shithub: clone

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correctly handle partial reads

--- a/clone.c

+++ b/clone.c

@@ -25,6 +25,7 @@

 typedef struct {

 	File *f;

+	long sz;

 	vlong offset;

 } Blk;

@@ -361,6 +362,7 @@

 vlong

 blklist(File *f, Blk **bp)

 {

+	long odd;

 	vlong i, nblk;

 	Blk *b, *p;

@@ -367,16 +369,20 @@

 	if(f->length == 0)

 		return 0;

 	nblk = f->length / blksz;

+	odd = f->length % blksz;

 	if(nblk == 0)

 		nblk = 1;

-	else if(nblk % blksz > 0)

+	else if(odd > 0)

 		nblk++;

 	b = p = emalloc(sizeof(Blk) * nblk);

 	for(i = 0; i < nblk; i++, p++){

 		p->f = f;

+		p->sz = blksz;

 		p->offset = blksz * i;

 	}

+	if(odd > 0)

+		b[nblk-1].sz = odd;

 	*bp = b;

 	return nblk;

@@ -416,12 +422,29 @@

 	return ret;

 }

+long

+preadn(int fd, void *buf, long nbytes, vlong offset)

+{

+	long nr, n;

+	vlong o;

+	char *p;

+	

+	nr = 0, n = nbytes, o = offset, p = buf;

+	while(nr < nbytes){

+		if((n = pread(fd, p, n, o)) < 0)

+			return -1;

+		if(n == 0)

+			break;

+		nr += n, o += n, p += n;

+	}

+	return nr;

+}

+

 void

 blkproc(void *)

 {

 	int sfd, dfd;

 	long n;

-	vlong off;

 	char *buf;

 	File *f;

 	Blk *b;

@@ -437,12 +460,11 @@

 		f = b->f;

 		sfd = f->sfd;

 		dfd = f->dfd;

-		off = b->offset;

-		if((n = pread(sfd, buf, blksz, off)) < 0){

+		if((n = preadn(sfd, buf, b->sz, b->offset)) < 0){

 			error("can't read: %r");

 			sendul(f->errchan, ~0);

 		}

-		if(n > 0 && pwrite(dfd, buf, n, off) != n){

+		if(n > 0 && pwrite(dfd, buf, n, b->offset) != n){

 			error("can't write: %r");

 			sendul(f->errchan, ~0);

 		}