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/* Coding system handler (conversion, detection, and etc).
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   Copyright (C) 1995, 1997, 1998 Electrotechnical Laboratory, JAPAN.
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   Licensed to the Free Software Foundation.
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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 2, or (at your option)
any later version.
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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.
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You should have received a copy of the GNU General Public License
along with GNU Emacs; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */
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/*** TABLE OF CONTENTS ***

  1. Preamble
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  2. Emacs' internal format (emacs-mule) handlers
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  3. ISO2022 handlers
  4. Shift-JIS and BIG5 handlers
  5. End-of-line handlers
  6. C library functions
  7. Emacs Lisp library functions
  8. Post-amble

*/

/*** GENERAL NOTE on CODING SYSTEM ***

  Coding system is an encoding mechanism of one or more character
  sets.  Here's a list of coding systems which Emacs can handle.  When
  we say "decode", it means converting some other coding system to
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  Emacs' internal format (emacs-internal), and when we say "encode",
  it means converting the coding system emacs-mule to some other
  coding system.
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  0. Emacs' internal format (emacs-mule)
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  Emacs itself holds a multi-lingual character in a buffer and a string
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  in a special format.  Details are described in section 2.
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  1. ISO2022

  The most famous coding system for multiple character sets.  X's
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  Compound Text, various EUCs (Extended Unix Code), and coding
  systems used in Internet communication such as ISO-2022-JP are
  all variants of ISO2022.  Details are described in section 3.
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  2. SJIS (or Shift-JIS or MS-Kanji-Code)
   
  A coding system to encode character sets: ASCII, JISX0201, and
  JISX0208.  Widely used for PC's in Japan.  Details are described in
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  section 4.
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  3. BIG5

  A coding system to encode character sets: ASCII and Big5.  Widely
  used by Chinese (mainly in Taiwan and Hong Kong).  Details are
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  described in section 4.  In this file, when we write "BIG5"
  (all uppercase), we mean the coding system, and when we write
  "Big5" (capitalized), we mean the character set.
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  4. Raw text

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  A coding system for a text containing random 8-bit code.  Emacs does
  no code conversion on such a text except for end-of-line format.
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  5. Other
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  If a user wants to read/write a text encoded in a coding system not
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  listed above, he can supply a decoder and an encoder for it in CCL
  (Code Conversion Language) programs.  Emacs executes the CCL program
  while reading/writing.

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  Emacs represents a coding system by a Lisp symbol that has a property
  `coding-system'.  But, before actually using the coding system, the
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  information about it is set in a structure of type `struct
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  coding_system' for rapid processing.  See section 6 for more details.
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*/

/*** GENERAL NOTES on END-OF-LINE FORMAT ***

  How end-of-line of a text is encoded depends on a system.  For
  instance, Unix's format is just one byte of `line-feed' code,
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  whereas DOS's format is two-byte sequence of `carriage-return' and
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  `line-feed' codes.  MacOS's format is usually one byte of
  `carriage-return'.
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  Since text characters encoding and end-of-line encoding are
  independent, any coding system described above can take
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  any format of end-of-line.  So, Emacs has information of format of
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  end-of-line in each coding-system.  See section 6 for more details.
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*/

/*** GENERAL NOTES on `detect_coding_XXX ()' functions ***

  These functions check if a text between SRC and SRC_END is encoded
  in the coding system category XXX.  Each returns an integer value in
  which appropriate flag bits for the category XXX is set.  The flag
  bits are defined in macros CODING_CATEGORY_MASK_XXX.  Below is the
  template of these functions.  */
#if 0
int
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detect_coding_emacs_mule (src, src_end)
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     unsigned char *src, *src_end;
{
  ...
}
#endif

/*** GENERAL NOTES on `decode_coding_XXX ()' functions ***

  These functions decode SRC_BYTES length text at SOURCE encoded in
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  CODING to Emacs' internal format (emacs-mule).  The resulting text
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  goes to a place pointed to by DESTINATION, the length of which
  should not exceed DST_BYTES.  These functions set the information of
  original and decoded texts in the members produced, produced_char,
  consumed, and consumed_char of the structure *CODING.

  The return value is an integer (CODING_FINISH_XXX) indicating how
  the decoding finished.

  DST_BYTES zero means that source area and destination area are
  overlapped, which means that we can produce a decoded text until it
  reaches at the head of not-yet-decoded source text.

  Below is a template of these functions.  */
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#if 0
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decode_coding_XXX (coding, source, destination, src_bytes, dst_bytes)
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     struct coding_system *coding;
     unsigned char *source, *destination;
     int src_bytes, dst_bytes;
{
  ...
}
#endif

/*** GENERAL NOTES on `encode_coding_XXX ()' functions ***

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  These functions encode SRC_BYTES length text at SOURCE of Emacs'
  internal format (emacs-mule) to CODING.  The resulting text goes to
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  a place pointed to by DESTINATION, the length of which should not
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  exceed DST_BYTES.  These functions set the information of
  original and encoded texts in the members produced, produced_char,
  consumed, and consumed_char of the structure *CODING.

  The return value is an integer (CODING_FINISH_XXX) indicating how
  the encoding finished.

  DST_BYTES zero means that source area and destination area are
  overlapped, which means that we can produce a decoded text until it
  reaches at the head of not-yet-decoded source text.

  Below is a template of these functions.  */
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#if 0
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encode_coding_XXX (coding, source, destination, src_bytes, dst_bytes)
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     struct coding_system *coding;
     unsigned char *source, *destination;
     int src_bytes, dst_bytes;
{
  ...
}
#endif

/*** COMMONLY USED MACROS ***/

/* The following three macros ONE_MORE_BYTE, TWO_MORE_BYTES, and
   THREE_MORE_BYTES safely get one, two, and three bytes from the
   source text respectively.  If there are not enough bytes in the
   source, they jump to `label_end_of_loop'.  The caller should set
   variables `src' and `src_end' to appropriate areas in advance.  */

#define ONE_MORE_BYTE(c1)   	\
  do {			     	\
    if (src < src_end)	     	\
      c1 = *src++;	     	\
    else		     	\
      goto label_end_of_loop;	\
  } while (0)

#define TWO_MORE_BYTES(c1, c2) 	\
  do {			       	\
    if (src + 1 < src_end)     	\
      c1 = *src++, c2 = *src++;	\
    else		       	\
      goto label_end_of_loop;  	\
  } while (0)

#define THREE_MORE_BYTES(c1, c2, c3)	    	\
  do {					    	\
    if (src + 2 < src_end)		    	\
      c1 = *src++, c2 = *src++, c3 = *src++;	\
    else				    	\
      goto label_end_of_loop;		    	\
  } while (0)

/* The following three macros DECODE_CHARACTER_ASCII,
   DECODE_CHARACTER_DIMENSION1, and DECODE_CHARACTER_DIMENSION2 put
   the multi-byte form of a character of each class at the place
   pointed by `dst'.  The caller should set the variable `dst' to
   point to an appropriate area and the variable `coding' to point to
   the coding-system of the currently decoding text in advance.  */

