makedevs: shrink by Vladimir
[oweals/busybox.git] / miscutils / less.c
index 03ffd78eda08e487ccc10f0d8ac5f7ccde82e64d..530a40a8c8314203a5b527f115a24a6eb236641b 100644 (file)
  */
 
 /*
- *      This program needs a lot of development, so consider it in a beta stage
- *      at best.
+ * TODO:
+ * - Add more regular expression support - search modifiers, certain matches, etc.
+ * - Add more complex bracket searching - currently, nested brackets are
+ *   not considered.
+ * - Add support for "F" as an input. This causes less to act in
+ *   a similar way to tail -f.
+ * - Allow horizontal scrolling.
  *
- *      TODO:
- *      - Add more regular expression support - search modifiers, certain matches, etc.
- *      - Add more complex bracket searching - currently, nested brackets are
- *      not considered.
- *      - Add support for "F" as an input. This causes less to act in
- *      a similar way to tail -f.
- *      - Check for binary files, and prompt the user if a binary file
- *      is detected.
- *      - Allow horizontal scrolling. Currently, lines simply continue onto
- *      the next line, per the terminal's discretion
- *
- *      Notes:
- *      - filename is an array and not a pointer because that avoids all sorts
- *      of complications involving the fact that something that is pointed to
- *      will be changed if the pointer is changed.
- *      - the inp file pointer is used so that keyboard input works after
- *      redirected input has been read from stdin
-*/
+ * Notes:
+ * - the inp file pointer is used so that keyboard input works after
+ *   redirected input has been read from stdin
+ */
 
-#include "busybox.h"
+#include <sched.h>     /* sched_yield() */
 
-#ifdef CONFIG_FEATURE_LESS_REGEXP
+#include "libbb.h"
+#if ENABLE_FEATURE_LESS_REGEXP
 #include "xregex.h"
 #endif
 
-
-/* These are the escape sequences corresponding to special keys */
-#define REAL_KEY_UP 'A'
-#define REAL_KEY_DOWN 'B'
-#define REAL_KEY_RIGHT 'C'
-#define REAL_KEY_LEFT 'D'
-#define REAL_PAGE_UP '5'
-#define REAL_PAGE_DOWN '6'
-#define REAL_KEY_HOME '7'
-#define REAL_KEY_END '8'
-
-/* These are the special codes assigned by this program to the special keys */
-#define KEY_UP 20
-#define KEY_DOWN 21
-#define KEY_RIGHT 22
-#define KEY_LEFT 23
-#define PAGE_UP 24
-#define PAGE_DOWN 25
-#define KEY_HOME 26
-#define KEY_END 27
+/* FIXME: currently doesn't work right */
+#undef ENABLE_FEATURE_LESS_FLAGCS
+#define ENABLE_FEATURE_LESS_FLAGCS 0
 
 /* The escape codes for highlighted and normal text */
 #define HIGHLIGHT "\033[7m"
 #define NORMAL "\033[0m"
-
 /* The escape code to clear the screen */
 #define CLEAR "\033[H\033[J"
+/* The escape code to clear to end of line */
+#define CLEAR_2_EOL "\033[K"
 
-/* Maximum number of lines in a file */
-#define MAXLINES 10000
+/* These are the escape sequences corresponding to special keys */
+enum {
+       REAL_KEY_UP = 'A',
+       REAL_KEY_DOWN = 'B',
+       REAL_KEY_RIGHT = 'C',
+       REAL_KEY_LEFT = 'D',
+       REAL_PAGE_UP = '5',
+       REAL_PAGE_DOWN = '6',
+       REAL_KEY_HOME = '7', // vt100? linux vt? or what?
+       REAL_KEY_END = '8',
+       REAL_KEY_HOME_ALT = '1', // ESC [1~ (vt100? linux vt? or what?)
+       REAL_KEY_END_ALT = '4', // ESC [4~
+       REAL_KEY_HOME_XTERM = 'H',
+       REAL_KEY_END_XTERM = 'F',
 
-static int height;
-static int width;
-static char **files;
-static char filename[256];
-static char **buffer;
-static char **flines;
-static int current_file = 1;
-static int line_pos;
-static int num_flines;
-static int num_files = 1;
+/* These are the special codes assigned by this program to the special keys */
+       KEY_UP = 20,
+       KEY_DOWN = 21,
+       KEY_RIGHT = 22,
+       KEY_LEFT = 23,
+       PAGE_UP = 24,
+       PAGE_DOWN = 25,
+       KEY_HOME = 26,
+       KEY_END = 27,
+
+/* Absolute max of lines eaten */
+       MAXLINES = CONFIG_FEATURE_LESS_MAXLINES,
+
+/* This many "after the end" lines we will show (at max) */
+       TILDES = 1,
+};
 
 /* Command line options */
-static unsigned flags;
-#define FLAG_E 1
-#define FLAG_M (1<<1)
-#define FLAG_m (1<<2)
-#define FLAG_N (1<<3)
-#define FLAG_TILDE (1<<4)
+enum {
+       FLAG_E = 1,
+       FLAG_M = 1 << 1,
+       FLAG_m = 1 << 2,
+       FLAG_N = 1 << 3,
+       FLAG_TILDE = 1 << 4,
 /* hijack command line options variable for internal state vars */
-#define LESS_STATE_INP_STDIN (1<<5)
-#define LESS_STATE_PAST_EOF  (1<<6)
-#define LESS_STATE_MATCH_BACKWARDS (1<<7)
-/* INP_STDIN is used to change behaviour when input comes from stdin */
-
-#ifdef CONFIG_FEATURE_LESS_MARKS
-static int mark_lines[15][2];
-static int num_marks;
-#endif
+       LESS_STATE_MATCH_BACKWARDS = 1 << 15,
+};
 
-#ifdef CONFIG_FEATURE_LESS_REGEXP
-static int match_found;
-static int *match_lines;
-static int match_pos;
-static int num_matches;
-static regex_t old_pattern;
+#if !ENABLE_FEATURE_LESS_REGEXP
+enum { pattern_valid = 0 };
 #endif
 
-/* Needed termios structures */
-static struct termios term_orig, term_vi;
-
-/* File pointer to get input from */
-static FILE *inp;
+struct globals {
+       int cur_fline; /* signed */
+       int kbd_fd;  /* fd to get input from */
+       int less_gets_pos;
+/* last position in last line, taking into account tabs */
+       size_t linepos;
+       unsigned max_displayed_line;
+       unsigned max_fline;
+       unsigned max_lineno; /* this one tracks linewrap */
+       unsigned width;
+       ssize_t eof_error; /* eof if 0, error if < 0 */
+       ssize_t readpos;
+       ssize_t readeof; /* must be signed */
+       const char **buffer;
+       const char **flines;
+       const char *empty_line_marker;
+       unsigned num_files;
+       unsigned current_file;
+       char *filename;
+       char **files;
+#if ENABLE_FEATURE_LESS_MARKS
+       unsigned num_marks;
+       unsigned mark_lines[15][2];
+#endif
+#if ENABLE_FEATURE_LESS_REGEXP
+       unsigned *match_lines;
+       int match_pos; /* signed! */
+       int wanted_match; /* signed! */
+       int num_matches;
+       regex_t pattern;
+       smallint pattern_valid;
+#endif
+       smallint terminated;
+       struct termios term_orig, term_less;
+};
+#define G (*ptr_to_globals)
+#define cur_fline           (G.cur_fline         )
+#define kbd_fd              (G.kbd_fd            )
+#define less_gets_pos       (G.less_gets_pos     )
+#define linepos             (G.linepos           )
+#define max_displayed_line  (G.max_displayed_line)
+#define max_fline           (G.max_fline         )
+#define max_lineno          (G.max_lineno        )
+#define width               (G.width             )
+#define eof_error           (G.eof_error         )
+#define readpos             (G.readpos           )
+#define readeof             (G.readeof           )
+#define buffer              (G.buffer            )
+#define flines              (G.flines            )
+#define empty_line_marker   (G.empty_line_marker )
+#define num_files           (G.num_files         )
+#define current_file        (G.current_file      )
+#define filename            (G.filename          )
+#define files               (G.files             )
+#define num_marks           (G.num_marks         )
+#define mark_lines          (G.mark_lines        )
+#if ENABLE_FEATURE_LESS_REGEXP
+#define match_lines         (G.match_lines       )
+#define match_pos           (G.match_pos         )
+#define num_matches         (G.num_matches       )
+#define wanted_match        (G.wanted_match      )
+#define pattern             (G.pattern           )
+#define pattern_valid       (G.pattern_valid     )
+#endif
+#define terminated          (G.terminated        )
+#define term_orig           (G.term_orig         )
+#define term_less           (G.term_less         )
+#define INIT_G() do { \
+       SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
+       less_gets_pos = -1; \
+       empty_line_marker = "~"; \
+       num_files = 1; \
+       current_file = 1; \
+       eof_error = 1; \
+       terminated = 1; \
+       USE_FEATURE_LESS_REGEXP(wanted_match = -1;) \
+} while (0)
 
