suppress warnings about easch <applet>_main() having
[oweals/busybox.git] / miscutils / less.c
index 0b0dc0c8bbd7244915a8eda90a81001b0f95c662..9aae81fa4a1cd763ef7194cb61fe1b51c2ed87c1 100644 (file)
 /*
  * Mini less implementation for busybox
  *
- *
  * Copyright (C) 2005 by Rob Sullivan <cogito.ergo.cogito@gmail.com>
  *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
- * 02111-1307 USA
- *
- *      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.
- *      - 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
+ * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
+ */
+
+/*
+ * 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.
  *
- *      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
-*/
-
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <termios.h>
-#include <unistd.h>
-#include <ctype.h>
+ * Notes:
+ * - the inp file pointer is used so that keyboard input works after
+ *   redirected input has been read from stdin
+ */
 
 #include "busybox.h"
-
-#ifdef CONFIG_FEATURE_LESS_REGEXP
+#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'
-
-/* These are the special codes assigned by this program to the special keys */
-#define PAGE_UP 20
-#define PAGE_DOWN 21
-#define KEY_UP 22
-#define KEY_DOWN 23
-#define KEY_RIGHT 24
-#define KEY_LEFT 25
+/* 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
-
-/* Get height and width of terminal */
-#define tty_width_height()              get_terminal_width_height(0, &width, &height)
+/* 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',
+       REAL_KEY_END = '8',
 
-static int height;
-static int width;
+/* 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,
+};
+
+static unsigned max_displayed_line;
+static unsigned width;
+static const char *empty_line_marker = "~";
+
+static char *filename;
 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;
-static int past_eof;
+static unsigned num_files = 1;
+static unsigned current_file = 1;
+static const char **buffer;
+static const char **flines;
+static int cur_fline; /* signed */
+static unsigned max_fline;
+static unsigned max_lineno; /* this one tracks linewrap */
+
+static ssize_t eof_error = 1; /* eof if 0, error if < 0 */
+static char terminated = 1;
+static size_t readpos;
+static size_t readeof;
+/* last position in last line, taking into account tabs */
+static size_t linepos;
 
 /* Command line options */
-static unsigned long 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)
-
-/* This is needed so that program behaviour changes when input comes from
-   stdin */
-static int inp_stdin;
-
-#ifdef CONFIG_FEATURE_LESS_MARKS
-static int mark_lines[15][2];
-static int num_marks;
+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 */
+       LESS_STATE_MATCH_BACKWARDS = 1 << 15,
+};
+
+#if ENABLE_FEATURE_LESS_MARKS
+static unsigned mark_lines[15][2];
+static unsigned num_marks;
 #endif
 
-#ifdef CONFIG_FEATURE_LESS_REGEXP
-static int match_found;
-static int match_lines[100];
-static int match_pos;
-static int num_matches;
-static int match_backwards;
-static int num_back_match = 1;
+#if ENABLE_FEATURE_LESS_REGEXP
+static unsigned *match_lines;
+static int match_pos; /* signed! */
+static unsigned num_matches;
+static regex_t pattern;
+static unsigned pattern_valid;
+#else
+enum { pattern_valid = 0 };
 #endif
 
-/* Needed termios structures */
 static struct termios term_orig, term_vi;
 
 /* File pointer to get input from */
-static FILE *inp;
+static int kbd_fd;
 
 /* Reset terminal input to normal */
-static void set_tty_cooked(void) {
+static void set_tty_cooked(void)
+{
        fflush(stdout);
-       tcsetattr(fileno(inp), TCSANOW, &term_orig);
-}
-
-/* Set terminal input to raw mode  (taken from vi.c) */
-static void set_tty_raw(void) {
-       tcsetattr(fileno(inp), TCSANOW, &term_vi);
+       tcsetattr(kbd_fd, TCSANOW, &term_orig);
 }
 