/* Decode one ASCII character C.  */

#define DECODE_CHARACTER_ASCII(c)				\
  do {								\
    if (COMPOSING_P (coding->composing))			\
      *dst++ = 0xA0, *dst++ = (c) | 0x80;			\
    else							\
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      {								\
	*dst++ = (c);						\
	coding->produced_char++;				\
      }								\
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  } while (0)

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/* Decode one DIMENSION1 character whose charset is CHARSET and whose
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   position-code is C.  */

#define DECODE_CHARACTER_DIMENSION1(charset, c)				\
  do {									\
    unsigned char leading_code = CHARSET_LEADING_CODE_BASE (charset);	\
    if (COMPOSING_P (coding->composing))				\
      *dst++ = leading_code + 0x20;					\
    else								\
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      {									\
	*dst++ = leading_code;						\
	coding->produced_char++;					\
      }									\
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    if (leading_code = CHARSET_LEADING_CODE_EXT (charset))		\
      *dst++ = leading_code;						\
    *dst++ = (c) | 0x80;						\
  } while (0)

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/* Decode one DIMENSION2 character whose charset is CHARSET and whose
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   position-codes are C1 and C2.  */

#define DECODE_CHARACTER_DIMENSION2(charset, c1, c2)	\
  do {							\
    DECODE_CHARACTER_DIMENSION1 (charset, c1);		\
    *dst++ = (c2) | 0x80;				\
  } while (0)


/*** 1. Preamble ***/

#include <stdio.h>

#ifdef emacs

#include <config.h>
#include "lisp.h"
#include "buffer.h"
#include "charset.h"
#include "ccl.h"
#include "coding.h"
#include "window.h"

#else  /* not emacs */

#include "mulelib.h"

#endif /* not emacs */

Lisp_Object Qcoding_system, Qeol_type;
Lisp_Object Qbuffer_file_coding_system;
Lisp_Object Qpost_read_conversion, Qpre_write_conversion;
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Lisp_Object Qno_conversion, Qundecided;
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Lisp_Object Qcoding_system_history;
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Lisp_Object Qsafe_charsets;
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extern Lisp_Object Qinsert_file_contents, Qwrite_region;
Lisp_Object Qcall_process, Qcall_process_region, Qprocess_argument;
Lisp_Object Qstart_process, Qopen_network_stream;
Lisp_Object Qtarget_idx;

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Lisp_Object Vselect_safe_coding_system_function;

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/* Mnemonic character of each format of end-of-line.  */
int eol_mnemonic_unix, eol_mnemonic_dos, eol_mnemonic_mac;
/* Mnemonic character to indicate format of end-of-line is not yet
   decided.  */
int eol_mnemonic_undecided;

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/* Format of end-of-line decided by system.  This is CODING_EOL_LF on
   Unix, CODING_EOL_CRLF on DOS/Windows, and CODING_EOL_CR on Mac.  */
int system_eol_type;

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#ifdef emacs

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Lisp_Object Vcoding_system_list, Vcoding_system_alist;

Lisp_Object Qcoding_system_p, Qcoding_system_error;
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/* Coding system emacs-mule and raw-text are for converting only
   end-of-line format.  */
Lisp_Object Qemacs_mule, Qraw_text;
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/* Coding-systems are handed between Emacs Lisp programs and C internal
   routines by the following three variables.  */
/* Coding-system for reading files and receiving data from process.  */
Lisp_Object Vcoding_system_for_read;
/* Coding-system for writing files and sending data to process.  */
Lisp_Object Vcoding_system_for_write;
/* Coding-system actually used in the latest I/O.  */
Lisp_Object Vlast_coding_system_used;

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/* A vector of length 256 which contains information about special
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   Latin codes (espepcially for dealing with Microsoft code).  */
Lisp_Object Vlatin_extra_code_table;
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/* Flag to inhibit code conversion of end-of-line format.  */
int inhibit_eol_conversion;

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/* Flag to make buffer-file-coding-system inherit from process-coding.  */
int inherit_process_coding_system;

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/* Coding system to be used to encode text for terminal display.  */
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struct coding_system terminal_coding;

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/* Coding system to be used to encode text for terminal display when
   terminal coding system is nil.  */
struct coding_system safe_terminal_coding;

/* Coding system of what is sent from terminal keyboard.  */
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struct coding_system keyboard_coding;

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Lisp_Object Vfile_coding_system_alist;
Lisp_Object Vprocess_coding_system_alist;
Lisp_Object Vnetwork_coding_system_alist;
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#endif /* emacs */

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Lisp_Object Qcoding_category, Qcoding_category_index;
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/* List of symbols `coding-category-xxx' ordered by priority.  */
Lisp_Object Vcoding_category_list;

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/* Table of coding categories (Lisp symbols).  */
Lisp_Object Vcoding_category_table;
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/* Table of names of symbol for each coding-category.  */
char *coding_category_name[CODING_CATEGORY_IDX_MAX] = {
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  "coding-category-emacs-mule",
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  "coding-category-sjis",
  "coding-category-iso-7",
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  "coding-category-iso-7-tight",
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  "coding-category-iso-8-1",
  "coding-category-iso-8-2",
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  "coding-category-iso-7-else",
  "coding-category-iso-8-else",
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  "coding-category-big5",
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  "coding-category-raw-text",
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  "coding-category-binary"
};

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/* Table pointers to coding systems corresponding to each coding
   categories.  */
struct coding_system *coding_system_table[CODING_CATEGORY_IDX_MAX];

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/* Flag to tell if we look up character translation table on character
   code conversion.  */
Lisp_Object Venable_character_translation;
/* Standard character translation table to look up on decoding (reading).  */
Lisp_Object Vstandard_character_translation_table_for_decode;
/* Standard character translation table to look up on encoding (writing).  */
Lisp_Object Vstandard_character_translation_table_for_encode;

Lisp_Object Qcharacter_translation_table;
Lisp_Object Qcharacter_translation_table_id;
Lisp_Object Qcharacter_translation_table_for_decode;
Lisp_Object Qcharacter_translation_table_for_encode;
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/* Alist of charsets vs revision number.  */
Lisp_Object Vcharset_revision_alist;

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/* Default coding systems used for process I/O.  */
Lisp_Object Vdefault_process_coding_system;

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/*** 2. Emacs internal format (emacs-mule) handlers ***/
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/* Emacs' internal format for encoding multiple character sets is a
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   kind of multi-byte encoding, i.e. characters are encoded by
   variable-length sequences of one-byte codes.  ASCII characters
   and control characters (e.g. `tab', `newline') are represented by
   one-byte sequences which are their ASCII codes, in the range 0x00
   through 0x7F.  The other characters are represented by a sequence
   of `base leading-code', optional `extended leading-code', and one
   or two `position-code's.  The length of the sequence is determined
   by the base leading-code.  Leading-code takes the range 0x80
   through 0x9F, whereas extended leading-code and position-code take
   the range 0xA0 through 0xFF.  See `charset.h' for more details
   about leading-code and position-code.

