[hackers] [ubase] Use select() in dd(1) || sin

From: <git_AT_suckless.org>
Date: Wed, 11 Jun 2014 14:03:01 +0200

commit 0ca8e52bc1fce74ba3d7ba9f07aa98bd22ae552a
Author: sin <sin_AT_2f30.org>
Date: Wed Jun 11 12:57:10 2014 +0100

    Use select() in dd(1)
    
    Avoid blocking in a call to splice() when no input is available.
    We can now break out of dd using ^C even if the input is coming from
    /dev/stdin.
    
    Use tabs instead of spaces.

diff --git a/dd.c b/dd.c
index f243fa7..47c2e2d 100644
--- a/dd.c
+++ b/dd.c
_AT_@ -17,6 +17,8 @@
 #include <sys/ioctl.h>
 #include <sys/mount.h>
 #include <sys/stat.h>
+#include <sys/select.h>
+#include <sys/time.h>
 #include <sys/types.h>
 #include <sys/vfs.h>
 #include <time.h>
_AT_@ -135,48 +137,60 @@ prepare_copy(struct dd_config *ddc, int *ifd, int *ofd)
 static int
 copy_splice(struct dd_config *ddc)
 {
- int ifd, ofd, p[2] = {-1, -1};
- ssize_t r = 0;
- size_t n = 0;
- if (prepare_copy(ddc, &ifd, &ofd) < 0)
- return -1;
- if (pipe(p) < 0) {
- ddc->saved_errno = errno;
- close(ifd); close(ofd);
- close(p[0]); close(p[1]);
- return -1;
- }
+ int ifd, ofd, p[2] = {-1, -1};
+ ssize_t r = 0;
+ size_t n = 0;
+ fd_set rfd, wfd;
+
+ if (prepare_copy(ddc, &ifd, &ofd) < 0)
+ return -1;
+ if (pipe(p) < 0) {
+ ddc->saved_errno = errno;
+ close(ifd); close(ofd);
+ close(p[0]); close(p[1]);
+ return -1;
+ }
 #ifdef F_SETPIPE_SZ
- for (n = 29; n >= 20; --n) {
- if (fcntl(p[0], F_SETPIPE_SZ, 1<<n) != -1)
- break;
- }
+ for (n = 29; n >= 20; --n) {
+ if (fcntl(p[0], F_SETPIPE_SZ, 1<<n) != -1)
+ break;
+ }
 #endif
- n = ddc->bs;
- for (;ddc->b_out != ddc->count && !sigint;) {
- if (n > ddc->count - ddc->b_out)
- n = ddc->count - ddc->b_out;
- r = splice(ifd, NULL, p[1], NULL, n, SPLICE_F_MORE);
- if (r <= 0) {
- ddc->saved_errno = errno;
- break;
- }
- ++ddc->rec_in;
- r = splice(p[0], NULL, ofd, NULL, r, SPLICE_F_MORE);
- if (r <= 0) {
- ddc->saved_errno = errno;
- break;
- }
- ddc->b_out += r;
- ++ddc->rec_out;
- }
- close(ifd);
- close(ofd);
- close(p[0]);
- close(p[1]);
- if (r < 0)
- return -1;
- return 0;
+ n = ddc->bs;
+ for (;ddc->b_out != ddc->count && !sigint;) {
+ if (n > ddc->count - ddc->b_out)
+ n = ddc->count - ddc->b_out;
+ FD_ZERO(&rfd);
+ FD_ZERO(&wfd);
+ FD_SET(ifd, &rfd);
+ FD_SET(ofd, &wfd);
+ if (select(ifd > ofd ? ifd + 1 : ofd + 1, &rfd, &wfd, NULL, NULL) < 0) {
+ ddc->saved_errno = errno;
+ break;
+ }
+ if (FD_ISSET(ifd, &rfd) == 1 && FD_ISSET(ofd, &wfd) == 1) {
+ r = splice(ifd, NULL, p[1], NULL, n, SPLICE_F_MORE);
+ if (r <= 0) {
+ ddc->saved_errno = errno;
+ break;
+ }
+ ++ddc->rec_in;
+ r = splice(p[0], NULL, ofd, NULL, r, SPLICE_F_MORE);
+ if (r <= 0) {
+ ddc->saved_errno = errno;
+ break;
+ }
+ ddc->b_out += r;
+ ++ddc->rec_out;
+ }
+ }
+ close(ifd);
+ close(ofd);
+ close(p[0]);
+ close(p[1]);
+ if (r < 0)
+ return -1;
+ return 0;
 }
 
 static int
Received on Wed Jun 11 2014 - 14:03:01 CEST