less: add a function to detect when display is at end of file

Add a function to package the test that detects whether enough has
been read from the file to allow a screenful to be displayed.

Also use this to determine when to display '(END)' in the status
line.  The previous code was incomplete and didn't handle truncated
lines (-S flag) properly.

function                                             old     new   delta
at_end                                                 -      63     +63
status_print                                         111     109      -2
read_lines                                           819     764     -55
getch_nowait                                         319     264     -55
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/3 up/down: 63/-112)           Total: -49 bytes

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

1 files changed, 12 insertions, 13 deletions

diff --git a/miscutils/less.c b/miscutils/less.c
index 91a933a3a..2a1797c7b 100644
--- a/miscutils/less.c
+++ b/miscutils/less.c
@@ -406,6 +406,14 @@ static void fill_match_lines(unsigned pos);
 #define fill_match_lines(pos) ((void)0)
 #endif
 
+static int at_end(void)
+{
+        return (option_mask32 & FLAG_S)
+                ? !(cur_fline <= max_fline &&
+                        max_lineno > LINENO(flines[cur_fline]) + max_displayed_line)
+                : !(max_fline > cur_fline + max_displayed_line);
+}
+
 /* Devilishly complex routine.
  *
  * Has to deal with EOF and EPIPE on input,
@@ -552,11 +560,7 @@ static void read_lines(void)
                         eof_error = 0; /* Pretend we saw EOF */
                         break;
                 }
-                if (!(option_mask32 & FLAG_S)
-                  ? (max_fline > cur_fline + max_displayed_line)
-                  : (max_fline >= cur_fline
-                     && max_lineno > LINENO(flines[cur_fline]) + max_displayed_line)
-                ) {
+                if (!at_end()) {
 #if !ENABLE_FEATURE_LESS_REGEXP
                         break;
 #else
@@ -662,7 +666,7 @@ static void m_status_print(void)
         if (num_lines >= 0)
                 printf("/%i", num_lines);
 
-        if (cur_fline >= (int)(max_fline - max_displayed_line)) {
+        if (at_end()) {
                 printf(" (END)");
                 if (num_files > 1 && current_file != num_files)
                         printf(" - next: %s", files[current_file]);
@@ -692,7 +696,7 @@ static void status_print(void)
 #endif
 
         clear_line();
-        if (cur_fline && cur_fline < (int)(max_fline - max_displayed_line)) {
+        if (cur_fline && !at_end()) {
                 bb_putchar(':');
                 return;
         }
@@ -1009,12 +1013,7 @@ static int64_t getch_nowait(void)
          */
         rd = 1;
         /* Are we interested in stdin? */
-//TODO: reuse code for determining this
-        if (!(option_mask32 & FLAG_S)
-           ? !(max_fline > cur_fline + max_displayed_line)
-           : !(max_fline >= cur_fline
-               && max_lineno > LINENO(flines[cur_fline]) + max_displayed_line)
-        ) {
+        if (at_end()) {
                 if (eof_error > 0) /* did NOT reach eof yet */
                         rd = 0; /* yes, we are interested in stdin */
         }