less: rearrange detection of non-regular files

Move the code to detect non-regular files to the point where the
file is being opened.  If num_lines == READING_FILE guarantees
that the file is regular.

Detect when a file becomes unreadable between it first being opened
and the call to update_num_lines.  Mark the file as being non-regular
so we don't try that again.

function                                             old     new   delta
reinitialize                                         197     245     +48
update_num_lines                                     159     127     -32
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/1 up/down: 48/-32)             Total: 16 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 15 insertions, 8 deletions

diff --git a/miscutils/less.c b/miscutils/less.c
index 8fd0874e2..91a933a3a 100644
--- a/miscutils/less.c
+++ b/miscutils/less.c
@@ -167,7 +167,8 @@ enum { pattern_valid = 0 };
 
 enum {
         READING_FILE = -1,
-        READING_STDIN = -2
+        READING_STDIN = -2,
+        READING_NONREG = -3
 };
 
 struct globals {
@@ -615,15 +616,16 @@ static void update_num_lines(void)
         int count, fd;
         ssize_t len, i;
         char buf[4096];
-        struct stat stbuf;
 
+        /* only do this for regular files */
         if (num_lines == READING_FILE) {
                 count = 0;
                 fd = open(filename, O_RDONLY);
-                if (fd < 0)
-                        goto skip;
-                if (fstat(fd, &stbuf) != 0 || !S_ISREG(stbuf.st_mode))
-                        goto do_close;
+                if (fd < 0) {
+                        /* somebody stole my file! */
+                        num_lines = READING_NONREG;
+                        return;
+                }
                 while ((len = safe_read(fd, buf, sizeof(buf))) > 0) {
                         for (i = 0; i < len; ++i) {
                                 if (buf[i] == '\n' && ++count == MAXLINES)
@@ -632,9 +634,7 @@ static void update_num_lines(void)
                 }
  done:
                 num_lines = count;
- do_close:
                 close(fd);
- skip: ;
         }
 }
 
@@ -943,6 +943,13 @@ static void buffer_line(int linenum)
 static void open_file_and_read_lines(void)
 {
         if (filename) {
+#if ENABLE_FEATURE_LESS_FLAGS
+                struct stat stbuf;
+
+                xstat(filename, &stbuf);
+                if (!S_ISREG(stbuf.st_mode))
+                        num_lines = READING_NONREG;
+#endif
                 xmove_fd(xopen(filename, O_RDONLY), STDIN_FILENO);
         } else {
                 /* "less" with no arguments in argv[] */