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line.c

/*
 * Copyright (C) 1984-2005  Mark Nudelman
 *
 * You may distribute under the terms of either the GNU General Public
 * License or the Less License, as specified in the README file.
 *
 * For more information about less, or for information on how to 
 * contact the author, see the README file.
 */


/*
 * Routines to manipulate the "line buffer".
 * The line buffer holds a line of output as it is being built
 * in preparation for output to the screen.
 */

#include "less.h"
#include "charset.h"

static char *linebuf = NULL;  /* Buffer which holds the current output line */
static char *attr = NULL;     /* Extension of linebuf to hold attributes */
public int size_linebuf = 0;  /* Size of line buffer (and attr buffer) */

static int cshift;            /* Current left-shift of output line buffer */
public int hshift;            /* Desired left-shift of output line buffer */
public int tabstops[TABSTOP_MAX] = { 0 }; /* Custom tabstops */
public int ntabstops = 1;     /* Number of tabstops */
public int tabdefault = 8;    /* Default repeated tabstops */

static int curr;        /* Index into linebuf */
static int column;            /* Printable length, accounting for
                           backspaces, etc. */
static int overstrike;        /* Next char should overstrike previous char */
static int last_overstrike = AT_NORMAL;
static int is_null_line;      /* There is no current line */
static int lmargin;           /* Left margin */
static int line_matches;      /* Number of search matches in this line */
static char pendc;
static POSITION pendpos;
static char *end_ansi_chars;
static char *mid_ansi_chars;

static int attr_swidth();
static int attr_ewidth();
static int do_append();

extern int sigs;
extern int bs_mode;
extern int linenums;
extern int ctldisp;
extern int twiddle;
extern int binattr;
extern int status_col;
extern int auto_wrap, ignaw;
extern int bo_s_width, bo_e_width;
extern int ul_s_width, ul_e_width;
extern int bl_s_width, bl_e_width;
extern int so_s_width, so_e_width;
extern int sc_width, sc_height;
extern int utf_mode;
extern POSITION start_attnpos;
extern POSITION end_attnpos;

static char mbc_buf[MAX_UTF_CHAR_LEN];
static int mbc_buf_len = 0;
static int mbc_buf_index = 0;
static POSITION mbc_pos;

/*
 * Initialize from environment variables.
 */
      public void
init_line()
{
      end_ansi_chars = lgetenv("LESSANSIENDCHARS");
      if (end_ansi_chars == NULL || *end_ansi_chars == '\0')
            end_ansi_chars = "m";

      mid_ansi_chars = lgetenv("LESSANSIMIDCHARS");
      if (mid_ansi_chars == NULL || *mid_ansi_chars == '\0')
            mid_ansi_chars = "0123456789;[?!\"'#%()*+ ";

      linebuf = (char *) ecalloc(LINEBUF_SIZE, sizeof(char));
      attr = (char *) ecalloc(LINEBUF_SIZE, sizeof(char));
      size_linebuf = LINEBUF_SIZE;
}

/*
 * Expand the line buffer.
 */
      static int
expand_linebuf()
{
      /* Double the size of the line buffer. */
      int new_size = size_linebuf * 2;

      /* Just realloc to expand the buffer, if we can. */
#if HAVE_REALLOC
      char *new_buf = (char *) realloc(linebuf, new_size);
      char *new_attr = (char *) realloc(attr, new_size);
#else
      char *new_buf = (char *) calloc(new_size, sizeof(char));
      char *new_attr = (char *) calloc(new_size, sizeof(char));
#endif
      if (new_buf == NULL || new_attr == NULL)
      {
            if (new_attr != NULL)
                  free(new_attr);
            if (new_buf != NULL)
                  free(new_buf);
            return 1;
      }
#if HAVE_REALLOC
      /*
       * We realloc'd the buffers; they already have the old contents.
       */
      #if 0
      memset(new_buf + size_linebuf, 0, new_size - size_linebuf);
      memset(new_attr + size_linebuf, 0, new_size - size_linebuf);
      #endif
#else
      /*
       * We just calloc'd the buffers; copy the old contents.
       */
      memcpy(new_buf, linebuf, size_linebuf * sizeof(char));
      memcpy(new_attr, attr, size_linebuf * sizeof(char));
      free(attr);
      free(linebuf);
#endif
      linebuf = new_buf;
      attr = new_attr;
      size_linebuf = new_size;
      return 0;
}

