fns.c

/* Random utility Lisp functions.

Copyright (C) 1985-1987, 1993-1995, 1997-2017 Free Software Foundation,
Inc.

This file is part of GNU Emacs.

GNU Emacs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

#include <stdlib.h>
#include <unistd.h>
#include <filevercmp.h>
#include <intprops.h>
#include <vla.h>
#include <errno.h>

#include "lisp.h"
#include "character.h"
#include "coding.h"
#include "composite.h"
#include "buffer.h"
#include "intervals.h"
#include "window.h"
#include "puresize.h"
#include "gnutls.h"

#if defined WINDOWSNT && defined HAVE_GNUTLS3
# define gnutls_rnd w32_gnutls_rnd
#endif

static void sort_vector_copy (Lisp_Object, ptrdiff_t,
			      Lisp_Object *restrict, Lisp_Object *restrict);
enum equal_kind { EQUAL_NO_QUIT, EQUAL_PLAIN, EQUAL_INCLUDING_PROPERTIES };
static bool internal_equal (Lisp_Object, Lisp_Object,
			    enum equal_kind, int, Lisp_Object);

DEFUN ("identity", Fidentity, Sidentity, 1, 1, 0,
       doc: /* Return the argument unchanged.  */
       attributes: const)
  (Lisp_Object arg)
{
  return arg;
}

DEFUN ("random", Frandom, Srandom, 0, 1, 0,
       doc: /* Return a pseudo-random number.
All integers representable in Lisp, i.e. between `most-negative-fixnum'
and `most-positive-fixnum', inclusive, are equally likely.

With positive integer LIMIT, return random number in interval [0,LIMIT).
With argument t, set the random number seed from the system's entropy
pool if available, otherwise from less-random volatile data such as the time.
With a string argument, set the seed based on the string's contents.
Other values of LIMIT are ignored.

See Info node `(elisp)Random Numbers' for more details.  */)
  (Lisp_Object limit)
{
  EMACS_INT val;

  if (EQ (limit, Qt))
    init_random ();
  else if (STRINGP (limit))
    seed_random (SSDATA (limit), SBYTES (limit));

  val = get_random ();
  if (INTEGERP (limit) && 0 < XINT (limit))
    while (true)
      {
	/* Return the remainder, except reject the rare case where
	   get_random returns a number so close to INTMASK that the
	   remainder isn't random.  */
	EMACS_INT remainder = val % XINT (limit);
	if (val - remainder <= INTMASK - XINT (limit) + 1)
	  return make_number (remainder);
	val = get_random ();
      }
  return make_number (val);
}

/* Random data-structure functions.  */

DEFUN ("length", Flength, Slength, 1, 1, 0,
       doc: /* Return the length of vector, list or string SEQUENCE.
A byte-code function object is also allowed.
If the string contains multibyte characters, this is not necessarily
the number of bytes in the string; it is the number of characters.
To get the number of bytes, use `string-bytes'.  */)
  (register Lisp_Object sequence)
{
  register Lisp_Object val;

  if (STRINGP (sequence))
    XSETFASTINT (val, SCHARS (sequence));
  else if (VECTORP (sequence))
    XSETFASTINT (val, ASIZE (sequence));
  else if (CHAR_TABLE_P (sequence))
    XSETFASTINT (val, MAX_CHAR);
  else if (BOOL_VECTOR_P (sequence))
    XSETFASTINT (val, bool_vector_size (sequence));
  else if (COMPILEDP (sequence) || RECORDP (sequence))
    XSETFASTINT (val, PVSIZE (sequence));
  else if (CONSP (sequence))
    {
      intptr_t i = 0;
      FOR_EACH_TAIL (sequence)
	i++;
      CHECK_LIST_END (sequence, sequence);
      if (MOST_POSITIVE_FIXNUM < i)
	error ("List too long");
      val = make_number (i);
    }
  else if (NILP (sequence))
    XSETFASTINT (val, 0);
  else
    wrong_type_argument (Qsequencep, sequence);

  return val;
}

DEFUN ("safe-length", Fsafe_length, Ssafe_length, 1, 1, 0,
       doc: /* Return the length of a list, but avoid error or infinite loop.
This function never gets an error.  If LIST is not really a list,
it returns 0.  If LIST is circular, it returns a finite value
which is at least the number of distinct elements.  */)
  (Lisp_Object list)
{
  intptr_t len = 0;
  FOR_EACH_TAIL_SAFE (list)
    len++;
  return make_fixnum_or_float (len);
}

