--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mathhalf.c	Fri Jun 14 23:27:16 2024 +0000
@@ -0,0 +1,1953 @@
+/***************************************************************************
+ *
+ *   File Name:  mathhalf.c
+ *
+ *   Purpose:  Contains functions which implement the primitive
+ *     arithmetic operations.
+ *
+ *      The functions in this file are listed below.  Some of them are
+ *      defined in terms of other basic operations.  One of the
+ *      routines, saturate() is static.  This is not a basic
+ *      operation, and is not referenced outside the scope of this
+ *      file.
+ *
+ *
+ *       abs_s()
+ *       add()
+ *       divide_s()
+ *       extract_h()
+ *       extract_l()
+ *       L_abs()
+ *       L_add()
+ *       L_deposit_h()
+ *       L_deposit_l()
+ *       L_mac()
+ *       L_msu()
+ *       L_mult()
+ *       L_negate()
+ *       L_shift_r()
+ *       L_shl()
+ *       L_shr()
+ *       L_sub()
+ *       mac_r()
+ *       msu_r()
+ *       mult()
+ *       mult_r()
+ *       negate()
+ *       norm_l()
+ *       norm_s()
+ *       round()
+ *       saturate()
+ *       shift_r()
+ *       shl()
+ *       shr()
+ *       sub()
+ *
+ **************************************************************************/
+
+/*_________________________________________________________________________
+ |                                                                         |
+ |                            Include Files                                |
+ |_________________________________________________________________________|
+*/
+
+#include "typedefs.h"
+#include "mathhalf.h"
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: saturate
+ *
+ *   PURPOSE:
+ *
+ *     Limit the 32 bit input to the range of a 16 bit word.
+ *
+ *
+ *   INPUTS:
+ *
+ *     L_var1
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0xffff 8000 <= swOut <= 0x0000 7fff.
+ *
+ *   KEYWORDS: saturation, limiting, limit, saturate, 16 bits
+ *
+ *************************************************************************/
+
+static Shortword saturate(Longword L_var1)
+{
+  Shortword swOut;
+
+  if (L_var1 > SW_MAX)
+  {
+    swOut = SW_MAX;
+  }
+  else if (L_var1 < SW_MIN)
+  {
+    swOut = SW_MIN;
+  }
+  else
+    swOut = (Shortword) L_var1;        /* automatic type conversion */
+  return (swOut);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: abs_s
+ *
+ *   PURPOSE:
+ *
+ *     Take the absolute value of the 16 bit input.  An input of
+ *     -0x8000 results in a return value of 0x7fff.
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0x0000 0000 <= swOut <= 0x0000 7fff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Take the absolute value of the 16 bit input.  An input of
+ *     -0x8000 results in a return value of 0x7fff.
+ *
+ *   KEYWORDS: absolute value, abs
+ *
+ *************************************************************************/
+
+Shortword abs_s(Shortword var1)
+{
+  Shortword swOut;
+
+  if (var1 == SW_MIN)
+  {
+    swOut = SW_MAX;
+  }
+  else
+  {
+    if (var1 < 0)
+      swOut = -var1;
+    else
+      swOut = var1;
+  }
+  return (swOut);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: add
+ *
+ *   PURPOSE:
+ *
+ *     Perform the addition of the two 16 bit input variable with
+ *     saturation.
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0xffff 8000 <= swOut <= 0x0000 7fff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Perform the addition of the two 16 bit input variable with
+ *     saturation.
+ *
+ *     swOut = var1 + var2
+ *
+ *     swOut is set to 0x7fff if the operation results in an
+ *     overflow.  swOut is set to 0x8000 if the operation results
+ *     in an underflow.
+ *
+ *   KEYWORDS: add, addition
+ *
+ *************************************************************************/
+
+Shortword add(Shortword var1, Shortword var2)
+{
+  Longword L_sum;
+  Shortword swOut;
+
+  L_sum = (Longword) var1 + var2;
+  swOut = saturate(L_sum);
+  return (swOut);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: divide_s
+ *
+ *   PURPOSE:
+ *
+ *     Divide var1 by var2.  Note that both must be positive, and
+ *     var1 >=  var2.  The output is set to 0 if invalid input is
+ *     provided.
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0xffff 8000 <= swOut <= 0x0000 7fff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     In the case where var1==var2 the function returns 0x7fff.  The output
+ *     is undefined for invalid inputs.  This implementation returns zero
+ *     and issues a warning via stdio if invalid input is presented.