   There's one exception to this rule.  Special leading-code
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   `leading-code-composition' denotes that the following several
   characters should be composed into one character.  Leading-codes of
   components (except for ASCII) are added 0x20.  An ASCII character
   component is represented by a 2-byte sequence of `0xA0' and
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   `ASCII-code + 0x80'.  See also the comments in `charset.h' for the
   details of composite character.  Hence, we can summarize the code
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   range as follows:

   --- CODE RANGE of Emacs' internal format ---
   (character set)	(range)
   ASCII		0x00 .. 0x7F
   ELSE (1st byte)	0x80 .. 0x9F
	(rest bytes)	0xA0 .. 0xFF
   ---------------------------------------------

  */

enum emacs_code_class_type emacs_code_class[256];

/* Go to the next statement only if *SRC is accessible and the code is
   greater than 0xA0.  */
#define CHECK_CODE_RANGE_A0_FF 	\
  do {			       	\
    if (src >= src_end)	       	\
      goto label_end_of_switch;	\
    else if (*src++ < 0xA0)    	\
      return 0;		       	\
  } while (0)

/* See the above "GENERAL NOTES on `detect_coding_XXX ()' functions".
   Check if a text is encoded in Emacs' internal format.  If it is,
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   return CODING_CATEGORY_MASK_EMACS_MULE, else return 0.  */
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int
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detect_coding_emacs_mule (src, src_end)
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     unsigned char *src, *src_end;
{
  unsigned char c;
  int composing = 0;

  while (src < src_end)
    {
      c = *src++;

      if (composing)
	{
	  if (c < 0xA0)
	    composing = 0;
	  else
	    c -= 0x20;
	}

      switch (emacs_code_class[c])
	{
	case EMACS_ascii_code:
	case EMACS_linefeed_code:
	  break;

	case EMACS_control_code:
	  if (c == ISO_CODE_ESC || c == ISO_CODE_SI || c == ISO_CODE_SO)
	    return 0;
	  break;

	case EMACS_invalid_code:
	  return 0;

	case EMACS_leading_code_composition: /* c == 0x80 */
	  if (composing)
	    CHECK_CODE_RANGE_A0_FF;
	  else
	    composing = 1;
	  break;

	case EMACS_leading_code_4:
	  CHECK_CODE_RANGE_A0_FF;
	  /* fall down to check it two more times ...  */

	case EMACS_leading_code_3:
	  CHECK_CODE_RANGE_A0_FF;
	  /* fall down to check it one more time ...  */

	case EMACS_leading_code_2:
	  CHECK_CODE_RANGE_A0_FF;
	  break;

	default:
	label_end_of_switch:
	  break;
	}
    }
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  return CODING_CATEGORY_MASK_EMACS_MULE;
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}


/*** 3. ISO2022 handlers ***/

/* The following note describes the coding system ISO2022 briefly.
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   Since the intention of this note is to help in understanding of
   the programs in this file, some parts are NOT ACCURATE or OVERLY
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   SIMPLIFIED.  For the thorough understanding, please refer to the
   original document of ISO2022.

   ISO2022 provides many mechanisms to encode several character sets
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   in 7-bit and 8-bit environment.  If one chooses 7-bite environment,
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   all text is encoded by codes of less than 128.  This may make the
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   encoded text a little bit longer, but the text gets more stability
   to pass through several gateways (some of them strip off the MSB).
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   There are two kinds of character set: control character set and
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   graphic character set.  The former contains control characters such
   as `newline' and `escape' to provide control functions (control
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   functions are provided also by escape sequences).  The latter
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   contains graphic characters such as ' A' and '-'.  Emacs recognizes
   two control character sets and many graphic character sets.

   Graphic character sets are classified into one of the following
   four classes, DIMENSION1_CHARS94, DIMENSION1_CHARS96,
   DIMENSION2_CHARS94, DIMENSION2_CHARS96 according to the number of
   bytes (DIMENSION) and the number of characters in one dimension
   (CHARS) of the set.  In addition, each character set is assigned an
   identification tag (called "final character" and denoted as <F>
   here after) which is unique in each class.  <F> of each character
   set is decided by ECMA(*) when it is registered in ISO.  Code range
   of <F> is 0x30..0x7F (0x30..0x3F are for private use only).

   Note (*): ECMA = European Computer Manufacturers Association

   Here are examples of graphic character set [NAME(<F>)]:
	o DIMENSION1_CHARS94 -- ASCII('B'), right-half-of-JISX0201('I'), ...
	o DIMENSION1_CHARS96 -- right-half-of-ISO8859-1('A'), ...
	o DIMENSION2_CHARS94 -- GB2312('A'), JISX0208('B'), ...
	o DIMENSION2_CHARS96 -- none for the moment

   A code area (1byte=8bits) is divided into 4 areas, C0, GL, C1, and GR.
	C0 [0x00..0x1F] -- control character plane 0
	GL [0x20..0x7F] -- graphic character plane 0
	C1 [0x80..0x9F] -- control character plane 1
	GR [0xA0..0xFF] -- graphic character plane 1

   A control character set is directly designated and invoked to C0 or
   C1 by an escape sequence.  The most common case is that ISO646's
   control character set is designated/invoked to C0 and ISO6429's
   control character set is designated/invoked to C1, and usually
   these designations/invocations are omitted in a coded text.  With
   7-bit environment, only C0 can be used, and a control character for
   C1 is encoded by an appropriate escape sequence to fit in the
   environment.  All control characters for C1 are defined the
   corresponding escape sequences.

   A graphic character set is at first designated to one of four
   graphic registers (G0 through G3), then these graphic registers are
   invoked to GL or GR.  These designations and invocations can be
   done independently.  The most common case is that G0 is invoked to
   GL, G1 is invoked to GR, and ASCII is designated to G0, and usually
   these invocations and designations are omitted in a coded text.
   With 7-bit environment, only GL can be used.

   When a graphic character set of CHARS94 is invoked to GL, code 0x20
   and 0x7F of GL area work as control characters SPACE and DEL
   respectively, and code 0xA0 and 0xFF of GR area should not be used.

   There are two ways of invocation: locking-shift and single-shift.
   With locking-shift, the invocation lasts until the next different
   invocation, whereas with single-shift, the invocation works only
   for the following character and doesn't affect locking-shift.
   Invocations are done by the following control characters or escape
   sequences.

