00001
00005 #include <bpm/bpm_messages.h>
00006 #include <bpm/bpm_nr.h>
00007
00008
00027 int nr_realft( double data[], unsigned long n, int isign ) {
00028
00029
00030 unsigned long i, i1,i2,i3,i4,np3;
00031 double c1=0.5,c2,h1r,h1i,h2r,h2i;
00032 double wr,wi,wpr,wpi,wtemp,theta;
00033
00034 if ( ! nr_is_pow2( n ) ) {
00035 bpm_error( "Data length is not power of 2 in nr_realft(...)",
00036 __FILE__, __LINE__ );
00037 return BPM_FAILURE;
00038 }
00039
00040 theta = PI/(double)(n>>1);
00041
00042 if (isign == 1){
00043 c2 = -0.5;
00044 nr_four1(data,n>>1,1);
00045 } else {
00046 c2=0.5;
00047 theta = -theta;
00048 }
00049
00050 wtemp=sin(0.5*theta);
00051 wpr = -2.0*wtemp*wtemp;
00052 wpi=sin(theta);
00053 wr=1.0+wpr;
00054 wi=wpi;
00055 np3=n+3;
00056 for(i=2;i<=(n>>2);i++)
00057 {
00058 i4=1+(i3=np3-(i2=1+(i1=i+i-1)));
00059 h1r=c1*(data[i1]+data[i3]);
00060 h1i=c1*(data[i2]-data[i4]);
00061 h2r = -c2*(data[i2]+data[i4]);
00062 h2i=c2*(data[i1]-data[i3]);
00063 data[i1]=h1r+wr*h2r-wi*h2i;
00064 data[i2]=h1i+wr*h2i+wi*h2r;
00065 data[i3]=h1r-wr*h2r+wi*h2i;
00066 data[i4] = -h1i+wr*h2i+wi*h2r;
00067 wr=(wtemp=wr)*wpr-wi*wpi+wr;
00068 wi=wi*wpr+wtemp*wpi+wi;
00069 }
00070 if (isign == 1)
00071 {
00072 data[1] = (h1r=data[1])+data[2];
00073 data[2] = h1r-data[2];
00074 }
00075 else
00076 {
00077 data[1]=c1*((h1r=data[1])+data[2]);
00078 data[2]=c1*(h1r-data[2]);
00079
00080 nr_four1(data,n>>1,-1);
00081 }
00082
00083 return BPM_SUCCESS;
00084 }
00085