DEFUN ("string-bytes", Fstring_bytes, Sstring_bytes, 1, 1, 0,
       doc: /* Return the number of bytes in STRING.
If STRING is multibyte, this may be greater than the length of STRING.  */)
  (Lisp_Object string)
{
  CHECK_STRING (string);
  return make_number (SBYTES (string));
}

DEFUN ("string-equal", Fstring_equal, Sstring_equal, 2, 2, 0,
       doc: /* Return t if two strings have identical contents.
Case is significant, but text properties are ignored.
Symbols are also allowed; their print names are used instead.  */)
  (register Lisp_Object s1, Lisp_Object s2)
{
  if (SYMBOLP (s1))
    s1 = SYMBOL_NAME (s1);
  if (SYMBOLP (s2))
    s2 = SYMBOL_NAME (s2);
  CHECK_STRING (s1);
  CHECK_STRING (s2);

  if (SCHARS (s1) != SCHARS (s2)
      || SBYTES (s1) != SBYTES (s2)
      || memcmp (SDATA (s1), SDATA (s2), SBYTES (s1)))
    return Qnil;
  return Qt;
}

DEFUN ("compare-strings", Fcompare_strings, Scompare_strings, 6, 7, 0,
       doc: /* Compare the contents of two strings, converting to multibyte if needed.
The arguments START1, END1, START2, and END2, if non-nil, are
positions specifying which parts of STR1 or STR2 to compare.  In
string STR1, compare the part between START1 (inclusive) and END1
\(exclusive).  If START1 is nil, it defaults to 0, the beginning of
the string; if END1 is nil, it defaults to the length of the string.
Likewise, in string STR2, compare the part between START2 and END2.
Like in `substring', negative values are counted from the end.

The strings are compared by the numeric values of their characters.
For instance, STR1 is "less than" STR2 if its first differing
character has a smaller numeric value.  If IGNORE-CASE is non-nil,
characters are converted to upper-case before comparing them.  Unibyte
strings are converted to multibyte for comparison.

The value is t if the strings (or specified portions) match.
If string STR1 is less, the value is a negative number N;
  - 1 - N is the number of characters that match at the beginning.
If string STR1 is greater, the value is a positive number N;
  N - 1 is the number of characters that match at the beginning.  */)
  (Lisp_Object str1, Lisp_Object start1, Lisp_Object end1, Lisp_Object str2,
   Lisp_Object start2, Lisp_Object end2, Lisp_Object ignore_case)
{
  ptrdiff_t from1, to1, from2, to2, i1, i1_byte, i2, i2_byte;

  CHECK_STRING (str1);
  CHECK_STRING (str2);

  /* For backward compatibility, silently bring too-large positive end
     values into range.  */
  if (INTEGERP (end1) && SCHARS (str1) < XINT (end1))
    end1 = make_number (SCHARS (str1));
  if (INTEGERP (end2) && SCHARS (str2) < XINT (end2))
    end2 = make_number (SCHARS (str2));

  validate_subarray (str1, start1, end1, SCHARS (str1), &from1, &to1);
  validate_subarray (str2, start2, end2, SCHARS (str2), &from2, &to2);

  i1 = from1;
  i2 = from2;

  i1_byte = string_char_to_byte (str1, i1);
  i2_byte = string_char_to_byte (str2, i2);

  while (i1 < to1 && i2 < to2)
    {
      /* When we find a mismatch, we must compare the
	 characters, not just the bytes.  */
      int c1, c2;

      FETCH_STRING_CHAR_AS_MULTIBYTE_ADVANCE (c1, str1, i1, i1_byte);
      FETCH_STRING_CHAR_AS_MULTIBYTE_ADVANCE (c2, str2, i2, i2_byte);

      if (c1 == c2)
	continue;

      if (! NILP (ignore_case))
	{
	  c1 = XINT (Fupcase (make_number (c1)));
	  c2 = XINT (Fupcase (make_number (c2)));
	}

      if (c1 == c2)
	continue;