   ----------------------------------------------------------------------
   function		control char	escape sequence	description
   ----------------------------------------------------------------------
   SI  (shift-in)		0x0F	none		invoke G0 to GL
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   SO  (shift-out)		0x0E	none		invoke G1 to GL
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   LS2 (locking-shift-2)	none	ESC 'n'		invoke G2 into GL
   LS3 (locking-shift-3)	none	ESC 'o'		invoke G3 into GL
   SS2 (single-shift-2)		0x8E	ESC 'N'		invoke G2 into GL
   SS3 (single-shift-3)		0x8F	ESC 'O'		invoke G3 into GL
   ----------------------------------------------------------------------
   The first four are for locking-shift.  Control characters for these
   functions are defined by macros ISO_CODE_XXX in `coding.h'.

   Designations are done by the following escape sequences.
   ----------------------------------------------------------------------
   escape sequence	description
   ----------------------------------------------------------------------
   ESC '(' <F>		designate DIMENSION1_CHARS94<F> to G0
   ESC ')' <F>		designate DIMENSION1_CHARS94<F> to G1
   ESC '*' <F>		designate DIMENSION1_CHARS94<F> to G2
   ESC '+' <F>		designate DIMENSION1_CHARS94<F> to G3
   ESC ',' <F>		designate DIMENSION1_CHARS96<F> to G0 (*)
   ESC '-' <F>		designate DIMENSION1_CHARS96<F> to G1
   ESC '.' <F>		designate DIMENSION1_CHARS96<F> to G2
   ESC '/' <F>		designate DIMENSION1_CHARS96<F> to G3
   ESC '$' '(' <F>	designate DIMENSION2_CHARS94<F> to G0 (**)
   ESC '$' ')' <F>	designate DIMENSION2_CHARS94<F> to G1
   ESC '$' '*' <F>	designate DIMENSION2_CHARS94<F> to G2
   ESC '$' '+' <F>	designate DIMENSION2_CHARS94<F> to G3
   ESC '$' ',' <F>	designate DIMENSION2_CHARS96<F> to G0 (*)
   ESC '$' '-' <F>	designate DIMENSION2_CHARS96<F> to G1
   ESC '$' '.' <F>	designate DIMENSION2_CHARS96<F> to G2
   ESC '$' '/' <F>	designate DIMENSION2_CHARS96<F> to G3
   ----------------------------------------------------------------------

   In this list, "DIMENSION1_CHARS94<F>" means a graphic character set
   of dimension 1, chars 94, and final character <F>, and etc.

   Note (*): Although these designations are not allowed in ISO2022,
   Emacs accepts them on decoding, and produces them on encoding
   CHARS96 character set in a coding system which is characterized as
   7-bit environment, non-locking-shift, and non-single-shift.

   Note (**): If <F> is '@', 'A', or 'B', the intermediate character
   '(' can be omitted.  We call this as "short-form" here after.

   Now you may notice that there are a lot of ways for encoding the
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   same multilingual text in ISO2022.  Actually, there exists many
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   coding systems such as Compound Text (used in X's inter client
   communication, ISO-2022-JP (used in Japanese Internet), ISO-2022-KR
   (used in Korean Internet), EUC (Extended UNIX Code, used in Asian
   localized platforms), and all of these are variants of ISO2022.

   In addition to the above, Emacs handles two more kinds of escape
   sequences: ISO6429's direction specification and Emacs' private
   sequence for specifying character composition.

   ISO6429's direction specification takes the following format:
	o CSI ']'      -- end of the current direction
	o CSI '0' ']'  -- end of the current direction
	o CSI '1' ']'  -- start of left-to-right text
	o CSI '2' ']'  -- start of right-to-left text
   The control character CSI (0x9B: control sequence introducer) is
   abbreviated to the escape sequence ESC '[' in 7-bit environment.
   
   Character composition specification takes the following format:
	o ESC '0' -- start character composition
	o ESC '1' -- end character composition
   Since these are not standard escape sequences of any ISO, the use
   of them for these meaning is restricted to Emacs only.  */

enum iso_code_class_type iso_code_class[256];

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#define CHARSET_OK(idx, charset)			\
  (coding_system_table[idx]->safe_charsets[charset]	\
   || (CODING_SPEC_ISO_REQUESTED_DESIGNATION		\
       (coding_system_table[idx], charset)		\
       != CODING_SPEC_ISO_NO_REQUESTED_DESIGNATION))
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#define SHIFT_OUT_OK(idx) \
  (CODING_SPEC_ISO_INITIAL_DESIGNATION (coding_system_table[idx], 1) >= 0)

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/* See the above "GENERAL NOTES on `detect_coding_XXX ()' functions".
   Check if a text is encoded in ISO2022.  If it is, returns an
   integer in which appropriate flag bits any of:
	CODING_CATEGORY_MASK_ISO_7
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	CODING_CATEGORY_MASK_ISO_7_TIGHT
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	CODING_CATEGORY_MASK_ISO_8_1
	CODING_CATEGORY_MASK_ISO_8_2
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	CODING_CATEGORY_MASK_ISO_7_ELSE
	CODING_CATEGORY_MASK_ISO_8_ELSE
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   are set.  If a code which should never appear in ISO2022 is found,
   returns 0.  */

int
detect_coding_iso2022 (src, src_end)
     unsigned char *src, *src_end;
{
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  int mask = CODING_CATEGORY_MASK_ISO;
  int mask_found = 0;
  int reg[4], shift_out = 0;
  int c, c1, i, charset;
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  reg[0] = CHARSET_ASCII, reg[1] = reg[2] = reg[3] = -1;
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  while (mask && src < src_end)
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    {
      c = *src++;
      switch (c)
	{
	case ISO_CODE_ESC:
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	  if (src >= src_end)
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	    break;
	  c = *src++;
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	  if (c >= '(' && c <= '/')
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	    {
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	      /* Designation sequence for a charset of dimension 1.  */
	      if (src >= src_end)
		break;
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	      c1 = *src++;
	      if (c1 < ' ' || c1 >= 0x80
		  || (charset = iso_charset_table[0][c >= ','][c1]) < 0)
		/* Invalid designation sequence.  Just ignore.  */
		break;
	      reg[(c - '(') % 4] = charset;
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	    }
	  else if (c == '$')
	    {
	      /* Designation sequence for a charset of dimension 2.  */
	      if (src >= src_end)
		break;
	      c = *src++;
	      if (c >= '@' && c <= 'B')
		/* Designation for JISX0208.1978, GB2312, or JISX0208.  */
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		reg[0] = charset = iso_charset_table[1][0][c];
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	      else if (c >= '(' && c <= '/')
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		{
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		  if (src >= src_end)
		    break;
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		  c1 = *src++;
		  if (c1 < ' ' || c1 >= 0x80
		      || (charset = iso_charset_table[1][c >= ','][c1]) < 0)
		    /* Invalid designation sequence.  Just ignore.  */
		    break;
		  reg[(c - '(') % 4] = charset;
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		}
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	      else
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		/* Invalid designation sequence.  Just ignore.  */
		break;
	    }
	  else if (c == 'N' || c == 'n')
	    {
	      if (shift_out == 0
		  && (reg[1] >= 0
		      || SHIFT_OUT_OK (CODING_CATEGORY_IDX_ISO_7_ELSE)
		      || SHIFT_OUT_OK (CODING_CATEGORY_IDX_ISO_8_ELSE)))
		{
		  /* Locking shift out.  */
		  mask &= ~CODING_CATEGORY_MASK_ISO_7BIT;
		  mask_found |= CODING_CATEGORY_MASK_ISO_SHIFT;
		  shift_out = 1;
		}
	      break;
	    }
	  else if (c == 'O' || c == 'o')
	    {
	      if (shift_out == 1)
		{
		  /* Locking shift in.  */
		  mask &= ~CODING_CATEGORY_MASK_ISO_7BIT;
		  mask_found |= CODING_CATEGORY_MASK_ISO_SHIFT;
		  shift_out = 0;
		}
	      break;
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	    }
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	  else if (c == '0' || c == '1' || c == '2')
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	    /* Start/end composition.  Just ignore.  */
	    break;
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	  else
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	    /* Invalid escape sequence.  Just ignore.  */
	    break;