/*
 * Is a character ASCII?
 */
      public int
is_ascii_char(ch)
      LWCHAR ch;
{
      return (ch <= 0x7F);
}

/*
 * Rewind the line buffer.
 */
      public void
prewind()
{
      curr = 0;
      column = 0;
      cshift = 0;
      overstrike = 0;
      last_overstrike = AT_NORMAL;
      mbc_buf_len = 0;
      is_null_line = 0;
      pendc = '\0';
      lmargin = 0;
      if (status_col)
            lmargin += 1;
#if HILITE_SEARCH
      line_matches = 0;
#endif
}

/*
 * Insert the line number (of the given position) into the line buffer.
 */
      public void
plinenum(pos)
      POSITION pos;
{
      register LINENUM linenum = 0;
      register int i;

      if (linenums == OPT_ONPLUS)
      {
            /*
             * Get the line number and put it in the current line.
             * {{ Note: since find_linenum calls forw_raw_line,
             *    it may seek in the input file, requiring the caller 
             *    of plinenum to re-seek if necessary. }}
             * {{ Since forw_raw_line modifies linebuf, we must
             *    do this first, before storing anything in linebuf. }}
             */
            linenum = find_linenum(pos);
      }

      /*
       * Display a status column if the -J option is set.
       */
      if (status_col)
      {
            linebuf[curr] = ' ';
            if (start_attnpos != NULL_POSITION &&
                pos >= start_attnpos && pos < end_attnpos)
                  attr[curr] = AT_NORMAL|AT_HILITE;
            else
                  attr[curr] = AT_NORMAL;
            curr++;
            column++;
      }
      /*
       * Display the line number at the start of each line
       * if the -N option is set.
       */
      if (linenums == OPT_ONPLUS)
      {
            char buf[INT_STRLEN_BOUND(pos) + 2];
            int n;

            linenumtoa(linenum, buf);
            n = strlen(buf);
            if (n < MIN_LINENUM_WIDTH)
                  n = MIN_LINENUM_WIDTH;
            sprintf(linebuf+curr, "%*s ", n, buf);
            n++;  /* One space after the line number. */
            for (i = 0; i < n; i++)
                  attr[curr+i] = AT_NORMAL;
            curr += n;
            column += n;
            lmargin += n;
      }

      /*
       * Append enough spaces to bring us to the lmargin.
       */
      while (column < lmargin)
      {
            linebuf[curr] = ' ';
            attr[curr++] = AT_NORMAL;
            column++;
      }
}

/*
 * Shift the input line left.
 * This means discarding N printable chars at the start of the buffer.
 */
      static void
pshift(shift)
      int shift;
{
      LWCHAR prev_ch = 0;
      unsigned char c;
      int shifted = 0;
      int to;
      int from;
      int len;
      int width;
      int prev_attr;
      int next_attr;

      if (shift > column - lmargin)
            shift = column - lmargin;
      if (shift > curr - lmargin)
            shift = curr - lmargin;

      to = from = lmargin;
      /*
       * We keep on going when shifted == shift
       * to get all combining chars.
       */
      while (shifted <= shift && from < curr)
      {
            c = linebuf[from];
            if (c == ESC && ctldisp == OPT_ONPLUS)
            {
                  /* Keep cumulative effect.  */
                  linebuf[to] = c;
                  attr[to++] = attr[from++];
                  while (from < curr && linebuf[from])
                  {
                        linebuf[to] = linebuf[from];
                        attr[to++] = attr[from];
                        if (!is_ansi_middle(linebuf[from++]))
                              break;
                  } 
                  continue;
            }