+ *
+ *   KEYWORDS: divide
+ *
+ *************************************************************************/
+
+Shortword divide_s(Shortword var1, Shortword var2)
+{
+  Longword L_div;
+  Shortword swOut;
+
+  if (var1 < 0 || var2 < 0 || var1 > var2)
+  {
+    /* undefined output for invalid input into divide_s */
+    return (0);
+  }
+
+  if (var1 == var2)
+    return (0x7fff);
+
+  L_div = ((0x00008000L * (Longword) var1) / (Longword) var2);
+  swOut = saturate(L_div);
+  return (swOut);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: extract_h
+ *
+ *   PURPOSE:
+ *
+ *     Extract the 16 MS bits of a 32 bit Longword.  Return the 16 bit
+ *     number as a Shortword.  This is used as a "truncation" of a fractional
+ *     number.
+ *
+ *   INPUTS:
+ *
+ *     L_var1
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0xffff 8000 <= swOut <= 0x0000 7fff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *   KEYWORDS: assign, truncate
+ *
+ *************************************************************************/
+
+Shortword extract_h(Longword L_var1)
+{
+  Shortword var2;
+
+  var2 = (Shortword) (0x0000ffffL & (L_var1 >> 16));
+  return (var2);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: extract_l
+ *
+ *   PURPOSE:
+ *
+ *     Extract the 16 LS bits of a 32 bit Longword.  Return the 16 bit
+ *     number as a Shortword.  The upper portion of the input Longword
+ *     has no impact whatsoever on the output.
+ *
+ *   INPUTS:
+ *
+ *     L_var1
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0xffff 8000 <= swOut <= 0x0000 7fff.
+ *
+ *
+ *   KEYWORDS: extract, assign
+ *
+ *************************************************************************/
+
+Shortword extract_l(Longword L_var1)
+{
+  Shortword var2;
+
+  var2 = (Shortword) (0x0000ffffL & L_var1);
+  return (var2);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: L_abs
+ *
+ *   PURPOSE:
+ *
+ *     Take the absolute value of the 32 bit input.  An input of
+ *     -0x8000 0000 results in a return value of 0x7fff ffff.
+ *
+ *   INPUTS:
+ *
+ *     L_var1
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     L_Out
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *
+ *
+ *
+ *   KEYWORDS: absolute value, abs
+ *
+ *************************************************************************/
+Longword L_abs(Longword L_var1)
+{
+  Longword L_Out;
+
+  if (L_var1 == LW_MIN)
+  {
+    L_Out = LW_MAX;
+  }
+  else
+  {
+    if (L_var1 < 0)
+      L_Out = -L_var1;
+    else
+      L_Out = L_var1;
+  }
+  return (L_Out);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: L_add
+ *
+ *   PURPOSE:
+ *
+ *     Perform the addition of the two 32 bit input variables with
+ *     saturation.
+ *
+ *   INPUTS:
+ *
+ *     L_var1
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *     L_var2
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var2 <= 0x7fff ffff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     L_Out
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Perform the addition of the two 32 bit input variables with
+ *     saturation.
+ *
+ *     L_Out = L_var1 + L_var2
+ *
+ *     L_Out is set to 0x7fff ffff if the operation results in an
+ *     overflow.  L_Out is set to 0x8000 0000 if the operation
+ *     results in an underflow.
+ *
+ *   KEYWORDS: add, addition
+ *
+ *************************************************************************/
+Longword L_add(Longword L_var1, Longword L_var2)
+{
+
+  Longword L_Sum,
+         L_SumLow,
+         L_SumHigh;
+
+  L_Sum = L_var1 + L_var2;
+
+  if ((L_var1 > 0 && L_var2 > 0) || (L_var1 < 0 && L_var2 < 0))
+  {
+
+    /* an overflow is possible */
+
+    L_SumLow = (L_var1 & 0xffff) + (L_var2 & 0xffff);
+    L_SumHigh = ((L_var1 >> 16) & 0xffff) + ((L_var2 >> 16) & 0xffff);
+    if (L_SumLow & 0x10000)
+    {
+      /* carry into high word is set */
+      L_SumHigh += 1;
+    }
+
+    /* update sum only if there is an overflow or underflow */
+    /*------------------------------------------------------*/
+
+    if ((0x10000 & L_SumHigh) && !(0x8000 & L_SumHigh))
+      L_Sum = LW_MIN;                  /* underflow */
+    else if (!(0x10000 & L_SumHigh) && (0x8000 & L_SumHigh))
+      L_Sum = LW_MAX;                  /* overflow */
+  }
+
+  return (L_Sum);
+
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: L_deposit_h
+ *
+ *   PURPOSE:
+ *
+ *     Put the 16 bit input into the 16 MSB's of the output Longword.  The
+ *     LS 16 bits are zeroed.
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     L_Out
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff 0000.
+ *
+ *
+ *   KEYWORDS: deposit, assign, fractional assign
+ *
+ *************************************************************************/
+
+Longword L_deposit_h(Shortword var1)
+{
+  Longword L_var2;
+
+  L_var2 = (Longword) var1 << 16;
+  return (L_var2);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: L_deposit_l
+ *
+ *   PURPOSE:
+ *
+ *     Put the 16 bit input into the 16 LSB's of the output Longword with
+ *     sign extension i.e. the top 16 bits are set to either 0 or 0xffff.