 /* Reset terminal input to normal */
 static void set_tty_cooked(void)
 {
        fflush(stdout);
-       tcsetattr(fileno(inp), TCSANOW, &term_orig);
+       tcsetattr(kbd_fd, TCSANOW, &term_orig);
 }
 
-/* Exit the program gracefully */
-static void tless_exit(int code)
+/* Move the cursor to a position (x,y), where (0,0) is the
+   top-left corner of the console */
+static void move_cursor(int line, int row)
 {
-       /* TODO: We really should save the terminal state when we start,
-                and restore it when we exit. Less does this with the
-                "ti" and "te" termcap commands; can this be done with
-                only termios.h? */
-
-       putchar('\n');
-       fflush_stdout_and_exit(code);
+       printf("\033[%u;%uH", line, row);
 }
 
-/* Grab a character from input without requiring the return key. If the
-   character is ASCII \033, get more characters and assign certain sequences
-   special return codes. Note that this function works best with raw input. */
-static int tless_getch(void)
+static void clear_line(void)
 {
-       int input;
-       /* Set terminal input to raw mode  (taken from vi.c) */
-       tcsetattr(fileno(inp), TCSANOW, &term_vi);
-
-       input = getc(inp);
-       /* Detect escape sequences (i.e. arrow keys) and handle
-          them accordingly */
-
-       if (input == '\033' && getc(inp) == '[') {
-               unsigned int i;
-               input = getc(inp);
-               set_tty_cooked();
-
-               i = input - REAL_KEY_UP;
-               if (i < 4)
-                       return 20 + i;
-               else if ((i = input - REAL_PAGE_UP) < 4)
-                       return 24 + i;
-       }
-       /* The input is a normal ASCII value */
-       else {
-               set_tty_cooked();
-               return input;
-       }
-       return 0;
+       printf("\033[%u;0H" CLEAR_2_EOL, max_displayed_line + 2);
 }
 
-/* Move the cursor to a position (x,y), where (0,0) is the
-   top-left corner of the console */
-static void move_cursor(int x, int y)
+static void print_hilite(const char *str)
 {
-       printf("\033[%i;%iH", x, y);
+       printf(HIGHLIGHT"%s"NORMAL, str);
 }
 
-static void clear_line(void)
+static void print_statusline(const char *str)
 {
-       move_cursor(height, 0);
-       printf("\033[K");
+       clear_line();
+       printf(HIGHLIGHT"%.*s"NORMAL, width - 1, str);
 }
 
-/* This adds line numbers to every line, as the -N flag necessitates */
-static void add_linenumbers(void)
+/* Exit the program gracefully */
+static void less_exit(int code)
 {
-       int i;
-
-       for (i = 0; i <= num_flines; i++) {
-               char *new = xasprintf("%5d %s", i + 1, flines[i]);
-               free(flines[i]);
-               flines[i] = new;
-       }
+       set_tty_cooked();
+       clear_line();
+       if (code < 0)
+               kill_myself_with_sig(- code); /* does not return */
+       exit(code);
 }
 
-static void data_readlines(void)
+#if ENABLE_FEATURE_LESS_REGEXP
+static void fill_match_lines(unsigned pos);
+#else
+#define fill_match_lines(pos) ((void)0)
+#endif
+
+/* Devilishly complex routine.
+ *
+ * Has to deal with EOF and EPIPE on input,
+ * with line wrapping, with last line not ending in '\n'
+ * (possibly not ending YET!), with backspace and tabs.
+ * It reads input again if last time we got an EOF (thus supporting
+ * growing files) or EPIPE (watching output of slow process like make).
+ *
+ * Variables used:
+ * flines[] - array of lines already read. Linewrap may cause
+ *      one source file line to occupy several flines[n].
+ * flines[max_fline] - last line, possibly incomplete.
+ * terminated - 1 if flines[max_fline] is 'terminated'
+ *      (if there was '\n' [which isn't stored itself, we just remember
+ *      that it was seen])
+ * max_lineno - last line's number, this one doesn't increment
+ *      on line wrap, only on "real" new lines.
+ * readbuf[0..readeof-1] - small preliminary buffer.
+ * readbuf[readpos] - next character to add to current line.
+ * linepos - screen line position of next char to be read
+ *      (takes into account tabs and backspaces)
+ * eof_error - < 0 error, == 0 EOF, > 0 not EOF/error
+ */
+static void read_lines(void)
 {
-       int i;
-       char current_line[256];
-       FILE *fp;
+#define readbuf bb_common_bufsiz1
+       char *current_line, *p;
+       int w = width;
+       char last_terminated = terminated;
+#if ENABLE_FEATURE_LESS_REGEXP
+       unsigned old_max_fline = max_fline;
+       time_t last_time = 0;
+       unsigned seconds_p1 = 3; /* seconds_to_loop + 1 */
+#endif
 
-       fp = (flags & LESS_STATE_INP_STDIN) ? stdin : xfopen(filename, "r");
-       flines = NULL;
-       for (i = 0; (feof(fp)==0) && (i <= MAXLINES); i++) {
-               strcpy(current_line, "");
-               fgets(current_line, 256, fp);
-               if (fp != stdin)
-                       die_if_ferror(fp, filename);
-               flines = xrealloc(flines, (i+1) * sizeof(char *));
-               flines[i] = xstrdup(current_line);
+       if (option_mask32 & FLAG_N)
+               w -= 8;
+
+ USE_FEATURE_LESS_REGEXP(again0:)
+
+       p = current_line = xmalloc(w);
+       max_fline += last_terminated;
+       if (!last_terminated) {
+               const char *cp = flines[max_fline];
+               if (option_mask32 & FLAG_N)
+                       cp += 8;
+               strcpy(current_line, cp);
+               p += strlen(current_line);
+               free((char*)flines[max_fline]);
+               /* linepos is still valid from previous read_lines() */
+       } else {
+               linepos = 0;
        }
-       num_flines = i - 2;
-
-       /* Reset variables for a new file */
-
-       line_pos = 0;
-       flags &= ~LESS_STATE_PAST_EOF;
 
-       fclose(fp);
-
-       if (inp == NULL)
-               inp = (flags & LESS_STATE_INP_STDIN) ? xfopen(CURRENT_TTY, "r") : stdin;
-
-       if (flags & FLAG_N)
-               add_linenumbers();
+       while (1) { /* read lines until we reach cur_fline or wanted_match */
+               *p = '\0';
+               terminated = 0;
+               while (1) { /* read chars until we have a line */
+                       char c;
+                       /* if no unprocessed chars left, eat more */
+                       if (readpos >= readeof) {
+                               ndelay_on(0);
+                               eof_error = safe_read(STDIN_FILENO, readbuf, sizeof(readbuf));
+                               ndelay_off(0);
+                               readpos = 0;
+                               readeof = eof_error;
+                               if (eof_error <= 0)
+                                       goto reached_eof;
+                       }
+                       c = readbuf[readpos];
+                       /* backspace? [needed for manpages] */
+                       /* <tab><bs> is (a) insane and */
+                       /* (b) harder to do correctly, so we refuse to do it */
+                       if (c == '\x8' && linepos && p[-1] != '\t') {
+                               readpos++; /* eat it */
+                               linepos--;
+                       /* was buggy (p could end up <= current_line)... */
+                               *--p = '\0';
+                               continue;
+                       }
+                       {
+                               size_t new_linepos = linepos + 1;
+                               if (c == '\t') {
+                                       new_linepos += 7;
+                                       new_linepos &= (~7);
+                               }
+                               if ((int)new_linepos >= w)
+                                       break;
+                               linepos = new_linepos;
+                       }
+                       /* ok, we will eat this char */
+                       readpos++;
+                       if (c == '\n') {
+                               terminated = 1;
+                               linepos = 0;
+                               break;
+                       }
+                       /* NUL is substituted by '\n'! */
+                       if (c == '\0') c = '\n';
+                       *p++ = c;
+                       *p = '\0';
+               } /* end of "read chars until we have a line" loop */
+               /* Corner case: linewrap with only "" wrapping to next line */
+               /* Looks ugly on screen, so we do not store this empty line */
+               if (!last_terminated && !current_line[0]) {
+                       last_terminated = 1;
+                       max_lineno++;
+                       continue;
+               }
+ reached_eof:
+               last_terminated = terminated;
+               flines = xrealloc_vector(flines, 8, max_fline);
+               if (option_mask32 & FLAG_N) {
+                       /* Width of 7 preserves tab spacing in the text */
+                       flines[max_fline] = xasprintf(
+                               (max_lineno <= 9999999) ? "%7u %s" : "%07u %s",
+                               max_lineno % 10000000, current_line);
+                       free(current_line);
+                       if (terminated)
+                               max_lineno++;
+               } else {
+                       flines[max_fline] = xrealloc(current_line, strlen(current_line) + 1);
+               }
+               if (max_fline >= MAXLINES) {
+                       eof_error = 0; /* Pretend we saw EOF */
+                       break;
+               }
+               if (max_fline > cur_fline + max_displayed_line) {
+#if !ENABLE_FEATURE_LESS_REGEXP
+                       break;
+#else
+                       if (wanted_match >= num_matches) { /* goto_match called us */
+                               fill_match_lines(old_max_fline);
+                               old_max_fline = max_fline;
+                       }
+                       if (wanted_match < num_matches)
+                               break;
+#endif
+               }
+               if (eof_error <= 0) {
+                       if (eof_error < 0) {
+                               if (errno == EAGAIN) {
+                                       /* not yet eof or error, reset flag (or else
+                                        * we will hog CPU - select() will return
+                                        * immediately */
+                                       eof_error = 1;
+                               } else {
+                                       print_statusline("read error");
+                               }
+                       }
+#if !ENABLE_FEATURE_LESS_REGEXP
+                       break;
+#else
+                       if (wanted_match < num_matches) {
+                               break;
+                       } else { /* goto_match called us */
+                               time_t t = time(NULL);
+                               if (t != last_time) {
+                                       last_time = t;
+                                       if (--seconds_p1 == 0)
+                                               break;
+                               }
+                               sched_yield();
+                               goto again0; /* go loop again (max 2 seconds) */
+                       }
+#endif
+               }
+               max_fline++;
+               current_line = xmalloc(w);
+               p = current_line;
+               linepos = 0;
+       } /* end of "read lines until we reach cur_fline" loop */
+       fill_match_lines(old_max_fline);
+#if ENABLE_FEATURE_LESS_REGEXP
+       /* prevent us from being stuck in search for a match */
+       wanted_match = -1;
+#endif
+#undef readbuf
 }
 