            width = 0;

            if (!IS_ASCII_OCTET(c) && utf_mode)
            {
                  /* Assumes well-formedness validation already done.  */
                  LWCHAR ch;

                  len = utf_len(c);
                  if (from + len > curr)
                        break;
                  ch = get_wchar(linebuf + from);
                  if (!is_composing_char(ch) && !is_combining_char(prev_ch, ch))
                        width = is_wide_char(ch) ? 2 : 1;
                  prev_ch = ch;
            } else
            {
                  len = 1;
                  if (c == '\b')
                        /* XXX - Incorrect if several '\b' in a row.  */
                        width = (utf_mode && is_wide_char(prev_ch)) ? -2 : -1;
                  else if (!control_char(c))
                        width = 1;
                  prev_ch = 0;
            }

            if (width == 2 && shift - shifted == 1) {
                  /* Should never happen when called by pshift_all().  */
                  attr[to] = attr[from];
                  /*
                   * Assume a wide_char will never be the first half of a
                   * combining_char pair, so reset prev_ch in case we're
                   * followed by a '\b'.
                   */
                  prev_ch = linebuf[to++] = ' ';
                  from += len;
                  shifted++;
                  continue;
            }

            /* Adjust width for magic cookies. */
            prev_attr = (to > 0) ? attr[to-1] : AT_NORMAL;
            next_attr = (from + len < curr) ? attr[from + len] : prev_attr;
            if (!is_at_equiv(attr[from], prev_attr) && 
                  !is_at_equiv(attr[from], next_attr))
            {
                  width += attr_swidth(attr[from]);
                  if (from + len < curr)
                        width += attr_ewidth(attr[from]);
                  if (is_at_equiv(prev_attr, next_attr))
                  {
                        width += attr_ewidth(prev_attr);
                        if (from + len < curr)
                              width += attr_swidth(next_attr);
                  }
            }

            if (shift - shifted < width)
                  break;
            from += len;
            shifted += width;
            if (shifted < 0)
                  shifted = 0;
      }
      while (from < curr)
      {
            linebuf[to] = linebuf[from];
            attr[to++] = attr[from++];
      }
      curr = to;
      column -= shifted;
      cshift += shifted;
}

/*
 *
 */
      public void
pshift_all()
{
      pshift(column);
}

/*
 * Return the printing width of the start (enter) sequence
 * for a given character attribute.
 */
      static int
attr_swidth(a)
      int a;
{
      int w = 0;

      a = apply_at_specials(a);

      if (a & AT_UNDERLINE)
            w += ul_s_width;
      if (a & AT_BOLD)
            w += bo_s_width;
      if (a & AT_BLINK)
            w += bl_s_width;
      if (a & AT_STANDOUT)
            w += so_s_width;

      return w;
}

/*
 * Return the printing width of the end (exit) sequence
 * for a given character attribute.
 */
      static int
attr_ewidth(a)
      int a;
{
      int w = 0;

      a = apply_at_specials(a);

      if (a & AT_UNDERLINE)
            w += ul_e_width;
      if (a & AT_BOLD)
            w += bo_e_width;
      if (a & AT_BLINK)
            w += bl_e_width;
      if (a & AT_STANDOUT)
            w += so_e_width;

      return w;
}

/*
 * Return the printing width of a given character and attribute,
 * if the character were added to the current position in the line buffer.
 * Adding a character with a given attribute may cause an enter or exit
 * attribute sequence to be inserted, so this must be taken into account.
 */
      static int
pwidth(ch, a, prev_ch)
      LWCHAR ch;
      int a;
      LWCHAR prev_ch;
{
      int w;

      if (ch == '\b')
            /*
             * Backspace moves backwards one or two positions.
             * XXX - Incorrect if several '\b' in a row.
             */
            return (utf_mode && is_wide_char(prev_ch)) ? -2 : -1;