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     L_Out
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0xffff 8000 <= L_var1 <= 0x0000 7fff.
+ *
+ *   KEYWORDS: deposit, assign
+ *
+ *************************************************************************/
+
+Longword L_deposit_l(Shortword var1)
+{
+  Longword L_Out;
+
+  L_Out = var1;
+  return (L_Out);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: L_mac
+ *
+ *   PURPOSE:
+ *
+ *     Multiply accumulate.  Fractionally multiply two 16 bit
+ *     numbers together with saturation.  Add that result to the
+ *     32 bit input with saturation.  Return the 32 bit result.
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *     L_var3
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var2 <= 0x7fff ffff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     L_Out
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Fractionally multiply two 16 bit numbers together with
+ *     saturation.  The only numbers which will cause saturation on
+ *     the multiply are 0x8000 * 0x8000.
+ *
+ *     Add that result to the 32 bit input with saturation.
+ *     Return the 32 bit result.
+ *
+ *     Please note that this is not a true multiply accumulate as
+ *     most processors would implement it.  The 0x8000*0x8000
+ *     causes and overflow for this instruction.  On most
+ *     processors this would cause an overflow only if the 32 bit
+ *     input added to it were positive or zero.
+ *
+ *   KEYWORDS: mac, multiply accumulate
+ *
+ *************************************************************************/
+
+Longword L_mac(Longword L_var3, Shortword var1, Shortword var2)
+{
+  return (L_add(L_var3, L_mult(var1, var2)));
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: L_msu
+ *
+ *   PURPOSE:
+ *
+ *     Multiply and subtract.  Fractionally multiply two 16 bit
+ *     numbers together with saturation.  Subtract that result from
+ *     the 32 bit input with saturation.  Return the 32 bit result.
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *     L_var3
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var2 <= 0x7fff ffff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     L_Out
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Fractionally multiply two 16 bit numbers together with
+ *     saturation.  The only numbers which will cause saturation on
+ *     the multiply are 0x8000 * 0x8000.
+ *
+ *     Subtract that result from the 32 bit input with saturation.
+ *     Return the 32 bit result.
+ *
+ *     Please note that this is not a true multiply accumulate as
+ *     most processors would implement it.  The 0x8000*0x8000
+ *     causes and overflow for this instruction.  On most
+ *     processors this would cause an overflow only if the 32 bit
+ *     input added to it were negative or zero.
+ *
+ *   KEYWORDS: mac, multiply accumulate, msu
+ *
+ *************************************************************************/
+
+Longword L_msu(Longword L_var3, Shortword var1, Shortword var2)
+{
+  return (L_sub(L_var3, L_mult(var1, var2)));
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: L_mult
+ *
+ *   PURPOSE:
+ *
+ *     Perform a fractional multipy of the two 16 bit input numbers
+ *     with saturation.  Output a 32 bit number.
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     L_Out
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Multiply the two the two 16 bit input numbers. If the
+ *     result is within this range, left shift the result by one
+ *     and output the 32 bit number.  The only possible overflow
+ *     occurs when var1==var2==-0x8000.  In this case output
+ *     0x7fff ffff.
+ *
+ *   KEYWORDS: multiply, mult, mpy
+ *
+ *************************************************************************/
+
+Longword L_mult(Shortword var1, Shortword var2)
+{
+  Longword L_product;
+
+  if (var1 == SW_MIN && var2 == SW_MIN)
+    L_product = LW_MAX;                /* overflow */
+  else
+  {
+    L_product = (Longword) var1 *var2; /* integer multiply */
+
+    L_product = L_product << 1;
+  }
+  return (L_product);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: L_negate
+ *
+ *   PURPOSE:
+ *
+ *     Negate the 32 bit input. 0x8000 0000's negated value is
+ *     0x7fff ffff.
+ *
+ *   INPUTS:
+ *
+ *     L_var1
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     L_Out
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0001 <= L_var1 <= 0x7fff ffff.
+ *
+ *   KEYWORDS: negate, negative
+ *
+ *************************************************************************/
+
+Longword L_negate(Longword L_var1)
+{
+  Longword L_Out;
+
+  if (L_var1 == LW_MIN)
+    L_Out = LW_MAX;
+  else
+    L_Out = -L_var1;
+  return (L_Out);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: L_shift_r
+ *
+ *   PURPOSE:
+ *
+ *     Shift and round.  Perform a shift right. After shifting, use
+ *     the last bit shifted out of the LSB to round the result up
+ *     or down.
+ *
+ *   INPUTS:
+ *
+ *     L_var1
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     L_var1
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Shift and round.  Perform a shift right. After shifting, use
+ *     the last bit shifted out of the LSB to round the result up
+ *     or down.  This is just like shift_r above except that the
+ *     input/output is 32 bits as opposed to 16.