 /* Exit the program gracefully */
-static void tless_exit(int code) {
-
+static void less_exit(int code)
+{
        /* 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? */
-
+        * 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');
-       exit(code);
-}
-
-/* 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) {
-
-       int input;
-
-       set_tty_raw();
-
-       input = getc(inp);
-       /* Detect escape sequences (i.e. arrow keys) and handle
-          them accordingly */
-
-       if (input == '\033' && getc(inp) == '[') {
-               input = getc(inp);
-               set_tty_cooked();
-               if (input == REAL_KEY_UP)
-                       return KEY_UP;
-               else if (input == REAL_KEY_DOWN)
-                       return KEY_DOWN;
-               else if (input == REAL_KEY_RIGHT)
-                       return KEY_RIGHT;
-               else if (input == REAL_KEY_LEFT)
-                       return KEY_LEFT;
-               else if (input == REAL_PAGE_UP)
-                       return PAGE_UP;
-               else if (input == REAL_PAGE_DOWN)
-                       return PAGE_DOWN;
-       }
-       /* The input is a normal ASCII value */
-       else {
-               set_tty_cooked();
-               return input;
-       }
-       return 0;
+       fflush_stdout_and_exit(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 x, int y) {
-       printf("\033[%i;%iH", x, y);
+static void move_cursor(int line, int row)
+{
+       printf("\033[%u;%uH", line, row);
 }
 
-static void clear_line(void) {
-       move_cursor(height, 0);
-       printf("\033[K");
-}
-
-/* This adds line numbers to every line, as the -N flag necessitates */
-static void add_linenumbers(void) {
-
-       char current_line[256];
-       int i;
-
-       for (i = 0; i <= num_flines; i++) {
-               safe_strncpy(current_line, flines[i], 256);
-               flines[i] = bb_xasprintf("%5d %s", i + 1, current_line);
-       }
+static void clear_line(void)
+{
+       printf("\033[%u;0H" CLEAR_2_EOL, max_displayed_line + 2);
 }
 
-static void data_readlines(void) {
-
-       int i;
-       char current_line[256];
-       FILE *fp;
-
-       fp = (inp_stdin) ? stdin : bb_xfopen(filename, "rt");
-       flines = NULL;
-       for (i = 0; (feof(fp)==0) && (i <= MAXLINES); i++) {
-               strcpy(current_line, "");
-               fgets(current_line, 256, fp);
-               if(fp != stdin)
-                       bb_xferror(fp, filename);
-               flines = xrealloc(flines, (i+1) * sizeof(char *));
-               flines[i] = bb_xstrdup(current_line);
-       }
-       num_flines = i - 2;
-
-       /* Reset variables for a new file */
-
-       line_pos = 0;
-       past_eof = 0;
-
-       fclose(fp);
-
-       if(inp == NULL)
-               inp = (inp_stdin) ? bb_xfopen(CURRENT_TTY, "r") : stdin;
-
-       if (flags & FLAG_N)
-               add_linenumbers();
+static void print_hilite(const char *str)
+{
+       printf(HIGHLIGHT"%s"NORMAL, str);
 }
 
-/* Turn a percentage into a line number */
-static int reverse_percent(int percentage) {
-       double linenum = percentage;
-       linenum = ((linenum / 100) * num_flines) - 1;
-       return(linenum);
+static void print_statusline(const char *str)
+{
+       clear_line();
+       printf(HIGHLIGHT"%.*s"NORMAL, width - 1, str);
 }
 
-#ifdef CONFIG_FEATURE_LESS_FLAGS
-
-/* Interestingly, writing calc_percent as a function and not a prototype saves around 32 bytes
- * on my build. */
-static int calc_percent(void) {
-       return ((100 * (line_pos + height - 2) / num_flines) + 1);
-}
+#if ENABLE_FEATURE_LESS_REGEXP
+static void fill_match_lines(unsigned pos);
+#else
+#define fill_match_lines(pos) ((void)0)
+#endif
 
-/* Print a status line if -M was specified */
-static void m_status_print(void) {
 