      if (!utf_mode || is_ascii_char(ch))
      {
            if (control_char((char)ch))
            {
                  /*
                   * Control characters do unpredictable things,
                   * so we don't even try to guess; say it doesn't move.
                   * This can only happen if the -r flag is in effect.
                   */
                  return (0);
            }
      } else
      {
            if (is_composing_char(ch) || is_combining_char(prev_ch, ch))
            {
                  /*
                   * Composing and combining chars take up no space.
                   *
                   * Some terminals, upon failure to compose a
                   * composing character with the character(s) that
                   * precede(s) it will actually take up one column
                   * for the composing character; there isn't much
                   * we could do short of testing the (complex)
                   * composition process ourselves and printing
                   * a binary representation when it fails.
                   */
                  return (0);
            }
      }

      /*
       * Other characters take one or two columns,
       * plus the width of any attribute enter/exit sequence.
       */
      w = 1;
      if (is_wide_char(ch))
            w++;
      if (curr > 0 && !is_at_equiv(attr[curr-1], a))
            w += attr_ewidth(attr[curr-1]);
      if ((apply_at_specials(a) != AT_NORMAL) &&
          (curr == 0 || !is_at_equiv(attr[curr-1], a)))
            w += attr_swidth(a);
      return (w);
}

/*
 * Delete to the previous base character in the line buffer.
 * Return 1 if one is found.
 */
      static int
backc()
{
      LWCHAR prev_ch;
      char *p = linebuf + curr;
      LWCHAR ch = step_char(&p, -1, linebuf + lmargin);
      int width;

      /* This assumes that there is no '\b' in linebuf.  */
      while (   curr > lmargin
             && column > lmargin
             && (!(attr[curr - 1] & (AT_ANSI|AT_BINARY))))
      {
            curr = p - linebuf;
            prev_ch = step_char(&p, -1, linebuf + lmargin);
            width = pwidth(ch, attr[curr], prev_ch);
            column -= width;
            if (width > 0)
                  return 1;
            ch = prev_ch;
      }

      return 0;
}

/*
 * Are we currently within a recognized ANSI escape sequence?
 */
      static int
in_ansi_esc_seq()
{
      char *p;

      /*
       * Search backwards for either an ESC (which means we ARE in a seq);
       * or an end char (which means we're NOT in a seq).
       */
      for (p = &linebuf[curr];  p > linebuf; )
      {
            LWCHAR ch = step_char(&p, -1, linebuf);
            if (ch == ESC)
                  return (1);
            if (!is_ansi_middle(ch))
                  return (0);
      }
      return (0);
}

/*
 * Is a character the end of an ANSI escape sequence?
 */
      public int
is_ansi_end(ch)
      LWCHAR ch;
{
      if (!is_ascii_char(ch))
            return (0);
      return (strchr(end_ansi_chars, (char) ch) != NULL);
}

/*
 *
 */
      public int
is_ansi_middle(ch)
      LWCHAR ch;
{
      if (!is_ascii_char(ch))
            return (0);
      if (is_ansi_end(ch))
            return (0);
      return (strchr(mid_ansi_chars, (char) ch) != NULL);
}

/*
 * Append a character and attribute to the line buffer.
 */
#define     STORE_CHAR(ch,a,rep,pos) \
      do { \
            if (store_char((ch),(a),(rep),(pos))) return (1); \
      } while (0)

      static int
store_char(ch, a, rep, pos)
      LWCHAR ch;
      int a;
      char *rep;
      POSITION pos;
{
      int w;
      int replen;
      char cs;

      w = (a & (AT_UNDERLINE|AT_BOLD));   /* Pre-use w.  */
      if (w != AT_NORMAL)
            last_overstrike = w;