-#ifdef CONFIG_FEATURE_LESS_FLAGS
-
-/* Interestingly, writing calc_percent as a function and not a prototype saves around 32 bytes
+#if ENABLE_FEATURE_LESS_FLAGS
+/* Interestingly, writing calc_percent as a function saves around 32 bytes
  * on my build. */
 static int calc_percent(void)
 {
-       return ((100 * (line_pos + height - 2) / num_flines) + 1);
+       unsigned p = (100 * (cur_fline+max_displayed_line+1) + max_fline/2) / (max_fline+1);
+       return p <= 100 ? p : 100;
 }
 
 /* Print a status line if -M was specified */
@@ -232,319 +405,456 @@ static void m_status_print(void)
 {
        int percentage;
 
-       if (!(flags & LESS_STATE_PAST_EOF)) {
-               if (!line_pos) {
-                       if (num_files > 1)
-                               printf("%s%s %s%i%s%i%s%i-%i/%i ", HIGHLIGHT,
-                                       filename, "(file ", current_file, " of ", num_files, ") lines ",
-                                       line_pos + 1, line_pos + height - 1, num_flines + 1);
-                       else {
-                               printf("%s%s lines %i-%i/%i ", HIGHLIGHT,
-                                       filename, line_pos + 1, line_pos + height - 1,
-                                       num_flines + 1);
-                       }
-               }
-               else {
-                       printf("%s %s lines %i-%i/%i ", HIGHLIGHT, filename,
-                               line_pos + 1, line_pos + height - 1, num_flines + 1);
-               }
+       if (less_gets_pos >= 0) /* don't touch statusline while input is done! */
+               return;
 
-               if (line_pos == num_flines - height + 2) {
-                       printf("(END) %s", NORMAL);
-                       if ((num_files > 1) && (current_file != num_files))
-                               printf("%s- Next: %s%s", HIGHLIGHT, files[current_file], NORMAL);
-               }
-               else {
-                       percentage = calc_percent();
-                       printf("%i%% %s", percentage, NORMAL);
-               }
-       }
-       else {
-               printf("%s%s lines %i-%i/%i (END) ", HIGHLIGHT, filename,
-                               line_pos + 1, num_flines + 1, num_flines + 1);
-               if ((num_files > 1) && (current_file != num_files))
-                       printf("- Next: %s", files[current_file]);
-               printf("%s", NORMAL);
+       clear_line();
+       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);
+       if (cur_fline >= (int)(max_fline - max_displayed_line)) {
+               printf("(END)"NORMAL);
+               if (num_files > 1 && current_file != num_files)
+                       printf(HIGHLIGHT" - next: %s"NORMAL, files[current_file]);
+               return;
        }
-}
-
-/* Print a status line if -m was specified */
-static void medium_status_print(void)
-{
-       int percentage;
        percentage = calc_percent();
-
-       if (!line_pos)
-               printf("%s%s %i%%%s", HIGHLIGHT, filename, percentage, NORMAL);
-       else if (line_pos == num_flines - height + 2)
-               printf("%s(END)%s", HIGHLIGHT, NORMAL);
-       else
-               printf("%s%i%%%s", HIGHLIGHT, percentage, NORMAL);
+       printf("%i%%"NORMAL, percentage);
 }
 #endif
 
 /* Print the status line */
 static void status_print(void)
 {
+       const char *p;
+
+       if (less_gets_pos >= 0) /* don't touch statusline while input is done! */
+               return;
+
        /* Change the status if flags have been set */
-#ifdef CONFIG_FEATURE_LESS_FLAGS
-       if (flags & FLAG_M)
+#if ENABLE_FEATURE_LESS_FLAGS
+       if (option_mask32 & (FLAG_M|FLAG_m)) {
                m_status_print();
-       else if (flags & FLAG_m)
-               medium_status_print();
+               return;
+       }
        /* No flags set */
-       else {
 #endif
-               if (!line_pos) {
-                       printf("%s%s %s", HIGHLIGHT, filename, NORMAL);
-                       if (num_files > 1)
-                               printf("%s%s%i%s%i%s%s", HIGHLIGHT, "(file ",
-                                       current_file, " of ", num_files, ")", NORMAL);
-               }
-               else if (line_pos == num_flines - height + 2) {
-                       printf("%s%s %s", HIGHLIGHT, "(END)", NORMAL);
-                       if ((num_files > 1) && (current_file != num_files))
-                               printf("%s%s%s%s", HIGHLIGHT, "- Next: ", files[current_file], NORMAL);
-               }
-               else {
-                       putchar(':');
-               }
-#ifdef CONFIG_FEATURE_LESS_FLAGS
+
+       clear_line();
+       if (cur_fline && cur_fline < (int)(max_fline - max_displayed_line)) {
+               bb_putchar(':');
+               return;
        }
-#endif
+       p = "(END)";
+       if (!cur_fline)
+               p = filename;
+       if (num_files > 1) {
+               printf(HIGHLIGHT"%s (file %i of %i)"NORMAL,
+                               p, current_file, num_files);
+               return;
+       }
+       print_hilite(p);
 }
 
-/* Print the buffer */
-static void buffer_print(void)
+static void cap_cur_fline(int nlines)
 {
-       int i;
+       int diff;
+       if (cur_fline < 0)
+               cur_fline = 0;
+       if (cur_fline + max_displayed_line > max_fline + TILDES) {
+               cur_fline -= nlines;
+               if (cur_fline < 0)
+                       cur_fline = 0;
+               diff = max_fline - (cur_fline + max_displayed_line) + TILDES;
+               /* As the number of lines requested was too large, we just move
+               to the end of the file */
+               if (diff > 0)
+                       cur_fline += diff;
+       }
+}
+
+static const char controls[] ALIGN1 =
+       /* NUL: never encountered; TAB: not converted */
+       /**/"\x01\x02\x03\x04\x05\x06\x07\x08"  "\x0a\x0b\x0c\x0d\x0e\x0f"
+       "\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f"
+       "\x7f\x9b"; /* DEL and infamous Meta-ESC :( */
+static const char ctrlconv[] ALIGN1 =
+       /* '\n': it's a former NUL - subst with '@', not 'J' */
+       "\x40\x41\x42\x43\x44\x45\x46\x47\x48\x49\x40\x4b\x4c\x4d\x4e\x4f"
+       "\x50\x51\x52\x53\x54\x55\x56\x57\x58\x59\x5a\x5b\x5c\x5d\x5e\x5f";
+
+#if ENABLE_FEATURE_LESS_REGEXP
+static void print_found(const char *line)
+{
+       int match_status;
+       int eflags;
+       char *growline;
+       regmatch_t match_structs;
 