+ *
+ *     if var2 is positve perform a arithmetic left shift
+ *     with saturation (see L_shl() above).
+ *
+ *     If var2 is zero simply return L_var1.
+ *
+ *     If var2 is negative perform a arithmetic right shift (L_shr)
+ *     of L_var1 by (-var2)+1.  Add the LS bit of the result to
+ *     L_var1 shifted right (L_shr) by -var2.
+ *
+ *     Note that there is no constraint on var2, so if var2 is
+ *     -0xffff 8000 then -var2 is 0x0000 8000, not 0x0000 7fff.
+ *     This is the reason the L_shl function is used.
+ *
+ *
+ *   KEYWORDS:
+ *
+ *************************************************************************/
+
+Longword L_shift_r(Longword L_var1, Shortword var2)
+{
+  Longword L_Out,
+         L_rnd;
+
+  if (var2 < -31)
+  {
+    L_Out = 0;
+  }
+  else if (var2 < 0)
+  {
+    /* right shift */
+    L_rnd = L_shl(L_var1, var2 + 1) & 0x1;
+    L_Out = L_add(L_shl(L_var1, var2), L_rnd);
+  }
+  else
+    L_Out = L_shl(L_var1, var2);
+
+  return (L_Out);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: L_shl
+ *
+ *   PURPOSE:
+ *
+ *     Arithmetic shift left (or right).
+ *     Arithmetically shift the input left by var2.   If var2 is
+ *     negative then an arithmetic shift right (L_shr) of L_var1 by
+ *     -var2 is performed.
+ *
+ *   INPUTS:
+ *
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *     L_var1
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     L_Out
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Arithmetically shift the 32 bit input left by var2.  This
+ *     operation maintains the sign of the input number. If var2 is
+ *     negative then an arithmetic shift right (L_shr) of L_var1 by
+ *     -var2 is performed.  See description of L_shr for details.
+ *
+ *     Equivalent to the Full-Rate GSM ">> n" operation.  Note that
+ *     ANSI-C does not guarantee operation of the C ">>" or "<<"
+ *     operator for negative numbers.
+ *
+ *   KEYWORDS: shift, arithmetic shift left,
+ *
+ *************************************************************************/
+
+Longword L_shl(Longword L_var1, Shortword var2)
+{
+
+  Longword L_Mask,
+         L_Out;
+  int    i,
+         iOverflow = 0;
+
+  if (var2 == 0 || L_var1 == 0)
+  {
+    L_Out = L_var1;
+  }
+  else if (var2 < 0)
+  {
+    if (var2 <= -31)
+    {
+      if (L_var1 > 0)
+        L_Out = 0;
+      else
+        L_Out = 0xffffffffL;
+    }
+    else
+      L_Out = L_shr(L_var1, -var2);
+  }
+  else
+  {
+
+    if (var2 >= 31)
+      iOverflow = 1;
+
+    else
+    {
+
+      if (L_var1 < 0)
+        L_Mask = LW_SIGN;              /* sign bit mask */
+      else
+        L_Mask = 0x0;
+      L_Out = L_var1;
+      for (i = 0; i < var2 && !iOverflow; i++)
+      {
+        /* check the sign bit */
+        L_Out = (L_Out & 0x7fffffffL) << 1;
+        if ((L_Mask ^ L_Out) & LW_SIGN)
+          iOverflow = 1;
+      }
+    }
+
+    if (iOverflow)
+    {
+      /* saturate */
+      if (L_var1 > 0)
+        L_Out = LW_MAX;
+      else
+        L_Out = LW_MIN;
+    }
+  }
+
+  return (L_Out);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: L_shr
+ *
+ *   PURPOSE:
+ *
+ *     Arithmetic shift right (or left).
+ *     Arithmetically shift the input right by var2.   If var2 is
+ *     negative then an arithmetic shift left (shl) of var1 by
+ *     -var2 is performed.
+ *
+ *   INPUTS:
+ *
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *     L_var1
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     L_Out
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Arithmetically shift the input right by var2.  This
+ *     operation maintains the sign of the input number. If var2 is
+ *     negative then an arithmetic shift left (shl) of L_var1 by
+ *     -var2 is performed.  See description of L_shl for details.
+ *
+ *     The input is a 32 bit number, as is the output.
+ *
+ *     Equivalent to the Full-Rate GSM ">> n" operation.  Note that
+ *     ANSI-C does not guarantee operation of the C ">>" or "<<"
+ *     operator for negative numbers.