#if HILITE_SEARCH
      {
            int matches;
            if (is_hilited(pos, pos+1, 0, &matches))
            {
                  /*
                   * This character should be highlighted.
                   * Override the attribute passed in.
                   */
                  if (a != AT_ANSI)
                        a |= AT_HILITE;
            }
            line_matches += matches;
      }
#endif

      if (ctldisp == OPT_ONPLUS && in_ansi_esc_seq())
      {
            if (!is_ansi_end(ch) && !is_ansi_middle(ch)) {
                  /* Remove whole unrecognized sequence.  */
                  do {
                        --curr;
                  } while (linebuf[curr] != ESC);
                  return 0;
            }
            a = AT_ANSI;      /* Will force re-AT_'ing around it.  */
            w = 0;
      }
      else if (ctldisp == OPT_ONPLUS && ch == ESC)
      {
            a = AT_ANSI;      /* Will force re-AT_'ing around it.  */
            w = 0;
      }
      else
      {
            char *p = &linebuf[curr];
            LWCHAR prev_ch = step_char(&p, -1, linebuf);
            w = pwidth(ch, a, prev_ch);
      }

      if (ctldisp != OPT_ON && column + w + attr_ewidth(a) > sc_width)
            /*
             * Won't fit on screen.
             */
            return (1);

      if (rep == NULL)
      {
            cs = (char) ch;
            rep = &cs;
            replen = 1;
      } else
      {
            replen = utf_len(rep[0]);
      }
      if (curr + replen >= size_linebuf-6)
      {
            /*
             * Won't fit in line buffer.
             * Try to expand it.
             */
            if (expand_linebuf())
                  return (1);
      }

      while (replen-- > 0)
      {
            linebuf[curr] = *rep++;
            attr[curr] = a;
            curr++;
      }
      column += w;
      return (0);
}

/*
 * Append a tab to the line buffer.
 * Store spaces to represent the tab.
 */
#define     STORE_TAB(a,pos) \
      do { if (store_tab((a),(pos))) return (1); } while (0)

      static int
store_tab(attr, pos)
      int attr;
      POSITION pos;
{
      int to_tab = column + cshift - lmargin;
      int i;

      if (ntabstops < 2 || to_tab >= tabstops[ntabstops-1])
            to_tab = tabdefault -
                 ((to_tab - tabstops[ntabstops-1]) % tabdefault);
      else
      {
            for (i = ntabstops - 2;  i >= 0;  i--)
                  if (to_tab >= tabstops[i])
                        break;
            to_tab = tabstops[i+1] - to_tab;
      }

      if (column + to_tab - 1 + pwidth(' ', attr, 0) + attr_ewidth(attr) > sc_width)
            return 1;

      do {
            STORE_CHAR(' ', attr, " ", pos);
      } while (--to_tab > 0);
      return 0;
}

#define STORE_PRCHAR(c, pos) \
      do { if (store_prchar((c), (pos))) return 1; } while (0)

      static int
store_prchar(c, pos)
      char c;
      POSITION pos;
{
      char *s;

      /*
       * Convert to printable representation.
       */
      s = prchar(c);

      /*
       * Make sure we can get the entire representation
       * of the character on this line.
       */
      if (column + (int) strlen(s) - 1 +
            pwidth(' ', binattr, 0) + attr_ewidth(binattr) > sc_width)
            return 1;

      for ( ;  *s != 0;  s++)
            STORE_CHAR(*s, AT_BINARY, NULL, pos);

      return 0;
}

      static int
flush_mbc_buf(pos)
      POSITION pos;
{
      int i;

      for (i = 0; i < mbc_buf_index; i++)
            if (store_prchar(mbc_buf[i], pos))
                  return mbc_buf_index - i;

      return 0;
}

/*
 * Append a character to the line buffer.
 * Expand tabs into spaces, handle underlining, boldfacing, etc.
 * Returns 0 if ok, 1 if couldn't fit in buffer.
 */
      public int
pappend(c, pos)
      char c;
      POSITION pos;
{
      int r;

      if (pendc)
      {
            if (do_append(pendc, NULL, pendpos))
                  /*
                   * Oops.  We've probably lost the char which
                   * was in pendc, since caller won't back up.
                   */
                  return (1);
            pendc = '\0';
      }

      if (c == '\r' && bs_mode == BS_SPECIAL)
      {
            if (mbc_buf_len > 0)  /* utf_mode must be on. */
            {
                  /* Flush incomplete (truncated) sequence. */
                  r = flush_mbc_buf(mbc_pos);
                  mbc_buf_index = r + 1;
                  mbc_buf_len = 0;
                  if (r)
                        return (mbc_buf_index);
            }