	  /* We found a valid designation sequence for CHARSET.  */
	  mask &= ~CODING_CATEGORY_MASK_ISO_8BIT;
	  if (CHARSET_OK (CODING_CATEGORY_IDX_ISO_7, charset))
	    mask_found |= CODING_CATEGORY_MASK_ISO_7;
	  else
	    mask &= ~CODING_CATEGORY_MASK_ISO_7;
	  if (CHARSET_OK (CODING_CATEGORY_IDX_ISO_7_TIGHT, charset))
	    mask_found |= CODING_CATEGORY_MASK_ISO_7_TIGHT;
	  else
	    mask &= ~CODING_CATEGORY_MASK_ISO_7_TIGHT;
	  if (! CHARSET_OK (CODING_CATEGORY_IDX_ISO_7_ELSE, charset))
	    mask &= ~CODING_CATEGORY_MASK_ISO_7_ELSE;
	  if (! CHARSET_OK (CODING_CATEGORY_IDX_ISO_8_ELSE, charset))
	    mask &= ~CODING_CATEGORY_MASK_ISO_8_ELSE;
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	  break;

	case ISO_CODE_SO:
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	  if (shift_out == 0
	      && (reg[1] >= 0
		  || SHIFT_OUT_OK (CODING_CATEGORY_IDX_ISO_7_ELSE)
		  || SHIFT_OUT_OK (CODING_CATEGORY_IDX_ISO_8_ELSE)))
	    {
	      /* Locking shift out.  */
	      mask &= ~CODING_CATEGORY_MASK_ISO_7BIT;
	      mask_found |= CODING_CATEGORY_MASK_ISO_SHIFT;
	    }
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	  break;
	  
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	case ISO_CODE_SI:
	  if (shift_out == 1)
	    {
	      /* Locking shift in.  */
	      mask &= ~CODING_CATEGORY_MASK_ISO_7BIT;
	      mask_found |= CODING_CATEGORY_MASK_ISO_SHIFT;
	    }
	  break;

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	case ISO_CODE_CSI:
	case ISO_CODE_SS2:
	case ISO_CODE_SS3:
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	  {
	    int newmask = CODING_CATEGORY_MASK_ISO_8_ELSE;

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	    if (c != ISO_CODE_CSI)
	      {
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		if (coding_system_table[CODING_CATEGORY_IDX_ISO_8_1]->flags
		    & CODING_FLAG_ISO_SINGLE_SHIFT)
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		  newmask |= CODING_CATEGORY_MASK_ISO_8_1;
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		if (coding_system_table[CODING_CATEGORY_IDX_ISO_8_2]->flags
		    & CODING_FLAG_ISO_SINGLE_SHIFT)
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		  newmask |= CODING_CATEGORY_MASK_ISO_8_2;
	      }
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	    if (VECTORP (Vlatin_extra_code_table)
		&& !NILP (XVECTOR (Vlatin_extra_code_table)->contents[c]))
	      {
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		if (coding_system_table[CODING_CATEGORY_IDX_ISO_8_1]->flags
		    & CODING_FLAG_ISO_LATIN_EXTRA)
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		  newmask |= CODING_CATEGORY_MASK_ISO_8_1;
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		if (coding_system_table[CODING_CATEGORY_IDX_ISO_8_2]->flags
		    & CODING_FLAG_ISO_LATIN_EXTRA)
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		  newmask |= CODING_CATEGORY_MASK_ISO_8_2;
	      }
	    mask &= newmask;
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	    mask_found |= newmask;
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	  }
	  break;
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	default:
	  if (c < 0x80)
	    break;
	  else if (c < 0xA0)
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	    {
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	      if (VECTORP (Vlatin_extra_code_table)
		  && !NILP (XVECTOR (Vlatin_extra_code_table)->contents[c]))
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		{
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		  int newmask = 0;

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		  if (coding_system_table[CODING_CATEGORY_IDX_ISO_8_1]->flags
		      & CODING_FLAG_ISO_LATIN_EXTRA)
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		    newmask |= CODING_CATEGORY_MASK_ISO_8_1;
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		  if (coding_system_table[CODING_CATEGORY_IDX_ISO_8_2]->flags
		      & CODING_FLAG_ISO_LATIN_EXTRA)
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		    newmask |= CODING_CATEGORY_MASK_ISO_8_2;
		  mask &= newmask;
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		  mask_found |= newmask;
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		}
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	      else
		return 0;
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	    }
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	  else
	    {
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	      unsigned char *src_begin = src;
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	      mask &= ~(CODING_CATEGORY_MASK_ISO_7BIT
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			| CODING_CATEGORY_MASK_ISO_7_ELSE);
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	      mask_found |= CODING_CATEGORY_MASK_ISO_8_1;
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	      while (src < src_end && *src >= 0xA0)
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		src++;
	      if ((src - src_begin - 1) & 1 && src < src_end)
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		mask &= ~CODING_CATEGORY_MASK_ISO_8_2;
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	      else
		mask_found |= CODING_CATEGORY_MASK_ISO_8_2;
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	    }
	  break;
	}
    }

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  return (mask & mask_found);
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}

/* Decode a character of which charset is CHARSET and the 1st position
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   code is C1.  If dimension of CHARSET is 2, the 2nd position code is
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   fetched from SRC and set to C2.  If CHARSET is negative, it means
   that we are decoding ill formed text, and what we can do is just to
   read C1 as is.  */