-       printf("%s", CLEAR);
-       if (num_flines >= height - 2) {
-               for (i = 0; i < height - 1; i++)
-                       printf("%s", buffer[i]);
+       char buf[width];
+       const char *str = line;
+       char *p = buf;
+       size_t n;
+
+       while (*str) {
+               n = strcspn(str, controls);
+               if (n) {
+                       if (!str[n]) break;
+                       memcpy(p, str, n);
+                       p += n;
+                       str += n;
+               }
+               n = strspn(str, controls);
+               memset(p, '.', n);
+               p += n;
+               str += n;
        }
-       else {
-               for (i = 1; i < (height - 1 - num_flines); i++)
-                       putchar('\n');
-               for (i = 0; i < height - 1; i++)
-                       printf("%s", buffer[i]);
+       strcpy(p, str);
+
+       /* buf[] holds quarantined version of str */
+
+       /* Each part of the line that matches has the HIGHLIGHT
+          and NORMAL escape sequences placed around it.
+          NB: we regex against line, but insert text
+          from quarantined copy (buf[]) */
+       str = buf;
+       growline = NULL;
+       eflags = 0;
+       goto start;
+
+       while (match_status == 0) {
+               char *new = xasprintf("%s%.*s"HIGHLIGHT"%.*s"NORMAL,
+                               growline ? : "",
+                               match_structs.rm_so, str,
+                               match_structs.rm_eo - match_structs.rm_so,
+                                               str + match_structs.rm_so);
+               free(growline); growline = new;
+               str += match_structs.rm_eo;
+               line += match_structs.rm_eo;
+               eflags = REG_NOTBOL;
+ start:
+               /* Most of the time doesn't find the regex, optimize for that */
+               match_status = regexec(&pattern, line, 1, &match_structs, eflags);
+               /* if even "" matches, treat it as "not a match" */
+               if (match_structs.rm_so >= match_structs.rm_eo)
+                       match_status = 1;
        }
 
-       status_print();
+       if (!growline) {
+               printf(CLEAR_2_EOL"%s\n", str);
+               return;
+       }
+       printf(CLEAR_2_EOL"%s%s\n", growline, str);
+       free(growline);
 }
+#else
+void print_found(const char *line);
+#endif
 
-/* Initialise the buffer */
-static void buffer_init(void)
+static void print_ascii(const char *str)
 {
-       int i;
-
-       if (buffer == NULL) {
-               /* malloc the number of lines needed for the buffer */
-               buffer = xrealloc(buffer, height * sizeof(char *));
-       } else {
-               for (i = 0; i < (height - 1); i++)
-                       free(buffer[i]);
+       char buf[width];
+       char *p;
+       size_t n;
+
+       printf(CLEAR_2_EOL);
+       while (*str) {
+               n = strcspn(str, controls);
+               if (n) {
+                       if (!str[n]) break;
+                       printf("%.*s", (int) n, str);
+                       str += n;
+               }
+               n = strspn(str, controls);
+               p = buf;
+               do {
+                       if (*str == 0x7f)
+                               *p++ = '?';
+                       else if (*str == (char)0x9b)
+                       /* VT100's CSI, aka Meta-ESC. Who's inventor? */
+                       /* I want to know who committed this sin */
+                               *p++ = '{';
+                       else
+                               *p++ = ctrlconv[(unsigned char)*str];
+                       str++;
+               } while (--n);
+               *p = '\0';
+               print_hilite(buf);
        }
+       puts(str);
+}
 
-       /* Fill the buffer until the end of the file or the
-          end of the buffer is reached */
-       for (i = 0; (i < (height - 1)) && (i <= num_flines); i++) {
-               buffer[i] = xstrdup(flines[i]);
-       }
+/* Print the buffer */
+static void buffer_print(void)
+{
+       unsigned i;
 
-       /* If the buffer still isn't full, fill it with blank lines */
-       for (; i < (height - 1); i++) {
-               buffer[i] = xstrdup("");
+       move_cursor(0, 0);
+       for (i = 0; i <= max_displayed_line; i++)
+               if (pattern_valid)
+                       print_found(buffer[i]);
+               else
+                       print_ascii(buffer[i]);
+       status_print();
+}
+
+static void buffer_fill_and_print(void)
+{
+       unsigned i;
+       for (i = 0; i <= max_displayed_line && cur_fline + i <= max_fline; i++) {
+               buffer[i] = flines[cur_fline + i];
        }
+       for (; i <= max_displayed_line; i++) {
+               buffer[i] = empty_line_marker;
+       }
+       buffer_print();
 }
 
 /* Move the buffer up and down in the file in order to scroll */
 static void buffer_down(int nlines)
 {
-       int i;
+       cur_fline += nlines;
+       read_lines();
+       cap_cur_fline(nlines);
+       buffer_fill_and_print();
+}
 
-       if (!(flags & LESS_STATE_PAST_EOF)) {
-               if (line_pos + (height - 3) + nlines < num_flines) {
-                       line_pos += nlines;
-                       for (i = 0; i < (height - 1); i++) {
-                               free(buffer[i]);
-                               buffer[i] = xstrdup(flines[line_pos + i]);
-                       }
-               }
-               else {
-                       /* As the number of lines requested was too large, we just move
-                       to the end of the file */
-                       while (line_pos + (height - 3) + 1 < num_flines) {
-                               line_pos += 1;
-                               for (i = 0; i < (height - 1); i++) {
-                                       free(buffer[i]);
-                                       buffer[i] = xstrdup(flines[line_pos + i]);
-                               }
-                       }
-               }
+static void buffer_up(int nlines)
+{
+       cur_fline -= nlines;
+       if (cur_fline < 0) cur_fline = 0;
+       read_lines();
+       buffer_fill_and_print();
+}
 
-               /* We exit if the -E flag has been set */
-               if ((flags & FLAG_E) && (line_pos + (height - 2) == num_flines))
-                       tless_exit(0);
-       }
+static void buffer_line(int linenum)
+{
+       if (linenum < 0)
+               linenum = 0;
+       cur_fline = linenum;
+       read_lines();
+       if (linenum + max_displayed_line > max_fline)
+               linenum = max_fline - max_displayed_line + TILDES;
+       if (linenum < 0)
+               linenum = 0;
+       cur_fline = linenum;
+       buffer_fill_and_print();
 }
 
-static void buffer_up(int nlines)
+static void open_file_and_read_lines(void)
 {
-       int i;
-       int tilde_line;
-
-       if (!(flags & LESS_STATE_PAST_EOF)) {
-               if (line_pos - nlines >= 0) {
-                       line_pos -= nlines;
-                       for (i = 0; i < (height - 1); i++) {
-                               free(buffer[i]);
-                               buffer[i] = xstrdup(flines[line_pos + i]);
-                       }
-               }
-               else {
-               /* As the requested number of lines to move was too large, we
-                  move one line up at a time until we can't. */
-                       while (line_pos != 0) {
-                               line_pos -= 1;
-                               for (i = 0; i < (height - 1); i++) {
-                                       free(buffer[i]);
-                                       buffer[i] = xstrdup(flines[line_pos + i]);
-                               }
-                       }
-               }
-       }
-       else {
-               /* Work out where the tildes start */
-               tilde_line = num_flines - line_pos + 3;
-
-               line_pos -= nlines;
-               /* Going backwards nlines lines has taken us to a point where
-                  nothing is past the EOF, so we revert to normal. */
-               if (line_pos < num_flines - height + 3) {
-                       flags &= ~LESS_STATE_PAST_EOF;
-                       buffer_up(nlines);
-               }
-               else {
-                       /* We only move part of the buffer, as the rest
-                       is past the EOF */
-                       for (i = 0; i < (height - 1); i++) {
-                               free(buffer[i]);
-                               if (i < tilde_line - nlines + 1)
-                                       buffer[i] = xstrdup(flines[line_pos + i]);
-                               else {
-                                       if (line_pos >= num_flines - height + 2)
-                                               buffer[i] = xstrdup("~\n");
-                               }
-                       }
-               }
+       if (filename) {
+               int fd = xopen(filename, O_RDONLY);
+               dup2(fd, 0);
+               if (fd) close(fd);
+       } else {
+               /* "less" with no arguments in argv[] */
+               /* For status line only */
+               filename = xstrdup(bb_msg_standard_input);
        }
+       readpos = 0;
+       readeof = 0;
+       linepos = 0;
+       terminated = 1;
+       read_lines();
 }
 
-static void buffer_line(int linenum)
+/* Reinitialize everything for a new file - free the memory and start over */
+static void reinitialize(void)
 {
-       int i;
-       flags &= ~LESS_STATE_PAST_EOF;
+       unsigned i;
 
