less: implement waiting for input using select(). Rather tricky business.

But we do not read entire input anymore up-front.


git-svn-id: svn://busybox.net/trunk/busybox@17067 69ca8d6d-28ef-0310-b511-8ec308f3f277

1 files changed, 516 insertions, 454 deletions

diff --git a/miscutils/less.c b/miscutils/less.c
index 03b93973f..66158899d 100644
--- a/miscutils/less.c
+++ b/miscutils/less.c
@@ -26,26 +26,9 @@
 #include "xregex.h"
 #endif
 
-
-/* These are the escape sequences corresponding to special keys */
-#define REAL_KEY_UP 'A'
-#define REAL_KEY_DOWN 'B'
-#define REAL_KEY_RIGHT 'C'
-#define REAL_KEY_LEFT 'D'
-#define REAL_PAGE_UP '5'
-#define REAL_PAGE_DOWN '6'
-#define REAL_KEY_HOME '7'
-#define REAL_KEY_END '8'
-
-/* These are the special codes assigned by this program to the special keys */
-#define KEY_UP 20
-#define KEY_DOWN 21
-#define KEY_RIGHT 22
-#define KEY_LEFT 23
-#define PAGE_UP 24
-#define PAGE_DOWN 25
-#define KEY_HOME 26
-#define KEY_END 27
+/* FIXME: currently doesn't work right */
+#undef ENABLE_FEATURE_LESS_FLAGCS
+#define ENABLE_FEATURE_LESS_FLAGCS 0
 
 /* The escape codes for highlighted and normal text */
 #define HIGHLIGHT "\033[7m"
@@ -55,124 +38,103 @@
 /* The escape code to clear to end of line */
 #define CLEAR_2_EOL "\033[K"
 
-#define MAXLINES CONFIG_FEATURE_LESS_MAXLINES
+/* 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',
+
+/* 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 int height;
-static int width;
-static char **files;
 static char *filename;
+static char **files;
+static unsigned num_files = 1;
+static unsigned current_file = 1;
 static const char **buffer;
-static char **flines;
-static int current_file = 1;
-static int line_pos;
-static int num_flines;
-static int num_files = 1;
-static const char *empty_line_marker = "~";
+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 */
-#define FLAG_E 1
-#define FLAG_M (1<<1)
-#define FLAG_m (1<<2)
-#define FLAG_N (1<<3)
-#define FLAG_TILDE (1<<4)
+enum {
+        FLAG_E = 1,
+        FLAG_M = 1 << 1,
+        FLAG_m = 1 << 2,
+        FLAG_N = 1 << 3,
+        FLAG_TILDE = 1 << 4,
 /* hijack command line options variable for internal state vars */
-#define LESS_STATE_MATCH_BACKWARDS (1<<6)
+        LESS_STATE_MATCH_BACKWARDS = 1 << 15,
+};
 
 #if ENABLE_FEATURE_LESS_MARKS
-static int mark_lines[15][2];
-static int num_marks;
+static unsigned mark_lines[15][2];
+static unsigned num_marks;
 #endif
 
 #if ENABLE_FEATURE_LESS_REGEXP
-static int *match_lines;
-static int match_pos;
-static int num_matches;
+static unsigned *match_lines;
+static int match_pos; /* signed! */
+static unsigned num_matches;
 static regex_t pattern;
-static int pattern_valid;
+static unsigned pattern_valid;
 #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)
 {
         fflush(stdout);
-        tcsetattr(fileno(inp), TCSANOW, &term_orig);
+        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');
         fflush_stdout_and_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 terminal input to raw mode (taken from vi.c) */
-        tcsetattr(fileno(inp), TCSANOW, &term_vi);
- again:
-        input = getc(inp);
-        /* Detect escape sequences (i.e. arrow keys) and handle
-           them accordingly */
-
-        if (input == '\033' && getc(inp) == '[') {
-                unsigned i;
-                input = getc(inp);
-                set_tty_cooked();
-
-                i = input - REAL_KEY_UP;
-                if (i < 4)
-                        return 20 + i;
-                i = input - REAL_PAGE_UP;
-                if (i < 4)
-                        return 24 + i;
-                return 0; /* ?? */
-        }
-        /* Reject almost all control chars */
-        if (input < ' ' && input != 0x0d && input != 8) goto again;
-        set_tty_cooked();
-        return input;
-}
-
-static char* tless_gets(int sz)
-{
-        int c;
-        int i = 0;
-        char *result = xzalloc(1);
-        while (1) {
-                c = tless_getch();
-                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';
-        }
-}
-
 /* 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)
@@ -182,7 +144,7 @@ static void move_cursor(int line, int row)
 
