tail: fix "tail -c 20 /dev/huge_disk" (was taking ages)
tail: a few variables renamed wc: tiny optimization.
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5233cd3800
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@ -74,7 +74,7 @@ static unsigned eat_num(const char *p)
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p++;
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else if (*p == '+') {
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p++;
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G.status = EXIT_FAILURE;
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G.status = 1; /* mark that we saw "+" */
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}
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return xatou_sfx(p, tail_suffixes);
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}
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@ -92,7 +92,7 @@ int tail_main(int argc, char **argv)
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char *tailbuf;
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size_t tailbufsize;
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int taillen = 0;
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int newline = 0;
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int newlines_seen = 0;
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int nfiles, nread, nwrite, seen, i, opt;
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int *fds;
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@ -128,12 +128,12 @@ int tail_main(int argc, char **argv)
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#endif
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argc -= optind;
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argv += optind;
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from_top = G.status;
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from_top = G.status; /* 1 if there was "-c +N" or "-n +N" */
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G.status = EXIT_SUCCESS;
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/* open all the files */
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fds = xmalloc(sizeof(int) * (argc + 1));
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nfiles = i = 0;
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G.status = EXIT_SUCCESS;
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if (argc == 0) {
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struct stat statbuf;
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@ -155,39 +155,49 @@ int tail_main(int argc, char **argv)
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if (!nfiles)
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bb_error_msg_and_die("no files");
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/* prepare the buffer */
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tailbufsize = BUFSIZ;
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/* tail the files */
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if (!from_top && COUNT_BYTES) {
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if (tailbufsize < count) {
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if (tailbufsize < count + BUFSIZ) {
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tailbufsize = count + BUFSIZ;
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}
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}
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tailbuf = xmalloc(tailbufsize);
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buf = tailbuf = xmalloc(tailbufsize);
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/* tail the files */
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fmt = header_fmt + 1; /* Skip header leading newline on first output. */
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i = 0;
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do {
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/* Be careful. It would be possible to optimize the count-bytes
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* case if the file is seekable. If you do though, remember that
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* starting file position may not be the beginning of the file.
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* Beware of backing up too far. See example in wc.c.
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*/
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if (!(count | from_top) && lseek(fds[i], 0, SEEK_END) >= 0) {
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continue;
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}
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off_t current;
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if (nfiles > header_threshhold) {
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tail_xprint_header(fmt, argv[i]);
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fmt = header_fmt;
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}
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/* Optimizing count-bytes case if the file is seekable.
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* Beware of backing up too far.
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* Also we exclude files with size 0 (because of /proc/xxx) */
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current = lseek(fds[i], 0, SEEK_END);
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if (current > 0) {
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if (!from_top) {
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if (count == 0)
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continue; /* showing zero lines is easy :) */
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if (COUNT_BYTES) {
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current -= count;
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if (current < 0)
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current = 0;
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xlseek(fds[i], current, SEEK_SET);
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bb_copyfd_size(fds[i], STDOUT_FILENO, count);
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continue;
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}
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}
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}
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buf = tailbuf;
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taillen = 0;
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seen = 1;
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newline = 0;
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newlines_seen = 0;
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while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
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if (from_top) {
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nwrite = nread;
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@ -215,34 +225,32 @@ int tail_main(int argc, char **argv)
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}
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} else {
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int k = nread;
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int nbuf = 0;
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int newlines_in_buf = 0;
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while (k) {
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--k;
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do { /* count '\n' in last read */
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k--;
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if (buf[k] == '\n') {
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++nbuf;
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newlines_in_buf++;
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}
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}
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} while (k);
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if (newline + nbuf < count) {
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newline += nbuf;
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if (newlines_seen + newlines_in_buf < count) {
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newlines_seen += newlines_in_buf;
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taillen += nread;
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} else {
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int extra = 0;
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int extra = (buf[nread-1] != '\n');
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if (buf[nread-1] != '\n')
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extra = 1;
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k = newline + nbuf + extra - count;
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k = newlines_seen + newlines_in_buf + extra - count;
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s = tailbuf;
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while (k) {
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if (*s == '\n') {
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--k;
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k--;
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}
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++s;
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s++;
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}
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taillen += nread - (s - tailbuf);
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memmove(tailbuf, s, taillen);
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newline = count - extra;
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newlines_seen = count - extra;
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}
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if (tailbufsize < taillen + BUFSIZ) {
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tailbufsize = taillen + BUFSIZ;
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@ -251,13 +259,10 @@ int tail_main(int argc, char **argv)
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}
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buf = tailbuf + taillen;
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}
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}
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} /* while (tail_read() > 0) */
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if (!from_top) {
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xwrite(STDOUT_FILENO, tailbuf, taillen);
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}
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taillen = 0;
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} while (++i < nfiles);
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buf = xrealloc(tailbuf, BUFSIZ);
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@ -73,7 +73,7 @@ int wc_main(int argc, char **argv)
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{
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FILE *fp;
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const char *s, *arg;
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const char *start_fmt = "%9"COUNT_FMT;
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const char *start_fmt = " %9"COUNT_FMT + 1;
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const char *fname_fmt = " %s\n";
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COUNT_T *pcounts;
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COUNT_T counts[4];
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