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decode.c

/*
 * Copyright (C) 1984-2004  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 decode user commands.
 *
 * This is all table driven.
 * A command table is a sequence of command descriptors.
 * Each command descriptor is a sequence of bytes with the following format:
 *    <c1><c2>...<cN><0><action>
 * The characters c1,c2,...,cN are the command string; that is,
 * the characters which the user must type.
 * It is terminated by a null <0> byte.
 * The byte after the null byte is the action code associated
 * with the command string.
 * If an action byte is OR-ed with A_EXTRA, this indicates
 * that the option byte is followed by an extra string.
 *
 * There may be many command tables.
 * The first (default) table is built-in.
 * Other tables are read in from "lesskey" files.
 * All the tables are linked together and are searched in order.
 */

#include "less.h"
#include "cmd.h"
#include "lesskey.h"

extern int erase_char, erase2_char, kill_char;
extern int secure;

#define SK(k) \
      SK_SPECIAL_KEY, (k), 6, 1, 1, 1
/*
 * Command table is ordered roughly according to expected
 * frequency of use, so the common commands are near the beginning.
 */

static unsigned char cmdtable[] =
{
      '\r',0,                       A_F_LINE,
      '\n',0,                       A_F_LINE,
      'e',0,                        A_F_LINE,
      'j',0,                        A_F_LINE,
      SK(SK_DOWN_ARROW),0,          A_F_LINE,
      CONTROL('E'),0,               A_F_LINE,
      CONTROL('N'),0,               A_F_LINE,
      'k',0,                        A_B_LINE,
      'y',0,                        A_B_LINE,
      CONTROL('Y'),0,               A_B_LINE,
      SK(SK_CONTROL_K),0,           A_B_LINE,
      CONTROL('P'),0,               A_B_LINE,
      SK(SK_UP_ARROW),0,            A_B_LINE,
      'J',0,                        A_FF_LINE,
      'K',0,                        A_BF_LINE,
      'Y',0,                        A_BF_LINE,
      'd',0,                        A_F_SCROLL,
      CONTROL('D'),0,               A_F_SCROLL,
      'u',0,                        A_B_SCROLL,
      CONTROL('U'),0,               A_B_SCROLL,
      ' ',0,                        A_F_SCREEN,
      'f',0,                        A_F_SCREEN,
      CONTROL('F'),0,               A_F_SCREEN,
      CONTROL('V'),0,               A_F_SCREEN,
      SK(SK_PAGE_DOWN),0,           A_F_SCREEN,
      'b',0,                        A_B_SCREEN,
      CONTROL('B'),0,               A_B_SCREEN,
      ESC,'v',0,              A_B_SCREEN,
      SK(SK_PAGE_UP),0,       A_B_SCREEN,
      'z',0,                        A_F_WINDOW,
      'w',0,                        A_B_WINDOW,
      ESC,' ',0,              A_FF_SCREEN,
      'F',0,                        A_F_FOREVER,
      'R',0,                        A_FREPAINT,
      'r',0,                        A_REPAINT,
      CONTROL('R'),0,               A_REPAINT,
      CONTROL('L'),0,               A_REPAINT,
      ESC,'u',0,              A_UNDO_SEARCH,
      'g',0,                        A_GOLINE,
      SK(SK_HOME),0,                A_GOLINE,
      '<',0,                        A_GOLINE,
      ESC,'<',0,              A_GOLINE,
      'p',0,                        A_PERCENT,
      '%',0,                        A_PERCENT,
      ESC,'[',0,              A_LSHIFT,
      ESC,']',0,              A_RSHIFT,
      ESC,'(',0,              A_LSHIFT,
      ESC,')',0,              A_RSHIFT,
      SK(SK_RIGHT_ARROW),0,         A_RSHIFT,
      SK(SK_LEFT_ARROW),0,          A_LSHIFT,
      '{',0,                        A_F_BRACKET|A_EXTRA,    '{','}',0,
      '}',0,                        A_B_BRACKET|A_EXTRA,    '{','}',0,
      '(',0,                        A_F_BRACKET|A_EXTRA,    '(',')',0,
      ')',0,                        A_B_BRACKET|A_EXTRA,    '(',')',0,
      '[',0,                        A_F_BRACKET|A_EXTRA,    '[',']',0,
      ']',0,                        A_B_BRACKET|A_EXTRA,    '[',']',0,
      ESC,CONTROL('F'),0,           A_F_BRACKET,
      ESC,CONTROL('B'),0,           A_B_BRACKET,
      'G',0,                        A_GOEND,
      ESC,'>',0,              A_GOEND,
      '>',0,                        A_GOEND,
      SK(SK_END),0,                 A_GOEND,
      'P',0,                        A_GOPOS,