            /*
             * Don't put the CR into the buffer until we see 
             * the next char.  If the next char is a newline,
             * discard the CR.
             */
            pendc = c;
            pendpos = pos;
            return (0);
      }

      if (!utf_mode)
      {
            r = do_append((LWCHAR) c, NULL, pos);
      } else
      {
            /* Perform strict validation in all possible cases. */
            if (mbc_buf_len == 0)
            {
            retry:
                  mbc_buf_index = 1;
                  *mbc_buf = c;
                  if (IS_ASCII_OCTET(c))
                        r = do_append((LWCHAR) c, NULL, pos);
                  else if (IS_UTF8_LEAD(c))
                  {
                        mbc_buf_len = utf_len(c);
                        mbc_pos = pos;
                        return (0);
                  } else
                        /* UTF8_INVALID or stray UTF8_TRAIL */
                        r = flush_mbc_buf(pos);
            } else if (IS_UTF8_TRAIL(c))
            {
                  mbc_buf[mbc_buf_index++] = c;
                  if (mbc_buf_index < mbc_buf_len)
                        return (0);
                  if (is_utf8_well_formed(mbc_buf))
                        r = do_append(get_wchar(mbc_buf), mbc_buf, mbc_pos);
                  else
                        /* Complete, but not shortest form, sequence. */
                        mbc_buf_index = r = flush_mbc_buf(mbc_pos);
                  mbc_buf_len = 0;
            } else
            {
                  /* Flush incomplete (truncated) sequence.  */
                  r = flush_mbc_buf(mbc_pos);
                  mbc_buf_index = r + 1;
                  mbc_buf_len = 0;
                  /* Handle new char.  */
                  if (!r)
                        goto retry;
            }
      }

      /*
       * If we need to shift the line, do it.
       * But wait until we get to at least the middle of the screen,
       * so shifting it doesn't affect the chars we're currently
       * pappending.  (Bold & underline can get messed up otherwise.)
       */
      if (cshift < hshift && column > sc_width / 2)
      {
            linebuf[curr] = '\0';
            pshift(hshift - cshift);
      }
      if (r)
      {
            /* How many chars should caller back up? */
            r = (!utf_mode) ? 1 : mbc_buf_index;
      }
      return (r);
}

      static int
do_append(ch, rep, pos)
      LWCHAR ch;
      char *rep;
      POSITION pos;
{
      register int a;
      LWCHAR prev_ch;

      a = AT_NORMAL;

      if (ch == '\b')
      {
            if (bs_mode == BS_CONTROL)
                  goto do_control_char;

            /*
             * A better test is needed here so we don't
             * backspace over part of the printed
             * representation of a binary character.
             */
            if (   curr <= lmargin
                || column <= lmargin
                || (attr[curr - 1] & (AT_ANSI|AT_BINARY)))
                  STORE_PRCHAR('\b', pos);
            else if (bs_mode == BS_NORMAL)
                  STORE_CHAR(ch, AT_NORMAL, NULL, pos);
            else if (bs_mode == BS_SPECIAL)
                  overstrike = backc();

