Editing Guide to madagascar programs (section)

==sfcmplx==
{| class="wikitable" align="center" cellspacing="0" border="1"
! colspan="4" style="background:#ffdead;" | Create a complex dataset from its real and imaginary parts.
|-
! colspan="4" | sfcmplx < real.rsf > cmplx.rsf real.rsf imag.rsf
|-
|  colspan="4" | There has to be only two input files specified and no additional parameters.
|}


<tt>sfcmplx</tt> simply creates a complex dataset from its real and
imaginary parts. The reverse operation can be accomplished with
<tt>sfreal</tt> and <tt>sfimag</tt>.
Example of <tt>sfcmplx</tt>:
<pre>
bash$ sfspike n1=2 n2=3 > one.rsf
bash$ sfin one.rsf
one.rsf:
    in="/tmp/one.rsf@"
    esize=4 type=float form=native
    n1=2           d1=0.004       o1=0          label1="Time" unit1="s"
    n2=3           d2=0.1         o2=0          label2="Distance" unit2="km"
        6 elements 24 bytes
bash$ sfcmplx one.rsf one.rsf > cmplx.rsf
bash$ sfin cmplx.rsf
cmplx.rsf:
    in="/tmp/cmplx.rsf@"
    esize=8 type=complex form=native
    n1=2           d1=0.004       o1=0          label1="Time" unit1="s"
    n2=3           d2=0.1         o2=0          label2="Distance" unit2="km"
        6 elements 48 bytes
</pre>

====Implementation: [https://github.com/ahay/src/blob/master/system/main/cmplx.c system/main/cmplx.c]====
The program flow is simple. First, get the names of the input files.
<syntaxhighlight lang="c">
    /* the first two non-parameters are real and imag files */
    for (i=1; i< argc; i++) { 
	if (NULL == strchr(argv[i],'=')) {
	    if (NULL == real) {
		real = sf_input (argv[i]);
	    } else {
		imag = sf_input (argv[i]);
		break;
	    }
	}
    }
    if (NULL == imag) {
	if (NULL == real) sf_error ("not enough input");
	/* if only one input, real is in stdin */
	imag = real;
	real = sf_input("in");
    }
</syntaxhighlight>

The main part of the program reads the real and imaginary parts buffer by buffer and assembles and writes out the complex input. 
<syntaxhighlight lang="c">
    for (nleft= (size_t) (rsize*resize); nleft > 0; nleft -= nbuf) {
	nbuf = (BUFSIZ < nleft)? BUFSIZ: nleft;
	sf_charread(rbuf,nbuf,real);
	sf_charread(ibuf,nbuf,imag);
	for (i=0; i < nbuf; i += resize) {
	    memcpy(cbuf+2*i,       rbuf+i,(size_t) resize);
	    memcpy(cbuf+2*i+resize,ibuf+i,(size_t) resize);
	}
	sf_charwrite(cbuf,2*nbuf,cmplx);
    }
</syntaxhighlight>