dd: fix conv=noerror w/o sync to not write out zeroed blocks

function                                             old     new   delta
dd_main                                             1480    1463     -17

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/coreutils/dd.c b/coreutils/dd.c
index 3fdfc23..627e7e7 100644 (file)
--- a/coreutils/dd.c
+++ b/coreutils/dd.c
@@ -286,25 +286,26 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
        }
 
        while (!(flags & FLAG_COUNT) || (G.in_full + G.in_part != count)) {
-               if (flags & FLAG_NOERROR) /* Pre-zero the buffer if conv=noerror */
-                       memset(ibuf, 0, ibs);
                n = safe_read(ifd, ibuf, ibs);
                if (n == 0)
                        break;
                if (n < 0) {
+                       /* "Bad block" */
                        if (!(flags & FLAG_NOERROR))
                                goto die_infile;
-                       n = ibs;
                        bb_simple_perror_msg(infile);
-                       /* GNU dd with conv=noerror skips over "bad blocks" */
+                       /* GNU dd with conv=noerror skips over bad blocks */
                        xlseek(ifd, ibs, SEEK_CUR);
+                       /* conv=noerror,sync writes NULs,
+                        * conv=noerror just ignores input bad blocks */
+                       n = 0;
                }
                if ((size_t)n == ibs)
                        G.in_full++;
                else {
                        G.in_part++;
                        if (flags & FLAG_SYNC) {
-                               memset(ibuf + n, '\0', ibs - n);
+                               memset(ibuf + n, 0, ibs - n);
                                n = ibs;
                        }
                }