source: MondoRescue/branches/stable/mindi-busybox/miscutils/less.c@ 1770

/* 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? */
    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) {
        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 */
        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();
    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;
        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();
    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();
    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':
        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);
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);
    }
}