            return 0;
      }

      if (overstrike > 0)
      {
            /*
             * Overstrike the character at the current position
             * in the line buffer.  This will cause either 
             * underline (if a "_" is overstruck), 
             * bold (if an identical character is overstruck),
             * or just deletion of the character in the buffer.
             */
            overstrike = utf_mode ? -1 : 0;
            /* To be correct, this must be a base character.  */
            prev_ch = get_wchar(linebuf + curr);
            a = attr[curr];
            if (ch == prev_ch)
            {
                  /*
                   * Overstriking a char with itself means make it bold.
                   * But overstriking an underscore with itself is
                   * ambiguous.  It could mean make it bold, or
                   * it could mean make it underlined.
                   * Use the previous overstrike to resolve it.
                   */
                  if (ch == '_')
                  {
                        if ((a & (AT_BOLD|AT_UNDERLINE)) != AT_NORMAL)
                              a |= (AT_BOLD|AT_UNDERLINE);
                        else if (last_overstrike != AT_NORMAL)
                              a |= last_overstrike;
                        else
                              a |= AT_BOLD;
                  } else
                        a |= AT_BOLD;
            } else if (ch == '_')
            {
                  a |= AT_UNDERLINE;
                  ch = prev_ch;
                  rep = linebuf + curr;
            } else if (prev_ch == '_')
            {
                  a |= AT_UNDERLINE;
            }
            /* Else we replace prev_ch, but we keep its attributes.  */
      } else if (overstrike < 0)
      {
            if (   is_composing_char(ch)
                || is_combining_char(get_wchar(linebuf + curr), ch))
                  /* Continuation of the same overstrike.  */
                  a = last_overstrike;
            else
                  overstrike = 0;
      }

      if (ch == '\t') 
      {
            /*
             * Expand a tab into spaces.
             */
            switch (bs_mode)
            {
            case BS_CONTROL:
                  goto do_control_char;
            case BS_NORMAL:
            case BS_SPECIAL:
                  STORE_TAB(a, pos);
                  break;
            }
      } else if ((!utf_mode || is_ascii_char(ch)) && control_char((char)ch))
      {
      do_control_char:
            if (ctldisp == OPT_ON || (ctldisp == OPT_ONPLUS && ch == ESC))
            {
                  /*
                   * Output as a normal character.
                   */
                  STORE_CHAR(ch, AT_NORMAL, rep, pos);
            } else 
            {
                  STORE_PRCHAR((char) ch, pos);
            }
      } else if (utf_mode && ctldisp != OPT_ON && is_ubin_char(ch))
      {
            char *s;

            s = prutfchar(ch);

            if (column + (int) strlen(s) - 1 +
                pwidth(' ', binattr, 0) + attr_ewidth(binattr) > sc_width)
                  return (1);

            for ( ;  *s != 0;  s++)
                  STORE_CHAR(*s, AT_BINARY, NULL, pos);
      } else
      {
            STORE_CHAR(ch, a, rep, pos);
      }
      return (0);
}

/*
 *
 */
      public int
pflushmbc()
{
      int r = 0;

      if (mbc_buf_len > 0)
      {
            /* Flush incomplete (truncated) sequence.  */
            r = flush_mbc_buf(mbc_pos);
            mbc_buf_len = 0;
      }
      return r;
}

/*
 * Terminate the line in the line buffer.
 */
      public void
pdone(endline)
      int endline;
{
      (void) pflushmbc();

      if (pendc && (pendc != '\r' || !endline))
            /*
             * If we had a pending character, put it in the buffer.
             * But discard a pending CR if we are at end of line
             * (that is, discard the CR in a CR/LF sequence).
             */
            (void) do_append(pendc, NULL, pendpos);

      /*
       * Make sure we've shifted the line, if we need to.
       */
      if (cshift < hshift)
            pshift(hshift - cshift);

      if (ctldisp == OPT_ONPLUS && is_ansi_end('m'))
      {
            /* Switch to normal attribute at end of line. */
            char *p = "\033[m";
            for ( ;  *p != '\0';  p++)
            {
                  linebuf[curr] = *p;
                  attr[curr++] = AT_ANSI;
            }
      }

      /*
       * Add a newline if necessary,
       * and append a '\0' to the end of the line.
       */
      if (column < sc_width || !auto_wrap || ignaw || ctldisp == OPT_ON)
      {
            linebuf[curr] = '\n';
            attr[curr] = AT_NORMAL;
            curr++;
      }
      linebuf[curr] = '\0';
      attr[curr] = AT_NORMAL;