-       int percentage;
+static void read_lines(void)
+{
+#define readbuf bb_common_bufsiz1
+       char *current_line, *p;
+       USE_FEATURE_LESS_REGEXP(unsigned old_max_fline = max_fline;)
+       int w = width;
+       char last_terminated = terminated;
+
+       if (option_mask32 & FLAG_N)
+               w -= 8;
+
+       current_line = xmalloc(w);
+       p = current_line;
+       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);
+       } else {
+               linepos = 0;
+       }
 
-       if (!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);
+       while (1) {
+ again:
+               *p = '\0';
+               terminated = 0;
+               while (1) {
+                       char c;
+                       if (readpos >= readeof) {
+                               ndelay_on(0);
+                               eof_error = safe_read(0, readbuf, sizeof(readbuf));
+                               ndelay_off(0);
+                               readpos = 0;
+                               readeof = eof_error;
+                               if (eof_error < 0) {
+                                       readeof = 0;
+                                       if (errno != EAGAIN)
+                                               print_statusline("read 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--;
+                               *--p = '\0';
+                               continue;
                        }
+                       if (c == '\t')
+                               linepos += (linepos^7) & 7;
+                       linepos++;
+                       if (linepos >= w)
+                               break;
+                       /* ok, we will eat this char */
+                       readpos++;
+                       if (c == '\n') { terminated = 1; break; }
+                       /* NUL is substituted by '\n'! */
+                       if (c == '\0') c = '\n';
+                       *p++ = c;
+                       *p = '\0';
                }
-               else {
-                       printf("%s %s lines %i-%i/%i ", HIGHLIGHT, filename, line_pos + 1, line_pos + height - 1, num_flines + 1);
+               /* 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++;
+                       goto again;
                }
-
-               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);
+ reached_eof:
+               last_terminated = terminated;
+               flines = xrealloc(flines, (max_fline+1) * sizeof(char *));
+               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);
                }
-               else {
-                       percentage = calc_percent();
-                       printf("%i%% %s", percentage, NORMAL);
+               if (max_fline >= MAXLINES)
+                       break;
+               if (max_fline > cur_fline + max_displayed_line)
+                       break;
+               if (eof_error <= 0) {
+                       if (eof_error < 0 && errno == EAGAIN) {
+                               /* not yet eof or error, reset flag (or else
+                                * we will hog CPU - select() will return
+                                * immediately */
+                               eof_error = 1;
+                       }
+                       break;
                }
+               max_fline++;
+               current_line = xmalloc(w);
+               p = current_line;
+               linepos = 0;
        }
-       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);
-       }
+       fill_match_lines(old_max_fline);
+#undef readbuf
 }
 
-/* Print a status line if -m was specified */
-static void medium_status_print(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)
+{
+       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 */
+static void m_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);
+       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 >= 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;
+       }
+       percentage = calc_percent();
+       printf("%i%%"NORMAL, percentage);
 }
 #endif
 
 /* Print the status line */
-static void status_print(void) {
+static void status_print(void)
+{
+       const char *p;
 
        /* 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 < max_fline - max_displayed_line) {
+               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) {
-
-       int i;
+static char controls[] =
+       /* 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 char ctrlconv[] =
+       /* '\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]);
-       }
-       else {
-               for (i = 1; i < (height - 1 - num_flines); i++)
-                       putchar('\n');
-               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;
        }
+       strcpy(p, str);
 
-       status_print();
-}
+       /* buf[] holds quarantined version of str */
 
-/* Initialise the buffer */
-static void buffer_init(void) {
+       /* 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;
 
-       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]);
+       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);
        }
 
-       /* 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] = bb_xstrdup(flines[i]);
+       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
 
-       /* If the buffer still isn't full, fill it with blank lines */
-       for (; i < (height - 1); i++) {
-               buffer[i] = bb_xstrdup("");
+static void print_ascii(const char *str)
+{
+       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);
 }
 
-/* Move the buffer up and down in the file in order to scroll */
-static void buffer_down(int nlines) {
-
+/* Print the buffer */
+static void buffer_print(void)
+{
        int i;
 