 static void clear_line(void)
 {
-        printf("\033[%u;0H" CLEAR_2_EOL, height);
+        printf("\033[%u;0H" CLEAR_2_EOL, max_displayed_line + 2);
 }
 
 static void print_hilite(const char *str)
@@ -193,90 +155,116 @@ static void print_hilite(const char *str)
 static void print_statusline(const char *str)
 {
         clear_line();
-        printf(HIGHLIGHT"%.*s"NORMAL, width-1, str);
+        printf(HIGHLIGHT"%.*s"NORMAL, width - 1, str);
 }
 
-static void data_readlines(void)
+static void read_lines(void)
 {
-        unsigned i, pos;
-        unsigned lineno = 1;
-        int w = width;
-        char terminated, last_terminated = 1;
-        char *current_line, *p;
-        FILE *fp;
+        /* TODO: regexp match array should be updated too */
 
-        if (filename)
-                fp = xfopen(filename, "r");
-        else {
-                /* "less" with no arguments in argv[] */
-                fp = stdin;
-                /* For status line only */
-                filename = xstrdup(bb_msg_standard_input);
-        }
+#define readbuf bb_common_bufsiz1
+        char *current_line, *p;
+        int w = width;
+        char last_terminated = terminated;
 
-        flines = NULL;
-        if (option_mask32 & FLAG_N) {
+        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);
         }
-        for (i = 0; !feof(fp) && i <= MAXLINES; i++) {
-                flines = xrealloc(flines, (i+1) * sizeof(char *));
-                current_line = xmalloc(w);
+
+        while (1) {
  again:
-                p = current_line;
-                pos = 0;
+                *p = '\0';
                 terminated = 0;
                 while (1) {
-                        int c = getc(fp);
-                        if (c == '\t') pos += (pos^7) & 7;
-                        pos++;
-                        if (pos >= w) { ungetc(c, fp); break; }
-                        if (c == EOF) break;
+                        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];
+                        if (c == '\t')
+                                linepos += (linepos^7) & 7;
+                        linepos++;
+                        if (linepos >= w)
+                                break;
+                        readpos++;
                         if (c == '\n') { terminated = 1; break; }
                         /* NUL is substituted by '\n'! */
                         if (c == '\0') c = '\n';
                         *p++ = c;
+                        *p = '\0';
                 }
-                *p = '\0';
-                if (fp != stdin)
-                        die_if_ferror(fp, filename);
-
                 /* 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;
-                        lineno++;
+                        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[i] = xasprintf(
-                                (lineno <= 9999999) ? "%7u %s" : "%07u %s",
-                                lineno % 10000000, current_line);
+                        flines[max_fline] = xasprintf(
+                                (max_lineno <= 9999999) ? "%7u %s" : "%07u %s",
+                                max_lineno % 10000000, current_line);
                         free(current_line);
                         if (terminated)
-                                lineno++;
+                                max_lineno++;
                 } else {
-                        flines[i] = xrealloc(current_line, strlen(current_line)+1);
+                        flines[max_fline] = xrealloc(current_line, strlen(current_line)+1);
                 }
+                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;
         }
-        num_flines = i - 1; /* buggie: 'num_flines' must be 'max_fline' */
-
-        /* Reset variables for a new file */
-
-        line_pos = 0;
-
-        fclose(fp);
+#undef readbuf
 }
 