      '0',0,                        A_DIGIT,
      '1',0,                        A_DIGIT,
      '2',0,                        A_DIGIT,
      '3',0,                        A_DIGIT,
      '4',0,                        A_DIGIT,
      '5',0,                        A_DIGIT,
      '6',0,                        A_DIGIT,
      '7',0,                        A_DIGIT,
      '8',0,                        A_DIGIT,
      '9',0,                        A_DIGIT,

      '=',0,                        A_STAT,
      CONTROL('G'),0,               A_STAT,
      ':','f',0,              A_STAT,
      '/',0,                        A_F_SEARCH,
      '?',0,                        A_B_SEARCH,
      ESC,'/',0,              A_F_SEARCH|A_EXTRA,     '*',0,
      ESC,'?',0,              A_B_SEARCH|A_EXTRA,     '*',0,
      'n',0,                        A_AGAIN_SEARCH,
      ESC,'n',0,              A_T_AGAIN_SEARCH,
      'N',0,                        A_REVERSE_SEARCH,
      ESC,'N',0,              A_T_REVERSE_SEARCH,
      'm',0,                        A_SETMARK,
      '\'',0,                       A_GOMARK,
      CONTROL('X'),CONTROL('X'),0,  A_GOMARK,
      'E',0,                        A_EXAMINE,
      ':','e',0,              A_EXAMINE,
      CONTROL('X'),CONTROL('V'),0,  A_EXAMINE,
      ':','n',0,              A_NEXT_FILE,
      ':','p',0,              A_PREV_FILE,
      't',0,                        A_NEXT_TAG,
      'T',0,                        A_PREV_TAG,
      ':','x',0,              A_INDEX_FILE,
      ':','d',0,              A_REMOVE_FILE,
      '-',0,                        A_OPT_TOGGLE,
      ':','t',0,              A_OPT_TOGGLE|A_EXTRA,   't',0,
      's',0,                        A_OPT_TOGGLE|A_EXTRA,   'o',0,
      '_',0,                        A_DISP_OPTION,
      '|',0,                        A_PIPE,
      'v',0,                        A_VISUAL,
      '!',0,                        A_SHELL,
      '+',0,                        A_FIRSTCMD,

      'H',0,                        A_HELP,
      'h',0,                        A_HELP,
      SK(SK_F1),0,                  A_HELP,
      'V',0,                        A_VERSION,
      'q',0,                        A_QUIT,
      'Q',0,                        A_QUIT,
      ':','q',0,              A_QUIT,
      ':','Q',0,              A_QUIT,
      'Z','Z',0,              A_QUIT
};

