,i,nc);
+      RESTORE_STACK;
+#ifndef SMALL_FOOTPRINT
+    }
+    break;
+  }
+#endif
+}
+
+void decode_pulses(int *_y,int _n,int _k,ec_dec *_dec)
+{
+  celt_assert(_k>0);
+#ifndef SMALL_FOOTPRINT
+   switch(_n){
+    case 2:cwrsi2(_k,ec_dec_uint(_dec,ncwrs2(_k)),_y);break;
+    case 3:cwrsi3(_k,ec_dec_uint(_dec,ncwrs3(_k)),_y);break;
+    case 4:cwrsi4(_k,ec_dec_uint(_dec,ncwrs4(_k)),_y);break;
+    default:
+    {
+#endif
+      VARDECL(opus_uint32,u);
+      SAVE_STACK;
+      ALLOC(u,_k+2U,opus_uint32);
+      cwrsi(_n,_k,ec_dec_uint(_dec,ncwrs_urow(_n,_k,u)),_y,u);
+      RESTORE_STACK;
+#ifndef SMALL_FOOTPRINT
+    }
+    break;
+  }
+#endif
+}