 #if ENABLE_FEATURE_LESS_FLAGS
 
-/* Interestingly, writing calc_percent as a function and not a prototype saves around 32 bytes
+/* Interestingly, writing calc_percent as a function saves around 32 bytes
  * on my build. */
 static int calc_percent(void)
 {
-        return ((100 * (line_pos + height - 2) / num_flines) + 1);
+        unsigned p = 100 * (cur_fline + max_displayed_line) / (max_fline + 1);
+        return p <= 100 ? p : 100;
 }
 
 /* Print a status line if -M was specified */
@@ -289,16 +277,16 @@ static void m_status_print(void)
         if (num_files > 1)
                 printf(" (file %i of %i)", current_file, num_files);
         printf(" lines %i-%i/%i ",
-                        line_pos + 1, line_pos + height - 1,
-                        num_flines + 1);
-        if (line_pos >= num_flines - height + 2) {
+                        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]);
+                        printf(HIGHLIGHT" - next: %s"NORMAL, files[current_file]);
                 return;
         }
         percentage = calc_percent();
-        printf("%i%% "NORMAL, percentage);
+        printf("%i%%"NORMAL, percentage);
 }
 
 #endif
@@ -318,15 +306,15 @@ static void status_print(void)
 #endif
 
         clear_line();
-        if (line_pos && line_pos < num_flines - height + 2) {
+        if (cur_fline && cur_fline < max_fline - max_displayed_line) {
                 putchar(':');
                 return;
         }
         p = "(END)";
-        if (!line_pos)
+        if (!cur_fline)
                 p = filename;
         if (num_files > 1) {
-                printf(HIGHLIGHT"%s (file %i of %i) "NORMAL,
+                printf(HIGHLIGHT"%s (file %i of %i)"NORMAL,
                                 p, current_file, num_files);
                 return;
         }
@@ -423,7 +411,7 @@ static void print_ascii(const char *str)
                 do {
                         if (*str == 0x7f)
                                 *p++ = '?';
-                        else if (*str == 0x9b)
+                        else if (*str == (char)0x9b)
                         /* VT100's CSI, aka Meta-ESC. Who's inventor? */
                         /* I want to know who committed this sin */
                                 *p++ = '{';
@@ -443,7 +431,7 @@ static void buffer_print(void)
         int i;
 
         move_cursor(0, 0);
-        for (i = 0; i < height - 1; i++)
+        for (i = 0; i <= max_displayed_line; i++)
                 if (pattern_valid)
                         print_found(buffer[i]);
                 else
@@ -451,111 +439,194 @@ static void buffer_print(void)
         status_print();
 }
 
-/* Initialise the buffer */
-static void buffer_init(void)
+static void buffer_fill_and_print(void)
 {
         int i;
-
-        /* 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] = flines[i];
+        for (i = 0; i <= max_displayed_line && cur_fline + i <= max_fline; i++) {
+                buffer[i] = flines[cur_fline + i];
         }
-
-        /* If the buffer still isn't full, fill it with blank lines */
-        for (; i < height - 1; i++) {
+        for (; i <= max_displayed_line; i++) {
                 buffer[i] = empty_line_marker;
         }
+        buffer_print();
 }
 
 /* Move the buffer up and down in the file in order to scroll */
 static void buffer_down(int nlines)
 {
-        int i;
+        int diff;
+        cur_fline += nlines;
+        read_lines();
 
-        if (line_pos + (height - 3) + nlines < num_flines) {
-                line_pos += nlines;
-                for (i = 0; i < (height - 1); i++) {
-                        buffer[i] = flines[line_pos + i];
-                }
-        } else {
+        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 */
-                while (line_pos + (height - 3) + 1 < num_flines) {
-                        line_pos += 1;
-                        for (i = 0; i < (height - 1); i++) {
-                                buffer[i] = flines[line_pos + i];
-                        }
-                }
+                if (diff > 0)
+                        cur_fline += diff;
         }
-
-        /* We exit if the -E flag has been set */
-        if ((option_mask32 & FLAG_E) && (line_pos + (height - 2) == num_flines))
-                tless_exit(0);
+        buffer_fill_and_print();
 }
 
 static void buffer_up(int nlines)
 {
-        int i;
+        cur_fline -= nlines;
+        if (cur_fline < 0) cur_fline = 0;
+        read_lines();
+        buffer_fill_and_print();
+}
 
