ref: 361710b16b1b6e564351178000d871f66a334849
dir: /src/reverse.c/
/*
* June 1, 1992
* Copyright 1992 Guido van Rossum And Sundry Contributors
* This source code is freely redistributable and may be used for
* any purpose. This copyright notice must be maintained.
* Guido van Rossum And Sundry Contributors are not responsible for
* the consequences of using this software.
*/
/*
* "reverse" effect, uses a temporary file created by tmpfile().
*/
#include <math.h>
#include <stdio.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h> /* For SEEK_* defines if not found in stdio */
#endif
#include "st.h"
/* Private data */
typedef struct reversestuff {
FILE *fp;
LONG pos;
int phase;
} *reverse_t;
#define WRITING 0
#define READING 1
/*
* Process options: none in our case.
*/
void reverse_getopts(effp, n, argv)
eff_t effp;
int n;
char **argv;
{
if (n)
fail("Reverse effect takes no options.");
}
/*
* Prepare processing: open temporary file.
*/
void reverse_start(effp)
eff_t effp;
{
reverse_t reverse = (reverse_t) effp->priv;
reverse->fp = tmpfile();
if (reverse->fp == NULL)
fail("Reverse effect can't create temporary file\n");
reverse->phase = WRITING;
}
/*
* Effect flow: a degenerate case: write input samples on temporary file,
* don't generate any output samples.
*/
void reverse_flow(effp, ibuf, obuf, isamp, osamp)
eff_t effp;
LONG *ibuf, *obuf;
int *isamp, *osamp;
{
reverse_t reverse = (reverse_t) effp->priv;
if (reverse->phase != WRITING)
fail("Internal error: reverse_flow called in wrong phase");
if (fwrite((char *)ibuf, sizeof(LONG), *isamp, reverse->fp)
!= *isamp)
fail("Reverse effect write error on temporary file\n");
*osamp = 0;
}
/*
* Effect drain: generate the actual samples in reverse order.
*/
void reverse_drain(effp, obuf, osamp)
eff_t effp;
LONG *obuf;
int *osamp;
{
reverse_t reverse = (reverse_t) effp->priv;
int len, nbytes;
register int i, j;
LONG temp;
if (reverse->phase == WRITING) {
fflush(reverse->fp);
fseek(reverse->fp, 0L, SEEK_END);
reverse->pos = ftell(reverse->fp);
if (reverse->pos % sizeof(LONG) != 0)
fail("Reverse effect finds odd temporary file\n");
reverse->phase = READING;
}
len = *osamp;
nbytes = len * sizeof(LONG);
if (reverse->pos < nbytes) {
nbytes = reverse->pos;
len = nbytes / sizeof(LONG);
}
reverse->pos -= nbytes;
fseek(reverse->fp, reverse->pos, SEEK_SET);
if (fread((char *)obuf, sizeof(LONG), len, reverse->fp) != len)
fail("Reverse effect read error from temporary file\n");
for (i = 0, j = len-1; i < j; i++, j--) {
temp = obuf[i];
obuf[i] = obuf[j];
obuf[j] = temp;
}
*osamp = len;
}
/*
* Close and unlink the temporary file.
*/
void reverse_stop(effp)
eff_t effp;
{
reverse_t reverse = (reverse_t) effp->priv;
fclose(reverse->fp);
}