-       if (linenum < 0 || linenum > num_flines) {
-               clear_line();
-               printf("%s%s%i%s", HIGHLIGHT, "Cannot seek to line number ", linenum + 1, NORMAL);
+       if (flines) {
+               for (i = 0; i <= max_fline; i++)
+                       free((void*)(flines[i]));
+               free(flines);
+               flines = NULL;
        }
-       else if (linenum < (num_flines - height - 2)) {
-               for (i = 0; i < (height - 1); i++) {
-                       free(buffer[i]);
-                       buffer[i] = xstrdup(flines[linenum + i]);
-               }
-               line_pos = linenum;
-               buffer_print();
+
+       max_fline = -1;
+       cur_fline = 0;
+       max_lineno = 0;
+       open_file_and_read_lines();
+       buffer_fill_and_print();
+}
+
+static ssize_t getch_nowait(char* input, int sz)
+{
+       ssize_t rd;
+       struct pollfd pfd[2];
+
+       pfd[0].fd = STDIN_FILENO;
+       pfd[0].events = POLLIN;
+       pfd[1].fd = kbd_fd;
+       pfd[1].events = POLLIN;
+ again:
+       tcsetattr(kbd_fd, TCSANOW, &term_less);
+       /* NB: select/poll returns whenever read will not block. Therefore:
+        * if eof is reached, select/poll will return immediately
+        * because read will immediately return 0 bytes.
+        * Even if select/poll says that input is available, read CAN block
+        * (switch fd into O_NONBLOCK'ed mode to avoid it)
+        */
+       rd = 1;
+       if (max_fline <= cur_fline + max_displayed_line
+        && eof_error > 0 /* did NOT reach eof yet */
+       ) {
+               /* We are interested in stdin */
+               rd = 0;
        }
-       else {
-               for (i = 0; i < (height - 1); i++) {
-                       free(buffer[i]);
-                       if (linenum + i < num_flines + 2)
-                               buffer[i] = xstrdup(flines[linenum + i]);
-                       else
-                               buffer[i] = xstrdup((flags & FLAG_TILDE) ? "\n" : "~\n");
-               }
-               line_pos = linenum;
-               /* Set past_eof so buffer_down and buffer_up act differently */
-               flags |= LESS_STATE_PAST_EOF;
-               buffer_print();
+       /* position cursor if line input is done */
+       if (less_gets_pos >= 0)
+               move_cursor(max_displayed_line + 2, less_gets_pos + 1);
+       fflush(stdout);
+       safe_poll(pfd + rd, 2 - rd, -1);
+
+       input[0] = '\0';
+       rd = safe_read(kbd_fd, input, sz); /* NB: kbd_fd is in O_NONBLOCK mode */
+       if (rd < 0 && errno == EAGAIN) {
+               /* No keyboard input -> we have input on stdin! */
+               read_lines();
+               buffer_fill_and_print();
+               goto again;
        }
+       set_tty_cooked();
+       return rd;
 }
 
-/* Reinitialise everything for a new file - free the memory and start over */
-static void reinitialise(void)
+/* Grab a character from input without requiring the return key. If the
+ * character is ASCII \033, get more characters and assign certain sequences
+ * special return codes. Note that this function works best with raw input. */
+static int less_getch(int pos)
 {
-       int i;
+       unsigned char input[16];
+       unsigned i;
 
-       for (i = 0; i <= num_flines; i++)
-               free(flines[i]);
-       free(flines);
+ again:
+       less_gets_pos = pos;
+       memset(input, 0, sizeof(input));
+       getch_nowait((char *)input, sizeof(input));
+       less_gets_pos = -1;
 
-       data_readlines();
-       buffer_init();
-       buffer_print();
+       /* Detect escape sequences (i.e. arrow keys) and handle
+        * them accordingly */
+       if (input[0] == '\033' && input[1] == '[') {
+               i = input[2] - REAL_KEY_UP;
+               if (i < 4)
+                       return 20 + i;
+               i = input[2] - REAL_PAGE_UP;
+               if (i < 4)
+                       return 24 + i;
+               if (input[2] == REAL_KEY_HOME_XTERM)
+                       return KEY_HOME;
+               if (input[2] == REAL_KEY_HOME_ALT)
+                       return KEY_HOME;
+               if (input[2] == REAL_KEY_END_XTERM)
+                       return KEY_END;
+               if (input[2] == REAL_KEY_END_ALT)
+                       return KEY_END;
+               return 0;
+       }
+       /* Reject almost all control chars */
+       i = input[0];
+       if (i < ' ' && i != 0x0d && i != 8)
+               goto again;
+       return i;
 }
 
-static void examine_file(void)
+static char* less_gets(int sz)
 {
-       int newline_offset;
+       char c;
+       unsigned i = 0;
+       char *result = xzalloc(1);
 
-       clear_line();
-       printf("Examine: ");
-       fgets(filename, 256, inp);
-
-       /* As fgets adds a newline to the end of an input string, we
-          need to remove it */
-       newline_offset = strlen(filename) - 1;
-       filename[newline_offset] = '\0';
+       while (1) {
+               c = '\0';
+               less_gets_pos = sz + i;
+               getch_nowait(&c, 1);
+               if (c == 0x0d) {
+                       result[i] = '\0';
+                       less_gets_pos = -1;
+                       return result;
+               }
+               if (c == 0x7f)
+                       c = 8;
+               if (c == 8 && i) {
+                       printf("\x8 \x8");
+                       i--;
+               }
+               if (c < ' ')
+                       continue;
+               if (i >= width - sz - 1)
+                       continue; /* len limit */
+               bb_putchar(c);
+               result[i++] = c;
+               result = xrealloc(result, i+1);
+       }
+}
 
-       files[num_files] = xstrdup(filename);
+static void examine_file(void)
+{
+       char *new_fname;
+
+       print_statusline("Examine: ");
+       new_fname = less_gets(sizeof("Examine: ") - 1);
+       if (!new_fname[0]) {
+               status_print();
+ err:
+               free(new_fname);
+               return;
+       }
+       if (access(new_fname, R_OK) != 0) {
+               print_statusline("Cannot read this file");
+               goto err;
+       }
+       free(filename);
+       filename = new_fname;
+       /* files start by = argv. why we assume that argv is infinitely long??
+       files[num_files] = filename;
        current_file = num_files + 1;
-       num_files++;
-
-       flags &= ~LESS_STATE_INP_STDIN;
-       reinitialise();
+       num_files++; */
+       files[0] = filename;
+       num_files = current_file = 1;
+       reinitialize();
 }
 
 /* This function changes the file currently being paged. direction can be one of the following:
  * -1: go back one file
  *  0: go to the first file
- *  1: go forward one file
-*/
+ *  1: go forward one file */
 static void change_file(int direction)
 {
        if (current_file != ((direction > 0) ? num_files : 1)) {
                current_file = direction ? current_file + direction : 1;
-               strcpy(filename, files[current_file - 1]);
-               reinitialise();
-       }
-       else {
-               clear_line();
-               printf("%s%s%s", HIGHLIGHT, (direction > 0) ? "No next file" : "No previous file", NORMAL);
+               free(filename);
+               filename = xstrdup(files[current_file - 1]);
+               reinitialize();
+       } else {
+               print_statusline(direction > 0 ? "No next file" : "No previous file");
        }
 }
 
 static void remove_current_file(void)
 {
-       int i;
+       unsigned i;
+
+       if (num_files < 2)
+               return;
 
        if (current_file != 1) {
                change_file(-1);
                for (i = 3; i <= num_files; i++)
                        files[i - 2] = files[i - 1];
                num_files--;
-               buffer_print();
-       }
-       else {
+       } else {
                change_file(1);
                for (i = 2; i <= num_files; i++)
                        files[i - 2] = files[i - 1];
                num_files--;
                current_file--;
-               buffer_print();
        }
 }
 
@@ -553,180 +863,140 @@ static void colon_process(void)
        int keypress;
 
        /* Clear the current line and print a prompt */
-       clear_line();
-       printf(" :");
+       print_statusline(" :");
 
-       keypress = tless_getch();
+       keypress = less_getch(2);
        switch (keypress) {
-               case 'd':
-                       remove_current_file();
-                       break;
-               case 'e':
-                       examine_file();
-                       break;
-#ifdef CONFIG_FEATURE_LESS_FLAGS
-               case 'f':
-                       clear_line();
-                       m_status_print();
-                       break;
+       case 'd':
+               remove_current_file();
+               break;
+       case 'e':
+               examine_file();
+               break;
+#if ENABLE_FEATURE_LESS_FLAGS
+       case 'f':
+               m_status_print();
+               break;
 #endif
-               case 'n':
-                       change_file(1);
-                       break;
-               case 'p':
-                       change_file(-1);
-                       break;
-               case 'q':
-                       tless_exit(0);
-                       break;
-               case 'x':
-                       change_file(0);
-                       break;
-               default:
-                       break;
+       case 'n':
+               change_file(1);
+               break;
+       case 'p':
+               change_file(-1);
+               break;
+       case 'q':
+               less_exit(EXIT_SUCCESS);
+               break;
+       case 'x':
+               change_file(0);
+               break;
        }
 }
 
-#ifdef CONFIG_FEATURE_LESS_REGEXP
-/* The below two regular expression handler functions NEED development. */
-
-/* Get a regular expression from the user, and then go through the current
-   file line by line, running a processing regex function on each one. */
-
-static char *process_regex_on_line(char *line, regex_t *pattern, int action)
+#if ENABLE_FEATURE_LESS_REGEXP
+static void normalize_match_pos(int match)
 {
-       /* This function takes the regex and applies it to the line.
-          Each part of the line that matches has the HIGHLIGHT
-          and NORMAL escape sequences placed around it by
-          insert_highlights if action = 1, or has the escape sequences
-          removed if action = 0, and then the line is returned. */
-       int match_status;
-       char *line2 = xmalloc((sizeof(char) * (strlen(line) + 1)) + 64);
-       char *growline = "";
-       regmatch_t match_structs;
-
-       line2 = xstrdup(line);
-
-       match_found = 0;
-       match_status = regexec(pattern, line2, 1, &match_structs, 0);
-
-       while (match_status == 0) {
-               if (match_found == 0)
-                       match_found = 1;
-
-               if (action) {
-                       growline = xasprintf("%s%.*s%s%.*s%s", growline,
-                               match_structs.rm_so, line2, HIGHLIGHT,
-                               match_structs.rm_eo - match_structs.rm_so,
-                               line2 + match_structs.rm_so, NORMAL);
-               }
-               else {
-                       growline = xasprintf("%s%.*s%.*s", growline,
-                               match_structs.rm_so - 4, line2,
-                               match_structs.rm_eo - match_structs.rm_so,
-                               line2 + match_structs.rm_so);
-               }
+       if (match >= num_matches)
+               match = num_matches - 1;
+       if (match < 0)
+               match = 0;
+       match_pos = match;
+}
 