      /* Note that I1 has already been incremented
	 past the character that we are comparing;
	 hence we don't add or subtract 1 here.  */
      if (c1 < c2)
	return make_number (- i1 + from1);
      else
	return make_number (i1 - from1);
    }

  if (i1 < to1)
    return make_number (i1 - from1 + 1);
  if (i2 < to2)
    return make_number (- i1 + from1 - 1);

  return Qt;
}

DEFUN ("string-lessp", Fstring_lessp, Sstring_lessp, 2, 2, 0,
       doc: /* Return non-nil if STRING1 is less than STRING2 in lexicographic order.
Case is significant.
Symbols are also allowed; their print names are used instead.  */)
  (register Lisp_Object string1, Lisp_Object string2)
{
  register ptrdiff_t end;
  register ptrdiff_t i1, i1_byte, i2, i2_byte;

  if (SYMBOLP (string1))
    string1 = SYMBOL_NAME (string1);
  if (SYMBOLP (string2))
    string2 = SYMBOL_NAME (string2);
  CHECK_STRING (string1);
  CHECK_STRING (string2);

  i1 = i1_byte = i2 = i2_byte = 0;

  end = SCHARS (string1);
  if (end > SCHARS (string2))
    end = SCHARS (string2);

  while (i1 < end)
    {
      /* When we find a mismatch, we must compare the
	 characters, not just the bytes.  */
      int c1, c2;

      FETCH_STRING_CHAR_ADVANCE (c1, string1, i1, i1_byte);
      FETCH_STRING_CHAR_ADVANCE (c2, string2, i2, i2_byte);

      if (c1 != c2)
	return c1 < c2 ? Qt : Qnil;
    }
  return i1 < SCHARS (string2) ? Qt : Qnil;
}

DEFUN ("string-version-lessp", Fstring_version_lessp,
       Sstring_version_lessp, 2, 2, 0,
       doc: /* Return non-nil if S1 is less than S2, as version strings.

This function compares version strings S1 and S2:
   1) By prefix lexicographically.
   2) Then by version (similarly to version comparison of Debian's dpkg).
      Leading zeros in version numbers are ignored.
   3) If both prefix and version are equal, compare as ordinary strings.

For example, \"foo2.png\" compares less than \"foo12.png\".
Case is significant.
Symbols are also allowed; their print names are used instead.  */)
  (Lisp_Object string1, Lisp_Object string2)
{
  if (SYMBOLP (string1))
    string1 = SYMBOL_NAME (string1);
  if (SYMBOLP (string2))
    string2 = SYMBOL_NAME (string2);
  CHECK_STRING (string1);
  CHECK_STRING (string2);

  char *p1 = SSDATA (string1);
  char *p2 = SSDATA (string2);
  char *lim1 = p1 + SBYTES (string1);
  char *lim2 = p2 + SBYTES (string2);
  int cmp;

  while ((cmp = filevercmp (p1, p2)) == 0)
    {
      /* If the strings are identical through their first null bytes,
	 skip past identical prefixes and try again.  */
      ptrdiff_t size = strlen (p1) + 1;
      p1 += size;
      p2 += size;
      if (lim1 < p1)
	return lim2 < p2 ? Qnil : Qt;
      if (lim2 < p2)
	return Qnil;
    }

  return cmp < 0 ? Qt : Qnil;
}

DEFUN ("string-collate-lessp", Fstring_collate_lessp, Sstring_collate_lessp, 2, 4, 0,
       doc: /* Return t if first arg string is less than second in collation order.
Symbols are also allowed; their print names are used instead.

This function obeys the conventions for collation order in your
locale settings.  For example, punctuation and whitespace characters
might be considered less significant for sorting:

\(sort \\='("11" "12" "1 1" "1 2" "1.1" "1.2") \\='string-collate-lessp)
  => ("11" "1 1" "1.1" "12" "1 2" "1.2")

The optional argument LOCALE, a string, overrides the setting of your
current locale identifier for collation.  The value is system
dependent; a LOCALE \"en_US.UTF-8\" is applicable on POSIX systems,
while it would be, e.g., \"enu_USA.1252\" on MS-Windows systems.

If IGNORE-CASE is non-nil, characters are converted to lower-case
before comparing them.

To emulate Unicode-compliant collation on MS-Windows systems,
bind `w32-collate-ignore-punctuation' to a non-nil value, since
the codeset part of the locale cannot be \"UTF-8\" on MS-Windows.