static unsigned char edittable[] =
{
      '\t',0,                       EC_F_COMPLETE,    /* TAB */
      '\17',0,                EC_B_COMPLETE,    /* BACKTAB */
      SK(SK_BACKTAB),0,       EC_B_COMPLETE,    /* BACKTAB */
      ESC,'\t',0,             EC_B_COMPLETE,    /* ESC TAB */
      CONTROL('L'),0,               EC_EXPAND,  /* CTRL-L */
      CONTROL('V'),0,               EC_LITERAL, /* BACKSLASH */
      CONTROL('A'),0,               EC_LITERAL, /* BACKSLASH */
      ESC,'l',0,              EC_RIGHT,   /* ESC l */
      SK(SK_RIGHT_ARROW),0,         EC_RIGHT,   /* RIGHTARROW */
      ESC,'h',0,              EC_LEFT,    /* ESC h */
      SK(SK_LEFT_ARROW),0,          EC_LEFT,    /* LEFTARROW */
      ESC,'b',0,              EC_W_LEFT,  /* ESC b */
      ESC,SK(SK_LEFT_ARROW),0,      EC_W_LEFT,  /* ESC LEFTARROW */
      SK(SK_CTL_LEFT_ARROW),0,      EC_W_LEFT,  /* CTRL-LEFTARROW */
      ESC,'w',0,              EC_W_RIGHT, /* ESC w */
      ESC,SK(SK_RIGHT_ARROW),0,     EC_W_RIGHT, /* ESC RIGHTARROW */
      SK(SK_CTL_RIGHT_ARROW),0,     EC_W_RIGHT, /* CTRL-RIGHTARROW */
      ESC,'i',0,              EC_INSERT,  /* ESC i */
      SK(SK_INSERT),0,        EC_INSERT,  /* INSERT */
      ESC,'x',0,              EC_DELETE,  /* ESC x */
      SK(SK_DELETE),0,        EC_DELETE,  /* DELETE */
      ESC,'X',0,              EC_W_DELETE,      /* ESC X */
      ESC,SK(SK_DELETE),0,          EC_W_DELETE,      /* ESC DELETE */
      SK(SK_CTL_DELETE),0,          EC_W_DELETE,      /* CTRL-DELETE */
      SK(SK_CTL_BACKSPACE),0,       EC_W_BACKSPACE, /* CTRL-BACKSPACE */
      ESC,'\b',0,             EC_W_BACKSPACE,   /* ESC BACKSPACE */
      ESC,'0',0,              EC_HOME,    /* ESC 0 */
      SK(SK_HOME),0,                EC_HOME,    /* HOME */
      ESC,'$',0,              EC_END,           /* ESC $ */
      SK(SK_END),0,                 EC_END,           /* END */
      ESC,'k',0,              EC_UP,            /* ESC k */
      SK(SK_UP_ARROW),0,            EC_UP,            /* UPARROW */
      ESC,'j',0,              EC_DOWN,    /* ESC j */
      SK(SK_DOWN_ARROW),0,          EC_DOWN,    /* DOWNARROW */
};

/*
 * Structure to support a list of command tables.
 */
struct tablelist
{
      struct tablelist *t_next;
      char *t_start;
      char *t_end;
};

/*
 * List of command tables and list of line-edit tables.
 */
static struct tablelist *list_fcmd_tables = NULL;
static struct tablelist *list_ecmd_tables = NULL;
static struct tablelist *list_var_tables = NULL;
static struct tablelist *list_sysvar_tables = NULL;


/*
 * Expand special key abbreviations in a command table.
 */
      static void
expand_special_keys(table, len)
      char *table;
      int len;
{
      register char *fm;
      register char *to;
      register int a;
      char *repl;
      int klen;

      for (fm = table;  fm < table + len; )
      {
            /*
             * Rewrite each command in the table with any
             * special key abbreviations expanded.
             */
            for (to = fm;  *fm != '\0'; )
            {
                  if (*fm != SK_SPECIAL_KEY)
                  {
                        *to++ = *fm++;
                        continue;
                  }
                  /*
                   * After SK_SPECIAL_KEY, next byte is the type
                   * of special key (one of the SK_* contants),
                   * and the byte after that is the number of bytes,
                   * N, reserved by the abbreviation (including the
                   * SK_SPECIAL_KEY and key type bytes).
                   * Replace all N bytes with the actual bytes
                   * output by the special key on this terminal.
                   */
                  repl = special_key_str(fm[1]);
                  klen = fm[2] & 0377;
                  fm += klen;
                  if (repl == NULL || (int) strlen(repl) > klen)
                        repl = "\377";
                  while (*repl != '\0')
                        *to++ = *repl++;
            }
            *to++ = '\0';
            /*
             * Fill any unused bytes between end of command and 
             * the action byte with A_SKIP.
             */
            while (to <= fm)
                  *to++ = A_SKIP;
            fm++;
            a = *fm++ & 0377;
            if (a & A_EXTRA)
            {
                  while (*fm++ != '\0')
                        continue;
            }
      }
}