-               line2 += match_structs.rm_eo;
-               match_status = regexec(pattern, line2, 1, &match_structs, REG_NOTBOL);
+static void goto_match(int match)
+{
+       if (!pattern_valid)
+               return;
+       if (match < 0)
+               match = 0;
+       /* Try to find next match if eof isn't reached yet */
+       if (match >= num_matches && eof_error > 0) {
+               wanted_match = match; /* "I want to read until I see N'th match" */
+               read_lines();
+       }
+       if (num_matches) {
+               normalize_match_pos(match);
+               buffer_line(match_lines[match_pos]);
+       } else {
+               print_statusline("No matches found");
        }
-
-       growline = xasprintf("%s%s", growline, line2);
-
-       return (match_found ? growline : line);
-
-       free(growline);
-       free(line2);
 }
 
-static void goto_match(int match)
+static void fill_match_lines(unsigned pos)
 {
-       /* This goes to a specific match - all line positions of matches are
-          stored within the match_lines[] array. */
-       if ((match < num_matches) && (match >= 0)) {
-               buffer_line(match_lines[match]);
-               match_pos = match;
+       if (!pattern_valid)
+               return;
+       /* Run the regex on each line of the current file */
+       while (pos <= max_fline) {
+               /* If this line matches */
+               if (regexec(&pattern, flines[pos], 0, NULL, 0) == 0
+               /* and we didn't match it last time */
+                && !(num_matches && match_lines[num_matches-1] == pos)
+               ) {
+                       match_lines = xrealloc_vector(match_lines, 4, num_matches);
+                       match_lines[num_matches++] = pos;
+               }
+               pos++;
        }
 }
 
 static void regex_process(void)
 {
-       char uncomp_regex[100];
-       char *current_line;
-       int i;
-       int j = 0;
-       regex_t pattern;
+       char *uncomp_regex, *err;
+
+       /* Reset variables */
+       free(match_lines);
+       match_lines = NULL;
+       match_pos = 0;
+       num_matches = 0;
+       if (pattern_valid) {
+               regfree(&pattern);
+               pattern_valid = 0;
+       }
+
        /* Get the uncompiled regular expression from the user */
        clear_line();
-       putchar((flags & LESS_STATE_MATCH_BACKWARDS) ? '?' : '/');
-       uncomp_regex[0] = 0;
-       fgets(uncomp_regex, sizeof(uncomp_regex), inp);
-
-       if (strlen(uncomp_regex) == 1) {
-               if (num_matches)
-                       goto_match((flags & LESS_STATE_MATCH_BACKWARDS)
-                                               ? match_pos - 1 : match_pos + 1);
-               else
-                       buffer_print();
+       bb_putchar((option_mask32 & LESS_STATE_MATCH_BACKWARDS) ? '?' : '/');
+       uncomp_regex = less_gets(1);
+       if (!uncomp_regex[0]) {
+               free(uncomp_regex);
+               buffer_print();
                return;
        }
-       uncomp_regex[strlen(uncomp_regex) - 1] = '\0';
 
        /* Compile the regex and check for errors */
-       xregcomp(&pattern, uncomp_regex, 0);
-
-       if (num_matches) {
-               /* Get rid of all the highlights we added previously */
-               for (i = 0; i <= num_flines; i++) {
-                       current_line = process_regex_on_line(flines[i], &old_pattern, 0);
-                       flines[i] = xstrdup(current_line);
-               }
+       err = regcomp_or_errmsg(&pattern, uncomp_regex, 0);
+       free(uncomp_regex);
+       if (err) {
+               print_statusline(err);
+               free(err);
+               return;
        }
-       old_pattern = pattern;
 
-       /* Reset variables */
-       match_lines = xrealloc(match_lines, sizeof(int));
-       match_lines[0] = -1;
+       pattern_valid = 1;
        match_pos = 0;
-       num_matches = 0;
-       match_found = 0;
-       /* Run the regex on each line of the current file here */
-       for (i = 0; i <= num_flines; i++) {
-               current_line = process_regex_on_line(flines[i], &pattern, 1);
-               flines[i] = xstrdup(current_line);
-               if (match_found) {
-                       match_lines = xrealloc(match_lines, (j + 1) * sizeof(int));
-                       match_lines[j] = i;
-                       j++;
-               }
+       fill_match_lines(0);
+       while (match_pos < num_matches) {
+               if ((int)match_lines[match_pos] > cur_fline)
+                       break;
+               match_pos++;
        }
+       if (option_mask32 & LESS_STATE_MATCH_BACKWARDS)
+               match_pos--;
 
-       num_matches = j;
-       if ((match_lines[0] != -1) && (num_flines > height - 2)) {
-               if (flags & LESS_STATE_MATCH_BACKWARDS) {
-                       for (i = 0; i < num_matches; i++) {
-                               if (match_lines[i] > line_pos) {
-                                       match_pos = i - 1;
-                                       buffer_line(match_lines[match_pos]);
-                                       break;
-                               }
-                       }
-               }
-               else
-                       buffer_line(match_lines[0]);
-       }
-       else
-               buffer_init();
+       /* It's possible that no matches are found yet.
+        * goto_match() will read input looking for match,
+        * if needed */
+       goto_match(match_pos);
 }
 #endif
 
 static void number_process(int first_digit)
 {
-       int i = 1;
+       unsigned i;
        int num;
-       char num_input[80];
+       char num_input[sizeof(int)*4]; /* more than enough */
        char keypress;
-       char *endptr;
 
        num_input[0] = first_digit;
 
@@ -734,78 +1004,83 @@ static void number_process(int first_digit)
        clear_line();
        printf(":%c", first_digit);
 
-       /* Receive input until a letter is given (max 80 chars)*/
-       while((i < 80) && (num_input[i] = tless_getch()) && isdigit(num_input[i])) {
-               putchar(num_input[i]);
+       /* Receive input until a letter is given */
+       i = 1;
+       while (i < sizeof(num_input)-1) {
+               num_input[i] = less_getch(i + 1);
+               if (!num_input[i] || !isdigit(num_input[i]))
+                       break;
+               bb_putchar(num_input[i]);
                i++;
        }
 
        /* Take the final letter out of the digits string */
        keypress = num_input[i];
        num_input[i] = '\0';
-       num = strtol(num_input, &endptr, 10);
-       if (endptr==num_input || *endptr!='\0' || num < 1 || num > MAXLINES) {
+       num = bb_strtou(num_input, NULL, 10);
+       /* on format error, num == -1 */
+       if (num < 1 || num > MAXLINES) {
                buffer_print();
                return;
        }
 
        /* We now know the number and the letter entered, so we process them */
        switch (keypress) {
-               case KEY_DOWN: case 'z': case 'd': case 'e': case ' ': case '\015':
-                       buffer_down(num);
-                       break;
-               case KEY_UP: case 'b': case 'w': case 'y': case 'u':
-                       buffer_up(num);
-                       break;
-               case 'g': case '<': case 'G': case '>':
-                       if (num_flines >= height - 2)
-                               buffer_line(num - 1);
-                       break;
-               case 'p': case '%':
-                       buffer_line(((num / 100) * num_flines) - 1);
-                       break;
-#ifdef CONFIG_FEATURE_LESS_REGEXP
-               case 'n':
-                       goto_match(match_pos + num);
-                       break;
-               case '/':
-                       flags &= ~LESS_STATE_MATCH_BACKWARDS;
-                       regex_process();
-                       break;
-               case '?':
-                       flags |= LESS_STATE_MATCH_BACKWARDS;
-                       regex_process();
-                       break;
+       case KEY_DOWN: case 'z': case 'd': case 'e': case ' ': case '\015':
+               buffer_down(num);
+               break;
+       case KEY_UP: case 'b': case 'w': case 'y': case 'u':
+               buffer_up(num);
+               break;
+       case 'g': case '<': case 'G': case '>':
+               cur_fline = num + max_displayed_line;
+               read_lines();
+               buffer_line(num - 1);
+               break;
+       case 'p': case '%':
+               num = num * (max_fline / 100); /* + max_fline / 2; */
+               cur_fline = num + max_displayed_line;
+               read_lines();
+               buffer_line(num);
+               break;
+#if ENABLE_FEATURE_LESS_REGEXP
+       case 'n':
+               goto_match(match_pos + num);
+               break;
+       case '/':
+               option_mask32 &= ~LESS_STATE_MATCH_BACKWARDS;
+               regex_process();
+               break;
+       case '?':
+               option_mask32 |= LESS_STATE_MATCH_BACKWARDS;
+               regex_process();
+               break;
 #endif
-               default:
-                       break;
        }
 }
 