If your system does not support a locale environment, this function
behaves like `string-lessp'.  */)
  (Lisp_Object s1, Lisp_Object s2, Lisp_Object locale, Lisp_Object ignore_case)
{
#if defined __STDC_ISO_10646__ || defined WINDOWSNT
  /* Check parameters.  */
  if (SYMBOLP (s1))
    s1 = SYMBOL_NAME (s1);
  if (SYMBOLP (s2))
    s2 = SYMBOL_NAME (s2);
  CHECK_STRING (s1);
  CHECK_STRING (s2);
  if (!NILP (locale))
    CHECK_STRING (locale);

  return (str_collate (s1, s2, locale, ignore_case) < 0) ? Qt : Qnil;

#else  /* !__STDC_ISO_10646__, !WINDOWSNT */
  return Fstring_lessp (s1, s2);
#endif /* !__STDC_ISO_10646__, !WINDOWSNT */
}

DEFUN ("string-collate-equalp", Fstring_collate_equalp, Sstring_collate_equalp, 2, 4, 0,
       doc: /* Return t if two strings have identical contents.
Symbols are also allowed; their print names are used instead.

This function obeys the conventions for collation order in your locale
settings.  For example, characters with different coding points but
the same meaning might be considered as equal, like different grave
accent Unicode characters:

\(string-collate-equalp (string ?\\uFF40) (string ?\\u1FEF))
  => t

The optional argument LOCALE, a string, overrides the setting of your
current locale identifier for collation.  The value is system
dependent; a LOCALE \"en_US.UTF-8\" is applicable on POSIX systems,
while it would be \"enu_USA.1252\" on MS Windows systems.

If IGNORE-CASE is non-nil, characters are converted to lower-case
before comparing them.

To emulate Unicode-compliant collation on MS-Windows systems,
bind `w32-collate-ignore-punctuation' to a non-nil value, since
the codeset part of the locale cannot be \"UTF-8\" on MS-Windows.

If your system does not support a locale environment, this function
behaves like `string-equal'.

Do NOT use this function to compare file names for equality.  */)
  (Lisp_Object s1, Lisp_Object s2, Lisp_Object locale, Lisp_Object ignore_case)
{
#if defined __STDC_ISO_10646__ || defined WINDOWSNT
  /* Check parameters.  */
  if (SYMBOLP (s1))
    s1 = SYMBOL_NAME (s1);
  if (SYMBOLP (s2))
    s2 = SYMBOL_NAME (s2);
  CHECK_STRING (s1);
  CHECK_STRING (s2);
  if (!NILP (locale))
    CHECK_STRING (locale);

  return (str_collate (s1, s2, locale, ignore_case) == 0) ? Qt : Qnil;

#else  /* !__STDC_ISO_10646__, !WINDOWSNT */
  return Fstring_equal (s1, s2);
#endif /* !__STDC_ISO_10646__, !WINDOWSNT */
}

static Lisp_Object concat (ptrdiff_t nargs, Lisp_Object *args,
			   enum Lisp_Type target_type, bool last_special);

/* ARGSUSED */
Lisp_Object
concat2 (Lisp_Object s1, Lisp_Object s2)
{
  return concat (2, ((Lisp_Object []) {s1, s2}), Lisp_String, 0);
}

/* ARGSUSED */
Lisp_Object
concat3 (Lisp_Object s1, Lisp_Object s2, Lisp_Object s3)
{
  return concat (3, ((Lisp_Object []) {s1, s2, s3}), Lisp_String, 0);
}

DEFUN ("append", Fappend, Sappend, 0, MANY, 0,
       doc: /* Concatenate all the arguments and make the result a list.
The result is a list whose elements are the elements of all the arguments.
Each argument may be a list, vector or string.
The last argument is not copied, just used as the tail of the new list.
usage: (append &rest SEQUENCES)  */)
  (ptrdiff_t nargs, Lisp_Object *args)
{
  return concat (nargs, args, Lisp_Cons, 1);
}

DEFUN ("concat", Fconcat, Sconcat, 0, MANY, 0,
       doc: /* Concatenate all the arguments and make the result a string.
The result is a string whose elements are the elements of all the arguments.
Each argument may be a string or a list or vector of characters (integers).
usage: (concat &rest SEQUENCES)  */)
  (ptrdiff_t nargs, Lisp_Object *args)
{
  return concat (nargs, args, Lisp_String, 0);
}

DEFUN ("vconcat", Fvconcat, Svconcat, 0, MANY, 0,
       doc: /* Concatenate all the arguments and make the result a vector.
The result is a vector whose elements are the elements of all the arguments.
Each argument may be a list, vector or string.
usage: (vconcat &rest SEQUENCES)   */)
  (ptrdiff_t nargs, Lisp_Object *args)
{
  return concat (nargs, args, Lisp_Vectorlike, 0);
}


