rosapps/smartpdf/poppler/goo/FixedPoint.cc

   1 //========================================================================
   2 //
   3 // FixedPoint.cc
   4 //
   5 // Fixed point type, with C++ operators.
   6 //
   7 // Copyright 2004 Glyph & Cog, LLC
   8 //
   9 //========================================================================
  10
  11 #include <config.h>
  12
  13 #if USE_FIXEDPOINT
  14
  15 #ifdef USE_GCC_PRAGMAS
  16 #pragma implementation
  17 #endif
  18
  19 #include "FixedPoint.h"
  20
  21 FixedPoint FixedPoint::sqrt(FixedPoint x) {
  22   FixedPoint y0, y1, z;
  23
  24   if (x.val <= 0) {
  25     y1.val = 0;
  26   } else {
  27     y1.val = x.val >> 1;
  28     do {
  29       y0.val = y1.val;
  30       z = x / y0;
  31       y1.val = (y0.val + z.val) >> 1;
  32     } while (::abs(y0.val - y1.val) > 1);
  33   }
  34   return y1;
  35 }
  36
  37 //~ this is not very accurate
  38 FixedPoint FixedPoint::pow(FixedPoint x, FixedPoint y) {
  39   FixedPoint t, t2, lnx0, lnx, z0, z;
  40   int d, i;
  41
  42   if (y.val <= 0) {
  43     z.val = 0;
  44   } else {
  45     // y * ln(x)
  46     t = (x - 1) / (x + 1);
  47     t2 = t * t;
  48     d = 1;
  49     lnx = 0;
  50     do {
  51       lnx0 = lnx;
  52       lnx += t / d;
  53       t *= t2;
  54       d += 2;
  55     } while (::abs(lnx.val - lnx0.val) > 2);
  56     lnx.val <<= 1;
  57     t = y * lnx;
  58     // exp(y * ln(x))
  59     t2 = t;
  60     d = 1;
  61     i = 1;
  62     z = 1;
  63     do {
  64       z0 = z;
  65       z += t2 / d;
  66       t2 *= t;
  67       ++i;
  68       d *= i;
  69     } while (::abs(z.val - z0.val) > 2 && d < (1 << fixptShift));
  70   }
  71   return z;
  72 }
  73
  74 int FixedPoint::mul(int x, int y) {
  75 #if 1 //~tmp
  76   return ((FixPtInt64)x * y) >> fixptShift;
  77 #else
  78   int ah0, ah, bh, al, bl;
  79   ah0 = x & fixptMaskH;
  80   ah = x >> fixptShift;
  81   al = x - ah0;
  82   bh = y >> fixptShift;
  83   bl = y - (bh << fixptShift);
  84   return ah0 * bh + ah * bl + al * bh + ((al * bl) >> fixptShift);
  85 #endif
  86 }
  87
  88 int FixedPoint::div(int x, int y) {
  89 #if 1 //~tmp
  90   return ((FixPtInt64)x << fixptShift) / y;
  91 #else
  92 #endif
  93 }
  94
  95 #endif // USE_FIXEDPOINT