svlogd: fix compat problem: svlogd -tt should timestanp stderr too

[busybox.git] / miscutils / less.c

/* vi: set sw=4 ts=4: */
/*
 * Mini less implementation for busybox
 *
 * Copyright (C) 2005 by Rob Sullivan <cogito.ergo.cogito@gmail.com>
 *
 * 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:
 * - the inp file pointer is used so that keyboard input works after
 *   redirected input has been read from stdin
 */

#include <sched.h>      /* sched_yield() */

#include "libbb.h"
#if ENABLE_FEATURE_LESS_REGEXP
#include "xregex.h"
#endif

/* 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"

/* 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',

/* 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 */
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_REGEXP
enum { pattern_valid = 0 };
#endif

struct globals {
        int cur_fline; /* signed */
        int kbd_fd;  /* fd to get input from */
/* 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 */
        size_t readpos;
        size_t readeof;
        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! */
        unsigned 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 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 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 { \
                PTR_TO_GLOBALS = xzalloc(sizeof(G)); \
                empty_line_marker = "~"; \
                num_files = 1; \
                current_file = 1; \
                eof_error = 1; \
                terminated = 1; \
        } while (0)

/* Reset terminal input to normal */
static void set_tty_cooked(void)
{
        fflush(stdout);
        tcsetattr(kbd_fd, TCSANOW, &term_orig);
}

/* Exit the program gracefully */
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? */
        bb_putchar('\n');
        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 line, int row)
{
        printf("\033[%u;%uH", line, row);
}

static void clear_line(void)
{
        printf("\033[%u;0H" CLEAR_2_EOL, max_displayed_line + 2);
}

static void print_hilite(const char *str)
{
        printf(HIGHLIGHT"%s"NORMAL, str);
}

static void print_statusline(const char *str)
{
        clear_line();
        printf(HIGHLIGHT"%.*s"NORMAL, width - 1, str);
}

#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)
{
#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);
                /* linepos is still valid from previous read_lines() */
        } else {
                linepos = 0;
        }

        while (1) {
 again:
                *p = '\0';
                terminated = 0;
                while (1) {
                        char c;
                        /* if no unprocessed chars left, eat more */
                        if (readpos >= readeof) {
                                smallint yielded = 0;

                                ndelay_on(0);
 read_again:
                                eof_error = safe_read(0, readbuf, sizeof(readbuf));
                                readpos = 0;
                                readeof = eof_error;
                                if (eof_error < 0) {
                                        if (errno == EAGAIN && !yielded) {
                        /* We can hit EAGAIN while searching for regexp match.
                         * Yield is not 100% reliable solution in general,
                         * but for less it should be good enough -
                         * we give stdin supplier some CPU time to produce
                         * more input. We do it just once.
                         * Currently, we do not stop when we found the Nth
                         * occurrence we were looking for. We read till end
                         * (or double EAGAIN). TODO? */
                                                sched_yield();
                                                yielded = 1;
                                                goto read_again;
                                        }
                                        readeof = 0;
                                        if (errno != EAGAIN)
                                                print_statusline("read error");
                                }
                                ndelay_off(0);

                                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 (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';
                }
                /* 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;
                }
 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);
                }
                if (max_fline >= MAXLINES) {
                        eof_error = 0; /* Pretend we saw EOF */
                        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;
        }
        fill_match_lines(old_max_fline);
#undef readbuf
}

#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;

        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)
{
        const char *p;

        /* Change the status if flags have been set */
#if ENABLE_FEATURE_LESS_FLAGS
        if (option_mask32 & (FLAG_M|FLAG_m)) {
                m_status_print();
                return;
        }
        /* No flags set */
#endif

        clear_line();
        if (cur_fline && cur_fline < max_fline - max_displayed_line) {
                bb_putchar(':');
                return;
        }
        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);
}

static void cap_cur_fline(int nlines)
{
        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;

        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);

        /* 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 (!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

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);
}

/* Print the buffer */
static void buffer_print(void)
{
        int i;

        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)
{
        int 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)
{
        cur_fline += nlines;
        read_lines();
        cap_cur_fline(nlines);
        buffer_fill_and_print();
}

static void buffer_up(int nlines)
{
        cur_fline -= nlines;
        if (cur_fline < 0) cur_fline = 0;
        read_lines();
        buffer_fill_and_print();
}

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 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();
}

/* Reinitialize everything for a new file - free the memory and start over */
static void reinitialize(void)
{
        int i;

        if (flines) {
                for (i = 0; i <= max_fline; i++)
                        free((void*)(flines[i]));
                free(flines);
                flines = NULL;
        }

        max_fline = -1;
        cur_fline = 0;
        max_lineno = 0;
        open_file_and_read_lines();
        buffer_fill_and_print();
}

static void getch_nowait(char* input, int sz)
{
        ssize_t rd;
        fd_set readfds;
 again:
        fflush(stdout);

        /* 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_less);
        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;
        }
}

/* 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:
        memset(input, 0, sizeof(input));
        getch_nowait(input, sizeof(input));

        /* Detect escape sequences (i.e. arrow keys) and handle
         * them accordingly */
        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;
                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;
        set_tty_cooked();
        return i;
}

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_less);

                c = '\0';
                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 */
                bb_putchar(c);
                result[i++] = c;
                result = xrealloc(result, i+1);
                result[i] = '\0';
        }
}

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)
{
        if (current_file != ((direction > 0) ? num_files : 1)) {
                current_file = direction ? current_file + direction : 1;
                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;