DEFUN ("copy-sequence", Fcopy_sequence, Scopy_sequence, 1, 1, 0,
       doc: /* Return a copy of a list, vector, string, char-table or record.
The elements of a list, vector or record are not copied; they are
shared with the original.  */)
  (Lisp_Object arg)
{
  if (NILP (arg)) return arg;

  if (RECORDP (arg))
    {
      return Frecord (PVSIZE (arg), XVECTOR (arg)->contents);
    }

  if (CHAR_TABLE_P (arg))
    {
      return copy_char_table (arg);
    }

  if (BOOL_VECTOR_P (arg))
    {
      EMACS_INT nbits = bool_vector_size (arg);
      ptrdiff_t nbytes = bool_vector_bytes (nbits);
      Lisp_Object val = make_uninit_bool_vector (nbits);
      memcpy (bool_vector_data (val), bool_vector_data (arg), nbytes);
      return val;
    }

  if (!CONSP (arg) && !VECTORP (arg) && !STRINGP (arg))
    wrong_type_argument (Qsequencep, arg);

  return concat (1, &arg, XTYPE (arg), 0);
}

/* This structure holds information of an argument of `concat' that is
   a string and has text properties to be copied.  */
struct textprop_rec
{
  ptrdiff_t argnum;		/* refer to ARGS (arguments of `concat') */
  ptrdiff_t from;		/* refer to ARGS[argnum] (argument string) */
  ptrdiff_t to;			/* refer to VAL (the target string) */
};

static Lisp_Object
concat (ptrdiff_t nargs, Lisp_Object *args,
	enum Lisp_Type target_type, bool last_special)
{
  Lisp_Object val;
  Lisp_Object tail;
  Lisp_Object this;
  ptrdiff_t toindex;
  ptrdiff_t toindex_byte = 0;
  EMACS_INT result_len;
  EMACS_INT result_len_byte;
  ptrdiff_t argnum;
  Lisp_Object last_tail;
  Lisp_Object prev;
  bool some_multibyte;
  /* When we make a multibyte string, we can't copy text properties
     while concatenating each string because the length of resulting
     string can't be decided until we finish the whole concatenation.
     So, we record strings that have text properties to be copied
     here, and copy the text properties after the concatenation.  */
  struct textprop_rec  *textprops = NULL;
  /* Number of elements in textprops.  */
  ptrdiff_t num_textprops = 0;
  USE_SAFE_ALLOCA;

  tail = Qnil;

  /* In append, the last arg isn't treated like the others */
  if (last_special && nargs > 0)
    {
      nargs--;
      last_tail = args[nargs];
    }
  else
    last_tail = Qnil;

  /* Check each argument.  */
  for (argnum = 0; argnum < nargs; argnum++)
    {
      this = args[argnum];
      if (!(CONSP (this) || NILP (this) || VECTORP (this) || STRINGP (this)
	    || COMPILEDP (this) || BOOL_VECTOR_P (this)))
	wrong_type_argument (Qsequencep, this);
    }

  /* Compute total length in chars of arguments in RESULT_LEN.
     If desired output is a string, also compute length in bytes
     in RESULT_LEN_BYTE, and determine in SOME_MULTIBYTE
     whether the result should be a multibyte string.  */
  result_len_byte = 0;
  result_len = 0;
  some_multibyte = 0;
  for (argnum = 0; argnum < nargs; argnum++)
    {
      EMACS_INT len;
      this = args[argnum];
      len = XFASTINT (Flength (this));
      if (target_type == Lisp_String)
	{
	  /* We must count the number of bytes needed in the string
	     as well as the number of characters.  */
	  ptrdiff_t i;
	  Lisp_Object ch;
	  int c;
	  ptrdiff_t this_len_byte;