-#ifdef CONFIG_FEATURE_LESS_FLAGCS
+#if ENABLE_FEATURE_LESS_FLAGCS
 static void flag_change(void)
 {
        int keypress;
 
        clear_line();
-       putchar('-');
-       keypress = tless_getch();
+       bb_putchar('-');
+       keypress = less_getch(1);
 
        switch (keypress) {
-               case 'M':
-                       flags ^= FLAG_M;
-                       break;
-               case 'm':
-                       flags ^= FLAG_m;
-                       break;
-               case 'E':
-                       flags ^= FLAG_E;
-                       break;
-               case '~':
-                       flags ^= FLAG_TILDE;
-                       break;
-               default:
-                       break;
+       case 'M':
+               option_mask32 ^= FLAG_M;
+               break;
+       case 'm':
+               option_mask32 ^= FLAG_m;
+               break;
+       case 'E':
+               option_mask32 ^= FLAG_E;
+               break;
+       case '~':
+               option_mask32 ^= FLAG_TILDE;
+               break;
        }
 }
 
@@ -815,87 +1090,78 @@ static void show_flag_status(void)
        int flag_val;
 
        clear_line();
-       putchar('_');
-       keypress = tless_getch();
+       bb_putchar('_');
+       keypress = less_getch(1);
 
        switch (keypress) {
-               case 'M':
-                       flag_val = flags & FLAG_M;
-                       break;
-               case 'm':
-                       flag_val = flags & FLAG_m;
-                       break;
-               case '~':
-                       flag_val = flags & FLAG_TILDE;
-                       break;
-               case 'N':
-                       flag_val = flags & FLAG_N;
-                       break;
-               case 'E':
-                       flag_val = flags & FLAG_E;
-                       break;
-               default:
-                       flag_val = 0;
-                       break;
+       case 'M':
+               flag_val = option_mask32 & FLAG_M;
+               break;
+       case 'm':
+               flag_val = option_mask32 & FLAG_m;
+               break;
+       case '~':
+               flag_val = option_mask32 & FLAG_TILDE;
+               break;
+       case 'N':
+               flag_val = option_mask32 & FLAG_N;
+               break;
+       case 'E':
+               flag_val = option_mask32 & FLAG_E;
+               break;
+       default:
+               flag_val = 0;
+               break;
        }
 
        clear_line();
-       printf("%s%s%i%s", HIGHLIGHT, "The status of the flag is: ", flag_val != 0, NORMAL);
+       printf(HIGHLIGHT"The status of the flag is: %u"NORMAL, flag_val != 0);
 }
 #endif
 
-static void full_repaint(void)
-{
-       int temp_line_pos = line_pos;
-       data_readlines();
-       buffer_init();
-       buffer_line(temp_line_pos);
-}
-
-
 static void save_input_to_file(void)
 {
-       char current_line[256];
-       int i;
+       const char *msg = "";
+       char *current_line;
+       unsigned i;
        FILE *fp;
 
-       clear_line();
-       printf("Log file: ");
-       fgets(current_line, 256, inp);
-       current_line[strlen(current_line) - 1] = '\0';
-       if (strlen(current_line) > 1) {
-               fp = xfopen(current_line, "w");
-               for (i = 0; i < num_flines; i++)
-                       fprintf(fp, "%s", flines[i]);
+       print_statusline("Log file: ");
+       current_line = less_gets(sizeof("Log file: ")-1);
+       if (current_line[0]) {
+               fp = fopen_for_write(current_line);
+               if (!fp) {
+                       msg = "Error opening log file";
+                       goto ret;
+               }
+               for (i = 0; i <= max_fline; i++)
+                       fprintf(fp, "%s\n", flines[i]);
                fclose(fp);
-               buffer_print();
+               msg = "Done";
        }
-       else
-               printf("%s%s%s", HIGHLIGHT, "No log file", NORMAL);
+ ret:
+       print_statusline(msg);
+       free(current_line);
 }
 
-#ifdef CONFIG_FEATURE_LESS_MARKS
+#if ENABLE_FEATURE_LESS_MARKS
 static void add_mark(void)
 {
        int letter;
 
-       clear_line();
-       printf("Mark: ");
-       letter = tless_getch();
+       print_statusline("Mark: ");
+       letter = less_getch(sizeof("Mark: ") - 1);
 
        if (isalpha(letter)) {
-
                /* If we exceed 15 marks, start overwriting previous ones */
                if (num_marks == 14)
                        num_marks = 0;
 
                mark_lines[num_marks][0] = letter;
-               mark_lines[num_marks][1] = line_pos;
+               mark_lines[num_marks][1] = cur_fline;
                num_marks++;
-       }
-       else {
-               clear_line();
-               printf("%s%s%s", HIGHLIGHT, "Invalid mark letter", NORMAL);
+       } else {
+               print_statusline("Invalid mark letter");
        }
 }
 
@@ -904,9 +1170,8 @@ static void goto_mark(void)
        int letter;
        int i;
 
-       clear_line();
-       printf("Go to mark: ");
-       letter = tless_getch();
+       print_statusline("Go to mark: ");
+       letter = less_getch(sizeof("Go to mark: ") - 1);
        clear_line();
 
        if (isalpha(letter)) {
@@ -915,230 +1180,233 @@ static void goto_mark(void)
                                buffer_line(mark_lines[i][1]);
                                break;
                        }
-               if ((num_marks == 14) && (letter != mark_lines[14][0]))
-                       printf("%s%s%s", HIGHLIGHT, "Mark not set", NORMAL);
-       }
-       else
-               printf("%s%s%s", HIGHLIGHT, "Invalid mark letter", NORMAL);
+               if (num_marks == 14 && letter != mark_lines[14][0])
+                       print_statusline("Mark not set");
+       } else
+               print_statusline("Invalid mark letter");
 }
 #endif
 
-
-#ifdef CONFIG_FEATURE_LESS_BRACKETS
-
+#if ENABLE_FEATURE_LESS_BRACKETS
 static char opp_bracket(char bracket)
 {
        switch (bracket) {
-               case '{': case '[':
-                       return bracket + 2;
-               case '(':
-                       return ')';
+               case '{': case '[': /* '}' == '{' + 2. Same for '[' */
+                       bracket++;
+               case '(':           /* ')' == '(' + 1 */
+                       bracket++;
+                       break;
                case '}': case ']':
-                       return bracket - 2;
+                       bracket--;
                case ')':
-                       return '(';
-               default:
-                       return 0;
-       }
+                       bracket--;
+                       break;
+       };
+       return bracket;
 }
 
 static void match_right_bracket(char bracket)
 {
-       int bracket_line = -1;
-       int i;
+       unsigned i;
 
-       clear_line();
-
-       if (strchr(flines[line_pos], bracket) == NULL)
-               printf("%s%s%s", HIGHLIGHT, "No bracket in top line", NORMAL);
-       else {
-               for (i = line_pos + 1; i < num_flines; i++) {
-                       if (strchr(flines[i], opp_bracket(bracket)) != NULL) {
-                               bracket_line = i;
-                               break;
-                       }
+       if (strchr(flines[cur_fline], bracket) == NULL) {
+               print_statusline("No bracket in top line");
+               return;
+       }
+       bracket = opp_bracket(bracket);
+       for (i = cur_fline + 1; i < max_fline; i++) {
+               if (strchr(flines[i], bracket) != NULL) {
+                       buffer_line(i);
+                       return;
                }
-
-               if (bracket_line == -1)
-                       printf("%s%s%s", HIGHLIGHT, "No matching bracket found", NORMAL);
-
-               buffer_line(bracket_line - height + 2);
        }
+       print_statusline("No matching bracket found");
 }
 
 static void match_left_bracket(char bracket)
 {
-       int bracket_line = -1;
        int i;
 
-       clear_line();
-
-       if (strchr(flines[line_pos + height - 2], bracket) == NULL) {
-               printf("%s%s%s", HIGHLIGHT, "No bracket in bottom line", NORMAL);
-               printf("%s", flines[line_pos + height]);
-               sleep(4);
+       if (strchr(flines[cur_fline + max_displayed_line], bracket) == NULL) {
+               print_statusline("No bracket in bottom line");
+               return;
        }
-       else {
-               for (i = line_pos + height - 2; i >= 0; i--) {
-                       if (strchr(flines[i], opp_bracket(bracket)) != NULL) {
-                               bracket_line = i;
-                               break;
-                       }
-               }
 
