more: by Tristan Schmelcher <tpkschme@engmail.uwaterloo.ca>:

- Fixed a number of deficiencies in the line wrapping.
- Fixed a bug where the page could scroll multiple times per keypress.
- Re-read terminal dimensions after user input, in case they
  resized the terminal while we were waiting.
- Added an 'R' key to print the rest of the file without prompting.
- Crudely support tabs in the line-wrapping code by converting
  them to 8 spaces.

1 files changed, 62 insertions, 46 deletions

diff --git a/util-linux/more.c b/util-linux/more.c
index 4083d8eea..92ebdfea9 100644
--- a/util-linux/more.c
+++ b/util-linux/more.c
@@ -29,11 +29,11 @@ struct globals {
 };
 #define G (*(struct globals*)bb_common_bufsiz1)
 //#define G (*ptr_to_globals)
+#define INIT_G() ((void)0)
+//#define INIT_G() PTR_TO_GLOBALS = xzalloc(sizeof(G))
 #define initial_settings (G.initial_settings)
 #define new_settings     (G.new_settings    )
 #define cin_fileno       (G.cin_fileno      )
-#define INIT_G() ((void)0)
-//#define INIT_G() PTR_TO_GLOBALS = xzalloc(sizeof(G))
 
 #define setTermSettings(fd, argp) tcsetattr(fd, TCSANOW, argp)
 #define getTermSettings(fd, argp) tcgetattr(fd, argp)
@@ -50,16 +50,20 @@ static void gotsig(int sig)
 #define setTermSettings(fd, argp) ((void)0)
 #endif /* FEATURE_USE_TERMIOS */
 
+#define CONVERTED_TAB_SIZE 8
 
 int more_main(int argc, char **argv);
 int more_main(int argc, char **argv)
 {
-        int c, lines, input = 0;
-        int please_display_more_prompt = 0;
+        int c = c; /* for gcc */
+        int lines;
+        int input = 0;
+        int spaces = 0;
+        int please_display_more_prompt;
         struct stat st;
         FILE *file;
         FILE *cin;
-        int len, page_height;
+        int len;
         int terminal_width;
         int terminal_height;
 
@@ -87,7 +91,6 @@ int more_main(int argc, char **argv)
         signal(SIGQUIT, gotsig);
         signal(SIGTERM, gotsig);
 #endif
-        please_display_more_prompt = 2;
 
         do {
                 file = stdin;
@@ -99,19 +102,21 @@ int more_main(int argc, char **argv)
                 st.st_size = 0;
                 fstat(fileno(file), &st);
 
-                please_display_more_prompt &= ~1;
+                please_display_more_prompt = 0;
                 /* never returns w, h <= 1 */
                 get_terminal_width_height(fileno(cin), &terminal_width, &terminal_height);
-                terminal_width -= 1;
                 terminal_height -= 1;
 
                 len = 0;
                 lines = 0;
-                page_height = terminal_height;
-                while ((c = getc(file)) != EOF) {
-                        if ((please_display_more_prompt & 3) == 3) {
+                while (spaces || (c = getc(file)) != EOF) {
+                        int wrap;
+                        if (spaces)
+                                spaces--;
+ loop_top:
+                        if (input != 'r' && please_display_more_prompt) {
                                 len = printf("--More-- ");
-                                if (/*file != stdin &&*/ st.st_size > 0) {
+                                if (st.st_size > 0) {
                                         len += printf("(%d%% of %"OFF_FMT"d bytes)",
                                                 (int) (ftello(file)*100 / st.st_size),
                                                 st.st_size);
@@ -122,23 +127,44 @@ int more_main(int argc, char **argv)
                                  * We've just displayed the "--More--" prompt, so now we need
                                  * to get input from the user.
                                  */
-                                input = getc(cin);
+                                for (;;) {
+                                        input = getc(cin);
+                                        input = tolower(input);
 #if !ENABLE_FEATURE_USE_TERMIOS
-                                printf("\033[A"); /* up cursor */
+                                        printf("\033[A"); /* up cursor */
 #endif
-                                /* Erase the "More" message */
-                                printf("\r%*s\r", len, "");
+                                        /* Erase the last message */
+                                        printf("\r%*s\r", len, "");
+
+                                        /* Due to various multibyte escape
+                                         * sequences, it's not ok to accept
+                                         * any input as a command to scroll
+                                         * the screen. We only allow known
+                                         * commands, else we show help msg. */
+                                        if (input == ' ' || input == '\n' || input == 'q' || input == 'r')
+                                                break;
+                                        len = printf("(Enter:next line Space:next page Q:quit R:show the rest)");
+                                }
                                 len = 0;
                                 lines = 0;
-                                /* Bottom line on page will become top line
-                                 * after one page forward. Thus -1: */
-                                page_height = terminal_height - 1;
-                                please_display_more_prompt &= ~1;
+                                please_display_more_prompt = 0;
 
                                 if (input == 'q')
                                         goto end;
+
+                                /* The user may have resized the terminal.
+                                 * Re-read the dimensions. */
+                                get_terminal_width_height(cin_fileno, &terminal_width, &terminal_height);
+                                terminal_height -= 1;
                         }
 
+                        /* Crudely convert tabs into spaces, which are
+                         * a bajillion times easier to deal with. */
+                        if (c == '\t') {
+                                spaces = CONVERTED_TAB_SIZE - 1;
+                                c = ' ';
+                        }
+
                         /*
                          * There are two input streams to worry about here:
                          *
@@ -149,34 +175,24 @@ int more_main(int argc, char **argv)
                          * see if any characters have been hit in the _input_ stream. This
                          * allows the user to quit while in the middle of a file.
                          */
-                        if (c == '\n') {
-                                /* increment by just one line if we are at
-                                 * the end of this line */
-                                if (input == '\n')
-                                        please_display_more_prompt |= 1;
-                                /* Adjust the terminal height for any overlap, so that
-                                 * no lines get lost off the top. */
-                                if (len >= terminal_width) {
-                                        int quot, rem;
-                                        quot = len / terminal_width;
-                                        rem  = len - (quot * terminal_width);
-                                        page_height -= (quot - 1);
-                                        if (rem)
-                                                page_height--;
-                                }
-                                if (++lines >= page_height) {
-                                        please_display_more_prompt |= 1;
-                                }
+                        wrap = (++len > terminal_width);
+                        if (c == '\n' || wrap) {
+                                /* Then outputting this character
+                                 * will move us to a new line. */
+                                if (++lines >= terminal_height || input == '\n')
+                                        please_display_more_prompt = 1;
                                 len = 0;
                         }
-                        /*
-                         * If we just read a newline from the file being 'mored' and any
-                         * key other than a return is hit, scroll by one page
-                         */
-                        putc(c, stdout);
-                        /* My small mind cannot fathom tabs, backspaces,
-                         * and UTF-8 */
-                        len++;
+                        if (c != '\n' && wrap) {
+                                /* Then outputting this will also put a character on
+                                 * the beginning of that new line. Thus we first want to
+                                 * display the prompt (if any), so we skip the putchar()
+                                 * and go back to the top of the loop, without reading
+                                 * a new character. */
+                                goto loop_top;
+                        }
+                        /* My small mind cannot fathom backspaces and UTF-8 */
+                        putchar(c);
                 }
                 fclose(file);
                 fflush(stdout);