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pcmmix: truncate to shortest buffer; heuristic for stdin

bleh
necessary for easy single track editing in pplay

--- a/pcmmix.c

+++ b/pcmmix.c

@@ -1,17 +1,22 @@

 #include <u.h>

 #include <libc.h>

+enum{

+	Bufsz = 8192,

+};

+

 typedef struct File File;

 struct File{

 	int fd;

 	char *path;

 	int n;

-	uchar buf[8192];

+	int Δ;

+	uchar buf[Bufsz];

 };

 void

 usage(void)

 {

-	fprint(2, "usage: %s [-f factor] [FILE..]\n", argv0);

+	fprint(2, "usage: %s [-t] [-f factor] [FILE..]\n", argv0);

 	exits("usage");

 }

@@ -18,17 +23,19 @@

 void

 main(int argc, char **argv)

 {

-	int n;

+	int n, m, notrunc, gotem;

 	double f;

-	uchar u[8192], *p, *q;

+	File *ftab, *fp;

+	uchar u[Bufsz], *p, *q;

 	s32int v;

 	int nf;

-	File *ftab, *fp;

 	Dir *d;

+	notrunc = 0;

 	f = 1.0;

 	ARGBEGIN{

 	case 'f': f = strtod(EARGF(usage()), nil); break;

+	case 't': notrunc = 1; break;

 	default: usage();

 	}ARGEND

 	nf = argc + 1;

@@ -35,34 +42,56 @@

 	if((ftab = mallocz(nf * sizeof *ftab, 1)) == nil)

 		sysfatal("mallocz: %r");

 	fp = ftab;

-	fp->path = "stdin";

-	if(nf > 1){

-		if((d = dirfstat(0)) == nil)

-			sysfatal("dirfstat: %r");

-		fp->fd = d->length > 0 ? 0 : -1;

-		free(d);

-	}

-	fp++;

+	(fp++)->path = "stdin";

 	while(*argv != nil){

 		if((fp->fd = open(*argv, OREAD)) < 0)

 			sysfatal("open: %r");

-		fp->path = *argv++;

-		fp++;

+		(fp++)->path = *argv++;

 	}

+	gotem = 0;

 	for(;;){

 		n = 0;

 		for(fp=ftab; fp<ftab+nf; fp++){

 			if(fp->fd < 0)

 				continue;

-			if((fp->n = read(fp->fd, fp->buf, sizeof fp->buf)) > 0)

+			if(fp == ftab){

+				if((d = dirfstat(0)) == nil)

+					sysfatal("dirfstat: %r");

+				m = d->length;

+				free(d);

+				if(m > 0)

+					gotem = 1;

+				else if(gotem){

+					if(!notrunc)

+						exits(nil);

+					fp->fd = -1;

+					continue;

+				}

+			}

+			m = sizeof fp->buf - fp->Δ;

+			if(m < 0)

+				m = sizeof fp->buf;

+			if(n > 0 && n < m)

+				m = n;

+			fp->n = read(fp->fd, fp->buf+fp->Δ, m);

+			if(n == 0 || notrunc && n < fp->n || !notrunc && n > fp->n)

+				n = fp->n;

+			fprint(2, "%zd n %d fp->n %d Δ %d\n", fp-ftab, n, fp->n, fp->Δ);

+			if(fp->n > 0)

 				continue;

 			fp->fd = -1;

+			if(!notrunc)

+				exits(nil);

 			if(fp->n < 0)

 				fprint(2, "file %s: read: %r\n", fp->path);

 		}

-		memset(u, 0, sizeof u);

+		if(n <= 0)

+			break;

+		memset(u, 0, n);

 		for(fp=ftab; fp<ftab+nf; fp++){

-			for(p=u, q=fp->buf; q<fp->buf+fp->n; p+=2, q+=2){

+			if(fp->fd < 0)

+				continue;

+			for(p=u, q=fp->buf; q<fp->buf+n; p+=2, q+=2){

 				v = (s16int)(q[1] << 8 | q[0]);

 				v *= f;

 				v += (s16int)(p[1] << 8 | p[0]);

@@ -73,11 +102,8 @@

 				p[0] = v;

 				p[1] = v >> 8;

 			}

-			if(fp->n > n)

-				n = fp->n;

+			fp->Δ = n < fp->n ? fp->n - n : 0;

 		}

-		if(n == 0)

-			break;

 		write(1, u, n);

 	}

 	exits(nil);