/*
 * Initialize the command lists.
 */
      public void
init_cmds()
{
      /*
       * Add the default command tables.
       */
      add_fcmd_table((char*)cmdtable, sizeof(cmdtable));
      add_ecmd_table((char*)edittable, sizeof(edittable));
#if USERFILE
      /*
       * For backwards compatibility,
       * try to add tables in the OLD system lesskey file.
       */
#ifdef BINDIR
      add_hometable(NULL, BINDIR "/.sysless", 1);
#endif
      /*
       * Try to add the tables in the system lesskey file.
       */
      add_hometable("LESSKEY_SYSTEM", LESSKEYFILE_SYS, 1);
      /*
       * Try to add the tables in the standard lesskey file "$HOME/.less".
       */
      add_hometable("LESSKEY", LESSKEYFILE, 0);
#endif
}

/*
 * Add a command table.
 */
      static int
add_cmd_table(tlist, buf, len)
      struct tablelist **tlist;
      char *buf;
      int len;
{
      register struct tablelist *t;

      if (len == 0)
            return (0);
      /*
       * Allocate a tablelist structure, initialize it, 
       * and link it into the list of tables.
       */
      if ((t = (struct tablelist *) 
                  calloc(1, sizeof(struct tablelist))) == NULL)
      {
            return (-1);
      }
      expand_special_keys(buf, len);
      t->t_start = buf;
      t->t_end = buf + len;
      t->t_next = *tlist;
      *tlist = t;
      return (0);
}

/*
 * Add a command table.
 */
      public void
add_fcmd_table(buf, len)
      char *buf;
      int len;
{
      if (add_cmd_table(&list_fcmd_tables, buf, len) < 0)
            error("Warning: some commands disabled", NULL_PARG);
}

/*
 * Add an editing command table.
 */
      public void
add_ecmd_table(buf, len)
      char *buf;
      int len;
{
      if (add_cmd_table(&list_ecmd_tables, buf, len) < 0)
            error("Warning: some edit commands disabled", NULL_PARG);
}

/*
 * Add an environment variable table.
 */
      static void
add_var_table(tlist, buf, len)
      struct tablelist **tlist;
      char *buf;
      int len;
{
      if (add_cmd_table(tlist, buf, len) < 0)
            error("Warning: environment variables from lesskey file unavailable", NULL_PARG);
}

/*
 * Search a single command table for the command string in cmd.
 */
      static int
cmd_search(cmd, table, endtable, sp)
      char *cmd;
      char *table;
      char *endtable;
      char **sp;
{
      register char *p;
      register char *q;
      register int a;

      *sp = NULL;
      for (p = table, q = cmd;  p < endtable;  p++, q++)
      {
            if (*p == *q)
            {
                  /*
                   * Current characters match.
                   * If we're at the end of the string, we've found it.
                   * Return the action code, which is the character
                   * after the null at the end of the string
                   * in the command table.
                   */
                  if (*p == '\0')
                  {
                        a = *++p & 0377;
                        while (a == A_SKIP)
                              a = *++p & 0377;
                        if (a == A_END_LIST)
                        {
                              /*
                               * We get here only if the original
                               * cmd string passed in was empty ("").
                               * I don't think that can happen,
                               * but just in case ...
                               */
                              return (A_UINVALID);
                        }
                        /*
                         * Check for an "extra" string.
                         */
                        if (a & A_EXTRA)
                        {
                              *sp = ++p;
                              a &= ~A_EXTRA;
                        }
                        return (a);
                  }
            } else if (*q == '\0')
            {
                  /*
                   * Hit the end of the user's command,
                   * but not the end of the string in the command table.
                   * The user's command is incomplete.
                   */
                  return (A_PREFIX);
            } else
            {
                  /*
                   * Not a match.
                   * Skip ahead to the next command in the
                   * command table, and reset the pointer
                   * to the beginning of the user's command.
                   */
                  if (*p == '\0' && p[1] == A_END_LIST)
                  {
                        /*
                         * A_END_LIST is a special marker that tells 
                         * us to abort the cmd search.
                         */
                        return (A_UINVALID);
                  }
                  while (*p++ != '\0')
                        continue;
                  while (*p == A_SKIP)
                        p++;
                  if (*p & A_EXTRA)
                        while (*++p != '\0')
                              continue;
                  q = cmd-1;
            }
      }
      /*
       * No match found in the entire command table.
       */
      return (A_INVALID);
}