+ *
+ *   KEYWORDS: shift, arithmetic shift right,
+ *
+ *************************************************************************/
+
+Longword L_shr(Longword L_var1, Shortword var2)
+{
+
+  Longword L_Mask,
+         L_Out;
+
+  if (var2 == 0 || L_var1 == 0)
+  {
+    L_Out = L_var1;
+  }
+  else if (var2 < 0)
+  {
+    /* perform a left shift */
+    /*----------------------*/
+    if (var2 <= -31)
+    {
+      /* saturate */
+      if (L_var1 > 0)
+        L_Out = LW_MAX;
+      else
+        L_Out = LW_MIN;
+    }
+    else
+      L_Out = L_shl(L_var1, -var2);
+  }
+  else
+  {
+
+    if (var2 >= 31)
+    {
+      if (L_var1 > 0)
+        L_Out = 0;
+      else
+        L_Out = 0xffffffffL;
+    }
+    else
+    {
+      L_Mask = 0;
+
+      if (L_var1 < 0)
+      {
+        L_Mask = ~L_Mask << (32 - var2);
+      }
+
+      L_var1 >>= var2;
+      L_Out = L_Mask | L_var1;
+    }
+  }
+  return (L_Out);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: L_sub
+ *
+ *   PURPOSE:
+ *
+ *     Perform the subtraction of the two 32 bit input variables with
+ *     saturation.
+ *
+ *   INPUTS:
+ *
+ *     L_var1
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *     L_var2
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var2 <= 0x7fff ffff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     L_Out
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Perform the subtraction of the two 32 bit input variables with
+ *     saturation.
+ *
+ *     L_Out = L_var1 - L_var2
+ *
+ *     L_Out is set to 0x7fff ffff if the operation results in an
+ *     overflow.  L_Out is set to 0x8000 0000 if the operation
+ *     results in an underflow.
+ *
+ *   KEYWORDS: sub, subtraction
+ *
+ *************************************************************************/
+Longword L_sub(Longword L_var1, Longword L_var2)
+{
+  Longword L_Sum;
+
+  /* check for overflow */
+  if ((L_var1 > 0 && L_var2 < 0) || (L_var1 < 0 && L_var2 > 0))
+  {
+    if (L_var2 == LW_MIN)
+    {
+      L_Sum = L_add(L_var1, LW_MAX);
+      L_Sum = L_add(L_Sum, 1);
+    }
+    else
+      L_Sum = L_add(L_var1, -L_var2);
+  }
+  else
+  {                                    /* no overflow possible */
+    L_Sum = L_var1 - L_var2;
+  }
+  return (L_Sum);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME:mac_r
+ *
+ *   PURPOSE:
+ *
+ *     Multiply accumulate and round.  Fractionally multiply two 16
+ *     bit numbers together with saturation.  Add that result to
+ *     the 32 bit input with saturation.  Finally round the result
+ *     into a 16 bit number.
+ *
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *     L_var3
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var2 <= 0x7fff ffff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0xffff 8000 <= swOut <= 0x0000 7fff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Fractionally multiply two 16 bit numbers together with
+ *     saturation.  The only numbers which will cause saturation on
+ *     the multiply are 0x8000 * 0x8000.
+ *
+ *     Add that result to the 32 bit input with saturation.
+ *     Round the 32 bit result by adding 0x0000 8000 to the input.
+ *     The result may overflow due to the add.  If so, the result
+ *     is saturated.  The 32 bit rounded number is then shifted
+ *     down 16 bits and returned as a Shortword.
+ *
+ *     Please note that this is not a true multiply accumulate as
+ *     most processors would implement it.  The 0x8000*0x8000
+ *     causes and overflow for this instruction.  On most
+ *     processors this would cause an overflow only if the 32 bit
+ *     input added to it were positive or zero.
+ *
+ *   KEYWORDS: mac, multiply accumulate, macr
+ *
+ *************************************************************************/
+
+Shortword mac_r(Longword L_var3, Shortword var1, Shortword var2)
+{
+  return (round(L_add(L_var3, L_mult(var1, var2))));
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME:  msu_r
+ *
+ *   PURPOSE:
+ *
+ *     Multiply subtract and round.  Fractionally multiply two 16
+ *     bit numbers together with saturation.  Subtract that result from
+ *     the 32 bit input with saturation.  Finally round the result
+ *     into a 16 bit number.
+ *
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *     L_var3
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var2 <= 0x7fff ffff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0xffff 8000 <= swOut <= 0x0000 7fff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Fractionally multiply two 16 bit numbers together with
+ *     saturation.  The only numbers which will cause saturation on
+ *     the multiply are 0x8000 * 0x8000.
+ *
+ *     Subtract that result from the 32 bit input with saturation.
+ *     Round the 32 bit result by adding 0x0000 8000 to the input.
+ *     The result may overflow due to the add.  If so, the result
+ *     is saturated.  The 32 bit rounded number is then shifted
+ *     down 16 bits and returned as a Shortword.
+ *
+ *     Please note that this is not a true multiply accumulate as
+ *     most processors would implement it.  The 0x8000*0x8000
+ *     causes and overflow for this instruction.  On most
+ *     processors this would cause an overflow only if the 32 bit
+ *     input added to it were positive or zero.