-        line_pos -= nlines;
-        if (line_pos < 0) line_pos = 0;
-        for (i = 0; i < height - 1; i++) {
-                if (line_pos + i <= num_flines) {
-                        buffer[i] = flines[line_pos + i];
-                } else {
-                        buffer[i] = empty_line_marker;
-                }
+static void buffer_line(int linenum)
+{
+        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();
 }
 
-static void buffer_line(int linenum)
+/* Reinitialize everything for a new file - free the memory and start over */
+static void reinitialize(void)
 {
         int i;
 
-        if (linenum < 0 || linenum > num_flines) {
-                clear_line();
-                printf(HIGHLIGHT"%s%u"NORMAL, "Cannot seek to line ", linenum + 1);
-                return;
+        if (flines) {
+                for (i = 0; i <= max_fline; i++)
+                        free((void*)(flines[i]));
+                free(flines);
+                flines = NULL;
         }
 
-        for (i = 0; i < height - 1; i++) {
-                if (linenum + i <= num_flines)
-                        buffer[i] = flines[linenum + i];
-                else {
-                        buffer[i] = empty_line_marker;
-                }
+        max_fline = -1;
+        cur_fline = 0;
+        max_lineno = 0;
+        open_file_and_read_lines();
+        buffer_fill_and_print();
+}
+
+static char* getch_nowait(void)
+{
+        static char input[16];
+        ssize_t sz;
+        fd_set readfds;
+ again:
+        fflush(stdout);
+        FD_ZERO(&readfds);
+        if (max_fline <= cur_fline + max_displayed_line && eof_error > 0) {
+                /* We are interested in stdin */
+                FD_SET(0, &readfds);
         }
-        line_pos = linenum;
-        buffer_print();
+        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);
+        sz = read(kbd_fd, input, sizeof(input));
+        ndelay_off(kbd_fd);
+        if (sz < 0) {
+                /* No keyboard input, but we have input on stdin! */
+                if (errno != EAGAIN) /* Huh?? */
+                        return input;
+                read_lines();
+                buffer_fill_and_print();
+                goto again;
+        }
+        return input;
 }
 
-/* Reinitialise everything for a new file - free the memory and start over */
-static void reinitialise(void)
+/* Grab a character from input without requiring the return key. If the
+   character is ASCII \033, get more characters and assign certain sequences
+   special return codes. Note that this function works best with raw input. */
+static int less_getch(void)
 {
-        int i;
+        char *input;
+        unsigned i;
+ again:
+        input = getch_nowait();
+        /* Detect escape sequences (i.e. arrow keys) and handle
+         * them accordingly */
 
-        for (i = 0; i <= num_flines; i++)
-                free(flines[i]);
-        free(flines);
+        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;
+}
 
-        data_readlines();
-        buffer_init();
-        buffer_print();
+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';
+        }
 }
 
 static void examine_file(void)
 {
         print_statusline("Examine: ");
         free(filename);
-        filename = tless_gets(sizeof("Examine: ")-1);
+        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;
-        reinitialise();
+        reinitialize();
 }
 
 /* This function changes the file currently being paged. direction can be one of the following:
@@ -569,7 +640,7 @@ static void change_file(int direction)
                 current_file = direction ? current_file + direction : 1;
                 free(filename);
                 filename = xstrdup(files[current_file - 1]);
-                reinitialise();
+                reinitialize();
         } else {
                 print_statusline(direction > 0 ? "No next file" : "No previous file");
         }
@@ -579,19 +650,20 @@ 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 {
                 change_file(1);
                 for (i = 2; i <= num_files; i++)
                         files[i - 2] = files[i - 1];
                 num_files--;
                 current_file--;
-                buffer_print();
         }
 }
 
