The translator, loader, and run-time monitor will treat your module just like any other provided you follow some conventions. You need a structure defining the inputs, outputs and workspace, plus some initialization code and some perf-time code. Let's put an example of these in two new files, newgen.h and newgen.c:
typedef struct { /* newgen.h - define a structure */
OPDS
h; /* required header */
float *result, *istrt, *incr, *itime, *icontin; /* addr outarg, inargs */
float curval, vincr; /* private dataspace */
long countdown; /* ditto */
} RMP;
#include "cs.h" /* newgen.c - init and perf code */
#include "newgen.h"
void rampset(RMP *p) /* at note initialization: */
{
if (*p->icontin == 0.)
p->curval = *p->istrt; /* optionally get new start value */
p->vincr = *p->incr / esr; /* set s-rate increment per sec. */
p->countdown = *p->itime * esr; /* counter for itime seconds */
}
void ramp(RMP *p) /* during note performance: */
{
float *rsltp = p->result; /* init an output array pointer */
int nn = ksmps; /* array size from orchestra */
do {
*rsltp++ = p->curval; /* copy current value to ouput */
if (--p->countdown >= 0) /* for the first itime seconds, */
p->curval += p->vincr; /* ramp the value */
} while (--nn);
}
Now we add this module to the translator table entry.c, under the
opcode name rampt:
#include "newgen.h"
void rampset(), ramp();
/* opcode dspace thread outarg inargs isub ksub asub */
{ "rampt", S(RMP), 5, "a", "iiio", rampset, NULL, ramp },
Finally we relink Csound to include the new module. If your Csound
installation has created a libcsound.a, you can do this by typing
Else copy *.c, *.h and Makefile from the Csound sources,
add newgen.o to the Makefile list OBJS, add newgen.h as a
dependency for entry.o, and a new dependency 'newgen.o: newgen.h',
then run 'make csound'. If your host is a Macintosh,
simply add newgen.h and newgen.c to one of the segments in the Csound
Project, and invoke the C compiler.
The above actions have added a new generator to the Csound language. It is an audio-rate linear ramp function which modifies an input value at a user-defined slope for some period. A ramp can optionally continue from the previous note's last value. The Csound manual entry would look like:
ar rampt istart, islope, itime [, icontin]istart - beginning value of an audio-rate linear ramp. Optionally overridden by a continue flag.
islope - slope of ramp, expressed as the y-interval change per second.
itime - ramp time in seconds, after which the value is held for the remainder of the note.
icontin (optional) - continue flag. If zero, ramping will proceed from input istart . If non-zero, ramping will proceed from the last value of the previous note. The default value is zero.
The file newgen.h includes a one-line list of output and input parameters. These are the ports through which the new generator will communicate with the other generators in an instrument. Communication is by address, not value, and this is a list of pointers to floats. There are no restrictions on names, but the input-output argument types are further defined by character strings in entry.c (inargs, outargs). Inarg types are commonly x, a, k, and i, in the normal Csound manual conventions; also available are o (optional, defaulting to 0), p (optional, defaulting to 1). Outarg types include a, k, i and s (asig or ksig). It is important that all listed argument names be assigned a corresponding argument type in entry.c. Also, i-type args are valid only at initialization time, and other-type args are available only at perf time. Subsequent lines in the RMP structure declare the work space needed to keep the code re-entrant. These enable the module to be used multiple times in multiple instrument copies while preserving all data.
The file newgen.c contains two subroutines, each called with
a pointer to the uniquely allocated RMP structure and its data. The subroutines
can be of three types: note initialization, k-rate signal generation, a-rate
signal generation. A module normally requires two of theseinitialization,
and either k-rate or a-rate subroutineswhich become inserted in various
threaded lists of runnable tasks when an instrument is activated. The thread-types
appear in entry.c in two forms: isub, ksub and asub
names; and a threading index which is the sum of isub=1, ksub=2, asub=4.
The code itself may reference global variables defined in cs.h and
oload.c, the most useful of which are:
extern OPARMS O ;
float esr
user-defined sampling rate
float ekr
user-defined control rate
float ensmps
user-defined ksmps
int ksmps
user-defined ksmps
int nchnls
user-defined nchnls
int O.odebug
command-line -v flag
int O.msglevel
command-line -m level
float pi, twopi obvious
constants
float tpidsr twopi / esr float
sstrcod
special code for string arguments
FUNC *ftp;initialized by the statement
ftp = ftpfind(p->ifuncno);where float *ifuncno is an i-type input argument containing the ftable number. The stored table is then at ftp->ftable, and other data such as length, phase masks, cps-to-incr converters, are also accessed from this pointer. See the FUNC structure in cs.h, the ftfind() code in fgens.c, and the code for oscset() and koscil() in ugens2.c.
AUXCH auxch;in the defined structure (*p), then using the following style of code in the init module:
if (p->auxch.auxp == NULL) auxalloc(npoints * sizeof(float), &p->auxch);The address of this auxilliary space is kept in a chain of such spaces belonging to this instrument, and is automatically managed while the instrument is being duplicated or garbage-collected during performance. The assignment
char *auxp = p->auxch.auxp;will find the allocated space for init-time and perf-time use. See the LINSEG structure in ugens1.h and the code for lsgset() and klnseg() in ugens1.c.
MEMFIL *mfp;in the defined structure (*p), then using the following style of code in the init module:
if (p->mfp == NULL) p->mfp = ldmemfile(filname);where char *filname is a string name of the file requested. The data read will be found between
(char *) p->mfp->beginp; and (char *) p->mfp->endp;Loaded files do not belong to a particular instrument, but are automatically shared for multiple access. See the ADSYN structure in ugens3.h and the code for adset() and adsyn() in ugens3.c.
TSTRARG( "rampt", RMP) \in the file oload.h, and include the following code in the init module:
if (*p->ifilnam == sstrcod) strcpy(filename, unquote(p->strarg));See the code for adset() in ugens3.c, lprdset() in ugens5.c, and pvset() in ugens8.c.