+ *
+ *   KEYWORDS: mac, multiply accumulate, macr
+ *
+ *************************************************************************/
+
+Shortword msu_r(Longword L_var3, Shortword var1, Shortword var2)
+{
+  return (round(L_sub(L_var3, L_mult(var1, var2))));
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: mult
+ *
+ *   PURPOSE:
+ *
+ *     Perform a fractional multipy of the two 16 bit input numbers
+ *     with saturation and truncation.
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0xffff 8000 <= swOut <= 0x0000 7fff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Perform a fractional multipy of the two 16 bit input
+ *     numbers.  If var1 == var2 == -0x8000, output 0x7fff.
+ *     Otherwise output var1*var2 >> 15.  The output is a
+ *     16 bit number.
+ *
+ *   KEYWORDS: mult, mulitply, mpy
+ *
+ *************************************************************************/
+
+Shortword mult(Shortword var1, Shortword var2)
+{
+  Longword L_product;
+  Shortword swOut;
+
+  L_product = L_mult(var1, var2);
+  swOut = extract_h(L_product);
+  return (swOut);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: mult_r
+ *
+ *   PURPOSE:
+ *
+ *     Perform a fractional multipy and round of the two 16 bit
+ *     input numbers with saturation.
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0xffff 8000 <= swOut <= 0x0000 7fff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     This routine is defined as the concatenation of the multiply
+ *     operation and the round operation.
+ *
+ *     The fractional multiply (L_mult) produces a saturated 32 bit
+ *     output.  This is followed by a an add of 0x0000 8000 to the
+ *     32 bit result.  The result may overflow due to the add.  If
+ *     so, the result is saturated.  The 32 bit rounded number is
+ *     then shifted down 16 bits and returned as a Shortword.
+ *
+ *
+ *   KEYWORDS: multiply and round, round, mult_r, mpyr
+ *
+ *************************************************************************/
+
+
+Shortword mult_r(Shortword var1, Shortword var2)
+{
+  Shortword swOut;
+
+  swOut = round(L_mult(var1, var2));
+  return (swOut);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: negate
+ *
+ *   PURPOSE:
+ *
+ *     Negate the 16 bit input. 0x8000's negated value is 0x7fff.
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0xffff 8001 <= swOut <= 0x0000 7fff.
+ *
+ *   KEYWORDS: negate, negative, invert
+ *
+ *************************************************************************/
+
+Shortword negate(Shortword var1)
+{
+  Shortword swOut;
+
+  if (var1 == SW_MIN)
+    swOut = SW_MAX;
+  else
+    swOut = -var1;
+  return (swOut);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: norm_l
+ *
+ *   PURPOSE:
+ *
+ *     Get normalize shift count:
+ *
+ *     A 32 bit number is input (possiblly unnormalized).  Output
+ *     the positive (or zero) shift count required to normalize the
+ *     input.
+ *
+ *   INPUTS:
+ *
+ *     L_var1
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0 <= swOut <= 31
+ *
+ *
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Get normalize shift count:
+ *
+ *     A 32 bit number is input (possiblly unnormalized).  Output
+ *     the positive (or zero) shift count required to normalize the
+ *     input.
+ *
+ *     If zero in input, return 0 as the shift count.
+ *
+ *     For non-zero numbers, count the number of left shift
+ *     required to get the number to fall into the range:
+ *
+ *     0x4000 0000 >= normlzd number >= 0x7fff ffff (positive number)
+ *     or
+ *     0x8000 0000 <= normlzd number < 0xc000 0000 (negative number)
+ *
+ *     Return the number of shifts.
+ *
+ *     This instruction corresponds exactly to the Full-Rate "norm"
+ *     instruction.
+ *
+ *   KEYWORDS: norm, normalization
+ *
+ *************************************************************************/
+
+Shortword norm_l(Longword L_var1)
+{
+
+  Shortword swShiftCnt;
+
+  if (L_var1 != 0)
+  {
+    if (!(L_var1 & LW_SIGN))
+    {
+
+      /* positive input */
+      for (swShiftCnt = 0; !(L_var1 <= LW_MAX && L_var1 >= 0x40000000L);
+           swShiftCnt++)
+      {
+        L_var1 = L_var1 << 1;
+      }
+
+    }
+    else
+    {
+      /* negative input */
+      for (swShiftCnt = 0;
+           !(L_var1 >= LW_MIN && L_var1 < (Longword) 0xc0000000L);
+           swShiftCnt++)
+      {
+        L_var1 = L_var1 << 1;
+      }
+    }
+  }
+  else
+  {
+    swShiftCnt = 0;
+  }
+  return (swShiftCnt);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: norm_s
+ *
+ *   PURPOSE:
+ *
+ *     Get normalize shift count:
+ *
+ *     A 16 bit number is input (possiblly unnormalized).  Output
+ *     the positive (or zero) shift count required to normalize the
+ *     input.