@@ -602,33 +674,31 @@ static void colon_process(void)
         /* Clear the current line and print a prompt */
         print_statusline(" :");
 
-        keypress = tless_getch();
+        keypress = less_getch();
         switch (keypress) {
-                case 'd':
-                        remove_current_file();
-                        break;
-                case 'e':
-                        examine_file();
-                        break;
+        case 'd':
+                remove_current_file();
+                break;
+        case 'e':
+                examine_file();
+                break;
 #if ENABLE_FEATURE_LESS_FLAGS
-                case 'f':
-                        m_status_print();
-                        break;
+        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;
         }
 }
 
@@ -638,7 +708,7 @@ static int normalize_match_pos(int match)
         if (match >= num_matches)
                 match_pos = num_matches - 1;
         if (match < 0)
-                return (match_pos = 0);
+                match_pos = 0;
         return match_pos;
 }
 
@@ -654,8 +724,8 @@ static void regex_process(void)
         char *uncomp_regex, *err;
 
         /* Reset variables */
-        match_lines = xrealloc(match_lines, sizeof(int));
-        match_lines[0] = -1;
+        free(match_lines);
+        match_lines = NULL;
         match_pos = 0;
         num_matches = 0;
         if (pattern_valid) {
@@ -666,8 +736,8 @@ static void regex_process(void)
         /* Get the uncompiled regular expression from the user */
         clear_line();
         putchar((option_mask32 & LESS_STATE_MATCH_BACKWARDS) ? '?' : '/');
-        uncomp_regex = tless_gets(1);
-        if (/*!uncomp_regex ||*/ !uncomp_regex[0]) {
+        uncomp_regex = less_gets(1);
+        if (!uncomp_regex[0]) {
                 free(uncomp_regex);
                 buffer_print();
                 return;
@@ -684,19 +754,19 @@ static void regex_process(void)
         pattern_valid = 1;
 
         /* Run the regex on each line of the current file */
-        for (match_pos = 0; match_pos <= num_flines; match_pos++) {
+        for (match_pos = 0; match_pos <= max_fline; match_pos++) {
                 if (regexec(&pattern, flines[match_pos], 0, NULL, 0) == 0) {
                         match_lines = xrealloc(match_lines, (num_matches+1) * sizeof(int));
                         match_lines[num_matches++] = match_pos;
                 }
         }
 
-        if (num_matches == 0 || num_flines <= height - 2) {
+        if (num_matches == 0 || max_fline <= max_displayed_line) {
                 buffer_print();
                 return;
         }
         for (match_pos = 0; match_pos < num_matches; match_pos++) {
-                if (match_lines[match_pos] > line_pos)
+                if (match_lines[match_pos] > cur_fline)
                         break;
         }
         if (option_mask32 & LESS_STATE_MATCH_BACKWARDS) match_pos--;
@@ -719,7 +789,7 @@ static void number_process(int first_digit)
 
         /* Receive input until a letter is given */
         while (i < sizeof(num_input)-1) {
-                num_input[i] = tless_getch();
+                num_input[i] = less_getch();
                 if (!num_input[i] || !isdigit(num_input[i]))
                         break;
                 putchar(num_input[i]);
@@ -738,34 +808,38 @@ static void number_process(int first_digit)
 
         /* We now know the number and the letter entered, so we process them */
         switch (keypress) {
-                case KEY_DOWN: case 'z': case 'd': case 'e': case ' ': case '\015':
-                        buffer_down(num);
-                        break;
-                case KEY_UP: case 'b': case 'w': case 'y': case 'u':
-                        buffer_up(num);
-                        break;
-                case 'g': case '<': case 'G': case '>':
-                        if (num_flines >= height - 2)
-                                buffer_line(num - 1);
-                        break;
-                case 'p': case '%':
-                        buffer_line(((num / 100) * num_flines) - 1);
-                        break;
+        case KEY_DOWN: case 'z': case 'd': case 'e': case ' ': case '\015':
+                buffer_down(num);
+                buffer_print();
+                break;
+        case KEY_UP: case 'b': case 'w': case 'y': case 'u':
+                buffer_up(num);
+                buffer_print();
+                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;
+        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;
         }
 }
 