        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--;
        } else {
                change_file(1);
                for (i = 2; i <= num_files; i++)
                        files[i - 2] = files[i - 1];
                num_files--;
                current_file--;
        }
}

static void colon_process(void)
{
        int keypress;

        /* Clear the current line and print a prompt */
        print_statusline(" :");

        keypress = less_getch();
        switch (keypress) {
        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':
                less_exit(0);
                break;
        case 'x':
                change_file(0);
                break;
        }
}

#if ENABLE_FEATURE_LESS_REGEXP
static void normalize_match_pos(int match)
{
        if (match >= num_matches)
                match = num_matches - 1;
        if (match < 0)
                match = 0;
        match_pos = match;
}

static void goto_match(int match)
{
        int sv;

        if (!pattern_valid)
                return;
        if (match < 0)
                match = 0;
        sv = cur_fline;
        /* Try to find next match if eof isn't reached yet */
        if (match >= num_matches && eof_error > 0) {
                cur_fline = MAXLINES; /* look as far as needed */
                read_lines();
        }
        if (num_matches) {
                cap_cur_fline(cur_fline);
                normalize_match_pos(match);
                buffer_line(match_lines[match_pos]);
        } else {
                cur_fline = sv;
                print_statusline("No matches found");
        }
}

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++;
        }
}

static void regex_process(void)
{
        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();
        bb_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 */
        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;
        fill_match_lines(0);
        while (match_pos < num_matches) {
                if (match_lines[match_pos] > cur_fline)
                        break;
                match_pos++;
        }
        if (option_mask32 & LESS_STATE_MATCH_BACKWARDS)
                match_pos--;

        /* 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;
        int num;
        char num_input[sizeof(int)*4]; /* more than enough */
        char keypress;

        num_input[0] = first_digit;

        /* Clear the current line, print a prompt, and then print the digit */
        clear_line();
        printf(":%c", first_digit);

        /* 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;
                bb_putchar(num_input[i]);
                i++;
        }

        /* Take the final letter out of the digits string */
        keypress = num_input[i];
        num_input[i] = '\0';
        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 '>':
                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
        }
}

#if ENABLE_FEATURE_LESS_FLAGCS
static void flag_change(void)
{
        int keypress;

        clear_line();
        bb_putchar('-');
        keypress = less_getch();

        switch (keypress) {
        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)
{
        int keypress;
        int flag_val;

        clear_line();
        bb_putchar('_');
        keypress = less_getch();

        switch (keypress) {
        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(HIGHLIGHT"The status of the flag is: %u"NORMAL, flag_val != 0);
}
#endif

static void save_input_to_file(void)
{
        const char *msg = "";
        char *current_line;
        int i;
        FILE *fp;

        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);
                msg = "Done";
        }
 ret:
        print_statusline(msg);
        free(current_line);
}

#if ENABLE_FEATURE_LESS_MARKS
static void add_mark(void)
{
        int letter;

        print_statusline("Mark: ");
        letter = less_getch();

        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] = cur_fline;
                num_marks++;
        } else {
                print_statusline("Invalid mark letter");
        }
}

static void goto_mark(void)
{
        int letter;
        int i;

        print_statusline("Go to mark: ");
        letter = less_getch();
        clear_line();

        if (isalpha(letter)) {
                for (i = 0; i <= num_marks; i++)
                        if (letter == mark_lines[i][0]) {
                                buffer_line(mark_lines[i][1]);
                                break;
                        }
                if (num_marks == 14 && letter != mark_lines[14][0])
                        print_statusline("Mark not set");
        } else
                print_statusline("Invalid mark letter");
}
#endif

#if ENABLE_FEATURE_LESS_BRACKETS
static char opp_bracket(char bracket)
{
        switch (bracket) {
        case '{': case '[':
                return bracket + 2;
        case '(':
                return ')';
        case '}': case ']':
                return bracket - 2;
        case ')':
                return '(';
        }
        return 0;
}

static void match_right_bracket(char bracket)
{
        int bracket_line = -1;
        int i;

        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)
                print_statusline("No matching bracket found");
        buffer_line(bracket_line - max_displayed_line);
}

static void match_left_bracket(char bracket)
{
        int bracket_line = -1;
        int i;

        if (strchr(flines[cur_fline + max_displayed_line], bracket) == NULL) {
                print_statusline("No bracket in bottom line");
                return;
        }

        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 */

static void keypress_process(int keypress)
{
        switch (keypress) {
        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(0);
                break;
#if ENABLE_FEATURE_LESS_MARKS
        case 'm':
                add_mark();
                buffer_print();
                break;
        case '\'':
                goto_mark();
                buffer_print();
                break;
#endif
        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
#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
#if ENABLE_FEATURE_LESS_FLAGCS
        case '-':
                flag_change();
                buffer_print();
                break;
        case '_':
                show_flag_status();
                break;
#endif
#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;
        }

        if (isdigit(keypress))
                number_process(keypress);
}

static void sig_catcher(int sig ATTRIBUTE_UNUSED)
{
        set_tty_cooked();
        exit(1);
}

int less_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int less_main(int argc, char **argv)
{
        int keypress;

        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;
        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);

        if (!num_files) {
                if (isatty(STDIN_FILENO)) {
                        /* Just "less"? No args and no redirection? */
                        bb_error_msg("missing filename");
                        bb_show_usage();
                }
        } 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)
                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_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;

        /* 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_less);*/

        reinitialize();
        while (1) {
                keypress = less_getch();
                keypress_process(keypress);
        }
}