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0 <= swOut <= 15
+ *
+ *
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Get normalize shift count:
+ *
+ *     A 16 bit number is input (possiblly unnormalized).  Output
+ *     the positive (or zero) shift count required to normalize the
+ *     input.
+ *
+ *     If zero in input, return 0 as the shift count.
+ *
+ *     For non-zero numbers, count the number of left shift
+ *     required to get the number to fall into the range:
+ *
+ *     0x4000 >= normlzd number >= 0x7fff (positive number)
+ *     or
+ *     0x8000 <= normlzd number <  0xc000 (negative number)
+ *
+ *     Return the number of shifts.
+ *
+ *     This instruction corresponds exactly to the Full-Rate "norm"
+ *     instruction.
+ *
+ *   KEYWORDS: norm, normalization
+ *
+ *************************************************************************/
+
+Shortword norm_s(Shortword var1)
+{
+
+  short  swShiftCnt;
+  Longword L_var1;
+
+  L_var1 = L_deposit_h(var1);
+  swShiftCnt = norm_l(L_var1);
+  return (swShiftCnt);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: round
+ *
+ *   PURPOSE:
+ *
+ *     Round the 32 bit Longword into a 16 bit shortword with saturation.
+ *
+ *   INPUTS:
+ *
+ *     L_var1
+ *                     32 bit long signed integer (Longword) whose value
+ *                     falls in the range
+ *                     0x8000 0000 <= L_var1 <= 0x7fff ffff.
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0xffff 8000 <= swOut <= 0x0000 7fff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Perform a two's complement round on the input Longword with
+ *     saturation.
+ *
+ *     This is equivalent to adding 0x0000 8000 to the input.  The
+ *     result may overflow due to the add.  If so, the result is
+ *     saturated.  The 32 bit rounded number is then shifted down
+ *     16 bits and returned as a Shortword.
+ *
+ *
+ *   KEYWORDS: round
+ *
+ *************************************************************************/
+
+Shortword round(Longword L_var1)
+{
+  Longword L_Prod;
+
+  L_Prod = L_add(L_var1, 0x00008000L); /* round MSP */
+  return (extract_h(L_Prod));
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: shift_r
+ *
+ *   PURPOSE:
+ *
+ *     Shift and round.  Perform a shift right. After shifting, use
+ *     the last bit shifted out of the LSB to round the result up
+ *     or down.
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0xffff 8000 <= swOut <= 0x0000 7fff.
+ *
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Shift and round.  Perform a shift right. After shifting, use
+ *     the last bit shifted out of the LSB to round the result up
+ *     or down.
+ *
+ *     If var2 is positive perform a arithmetic left shift
+ *     with saturation (see shl() above).
+ *
+ *     If var2 is zero simply return var1.
+ *
+ *     If var2 is negative perform a arithmetic right shift (shr)
+ *     of var1 by (-var2)+1.  Add the LS bit of the result to var1
+ *     shifted right (shr) by -var2.
+ *
+ *     Note that there is no constraint on var2, so if var2 is
+ *     -0xffff 8000 then -var2 is 0x0000 8000, not 0x0000 7fff.
+ *     This is the reason the shl function is used.
+ *
+ *
+ *   KEYWORDS:
+ *
+ *************************************************************************/
+
+Shortword shift_r(Shortword var1, Shortword var2)
+{
+  Shortword swOut,
+         swRnd;
+
+  if (var2 >= 0)
+    swOut = shl(var1, var2);
+  else
+  {
+
+    /* right shift */
+
+    if (var2 < -15)
+    {
+
+      swOut = 0;
+
+    }
+    else
+    {
+
+      swRnd = shl(var1, var2 + 1) & 0x1;
+      swOut = add(shl(var1, var2), swRnd);
+
+    }
+  }
+  return (swOut);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: shl
+ *
+ *   PURPOSE:
+ *
+ *     Arithmetically shift the input left by var2.
+ *
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0xffff 8000 <= swOut <= 0x0000 7fff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     If Arithmetically shift the input left by var2.  If var2 is
+ *     negative then an arithmetic shift right (shr) of var1 by
+ *     -var2 is performed.  See description of shr for details.
+ *     When an arithmetic shift left is performed the var2 LS bits
+ *     are zero filled.
+ *
+ *     The only exception is if the left shift causes an overflow
+ *     or underflow.  In this case the LS bits are not modified.
+ *     The number returned is 0x8000 in the case of an underflow or
+ *     0x7fff in the case of an overflow.
+ *
+ *     The shl is equivalent to the Full-Rate GSM "<< n" operation.
+ *     Note that ANSI-C does not guarantee operation of the C ">>"
+ *     or "<<" operator for negative numbers - it is not specified
+ *     whether this shift is an arithmetic or logical shift.