/*
 * Decode a command character and return the associated action.
 * The "extra" string, if any, is returned in sp.
 */
      static int
cmd_decode(tlist, cmd, sp)
      struct tablelist *tlist;
      char *cmd;
      char **sp;
{
      register struct tablelist *t;
      register int action = A_INVALID;

      /*
       * Search thru all the command tables.
       * Stop when we find an action which is not A_INVALID.
       */
      for (t = tlist;  t != NULL;  t = t->t_next)
      {
            action = cmd_search(cmd, t->t_start, t->t_end, sp);
            if (action != A_INVALID)
                  break;
      }
      if (action == A_UINVALID)
            action = A_INVALID;
      return (action);
}

/*
 * Decode a command from the cmdtables list.
 */
      public int
fcmd_decode(cmd, sp)
      char *cmd;
      char **sp;
{
      return (cmd_decode(list_fcmd_tables, cmd, sp));
}

/*
 * Decode a command from the edittables list.
 */
      public int
ecmd_decode(cmd, sp)
      char *cmd;
      char **sp;
{
      return (cmd_decode(list_ecmd_tables, cmd, sp));
}

/*
 * Get the value of an environment variable.
 * Looks first in the lesskey file, then in the real environment.
 */
      public char *
lgetenv(var)
      char *var;
{
      int a;
      char *s;

      a = cmd_decode(list_var_tables, var, &s);
      if (a == EV_OK)
            return (s);
      s = getenv(var);
      if (s != NULL && *s != '\0')
            return (s);
      a = cmd_decode(list_sysvar_tables, var, &s);
      if (a == EV_OK)
            return (s);
      return (NULL);
}

#if USERFILE
/*
 * Get an "integer" from a lesskey file.
 * Integers are stored in a funny format: 
 * two bytes, low order first, in radix KRADIX.
 */
      static int
gint(sp)
      char **sp;
{
      int n;

      n = *(*sp)++;
      n += *(*sp)++ * KRADIX;
      return (n);
}

/*
 * Process an old (pre-v241) lesskey file.
 */
      static int
old_lesskey(buf, len)
      char *buf;
      int len;
{
      /*
       * Old-style lesskey file.
       * The file must end with either 
       *     ...,cmd,0,action
       * or  ...,cmd,0,action|A_EXTRA,string,0
       * So the last byte or the second to last byte must be zero.
       */
      if (buf[len-1] != '\0' && buf[len-2] != '\0')
            return (-1);
      add_fcmd_table(buf, len);
      return (0);
}

/* 
 * Process a new (post-v241) lesskey file.
 */
      static int
new_lesskey(buf, len, sysvar)
      char *buf;
      int len;
      int sysvar;
{
      char *p;
      register int c;
      register int n;

      /*
       * New-style lesskey file.
       * Extract the pieces.
       */
      if (buf[len-3] != C0_END_LESSKEY_MAGIC ||
          buf[len-2] != C1_END_LESSKEY_MAGIC ||
          buf[len-1] != C2_END_LESSKEY_MAGIC)
            return (-1);
      p = buf + 4;
      for (;;)
      {
            c = *p++;
            switch (c)
            {
            case CMD_SECTION:
                  n = gint(&p);
                  add_fcmd_table(p, n);
                  p += n;
                  break;
            case EDIT_SECTION:
                  n = gint(&p);
                  add_ecmd_table(p, n);
                  p += n;
                  break;
            case VAR_SECTION:
                  n = gint(&p);
                  add_var_table((sysvar) ? 
                        &list_sysvar_tables : &list_var_tables, p, n);
                  p += n;
                  break;
            case END_SECTION:
                  return (0);
            default:
                  /*
                   * Unrecognized section type.
                   */
                  return (-1);
            }
      }
}

/*
 * Set up a user command table, based on a "lesskey" file.
 */
      public int
lesskey(filename, sysvar)
      char *filename;
      int sysvar;
{
      register char *buf;
      register POSITION len;
      register long n;
      register int f;

      if (secure)
            return (1);
      /*
       * Try to open the lesskey file.
       */
      filename = shell_unquote(filename);
      f = open(filename, OPEN_READ);
      free(filename);
      if (f < 0)
            return (1);