-       if (!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] = bb_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] = bb_xstrdup(flines[line_pos + i]);
-                               }
-                       }
-               }
-
-               /* We exit if the -E flag has been set */
-               if ((flags & FLAG_E) && (line_pos + (height - 2) == num_flines))
-                       tless_exit(0);
-       }
+       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_up(int nlines) {
-
+static void buffer_fill_and_print(void)
+{
        int i;
-       int tilde_line;
-
-       if (!past_eof) {
-               if (line_pos - nlines >= 0) {
-                       line_pos -= nlines;
-                       for (i = 0; i < (height - 1); i++) {
-                               free(buffer[i]);
-                               buffer[i] = bb_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] = bb_xstrdup(flines[line_pos + i]);
-                               }
-                       }
-               }
+       for (i = 0; i <= max_displayed_line && cur_fline + i <= max_fline; i++) {
+               buffer[i] = flines[cur_fline + 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) {
-                       past_eof = 0;
-                       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] = bb_xstrdup(flines[line_pos + i]);
-                               else {
-                                       if (line_pos >= num_flines - height + 2)
-                                               buffer[i] = bb_xstrdup("~\n");
-                               }
-                       }
-               }
+       for (; i <= max_displayed_line; i++) {
+               buffer[i] = empty_line_marker;
        }
+       buffer_print();
 }
 
-static void buffer_line(int linenum) {
+/* Move the buffer up and down in the file in order to scroll */
+static void buffer_down(int nlines)
+{
+       int diff;
+       cur_fline += nlines;
+       read_lines();
+
+       if (cur_fline + max_displayed_line > max_fline + TILDES) {
+               cur_fline -= nlines;
+               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;
+       }
+       buffer_fill_and_print();
+}
 
-       int i;
+static void buffer_up(int nlines)
+{
+       cur_fline -= nlines;
+       if (cur_fline < 0) cur_fline = 0;
+       read_lines();
+       buffer_fill_and_print();
+}
 
-       past_eof = 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;
+       cur_fline = linenum;
+       buffer_fill_and_print();
+}
 
-       if (linenum < 1 || linenum > num_flines) {
-               clear_line();
-               printf("%s%s%i%s", HIGHLIGHT, "Cannot seek to line number ", linenum, NORMAL);
-       }
-       else if (linenum < (num_flines - height - 2)) {
-               for (i = 0; i < (height - 1); i++) {
-                       free(buffer[i]);
-                       buffer[i] = bb_xstrdup(flines[linenum + i]);
-               }
-               line_pos = linenum;
-       }
-       else {
-               for (i = 0; i < (height - 1); i++) {
-                       free(buffer[i]);
-                       if (linenum + i < num_flines + 2)
-                               buffer[i] = bb_xstrdup(flines[linenum + i]);
-                       else
-                               buffer[i] = bb_xstrdup((flags & FLAG_TILDE) ? "\n" : "~\n");
-               }
-               line_pos = linenum;
-               /* Set past_eof so buffer_down and buffer_up act differently */
-               past_eof = 1;
+static void open_file_and_read_lines(void)
+{
+       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();
 }
 
-/* Reinitialise everything for a new file - free the memory and start over */
-static void reinitialise(void) {
-
+/* Reinitialize everything for a new file - free the memory and start over */
+static void reinitialize(void)
+{
        int i;
 
-       for (i = 0; i <= num_flines; i++)
-               free(flines[i]);
-       free(flines);
+       if (flines) {
+               for (i = 0; i <= max_fline; i++)
+                       free((void*)(flines[i]));
+               free(flines);
+               flines = NULL;
+       }
 
-       data_readlines();
-       buffer_init();
-       buffer_print();
+       max_fline = -1;
+       cur_fline = 0;
+       max_lineno = 0;
+       open_file_and_read_lines();
+       buffer_fill_and_print();
 }
 
-static void examine_file(void) {
+static void getch_nowait(char* input, int sz)
+{
+       ssize_t rd;
+       fd_set readfds;
+ again:
+       fflush(stdout);
 