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#define DECODE_ISO_CHARACTER(charset, c1)				\
  do {									\
    int c_alt, charset_alt = (charset);					\
    if (COMPOSING_HEAD_P (coding->composing))				\
      {									\
	*dst++ = LEADING_CODE_COMPOSITION;				\
	if (COMPOSING_WITH_RULE_P (coding->composing))			\
	  /* To tell composition rules are embeded.  */			\
	  *dst++ = 0xFF;						\
	coding->composing += 2;						\
      }									\
    if ((charset) >= 0)							\
      {									\
	if (CHARSET_DIMENSION (charset) == 2)				\
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	  {								\
	    ONE_MORE_BYTE (c2);						\
	    if (iso_code_class[(c2) & 0x7F] != ISO_0x20_or_0x7F		\
		&& iso_code_class[(c2) & 0x7F] != ISO_graphic_plane_0)	\
	      {								\
		src--;							\
		c2 = ' ';						\
	      }								\
	  }								\
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	if (!NILP (translation_table)					\
	    && ((c_alt = translate_char (translation_table,		\
					 -1, (charset), c1, c2)) >= 0))	\
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	  SPLIT_CHAR (c_alt, charset_alt, c1, c2);			\
      }									\
    if (charset_alt == CHARSET_ASCII || charset_alt < 0)		\
      DECODE_CHARACTER_ASCII (c1);					\
    else if (CHARSET_DIMENSION (charset_alt) == 1)			\
      DECODE_CHARACTER_DIMENSION1 (charset_alt, c1);			\
    else								\
      DECODE_CHARACTER_DIMENSION2 (charset_alt, c1, c2);		\
    if (COMPOSING_WITH_RULE_P (coding->composing))			\
      /* To tell a composition rule follows.  */			\
      coding->composing = COMPOSING_WITH_RULE_RULE;			\
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  } while (0)

/* Set designation state into CODING.  */
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#define DECODE_DESIGNATION(reg, dimension, chars, final_char)		   \
  do {									   \
    int charset = ISO_CHARSET_TABLE (make_number (dimension),		   \
				     make_number (chars),		   \
				     make_number (final_char));		   \
    if (charset >= 0							   \
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	&& (CODING_SPEC_ISO_REQUESTED_DESIGNATION (coding, charset) == reg \
	    || coding->safe_charsets[charset]))				   \
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      {									   \
	if (coding->spec.iso2022.last_invalid_designation_register == 0	   \
	    && reg == 0							   \
	    && charset == CHARSET_ASCII)				   \
	  {								   \
	    /* We should insert this designation sequence as is so	   \
               that it is surely written back to a file.  */		   \
	    coding->spec.iso2022.last_invalid_designation_register = -1;   \
	    goto label_invalid_code;					   \
	  }								   \
	coding->spec.iso2022.last_invalid_designation_register = -1;	   \
        if ((coding->mode & CODING_MODE_DIRECTION)			   \
	    && CHARSET_REVERSE_CHARSET (charset) >= 0)			   \
          charset = CHARSET_REVERSE_CHARSET (charset);			   \
        CODING_SPEC_ISO_DESIGNATION (coding, reg) = charset;		   \
      }									   \
    else								   \
      {									   \
	coding->spec.iso2022.last_invalid_designation_register = reg;	   \
	goto label_invalid_code;					   \
      }									   \
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  } while (0)

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/* Check if the current composing sequence contains only valid codes.
   If the composing sequence doesn't end before SRC_END, return -1.
   Else, if it contains only valid codes, return 0.
   Else return the length of the composing sequence.  */

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int
check_composing_code (coding, src, src_end)
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     struct coding_system *coding;
     unsigned char *src, *src_end;
{
  unsigned char *src_start = src;
  int invalid_code_found = 0;
  int charset, c, c1, dim;

  while (src < src_end)
    {
      if (*src++ != ISO_CODE_ESC) continue;
      if (src >= src_end) break;
      if ((c = *src++) == '1') /* end of compsition */
	return (invalid_code_found ? src - src_start : 0);
      if (src + 2 >= src_end) break;
      if (!coding->flags & CODING_FLAG_ISO_DESIGNATION)
	invalid_code_found = 1;
      else
	{
	  dim = 0;
	  if (c == '$')
	    {
	      dim = 1;
	      c = (*src >= '@' && *src <= 'B') ? '(' : *src++;
	    }
	  if (c >= '(' && c <= '/')
	    {
	      c1 = *src++;
	      if ((c1 < ' ' || c1 >= 0x80)
		  || (charset = iso_charset_table[dim][c >= ','][c1]) < 0
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		  || ! coding->safe_charsets[charset]
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		  || (CODING_SPEC_ISO_REQUESTED_DESIGNATION (coding, charset)
		      == CODING_SPEC_ISO_NO_REQUESTED_DESIGNATION))
		invalid_code_found = 1;
	    }
	  else
	    invalid_code_found = 1;
	}
    }
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  return (invalid_code_found
	  ? src - src_start
	  : (coding->mode & CODING_MODE_LAST_BLOCK ? 0 : -1));
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}

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/* See the above "GENERAL NOTES on `decode_coding_XXX ()' functions".  */

int
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decode_coding_iso2022 (coding, source, destination, src_bytes, dst_bytes)
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     struct coding_system *coding;
     unsigned char *source, *destination;
     int src_bytes, dst_bytes;
{
  unsigned char *src = source;
  unsigned char *src_end = source + src_bytes;
  unsigned char *dst = destination;
  unsigned char *dst_end = destination + dst_bytes;
  /* Since the maximum bytes produced by each loop is 7, we subtract 6
     from DST_END to assure that overflow checking is necessary only
     at the head of loop.  */
  unsigned char *adjusted_dst_end = dst_end - 6;
  int charset;
  /* Charsets invoked to graphic plane 0 and 1 respectively.  */
  int charset0 = CODING_SPEC_ISO_PLANE_CHARSET (coding, 0);
  int charset1 = CODING_SPEC_ISO_PLANE_CHARSET (coding, 1);
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  Lisp_Object translation_table
    = coding->character_translation_table_for_decode;
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  int result = CODING_FINISH_NORMAL;
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  if (!NILP (Venable_character_translation) && NILP (translation_table))
    translation_table = Vstandard_character_translation_table_for_decode;
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  coding->produced_char = 0;
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  coding->fake_multibyte = 0;
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  while (src < src_end && (dst_bytes
			   ? (dst < adjusted_dst_end)
			   : (dst < src - 6)))
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    {
      /* SRC_BASE remembers the start position in source in each loop.
	 The loop will be exited when there's not enough source text
	 to analyze long escape sequence or 2-byte code (within macros
	 ONE_MORE_BYTE or TWO_MORE_BYTES).  In that case, SRC is reset
	 to SRC_BASE before exiting.  */
      unsigned char *src_base = src;
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      int c1 = *src++, c2;
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      switch (iso_code_class [c1])
	{
	case ISO_0x20_or_0x7F:
	  if (!coding->composing
	      && (charset0 < 0 || CHARSET_CHARS (charset0) == 94))
	    {
	      /* This is SPACE or DEL.  */
	      *dst++ = c1;
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	      coding->produced_char++;
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	      break;
	    }
	  /* This is a graphic character, we fall down ...  */

	case ISO_graphic_plane_0:
	  if (coding->composing == COMPOSING_WITH_RULE_RULE)
	    {
	      /* This is a composition rule.  */
	      *dst++ = c1 | 0x80;
	      coding->composing = COMPOSING_WITH_RULE_TAIL;
	    }
	  else
	    DECODE_ISO_CHARACTER (charset0, c1);
	  break;