      /*
       * Read the file into a buffer.
       * We first figure out the size of the file and allocate space for it.
       * {{ Minimal error checking is done here.
       *    A garbage .less file will produce strange results.
       *    To avoid a large amount of error checking code here, we
       *    rely on the lesskey program to generate a good .less file. }}
       */
      len = filesize(f);
      if (len == NULL_POSITION || len < 3)
      {
            /*
             * Bad file (valid file must have at least 3 chars).
             */
            close(f);
            return (-1);
      }
      if ((buf = (char *) calloc((int)len, sizeof(char))) == NULL)
      {
            close(f);
            return (-1);
      }
      if (lseek(f, (off_t)0, 0) == BAD_LSEEK)
      {
            free(buf);
            close(f);
            return (-1);
      }
      n = read(f, buf, (unsigned int) len);
      close(f);
      if (n != len)
      {
            free(buf);
            return (-1);
      }

      /*
       * Figure out if this is an old-style (before version 241)
       * or new-style lesskey file format.
       */
      if (buf[0] != C0_LESSKEY_MAGIC || buf[1] != C1_LESSKEY_MAGIC ||
          buf[2] != C2_LESSKEY_MAGIC || buf[3] != C3_LESSKEY_MAGIC)
            return (old_lesskey(buf, (int)len));
      return (new_lesskey(buf, (int)len, sysvar));
}

/*
 * Add the standard lesskey file "$HOME/.less"
 */
      public void
add_hometable(envname, def_filename, sysvar)
      char *envname;
      char *def_filename;
      int sysvar;
{
      char *filename;
      PARG parg;

      if (envname != NULL && (filename = lgetenv(envname)) != NULL)
            filename = save(filename);
      else if (sysvar)
            filename = save(def_filename);
      else
            filename = homefile(def_filename);
      if (filename == NULL)
            return;
      if (lesskey(filename, sysvar) < 0)
      {
            parg.p_string = filename;
            error("Cannot use lesskey file \"%s\"", &parg);
      }
      free(filename);
}
#endif

/*
 * See if a char is a special line-editing command.
 */
      public int
editchar(c, flags)
      int c;
      int flags;
{
      int action;
      int nch;
      char *s;
      char usercmd[MAX_CMDLEN+1];
      
      /*
       * An editing character could actually be a sequence of characters;
       * for example, an escape sequence sent by pressing the uparrow key.
       * To match the editing string, we use the command decoder
       * but give it the edit-commands command table
       * This table is constructed to match the user's keyboard.
       */
      if (c == erase_char || c == erase2_char)
            return (EC_BACKSPACE);
      if (c == kill_char)
            return (EC_LINEKILL);
            
      /*
       * Collect characters in a buffer.
       * Start with the one we have, and get more if we need them.
       */
      nch = 0;
      do {
            if (nch > 0)
                  c = getcc();
            usercmd[nch] = c;
            usercmd[nch+1] = '\0';
            nch++;
            action = ecmd_decode(usercmd, &s);
      } while (action == A_PREFIX);
      
      if (flags & EC_NORIGHTLEFT)
      {
            switch (action)
            {
            case EC_RIGHT:
            case EC_LEFT:
                  action = A_INVALID;
                  break;
            }
      }
#if CMD_HISTORY
      if (flags & EC_NOHISTORY) 
      {
            /*
             * The caller says there is no history list.
             * Reject any history-manipulation action.
             */
            switch (action)
            {
            case EC_UP:
            case EC_DOWN:
                  action = A_INVALID;
                  break;
            }
      }
#endif
#if TAB_COMPLETE_FILENAME
      if (flags & EC_NOCOMPLETE) 
      {
            /*
             * The caller says we don't want any filename completion cmds.
             * Reject them.
             */
            switch (action)
            {
            case EC_F_COMPLETE:
            case EC_B_COMPLETE:
            case EC_EXPAND:
                  action = A_INVALID;
                  break;
            }
      }
#endif
      if ((flags & EC_PEEK) || action == A_INVALID)
      {
            /*
             * We're just peeking, or we didn't understand the command.
             * Unget all the characters we read in the loop above.
             * This does NOT include the original character that was 
             * passed in as a parameter.
             */
            while (nch > 1) 
            {
                  ungetcc(usercmd[--nch]);
            }
      } else
      {
            if (s != NULL)
                  ungetsc(s);
      }
      return action;
}


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