-       int newline_offset;
+       /* NB: select returns whenever read will not block. Therefore:
+        * (a) with O_NONBLOCK'ed fds select will return immediately
+        * (b) if eof is reached, select will also return
+        *     because read will immediately return 0 bytes.
+        * Even if select says that input is available, read CAN block
+        * (switch fd into O_NONBLOCK'ed mode to avoid it)
+        */
+       FD_ZERO(&readfds);
+       if (max_fline <= cur_fline + max_displayed_line
+        && eof_error > 0 /* did NOT reach eof yet */
+       ) {
+               /* We are interested in stdin */
+               FD_SET(0, &readfds);
+       }
+       FD_SET(kbd_fd, &readfds);
+       tcsetattr(kbd_fd, TCSANOW, &term_vi);
+       select(kbd_fd + 1, &readfds, NULL, NULL, NULL);
+
+       input[0] = '\0';
+       ndelay_on(kbd_fd);
+       rd = read(kbd_fd, input, sz);
+       ndelay_off(kbd_fd);
+       if (rd < 0) {
+               /* No keyboard input, but we have input on stdin! */
+               if (errno != EAGAIN) /* Huh?? */
+                       return;
+               read_lines();
+               buffer_fill_and_print();
+               goto again;
+       }
+}
 
-       clear_line();
-       printf("Examine: ");
-       fgets(filename, 256, inp);
+/* 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(void)
+{
+       char input[16];
+       unsigned i;
+ again:
+       getch_nowait(input, sizeof(input));
+       /* Detect escape sequences (i.e. arrow keys) and handle
+        * them accordingly */
 
-       /* 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';
+       if (input[0] == '\033' && input[1] == '[') {
+               set_tty_cooked();
+               i = input[2] - REAL_KEY_UP;
+               if (i < 4)
+                       return 20 + i;
+               i = input[2] - REAL_PAGE_UP;
+               if (i < 4)
+                       return 24 + i;
+               return 0;
+       }
+       /* Reject almost all control chars */
+       i = input[0];
+       if (i < ' ' && i != 0x0d && i != 8) goto again;
+       set_tty_cooked();
+       return i;
+}
 
-       files[num_files] = bb_xstrdup(filename);
-       current_file = num_files + 1;
-       num_files++;
+static char* less_gets(int sz)
+{
+       char c;
+       int i = 0;
+       char *result = xzalloc(1);
+       while (1) {
+               fflush(stdout);
+
+               /* I be damned if I know why is it needed *repeatedly*,
+                * but it is needed. Is it because of stdio? */
+               tcsetattr(kbd_fd, TCSANOW, &term_vi);
+
+               read(kbd_fd, &c, 1);
+               if (c == 0x0d)
+                       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 */
+               putchar(c);
+               result[i++] = c;
+               result = xrealloc(result, i+1);
+               result[i] = '\0';
+       }
+}
 
-       inp_stdin = 0;
-       reinitialise();
+static void examine_file(void)
+{
+       print_statusline("Examine: ");
+       free(filename);
+       filename = less_gets(sizeof("Examine: ")-1);
+       /* files start by = argv. why we assume that argv is infinitely long??
+       files[num_files] = filename;
+       current_file = num_files + 1;
+       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
-*/
-static void change_file (int direction) {
+ *  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) {
-
+static void remove_current_file(void)
+{
        int 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();
        }
 }
 
-static void colon_process(void) {
-
+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();
        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(0);
+               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 *insert_highlights (char *line, int start, int end) {
-
-       return bb_xasprintf("%.*s%s%.*s%s%s", start, line, HIGHLIGHT,
-                       end - start, line + start, NORMAL, line + end);
+#if ENABLE_FEATURE_LESS_REGEXP
+static int normalize_match_pos(int match)
+{
+       match_pos = match;
+       if (match >= num_matches)
+               match_pos = num_matches - 1;
+       if (match < 0)
+               match_pos = 0;
+       return match_pos;
 }
 