+ *
+ *   KEYWORDS: asl, arithmetic shift left, shift
+ *
+ *************************************************************************/
+
+Shortword shl(Shortword var1, Shortword var2)
+{
+  Shortword swOut;
+  Longword L_Out;
+
+  if (var2 == 0 || var1 == 0)
+  {
+    swOut = var1;
+  }
+  else if (var2 < 0)
+  {
+
+    /* perform a right shift */
+    /*-----------------------*/
+
+    if (var2 <= -15)
+    {
+      if (var1 < 0)
+        swOut = (Shortword) 0xffff;
+      else
+        swOut = 0x0;
+    }
+    else
+      swOut = shr(var1, -var2);
+
+  }
+  else
+  {
+    /* var2 > 0 */
+    if (var2 >= 15)
+    {
+      /* saturate */
+      if (var1 > 0)
+        swOut = SW_MAX;
+      else
+        swOut = SW_MIN;
+    }
+    else
+    {
+
+      L_Out = (Longword) var1 *(1 << var2);
+
+      swOut = (Shortword) L_Out;       /* copy low portion to swOut, overflow
+                                        * could have hpnd */
+      if (swOut != L_Out)
+      {
+        /* overflow  */
+        if (var1 > 0)
+          swOut = SW_MAX;              /* saturate */
+        else
+          swOut = SW_MIN;              /* saturate */
+      }
+    }
+  }
+  return (swOut);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: shr
+ *
+ *   PURPOSE:
+ *
+ *     Arithmetic shift right (or left).
+ *     Arithmetically shift the input right by var2.   If var2 is
+ *     negative then an arithmetic shift left (shl) of var1 by
+ *     -var2 is performed.
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0xffff 8000 <= swOut <= 0x0000 7fff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Arithmetically shift the input right by var2.  This
+ *     operation maintains the sign of the input number. If var2 is
+ *     negative then an arithmetic shift left (shl) of var1 by
+ *     -var2 is performed.  See description of shl for details.
+ *
+ *     Equivalent to the Full-Rate GSM ">> n" operation.  Note that
+ *     ANSI-C does not guarantee operation of the C ">>" or "<<"
+ *     operator for negative numbers.
+ *
+ *   KEYWORDS: shift, arithmetic shift right,
+ *
+ *************************************************************************/
+
+Shortword shr(Shortword var1, Shortword var2)
+{
+
+  Shortword swMask,
+         swOut;
+
+  if (var2 == 0 || var1 == 0)
+    swOut = var1;
+
+  else if (var2 < 0)
+  {
+    /* perform an arithmetic left shift */
+    /*----------------------------------*/
+    if (var2 <= -15)
+    {
+      /* saturate */
+      if (var1 > 0)
+        swOut = SW_MAX;
+      else
+        swOut = SW_MIN;
+    }
+    else
+      swOut = shl(var1, -var2);
+  }
+
+  else
+  {
+
+    /* positive shift count */
+    /*----------------------*/
+
+    if (var2 >= 15)
+    {
+      if (var1 < 0)
+        swOut = (Shortword) 0xffff;
+      else
+        swOut = 0x0;
+    }
+    else
+    {
+      /* take care of sign extension */
+      /*-----------------------------*/
+
+      swMask = 0;
+      if (var1 < 0)
+      {
+        swMask = ~swMask << (16 - var2);
+      }
+
+      var1 >>= var2;
+      swOut = swMask | var1;
+
+    }
+  }
+  return (swOut);
+}
+
+/***************************************************************************
+ *
+ *   FUNCTION NAME: sub
+ *
+ *   PURPOSE:
+ *
+ *     Perform the subtraction of the two 16 bit input variable with
+ *     saturation.
+ *
+ *   INPUTS:
+ *
+ *     var1
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff.
+ *     var2
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff.
+ *
+ *   OUTPUTS:
+ *
+ *     none
+ *
+ *   RETURN VALUE:
+ *
+ *     swOut
+ *                     16 bit short signed integer (Shortword) whose value
+ *                     falls in the range
+ *                     0xffff 8000 <= swOut <= 0x0000 7fff.
+ *
+ *   IMPLEMENTATION:
+ *
+ *     Perform the subtraction of the two 16 bit input variable with
+ *     saturation.
+ *
+ *     swOut = var1 - var2
+ *
+ *     swOut is set to 0x7fff if the operation results in an
+ *     overflow.  swOut is set to 0x8000 if the operation results
+ *     in an underflow.
+ *
+ *   KEYWORDS: sub, subtraction
+ *
+ *************************************************************************/
+Shortword sub(Shortword var1, Shortword var2)
+{
+  Longword L_diff;
+  Shortword swOut;
+
+  L_diff = (Longword) var1 - var2;
+  swOut = saturate(L_diff);
+
+  return (swOut);
+}