#if HILITE_SEARCH
      if (status_col && line_matches > 0)
      {
            linebuf[0] = '*';
            attr[0] = AT_NORMAL|AT_HILITE;
      }
#endif
}

/*
 * Get a character from the current line.
 * Return the character as the function return value,
 * and the character attribute in *ap.
 */
      public int
gline(i, ap)
      register int i;
      register int *ap;
{
      if (is_null_line)
      {
            /*
             * If there is no current line, we pretend the line is
             * either "~" or "", depending on the "twiddle" flag.
             */
            if (twiddle)
            {
                  if (i == 0)
                  {
                        *ap = AT_BOLD;
                        return '~';
                  }
                  --i;
            }
            /* Make sure we're back to AT_NORMAL before the '\n'.  */
            *ap = AT_NORMAL;
            return i ? '\0' : '\n';
      }

      *ap = attr[i];
      return (linebuf[i] & 0xFF);
}

/*
 * Indicate that there is no current line.
 */
      public void
null_line()
{
      is_null_line = 1;
      cshift = 0;
}

/*
 * Analogous to forw_line(), but deals with "raw lines":
 * lines which are not split for screen width.
 * {{ This is supposed to be more efficient than forw_line(). }}
 */
      public POSITION
forw_raw_line(curr_pos, linep)
      POSITION curr_pos;
      char **linep;
{
      register int n;
      register int c;
      POSITION new_pos;

      if (curr_pos == NULL_POSITION || ch_seek(curr_pos) ||
            (c = ch_forw_get()) == EOI)
            return (NULL_POSITION);

      n = 0;
      for (;;)
      {
            if (c == '\n' || c == EOI || ABORT_SIGS())
            {
                  new_pos = ch_tell();
                  break;
            }
            if (n >= size_linebuf-1)
            {
                  if (expand_linebuf())
                  {
                        /*
                         * Overflowed the input buffer.
                         * Pretend the line ended here.
                         */
                        new_pos = ch_tell() - 1;
                        break;
                  }
            }
            linebuf[n++] = c;
            c = ch_forw_get();
      }
      linebuf[n] = '\0';
      if (linep != NULL)
            *linep = linebuf;
      return (new_pos);
}

/*
 * Analogous to back_line(), but deals with "raw lines".
 * {{ This is supposed to be more efficient than back_line(). }}
 */
      public POSITION
back_raw_line(curr_pos, linep)
      POSITION curr_pos;
      char **linep;
{
      register int n;
      register int c;
      POSITION new_pos;

      if (curr_pos == NULL_POSITION || curr_pos <= ch_zero() ||
            ch_seek(curr_pos-1))
            return (NULL_POSITION);

      n = size_linebuf;
      linebuf[--n] = '\0';
      for (;;)
      {
            c = ch_back_get();
            if (c == '\n' || ABORT_SIGS())
            {
                  /*
                   * This is the newline ending the previous line.
                   * We have hit the beginning of the line.
                   */
                  new_pos = ch_tell() + 1;
                  break;
            }
            if (c == EOI)
            {
                  /*
                   * We have hit the beginning of the file.
                   * This must be the first line in the file.
                   * This must, of course, be the beginning of the line.
                   */
                  new_pos = ch_zero();
                  break;
            }
            if (n <= 0)
            {
                  int old_size_linebuf = size_linebuf;
                  char *fm;
                  char *to;
                  if (expand_linebuf())
                  {
                        /*
                         * Overflowed the input buffer.
                         * Pretend the line ended here.
                         */
                        new_pos = ch_tell() + 1;
                        break;
                  }
                  /*
                   * Shift the data to the end of the new linebuf.
                   */
                  for (fm = linebuf + old_size_linebuf - 1,
                        to = linebuf + size_linebuf - 1;
                       fm >= linebuf;  fm--, to--)
                        *to = *fm;
                  n = size_linebuf - old_size_linebuf;
            }
            linebuf[--n] = c;
      }
      if (linep != NULL)
            *linep = &linebuf[n];
      return (new_pos);
}

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