-static char *process_regex_on_line(char *line, regex_t *pattern) {
-       /* 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, and then the line is returned. */
-
-       int match_status;
-       char *line2 = (char *) malloc((sizeof(char) * (strlen(line) + 1)) + 64);
-       char sub_line[256];
-       int prev_eo = 0;
-       regmatch_t match_structs;
-
-       memset(sub_line, 0, 256);
-       strcpy(line2, line);
-
-       match_found = 0;
-       match_status = regexec(pattern, line2, 1, &match_structs, 0);
-
-       while (match_status == 0) {
-
-               memset(sub_line, 0, 256);
-
-               if (match_found == 0)
-                       match_found = 1;
-
-               line2 = insert_highlights(line2, match_structs.rm_so + prev_eo, match_structs.rm_eo + prev_eo);
-               if (match_structs.rm_eo + 11 + prev_eo < strlen(line2))
-                       strcat(sub_line, line2 + match_structs.rm_eo + 11 + prev_eo);
+static void goto_match(int match)
+{
+       if (num_matches)
+               buffer_line(match_lines[normalize_match_pos(match)]);
+}
 
-               prev_eo += match_structs.rm_eo + 11;
-               match_status = regexec(pattern, sub_line, 1, &match_structs, REG_NOTBOL);
+static void fill_match_lines(unsigned pos)
+{
+       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(match_lines, (num_matches+1) * sizeof(int));
+                       match_lines[num_matches++] = pos;
+               }
+               pos++;
        }
-
-       return line2;
 }
 
-static void regex_process(void) {
-
-       char uncomp_regex[100];
-       char current_line[256];
-       int i;
-       int j = 0;
-       regex_t *pattern;
+static void regex_process(void)
+{
+       char *uncomp_regex, *err;
 
        /* Reset variables */
-       match_lines[0] = -1;
+       free(match_lines);
+       match_lines = NULL;
        match_pos = 0;
        num_matches = 0;
-       match_found = 0;
-
-       pattern = (regex_t *) malloc(sizeof(regex_t));
-       memset(pattern, 0, sizeof(regex_t));
+       if (pattern_valid) {
+               regfree(&pattern);
+               pattern_valid = 0;
+       }
 
        /* Get the uncompiled regular expression from the user */
        clear_line();
-       putchar((match_backwards) ? '?' : '/');
-       uncomp_regex[0] = 0;
-       fgets(uncomp_regex, sizeof(uncomp_regex), stdin);
-       i = strlen(uncomp_regex);
-       if(i > 0) {
-               if(uncomp_regex[i-1] == '\n')
-                       uncomp_regex[i-1] = '\0';
-               else
-                       while((i = getchar()) != '\n' && i != EOF);
+       putchar((option_mask32 & LESS_STATE_MATCH_BACKWARDS) ? '?' : '/');
+       uncomp_regex = less_gets(1);
+       if (!uncomp_regex[0]) {
+               free(uncomp_regex);
+               buffer_print();
+               return;
        }
 
        /* Compile the regex and check for errors */
-       xregcomp(pattern, uncomp_regex, 0);
-
-       /* Run the regex on each line of the current file here */
-       for (i = 0; i <= num_flines; i++) {
-               strcpy(current_line, process_regex_on_line(flines[i], pattern));
-               flines[i] = bb_xstrdup(current_line);
-               if (match_found) {
-                       match_lines[j] = i;
-                       j++;
-               }
+       err = regcomp_or_errmsg(&pattern, uncomp_regex, 0);
+       free(uncomp_regex);
+       if (err) {
+               print_statusline(err);
+               free(err);
+               return;
        }
+       pattern_valid = 1;
+       match_pos = 0;
 
-       num_matches = j;
-       if ((match_lines[0] != -1) && (num_flines > height - 2))
-               buffer_line(match_lines[0]);
-       else
-               buffer_init();
-}
-
-static void goto_match(int match) {
+       fill_match_lines(0);
 