	  if (VECTORP (this) || COMPILEDP (this))
	    for (i = 0; i < len; i++)
	      {
		ch = AREF (this, i);
		CHECK_CHARACTER (ch);
		c = XFASTINT (ch);
		this_len_byte = CHAR_BYTES (c);
		if (STRING_BYTES_BOUND - result_len_byte < this_len_byte)
		  string_overflow ();
		result_len_byte += this_len_byte;
		if (! ASCII_CHAR_P (c) && ! CHAR_BYTE8_P (c))
		  some_multibyte = 1;
	      }
	  else if (BOOL_VECTOR_P (this) && bool_vector_size (this) > 0)
	    wrong_type_argument (Qintegerp, Faref (this, make_number (0)));
	  else if (CONSP (this))
	    for (; CONSP (this); this = XCDR (this))
	      {
		ch = XCAR (this);
		CHECK_CHARACTER (ch);
		c = XFASTINT (ch);
		this_len_byte = CHAR_BYTES (c);
		if (STRING_BYTES_BOUND - result_len_byte < this_len_byte)
		  string_overflow ();
		result_len_byte += this_len_byte;
		if (! ASCII_CHAR_P (c) && ! CHAR_BYTE8_P (c))
		  some_multibyte = 1;
	      }
	  else if (STRINGP (this))
	    {
	      if (STRING_MULTIBYTE (this))
		{
		  some_multibyte = 1;
		  this_len_byte = SBYTES (this);
		}
	      else
		this_len_byte = count_size_as_multibyte (SDATA (this),
							 SCHARS (this));
	      if (STRING_BYTES_BOUND - result_len_byte < this_len_byte)
		string_overflow ();
	      result_len_byte += this_len_byte;
	    }
	}

      result_len += len;
      if (MOST_POSITIVE_FIXNUM < result_len)
	memory_full (SIZE_MAX);
    }

  if (! some_multibyte)
    result_len_byte = result_len;

  /* Create the output object.  */
  if (target_type == Lisp_Cons)
    val = Fmake_list (make_number (result_len), Qnil);
  else if (target_type == Lisp_Vectorlike)
    val = Fmake_vector (make_number (result_len), Qnil);
  else if (some_multibyte)
    val = make_uninit_multibyte_string (result_len, result_len_byte);
  else
    val = make_uninit_string (result_len);

  /* In `append', if all but last arg are nil, return last arg.  */
  if (target_type == Lisp_Cons && EQ (val, Qnil))
    return last_tail;

  /* Copy the contents of the args into the result.  */
  if (CONSP (val))
    tail = val, toindex = -1; /* -1 in toindex is flag we are making a list */
  else
    toindex = 0, toindex_byte = 0;

  prev = Qnil;
  if (STRINGP (val))
    SAFE_NALLOCA (textprops, 1, nargs);

  for (argnum = 0; argnum < nargs; argnum++)
    {
      Lisp_Object thislen;
      ptrdiff_t thisleni = 0;
      register ptrdiff_t thisindex = 0;
      register ptrdiff_t thisindex_byte = 0;

      this = args[argnum];
      if (!CONSP (this))
	thislen = Flength (this), thisleni = XINT (thislen);

      /* Between strings of the same kind, copy fast.  */
      if (STRINGP (this) && STRINGP (val)
	  && STRING_MULTIBYTE (this) == some_multibyte)
	{
	  ptrdiff_t thislen_byte = SBYTES (this);

	  memcpy (SDATA (val) + toindex_byte, SDATA (this), SBYTES (this));
	  if (string_intervals (this))
	    {
	      textprops[num_textprops].argnum = argnum;
	      textprops[num_textprops].from = 0;
	      textprops[num_textprops++].to = toindex;
	    }
	  toindex_byte += thislen_byte;
	  toindex += thisleni;
	}
      /* Copy a single-byte string to a multibyte string.  */
      else if (STRINGP (this) && STRINGP (val))
	{
	  if (string_intervals (this))
	    {
	      textprops[num_textprops].argnum = argnum;
	      textprops[num_textprops].from = 0;
	      textprops[num_textprops++].to = toindex;
	    }
	  toindex_byte += copy_text (SDATA (this),
				     SDATA (val) + toindex_byte,
				     SCHARS (this), 0, 1);
	  toindex += thisleni;
	}
      else
	/* Copy element by element.  */
	while (1)
	  {
	    register Lisp_Object elt;

	    /* Fetch next element of `this' arg into `elt', or break if
	       `this' is exhausted. */
	    if (NILP (this)) break;
	    if (CONSP (this))
	      elt = XCAR (this), this = XCDR (this);
	    else if (thisindex >= thisleni)
	      break;
	    else if (STRINGP (this))
	      {
		int c;
		if (STRING_MULTIBYTE (this))
		  FETCH_STRING_CHAR_ADVANCE_NO_CHECK (c, this,
						      thisindex,
						      thisindex_byte);
		else
		  {
		    c = SREF (this, thisindex); thisindex++;
		    if (some_multibyte && !ASCII_CHAR_P (c))
		      c = BYTE8_TO_CHAR (c);
		  }
		XSETFASTINT (elt, c);
	      }
	    else if (BOOL_VECTOR_P (this))
	      {
		elt = bool_vector_ref (this, thisindex);
		thisindex++;
	      }