On Sun, Dec 12, 2021 at 07:15:51PM -0600, Scott Cheloha wrote:
> cat(1) sizes its I/O buffer according to the st_blksize of the first
> file it processes. We don't do this very often in the tree. I'm not
> sure if we should trust st_blksize.
>
> It would be simpler to just choose a value that works in practice and
> always use it.
>
> 64K works well. We settled on that for tee(1) recently.
Why are you also change the allocation to be per-file? You might as
well go for a static buffer if you make it fixed size.
-Otto
>
> Thoughts?
>
> Index: cat.c
> ===================================================================
> RCS file: /cvs/src/bin/cat/cat.c,v
> retrieving revision 1.32
> diff -u -p -r1.32 cat.c
> --- cat.c 24 Oct 2021 21:24:21 -0000 1.32
> +++ cat.c 13 Dec 2021 00:57:48 -0000
> @@ -33,9 +33,6 @@
> * SUCH DAMAGE.
> */
>
> -#include <sys/types.h>
> -#include <sys/stat.h>
> -
> #include <ctype.h>
> #include <err.h>
> #include <errno.h>
> @@ -45,7 +42,7 @@
> #include <string.h>
> #include <unistd.h>
>
> -#define MAXIMUM(a, b) (((a) > (b)) ? (a) : (b))
> +#define BSIZE (64 * 1024)
>
> int bflag, eflag, nflag, sflag, tflag, vflag;
> int rval;
> @@ -221,26 +218,20 @@ raw_args(char **argv)
> void
> raw_cat(int rfd, const char *filename)
> {
> - int wfd;
> + char *buf;
> ssize_t nr, nw, off;
> - static size_t bsize;
> - static char *buf = NULL;
> - struct stat sbuf;
> + int wfd;
>
> wfd = fileno(stdout);
> - if (buf == NULL) {
> - if (fstat(wfd, &sbuf) == -1)
> - err(1, "stdout");
> - bsize = MAXIMUM(sbuf.st_blksize, BUFSIZ);
> - if ((buf = malloc(bsize)) == NULL)
> - err(1, NULL);
> - }
> - while ((nr = read(rfd, buf, bsize)) != -1 && nr != 0) {
> + if ((buf = malloc(BSIZE)) == NULL)
> + err(1, NULL);
> + while ((nr = read(rfd, buf, BSIZE)) != -1 && nr != 0) {
> for (off = 0; nr; nr -= nw, off += nw) {
> if ((nw = write(wfd, buf + off, nr)) == -1 || nw == 0)
> err(1, "stdout");
> }
> }
> + free(buf);
> if (nr == -1) {
> warn("%s", filename);
> rval = 1;
>
