[PATCH] less: improvements to verbose status messages

Ron Yorston rmy at pobox.com
Tue Jul 21 10:24:12 UTC 2015


Make verbose status messages (-m/-M flags) behave more like the
real `less` command:

- fix display of line numbers so they're correct whether lines are
  being truncated (-S flag) or wrapped.
- don't display total lines or percentage when lines are read from
  stdin:  we don't have that information until we reach EOF.  When
  we do reach EOF the additional information is displayed.
- when lines are read from a file count the total number of lines
  so that we can display percentages.  Counting lines is avoided
  until the information is actually needed.  If the user pages to
  EOF the separate read pass can be avoided entirely.

Fixes Bug 7586

function                                             old     new   delta
m_status_print                                       200     364    +164
safe_lineno                                            -      41     +41
reinitialize                                         186     197     +11
read_lines                                           809     819     +10
less_main                                           2600    2606      +6
.rodata                                           156077  156045     -32
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 4/1 up/down: 232/-32)           Total: 200 bytes

Signed-off-by: Ron Yorston <rmy at pobox.com>
---
 miscutils/less.c | 73 +++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 59 insertions(+), 14 deletions(-)

diff --git a/miscutils/less.c b/miscutils/less.c
index 90c1038..c09930f 100644
--- a/miscutils/less.c
+++ b/miscutils/less.c
@@ -165,6 +165,11 @@ enum {
 enum { pattern_valid = 0 };
 #endif
 
+enum {
+	READING_FILE = -1,
+	READING_STDIN = -2
+};
+
 struct globals {
 	int cur_fline; /* signed */
 	int kbd_fd;  /* fd to get input from */
@@ -188,6 +193,9 @@ struct globals {
 	unsigned current_file;
 	char *filename;
 	char **files;
+#if ENABLE_FEATURE_LESS_FLAGS
+	int num_lines; /* input source if < 0, line count if >= 0 */
+#endif
 #if ENABLE_FEATURE_LESS_MARKS
 	unsigned num_marks;
 	unsigned mark_lines[15][2];
@@ -229,6 +237,7 @@ struct globals {
 #define current_file        (G.current_file      )
 #define filename            (G.filename          )
 #define files               (G.files             )
+#define num_lines           (G.num_lines         )
 #define num_marks           (G.num_marks         )
 #define mark_lines          (G.mark_lines        )
 #if ENABLE_FEATURE_LESS_REGEXP
@@ -574,6 +583,10 @@ static void read_lines(void)
 			print_statusline(bb_msg_read_error);
 		}
 	}
+#if ENABLE_FEATURE_LESS_FLAGS
+	else if (eof_error == 0)
+		num_lines = max_lineno;
+#endif
 
 	fill_match_lines(old_max_fline);
 #if ENABLE_FEATURE_LESS_REGEXP
@@ -584,18 +597,25 @@ static void read_lines(void)
 }
 
 #if ENABLE_FEATURE_LESS_FLAGS
-/* Interestingly, writing calc_percent as a function saves around 32 bytes
- * on my build. */
-static int calc_percent(void)
+static int safe_lineno(int fline)
 {
-	unsigned p = (100 * (cur_fline+max_displayed_line+1) + max_fline/2) / (max_fline+1);
-	return p <= 100 ? p : 100;
+	if (fline >= max_fline)
+		fline = max_fline - 1;
+
+	/* also catches empty file (max_fline == 0) */
+	if (fline < 0)
+		return 0;
+
+	return LINENO(flines[fline]) + 1;
 }
 
 /* Print a status line if -M was specified */
 static void m_status_print(void)
 {
-	int percentage;
+	int first, last, fd, count;
+	char buf[4096];
+	ssize_t len, i;
+	unsigned percent;
 
 	if (less_gets_pos >= 0) /* don't touch statusline while input is done! */
 		return;
@@ -604,17 +624,39 @@ static void m_status_print(void)
 	printf(HIGHLIGHT"%s", filename);
 	if (num_files > 1)
 		printf(" (file %i of %i)", current_file, num_files);
-	printf(" lines %i-%i/%i ",
-			cur_fline + 1, cur_fline + max_displayed_line + 1,
-			max_fline + 1);
+
+	first = safe_lineno(cur_fline);
+	last = (option_mask32 & FLAG_S) ?
+			MIN(first + max_displayed_line, max_lineno) :
+			safe_lineno(cur_fline + max_displayed_line);
+	printf(" lines %i-%i", first, last);
+
+	if (num_lines == READING_FILE) {
+		/* count number of lines in file */
+		count = 0;
+		fd = xopen(filename, O_RDONLY);
+		while ((len=safe_read(fd, buf, 4096)) > 0) {
+			for (i=0; i<len; ++i) {
+				if (buf[i] == '\n' && ++count == MAXLINES)
+					break;
+			}
+		}
+		close(fd);
+		num_lines = count;
+	}
+
+	if (num_lines >= 0)
+		printf("/%i", num_lines);
+
 	if (cur_fline >= (int)(max_fline - max_displayed_line)) {
-		printf("(END)"NORMAL);
+		printf(" (END)");
 		if (num_files > 1 && current_file != num_files)
-			printf(HIGHLIGHT" - next: %s"NORMAL, files[current_file]);
-		return;
+			printf(" - next: %s", files[current_file]);
+	} else if (num_lines > 0) {
+		percent = (100 * last + num_lines/2) / num_lines;
+		printf(" %i%%", percent <= 100 ? percent : 100);
 	}
-	percentage = calc_percent();
-	printf("%i%%"NORMAL, percentage);
+	printf(NORMAL);
 }
 #endif
 
@@ -915,6 +957,9 @@ static void reinitialize(void)
 	max_fline = -1;
 	cur_fline = 0;
 	max_lineno = 0;
+#if ENABLE_FEATURE_LESS_FLAGS
+	num_lines = filename ? READING_FILE : READING_STDIN;
+#endif
 	open_file_and_read_lines();
 #if ENABLE_FEATURE_LESS_ASK_TERMINAL
 	if (G.winsize_err)
-- 
2.4.3



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