-               if (bracket_line == -1)
-                       printf("%s%s%s", HIGHLIGHT, "No matching bracket found", NORMAL);
-
-               buffer_line(bracket_line);
+       bracket = opp_bracket(bracket);
+       for (i = cur_fline + max_displayed_line; i >= 0; i--) {
+               if (strchr(flines[i], bracket) != NULL) {
+                       buffer_line(i);
+                       return;
+               }
        }
+       print_statusline("No matching bracket found");
 }
-
-#endif  /* CONFIG_FEATURE_LESS_BRACKETS */
+#endif  /* FEATURE_LESS_BRACKETS */
 
 static void keypress_process(int keypress)
 {
        switch (keypress) {
-               case KEY_DOWN: case 'e': case 'j': case '\015':
-                       buffer_down(1);
-                       buffer_print();
-                       break;
-               case KEY_UP: case 'y': case 'k':
-                       buffer_up(1);
-                       buffer_print();
-                       break;
-               case PAGE_DOWN: case ' ': case 'z':
-                       buffer_down(height - 1);
-                       buffer_print();
-                       break;
-               case PAGE_UP: case 'w': case 'b':
-                       buffer_up(height - 1);
-                       buffer_print();
-                       break;
-               case 'd':
-                       buffer_down((height - 1) / 2);
-                       buffer_print();
-                       break;
-               case 'u':
-                       buffer_up((height - 1) / 2);
-                       buffer_print();
-                       break;
-               case KEY_HOME: case 'g': case 'p': case '<': case '%':
-                       buffer_line(0);
-                       break;
-               case KEY_END: case 'G': case '>':
-                       buffer_line(num_flines - height + 2);
-                       break;
-               case 'q': case 'Q':
-                       tless_exit(0);
-                       break;
-#ifdef CONFIG_FEATURE_LESS_MARKS
-               case 'm':
-                       add_mark();
-                       buffer_print();
-                       break;
-               case '\'':
-                       goto_mark();
-                       buffer_print();
-                       break;
+       case KEY_DOWN: case 'e': case 'j': case 0x0d:
+               buffer_down(1);
+               break;
+       case KEY_UP: case 'y': case 'k':
+               buffer_up(1);
+               break;
+       case PAGE_DOWN: case ' ': case 'z': case 'f':
+               buffer_down(max_displayed_line + 1);
+               break;
+       case PAGE_UP: case 'w': case 'b':
+               buffer_up(max_displayed_line + 1);
+               break;
+       case 'd':
+               buffer_down((max_displayed_line + 1) / 2);
+               break;
+       case 'u':
+               buffer_up((max_displayed_line + 1) / 2);
+               break;
+       case KEY_HOME: case 'g': case 'p': case '<': case '%':
+               buffer_line(0);
+               break;
+       case KEY_END: case 'G': case '>':
+               cur_fline = MAXLINES;
+               read_lines();
+               buffer_line(cur_fline);
+               break;
+       case 'q': case 'Q':
+               less_exit(EXIT_SUCCESS);
+               break;
+#if ENABLE_FEATURE_LESS_MARKS
+       case 'm':
+               add_mark();
+               buffer_print();
+               break;
+       case '\'':
+               goto_mark();
+               buffer_print();
+               break;
 #endif
-               case 'r':
-                       buffer_print();
-                       break;
-               case 'R':
-                       full_repaint();
-                       break;
-               case 's':
-                       if (flags & LESS_STATE_INP_STDIN)
-                               save_input_to_file();
-                       break;
-               case 'E':
-                       examine_file();
-                       break;
-#ifdef CONFIG_FEATURE_LESS_FLAGS
-               case '=':
-                       clear_line();
-                       m_status_print();
-                       break;
+       case 'r': case 'R':
+               buffer_print();
+               break;
+       /*case 'R':
+               full_repaint();
+               break;*/
+       case 's':
+               save_input_to_file();
+               break;
+       case 'E':
+               examine_file();
+               break;
+#if ENABLE_FEATURE_LESS_FLAGS
+       case '=':
+               m_status_print();
+               break;
 #endif
-#ifdef CONFIG_FEATURE_LESS_REGEXP
-               case '/':
-                       flags &= ~LESS_STATE_MATCH_BACKWARDS;
-                       regex_process();
-                       break;
-               case 'n':
-                       goto_match(match_pos + 1);
-                       break;
-               case 'N':
-                       goto_match(match_pos - 1);
-                       break;
-               case '?':
-                       flags |= LESS_STATE_MATCH_BACKWARDS;
-                       regex_process();
-                       break;
+#if ENABLE_FEATURE_LESS_REGEXP
+       case '/':
+               option_mask32 &= ~LESS_STATE_MATCH_BACKWARDS;
+               regex_process();
+               break;
+       case 'n':
+               goto_match(match_pos + 1);
+               break;
+       case 'N':
+               goto_match(match_pos - 1);
+               break;
+       case '?':
+               option_mask32 |= LESS_STATE_MATCH_BACKWARDS;
+               regex_process();
+               break;
 #endif
-#ifdef CONFIG_FEATURE_LESS_FLAGCS
-               case '-':
-                       flag_change();
-                       buffer_print();
-                       break;
-               case '_':
-                       show_flag_status();
-                       break;
+#if ENABLE_FEATURE_LESS_FLAGCS
+       case '-':
+               flag_change();
+               buffer_print();
+               break;
+       case '_':
+               show_flag_status();
+               break;
 #endif
-#ifdef CONFIG_FEATURE_LESS_BRACKETS
-               case '{': case '(': case '[':
-                       match_right_bracket(keypress);
-                       break;
-               case '}': case ')': case ']':
-                       match_left_bracket(keypress);
-                       break;
+#if ENABLE_FEATURE_LESS_BRACKETS
+       case '{': case '(': case '[':
+               match_right_bracket(keypress);
+               break;
+       case '}': case ')': case ']':
+               match_left_bracket(keypress);
+               break;
 #endif
-               case ':':
-                       colon_process();
-                       break;
-               default:
-                       break;
+       case ':':
+               colon_process();
+               break;
        }
 
        if (isdigit(keypress))
                number_process(keypress);
 }
 
-int less_main(int argc, char **argv) {
+static void sig_catcher(int sig)
+{
+       less_exit(- sig);
+}
 
+int less_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int less_main(int argc, char **argv)
+{
        int keypress;
 
-       flags = getopt32(argc, argv, "EMmN~");
+       INIT_G();
 
+       /* TODO: -x: do not interpret backspace, -xx: tab also */
+       /* -xxx: newline also */
+       /* -w N: assume width N (-xxx -w 32: hex viewer of sorts) */
+       getopt32(argv, "EMmN~");
        argc -= optind;
        argv += optind;
-       files = argv;
        num_files = argc;
+       files = argv;
+
+       /* Another popular pager, most, detects when stdout
+        * is not a tty and turns into cat. This makes sense. */
+       if (!isatty(STDOUT_FILENO))
+               return bb_cat(argv);
+       kbd_fd = open(CURRENT_TTY, O_RDONLY);
+       if (kbd_fd < 0)
+               return bb_cat(argv);
+       ndelay_on(kbd_fd);
 
        if (!num_files) {
-               if (ttyname(STDIN_FILENO) == NULL)
-                       flags |= LESS_STATE_INP_STDIN;
-               else {
+               if (isatty(STDIN_FILENO)) {
+                       /* Just "less"? No args and no redirection? */
                        bb_error_msg("missing filename");
                        bb_show_usage();
                }
-       }
-
-       strcpy(filename, (flags & LESS_STATE_INP_STDIN) ? bb_msg_standard_input : files[0]);
-       get_terminal_width_height(0, &width, &height);
-       data_readlines();
-       tcgetattr(fileno(inp), &term_orig);
-       term_vi = term_orig;
-       term_vi.c_lflag &= (~ICANON & ~ECHO);
-       term_vi.c_iflag &= (~IXON & ~ICRNL);
-       term_vi.c_oflag &= (~ONLCR);
-       term_vi.c_cc[VMIN] = 1;
-       term_vi.c_cc[VTIME] = 0;
-       buffer_init();
-       buffer_print();
-
+       } else
+               filename = xstrdup(files[0]);
+
+       get_terminal_width_height(kbd_fd, &width, &max_displayed_line);
+       /* 20: two tabstops + 4 */
+       if (width < 20 || max_displayed_line < 3)
+               return bb_cat(argv);
+       max_displayed_line -= 2;
+
+       buffer = xmalloc((max_displayed_line+1) * sizeof(char *));
+       if (option_mask32 & FLAG_TILDE)
+               empty_line_marker = "";
+
+       tcgetattr(kbd_fd, &term_orig);
+       term_less = term_orig;
+       term_less.c_lflag &= ~(ICANON | ECHO);
+       term_less.c_iflag &= ~(IXON | ICRNL);
+       /*term_less.c_oflag &= ~ONLCR;*/
+       term_less.c_cc[VMIN] = 1;
+       term_less.c_cc[VTIME] = 0;
+
+       /* We want to restore term_orig on exit */
+       bb_signals(BB_FATAL_SIGS, sig_catcher);
+
+       reinitialize();
        while (1) {
-               keypress = tless_getch();
+               keypress = less_getch(-1); /* -1: do not position cursor */
                keypress_process(keypress);
        }
 }