	case ISO_0xA0_or_0xFF:
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	  if (charset1 < 0 || CHARSET_CHARS (charset1) == 94
	      || coding->flags & CODING_FLAG_ISO_SEVEN_BITS)
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	    goto label_invalid_code;
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	  /* This is a graphic character, we fall down ... */

	case ISO_graphic_plane_1:
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	  if (coding->flags & CODING_FLAG_ISO_SEVEN_BITS)
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	    goto label_invalid_code;
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	  else
	    DECODE_ISO_CHARACTER (charset1, c1);
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	  break;

	case ISO_control_code:
	  /* All ISO2022 control characters in this class have the
             same representation in Emacs internal format.  */
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	  if (c1 == '\n'
	      && (coding->mode & CODING_MODE_INHIBIT_INCONSISTENT_EOL)
	      && (coding->eol_type == CODING_EOL_CR
		  || coding->eol_type == CODING_EOL_CRLF))
	    {
	      result = CODING_FINISH_INCONSISTENT_EOL;
	      goto label_end_of_loop_2;
	    }
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	  *dst++ = c1;
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	  coding->produced_char++;
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	  break;

	case ISO_carriage_return:
	  if (coding->eol_type == CODING_EOL_CR)
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	    *dst++ = '\n';
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	  else if (coding->eol_type == CODING_EOL_CRLF)
	    {
	      ONE_MORE_BYTE (c1);
	      if (c1 == ISO_CODE_LF)
		*dst++ = '\n';
	      else
		{
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		  if (coding->mode & CODING_MODE_INHIBIT_INCONSISTENT_EOL)
		    {
		      result = CODING_FINISH_INCONSISTENT_EOL;
		      goto label_end_of_loop_2;
		    }
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		  src--;
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		  *dst++ = '\r';
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		}
	    }
	  else
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	    *dst++ = c1;
	  coding->produced_char++;
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	  break;

	case ISO_shift_out:
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	  if (! (coding->flags & CODING_FLAG_ISO_LOCKING_SHIFT)
	      || CODING_SPEC_ISO_DESIGNATION (coding, 1) < 0)
	    goto label_invalid_code;
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	  CODING_SPEC_ISO_INVOCATION (coding, 0) = 1;
	  charset0 = CODING_SPEC_ISO_PLANE_CHARSET (coding, 0);
	  break;

	case ISO_shift_in:
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	  if (! (coding->flags & CODING_FLAG_ISO_LOCKING_SHIFT))
	    goto label_invalid_code;
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	  CODING_SPEC_ISO_INVOCATION (coding, 0) = 0;
	  charset0 = CODING_SPEC_ISO_PLANE_CHARSET (coding, 0);
	  break;

	case ISO_single_shift_2_7:
	case ISO_single_shift_2:
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	  if (! (coding->flags & CODING_FLAG_ISO_SINGLE_SHIFT))
	    goto label_invalid_code;
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	  /* SS2 is handled as an escape sequence of ESC 'N' */
	  c1 = 'N';
	  goto label_escape_sequence;

	case ISO_single_shift_3:
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	  if (! (coding->flags & CODING_FLAG_ISO_SINGLE_SHIFT))
	    goto label_invalid_code;
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	  /* SS2 is handled as an escape sequence of ESC 'O' */
	  c1 = 'O';
	  goto label_escape_sequence;

	case ISO_control_sequence_introducer:
	  /* CSI is handled as an escape sequence of ESC '[' ...  */
	  c1 = '[';
	  goto label_escape_sequence;

	case ISO_escape:
	  ONE_MORE_BYTE (c1);
	label_escape_sequence:
	  /* Escape sequences handled by Emacs are invocation,
	     designation, direction specification, and character
	     composition specification.  */
	  switch (c1)
	    {
	    case '&':		/* revision of following character set */
	      ONE_MORE_BYTE (c1);
	      if (!(c1 >= '@' && c1 <= '~'))
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		goto label_invalid_code;
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	      ONE_MORE_BYTE (c1);
	      if (c1 != ISO_CODE_ESC)
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		goto label_invalid_code;
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	      ONE_MORE_BYTE (c1);
	      goto label_escape_sequence;

	    case '$':		/* designation of 2-byte character set */
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	      if (! (coding->flags & CODING_FLAG_ISO_DESIGNATION))
		goto label_invalid_code;
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	      ONE_MORE_BYTE (c1);
	      if (c1 >= '@' && c1 <= 'B')
		{	/* designation of JISX0208.1978, GB2312.1980,
				   or JISX0208.1980 */
		  DECODE_DESIGNATION (0, 2, 94, c1);
		}
	      else if (c1 >= 0x28 && c1 <= 0x2B)
		{	/* designation of DIMENSION2_CHARS94 character set */
		  ONE_MORE_BYTE (c2);
		  DECODE_DESIGNATION (c1 - 0x28, 2, 94, c2);
		}
	      else if (c1 >= 0x2C && c1 <= 0x2F)
		{	/* designation of DIMENSION2_CHARS96 character set */
		  ONE_MORE_BYTE (c2);
		  DECODE_DESIGNATION (c1 - 0x2C, 2, 96, c2);
		}
	      else
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		goto label_invalid_code;
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	      break;

	    case 'n':		/* invocation of locking-shift-2 */
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	      if (! (coding->flags & CODING_FLAG_ISO_LOCKING_SHIFT)
		  || CODING_SPEC_ISO_DESIGNATION (coding, 2) < 0)
		goto label_invalid_code;
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	      CODING_SPEC_ISO_INVOCATION (coding, 0) = 2;
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	      charset0 = CODING_SPEC_ISO_PLANE_CHARSET (coding, 0);
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	      break;

	    case 'o':		/* invocation of locking-shift-3 */
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	      if (! (coding->flags & CODING_FLAG_ISO_LOCKING_SHIFT)
		  || CODING_SPEC_ISO_DESIGNATION (coding, 3) < 0)
		goto label_invalid_code;
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	      CODING_SPEC_ISO_INVOCATION (coding, 0) = 3;
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	      charset0 = CODING_SPEC_ISO_PLANE_CHARSET (coding, 0);
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	      break;

	    case 'N':		/* invocation of single-shift-2 */
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	      if (! (coding->flags & CODING_FLAG_ISO_SINGLE_SHIFT)
		  || CODING_SPEC_ISO_DESIGNATION (coding, 2) < 0)
		goto label_invalid_code;
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	      ONE_MORE_BYTE (c1);
	      charset = CODING_SPEC_ISO_DESIGNATION (coding, 2);
	      DECODE_ISO_CHARACTER (charset, c1);
	      break;

	    case 'O':		/* invocation of single-shift-3 */
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	      if (! (coding->flags & CODING_FLAG_ISO_SINGLE_SHIFT)
		  || CODING_SPEC_ISO_DESIGNATION (coding, 3) < 0)
		goto label_invalid_code;
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	      ONE_MORE_BYTE (c1);
	      charset = CODING_SPEC_ISO_DESIGNATION (coding, 3);
	      DECODE_ISO_CHARACTER (charset, c1);
	      break;