@@ -776,23 +850,21 @@ static void flag_change(void)
 
         clear_line();
         putchar('-');
-        keypress = tless_getch();
+        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;
-                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;
         }
 }
 
@@ -803,27 +875,27 @@ static void show_flag_status(void)
 
         clear_line();
         putchar('_');
-        keypress = tless_getch();
+        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;
+        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();
@@ -831,15 +903,6 @@ static void show_flag_status(void)
 }
 #endif
 
-static void full_repaint(void)
-{
-        int temp_line_pos = line_pos;
-        data_readlines();
-        buffer_init();
-        buffer_line(temp_line_pos);
-}
-
-
 static void save_input_to_file(void)
 {
         char *current_line;
@@ -847,7 +910,7 @@ static void save_input_to_file(void)
         FILE *fp;
 
         print_statusline("Log file: ");
-        current_line = tless_gets(sizeof("Log file: ")-1);
+        current_line = less_gets(sizeof("Log file: ")-1);
         if (strlen(current_line) > 0) {
                 fp = fopen(current_line, "w");
                 free(current_line);
@@ -855,7 +918,7 @@ static void save_input_to_file(void)
                         print_statusline("Error opening log file");
                         return;
                 }
-                for (i = 0; i < num_flines; i++)
+                for (i = 0; i < max_fline; i++)
                         fprintf(fp, "%s\n", flines[i]);
                 fclose(fp);
                 buffer_print();
@@ -871,16 +934,15 @@ static void add_mark(void)
         int letter;
 
         print_statusline("Mark: ");
-        letter = tless_getch();
+        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] = line_pos;
+                mark_lines[num_marks][1] = cur_fline;
                 num_marks++;
         } else {
                 print_statusline("Invalid mark letter");
@@ -893,7 +955,7 @@ static void goto_mark(void)
         int i;
 
         print_statusline("Go to mark: ");
-        letter = tless_getch();
+        letter = less_getch();
         clear_line();
 
         if (isalpha(letter)) {
@@ -915,17 +977,16 @@ static void goto_mark(void)
 static char opp_bracket(char bracket)
 {
         switch (bracket) {
-                case '{': case '[':
-                        return bracket + 2;
-                case '(':
-                        return ')';
-                case '}': case ']':
-                        return bracket - 2;
-                case ')':
-                        return '(';
-                default:
-                        return 0;
+        case '{': case '[':
+                return bracket + 2;
+        case '(':
+                return ')';
+        case '}': case ']':
+                return bracket - 2;
+        case ')':
+                return '(';
         }
+        return 0;
 }
 
 static void match_right_bracket(char bracket)
@@ -933,11 +994,11 @@ static void match_right_bracket(char bracket)
         int bracket_line = -1;
         int i;
 
-        if (strchr(flines[line_pos], bracket) == NULL) {
+        if (strchr(flines[cur_fline], bracket) == NULL) {
                 print_statusline("No bracket in top line");
                 return;
         }
-        for (i = line_pos + 1; i < num_flines; i++) {
+        for (i = cur_fline + 1; i < max_fline; i++) {
                 if (strchr(flines[i], opp_bracket(bracket)) != NULL) {
                         bracket_line = i;
                         break;
@@ -945,7 +1006,7 @@ static void match_right_bracket(char bracket)
         }
         if (bracket_line == -1)
                 print_statusline("No matching bracket found");
-        buffer_line(bracket_line - height + 2);
+        buffer_line(bracket_line - max_displayed_line);
 }
 
 static void match_left_bracket(char bracket)
@@ -953,12 +1014,12 @@ static void match_left_bracket(char bracket)
         int bracket_line = -1;
         int i;
 