-       /* 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 (num_matches == 0 || max_fline <= max_displayed_line) {
+               buffer_print();
+               return;
        }
-}
-
-static void search_backwards(void) {
-
-       int current_linepos = line_pos;
-       int i;
-
-       match_backwards = 1;
-       regex_process();
-
-       for (i = 0; i < num_matches; i++) {
-               if (match_lines[i] > current_linepos) {
-                       buffer_line(match_lines[i - num_back_match]);
+       while (match_pos < num_matches) {
+               if (match_lines[match_pos] > cur_fline)
                        break;
-               }
+               match_pos++;
        }
-
-       /* Reset variables */
-       match_backwards = 0;
-       num_back_match = 1;
-
+       if (option_mask32 & LESS_STATE_MATCH_BACKWARDS)
+               match_pos--;
+       buffer_line(match_lines[normalize_match_pos(match_pos)]);
 }
 #endif
 
-static void number_process(int first_digit) {
-
+static void number_process(int first_digit)
+{
        int i = 1;
        int num;
-       char num_input[80];
+       char num_input[sizeof(int)*4]; /* more than enough */
        char keypress;
-       char *endptr;
 
        num_input[0] = first_digit;
 
@@ -754,8 +834,11 @@ 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])) {
+       /* Receive input until a letter is given */
+       while (i < sizeof(num_input)-1) {
+               num_input[i] = less_getch();
+               if (!num_input[i] || !isdigit(num_input[i]))
+                       break;
                putchar(num_input[i]);
                i++;
        }
@@ -763,173 +846,161 @@ static void number_process(int first_digit) {
        /* 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)
-               goto END;
+       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(reverse_percent(num));
-                       break;
-#ifdef CONFIG_FEATURE_LESS_REGEXP
-               case 'n':
-                       goto_match(match_pos + num - 1);
-                       break;
-               case '/':
-                       regex_process();
-                       goto_match(num - 1);
-                       break;
-               case '?':
-                       num_back_match = num;
-                       search_backwards();
-                       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;
        }
-END:
-       buffer_print();
 }
 
-#ifdef CONFIG_FEATURE_LESS_FLAGCS
-static void flag_change(void) {
-
+#if ENABLE_FEATURE_LESS_FLAGCS
+static void flag_change(void)
+{
        int keypress;
 
        clear_line();
        putchar('-');
-       keypress = tless_getch();
+       keypress = less_getch();
 
        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;
        }
 }
 
-static void show_flag_status(void) {
-
+static void show_flag_status(void)
+{
        int keypress;
        int flag_val;
 
        clear_line();
        putchar('_');
-       keypress = tless_getch();
+       keypress = less_getch();
 
        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);
-       buffer_print();
-}
-
-
-static void save_input_to_file(void) {
-
-       char current_line[256];
+static void save_input_to_file(void)
+{
+       const char *msg = "";
+       char *current_line;
        int i;
        FILE *fp;
 
-       clear_line();
-       printf("Log file: ");
-       fgets(current_line, 256, inp);
-       current_line[strlen(current_line) - 1] = '\0';
-       if (strlen(current_line)) {
-               fp = bb_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 (strlen(current_line) > 0) {
+               fp = fopen(current_line, "w");
+               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("%sNo log file%s", HIGHLIGHT, NORMAL);
+ ret:
+       print_statusline(msg);
+       free(current_line);
 }
 
-#ifdef CONFIG_FEATURE_LESS_MARKS
-static void add_mark(void) {
-
+#if ENABLE_FEATURE_LESS_MARKS
+static void add_mark(void)
+{
        int letter;
-       int mark_line;
 
-       clear_line();
-       printf("Mark: ");
-       letter = tless_getch();
+       print_statusline("Mark: ");
+       letter = less_getch();
 
        if (isalpha(letter)) {
-               mark_line = line_pos;
-
                /* 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");
        }
 }
 
-static void goto_mark(void) {
-
+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();
        clear_line();
 
        if (isalpha(letter)) {
@@ -938,240 +1009,235 @@ 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
-
-static char opp_bracket (char bracket) {
-
+#if ENABLE_FEATURE_LESS_BRACKETS
+static char opp_bracket(char bracket)
+{
        switch (bracket) {
-               case '{': case '[':
-                       return bracket + 2;
-                       break;
-               case '(':
-                       return ')';
-                       break;
-               case '}': case ']':
-                       return bracket - 2;
-                       break;
-               case ')':
-                       return '(';
-                       break;
-               default:
-                       return 0;
-                       break;
+       case '{': case '[':
+               return bracket + 2;
+       case '(':
+               return ')';
+       case '}': case ']':
+               return bracket - 2;
+       case ')':
+               return '(';
        }
+       return 0;
 }
 