-        if (strchr(flines[line_pos + height - 2], bracket) == NULL) {
+        if (strchr(flines[cur_fline + max_displayed_line], bracket) == NULL) {
                 print_statusline("No bracket in bottom line");
                 return;
         }
 
-        for (i = line_pos + height - 2; i >= 0; i--) {
+        for (i = cur_fline + max_displayed_line; i >= 0; i--) {
                 if (strchr(flines[i], opp_bracket(bracket)) != NULL) {
                         bracket_line = i;
                         break;
@@ -974,105 +1035,104 @@ static void match_left_bracket(char bracket)
 static void keypress_process(int keypress)
 {
         switch (keypress) {
-                case KEY_DOWN: case 'e': case 'j': case 0x0d:
-                        buffer_down(1);
-                        buffer_print();
-                        break;
-                case KEY_UP: case 'y': case 'k':
-                        buffer_up(1);
-                        buffer_print();
-                        break;
-                case PAGE_DOWN: case ' ': case 'z':
-                        buffer_down(height - 1);
-                        buffer_print();
-                        break;
-                case PAGE_UP: case 'w': case 'b':
-                        buffer_up(height - 1);
-                        buffer_print();
-                        break;
-                case 'd':
-                        buffer_down((height - 1) / 2);
-                        buffer_print();
-                        break;
-                case 'u':
-                        buffer_up((height - 1) / 2);
-                        buffer_print();
-                        break;
-                case KEY_HOME: case 'g': case 'p': case '<': case '%':
-                        buffer_line(0);
-                        break;
-                case KEY_END: case 'G': case '>':
-                        buffer_line(num_flines - height + 2);
-                        break;
-                case 'q': case 'Q':
-                        tless_exit(0);
-                        break;
+        case KEY_DOWN: case 'e': case 'j': case 0x0d:
+                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(max_displayed_line + 1);
+                buffer_print();
+                break;
+        case PAGE_UP: case 'w': case 'b':
+                buffer_up(max_displayed_line + 1);
+                buffer_print();
+                break;
+        case 'd':
+                buffer_down((max_displayed_line + 1) / 2);
+                buffer_print();
+                break;
+        case 'u':
+                buffer_up((max_displayed_line + 1) / 2);
+                buffer_print();
+                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;
+        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':
-                        save_input_to_file();
-                        break;
-                case 'E':
-                        examine_file();
-                        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;
+        case '=':
+                m_status_print();
+                break;
 #endif
 #if ENABLE_FEATURE_LESS_REGEXP
-                case '/':
-                        option_mask32 &= ~LESS_STATE_MATCH_BACKWARDS;
-                        regex_process();
-                        break;
-                case 'n':
-//printf("HERE 3\n");sleep(1);
-                        goto_match(match_pos + 1);
-                        break;
-                case 'N':
-                        goto_match(match_pos - 1);
-                        break;
-                case '?':
-                        option_mask32 |= LESS_STATE_MATCH_BACKWARDS;
-                        regex_process();
-                        break;
+        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;
+        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;
+        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))
@@ -1092,8 +1152,8 @@ int less_main(int argc, char **argv)
         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. */
@@ -1109,33 +1169,35 @@ int less_main(int argc, char **argv)
         } else
                 filename = xstrdup(files[0]);
 
-        inp = xfopen(CURRENT_TTY, "r");
+        kbd_fd = xopen(CURRENT_TTY, O_RDONLY);
 
-        get_terminal_width_height(fileno(inp), &width, &height);
-        if (width < 10 || height < 3)
+        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(height * sizeof(char *));
+        buffer = xmalloc((max_displayed_line+1) * sizeof(char *));
         if (option_mask32 & FLAG_TILDE)
                 empty_line_marker = "";
 
-        data_readlines();
-
-        tcgetattr(fileno(inp), &term_orig);
+        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);
         }
 }