-static void match_right_bracket(char bracket) {
-
+static void match_right_bracket(char bracket)
+{
        int bracket_line = -1;
        int 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;
+       }
+       for (i = cur_fline + 1; i < max_fline; 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 - height + 2);
-               buffer_print();
        }
+       if (bracket_line == -1)
+               print_statusline("No matching bracket found");
+       buffer_line(bracket_line - max_displayed_line);
 }
 
-static void match_left_bracket (char bracket) {
-
+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);
-               buffer_print();
+       for (i = cur_fline + max_displayed_line; i >= 0; i--) {
+               if (strchr(flines[i], opp_bracket(bracket)) != NULL) {
+                       bracket_line = i;
+                       break;
+               }
        }
+       if (bracket_line == -1)
+               print_statusline("No matching bracket found");
+       buffer_line(bracket_line);
 }
+#endif  /* FEATURE_LESS_BRACKETS */
 
-#endif  /* CONFIG_FEATURE_LESS_BRACKETS */
-
-static void keypress_process(int keypress) {
+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 'g': case 'p': case '<': case '%':
-                       buffer_up(num_flines + 1);
-                       buffer_print();
-                       break;
-               case 'G': case '>':
-                       buffer_down(num_flines + 1);
-                       buffer_print();
-                       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':
+               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(0);
+               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 (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 '/':
-                       regex_process();
-                       buffer_print();
-                       break;
-               case 'n':
-                       goto_match(match_pos + 1);
-                       buffer_print();
-                       break;
-               case 'N':
-                       goto_match(match_pos - 1);
-                       buffer_print();
-                       break;
-               case '?':
-                       search_backwards();
-                       buffer_print();
-                       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 ATTRIBUTE_UNUSED)
+{
+       set_tty_cooked();
+       exit(1);
+}
 
+int less_main(int argc, char **argv);
+int less_main(int argc, char **argv)
+{
        int keypress;
 
-       flags = bb_getopt_ulflags(argc, argv, "EMmN~");
-
+       /* 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(argc, 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);
 
        if (!num_files) {
-               if (ttyname(STDIN_FILENO) == NULL)
-                       inp_stdin = 1;
-               else {
-                       bb_error_msg("Missing filename");
+               if (isatty(STDIN_FILENO)) {
+                       /* Just "less"? No args and no redirection? */
+                       bb_error_msg("missing filename");
                        bb_show_usage();
                }
-       }
+       } else
+               filename = xstrdup(files[0]);
 
-       strcpy(filename, (inp_stdin) ? bb_msg_standard_input : files[0]);
-       tty_width_height();
-       data_readlines();
-       tcgetattr(fileno(inp), &term_orig);
+       kbd_fd = xopen(CURRENT_TTY, O_RDONLY);
+
+       get_terminal_width_height(kbd_fd, &width, &max_displayed_line);
+       /* 20: two tabstops + 4 */
+       if (width < 20 || max_displayed_line < 3)
+               bb_error_msg_and_die("too narrow here");
+       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);
+       signal(SIGTERM, sig_catcher);
+       signal(SIGINT, sig_catcher);
        term_vi = term_orig;
-       term_vi.c_lflag &= (~ICANON & ~ECHO);
-       term_vi.c_iflag &= (~IXON & ~ICRNL);
-       term_vi.c_oflag &= (~ONLCR);
+       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();
 
+       /* Want to do it just once, but it doesn't work, */
+       /* so we are redoing it (see code above). Mystery... */
+       /*tcsetattr(kbd_fd, TCSANOW, &term_vi);*/
+
+       reinitialize();
        while (1) {
-               keypress = tless_getch();
+               keypress = less_getch();
                keypress_process(keypress);
        }
 }