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	    case '0': case '2':	/* start composing */
	      /* Before processing composing, we must be sure that all
		 characters being composed are supported by CODING.
		 If not, we must give up composing and insert the
		 bunch of codes for composing as is without decoding.  */
	      {
		int result1;

		result1 = check_composing_code (coding, src, src_end);
		if (result1 == 0)
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		  {
		    coding->composing = (c1 == '0'
					 ? COMPOSING_NO_RULE_HEAD
					 : COMPOSING_WITH_RULE_HEAD);
		    coding->produced_char++;
		  }
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		else if (result1 > 0)
		  {
		    if (result1 + 2 < (dst_bytes ? dst_end : src_base) - dst)
		      {
			bcopy (src_base, dst, result1 + 2);
			src += result1;
			dst += result1 + 2;
			coding->produced_char += result1 + 2;
		      }
		    else
		      {
			result = CODING_FINISH_INSUFFICIENT_DST;
			goto label_end_of_loop_2;
		      }
		  }
		else
		  goto label_end_of_loop;
	      }
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	      break;

	    case '1':		/* end composing */
	      coding->composing = COMPOSING_NO;
	      break;

	    case '[':		/* specification of direction */
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	      if (coding->flags & CODING_FLAG_ISO_NO_DIRECTION)
		goto label_invalid_code;
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	      /* For the moment, nested direction is not supported.
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		 So, `coding->mode & CODING_MODE_DIRECTION' zero means
		 left-to-right, and nozero means right-to-left.  */
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	      ONE_MORE_BYTE (c1);
	      switch (c1)
		{
		case ']':	/* end of the current direction */
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		  coding->mode &= ~CODING_MODE_DIRECTION;
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		case '0':	/* end of the current direction */
		case '1':	/* start of left-to-right direction */
		  ONE_MORE_BYTE (c1);
		  if (c1 == ']')
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		    coding->mode &= ~CODING_MODE_DIRECTION;
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		  else
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		    goto label_invalid_code;
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		  break;

		case '2':	/* start of right-to-left direction */
		  ONE_MORE_BYTE (c1);
		  if (c1 == ']')
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		    coding->mode |= CODING_MODE_DIRECTION;
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		  else
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		    goto label_invalid_code;
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		  break;

		default:
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		  goto label_invalid_code;
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		}
	      break;

	    default:
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	      if (! (coding->flags & CODING_FLAG_ISO_DESIGNATION))
		goto label_invalid_code;
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	      if (c1 >= 0x28 && c1 <= 0x2B)
		{	/* designation of DIMENSION1_CHARS94 character set */
		  ONE_MORE_BYTE (c2);
		  DECODE_DESIGNATION (c1 - 0x28, 1, 94, c2);
		}
	      else if (c1 >= 0x2C && c1 <= 0x2F)
		{	/* designation of DIMENSION1_CHARS96 character set */
		  ONE_MORE_BYTE (c2);
		  DECODE_DESIGNATION (c1 - 0x2C, 1, 96, c2);
		}
	      else
		{
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		  goto label_invalid_code;
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		}
	    }
	  /* We must update these variables now.  */
	  charset0 = CODING_SPEC_ISO_PLANE_CHARSET (coding, 0);
	  charset1 = CODING_SPEC_ISO_PLANE_CHARSET (coding, 1);
	  break;

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	label_invalid_code:
	  while (src_base < src)
	    *dst++ = *src_base++;
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	  coding->fake_multibyte = 1;
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	}
      continue;

    label_end_of_loop:
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      result = CODING_FINISH_INSUFFICIENT_SRC;
    label_end_of_loop_2:
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      src = src_base;
      break;
    }

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  if (src < src_end)
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    {
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      if (result == CODING_FINISH_NORMAL)
	result = CODING_FINISH_INSUFFICIENT_DST;
      else if (result != CODING_FINISH_INCONSISTENT_EOL
	       && coding->mode & CODING_MODE_LAST_BLOCK)
	{
	  /* This is the last block of the text to be decoded.  We had
	     better just flush out all remaining codes in the text
	     although they are not valid characters.  */
	  src_bytes = src_end - src;
	  if (dst_bytes && (dst_end - dst < src_bytes))
	    src_bytes = dst_end - dst;
	  bcopy (src, dst, src_bytes);
	  dst += src_bytes;
	  src += src_bytes;
	  coding->fake_multibyte = 1;
	}
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    }
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  coding->consumed = coding->consumed_char = src - source;
  coding->produced = dst - destination;
  return result;
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}

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/* ISO2022 encoding stuff.  */
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/*
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   It is not enough to say just "ISO2022" on encoding, we have to
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   specify more details.  In Emacs, each coding system of ISO2022
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   variant has the following specifications:
	1. Initial designation to G0 thru G3.
	2. Allows short-form designation?
	3. ASCII should be designated to G0 before control characters?
	4. ASCII should be designated to G0 at end of line?
	5. 7-bit environment or 8-bit environment?
	6. Use locking-shift?
	7. Use Single-shift?
   And the following two are only for Japanese:
	8. Use ASCII in place of JIS0201-1976-Roman?
	9. Use JISX0208-1983 in place of JISX0208-1978?
   These specifications are encoded in `coding->flags' as flag bits
   defined by macros CODING_FLAG_ISO_XXX.  See `coding.h' for more
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   details.
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*/

/* Produce codes (escape sequence) for designating CHARSET to graphic
   register REG.  If <final-char> of CHARSET is '@', 'A', or 'B' and
   the coding system CODING allows, produce designation sequence of
   short-form.  */

#define ENCODE_DESIGNATION(charset, reg, coding)			\
  do {									\
    unsigned char final_char = CHARSET_ISO_FINAL_CHAR (charset);	\
    char *intermediate_char_94 = "()*+";				\
    char *intermediate_char_96 = ",-./";				\
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    int revision = CODING_SPEC_ISO_REVISION_NUMBER(coding, charset);	\
    if (revision < 255)							\
      {									\
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	*dst++ = ISO_CODE_ESC;						\
	*dst++ = '&';							\
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	*dst++ = '@' + revision;					\
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      }									\
    *dst++ = ISO_CODE_ESC;				       		\
    if (CHARSET_DIMENSION (charset) == 1)				\
      {									\
	if (CHARSET_CHARS (charset) == 94)				\
	  *dst++ = (unsigned char) (intermediate_char_94[reg]);		\
	else								\
	  *dst++ = (unsigned char) (intermediate_char_96[reg]);		\
      }									\
    else								\
      {									\
	*dst++ = '$';							\
	if (CHARSET_CHARS (charset) == 94)				\
	  {								\
	    if (! (coding->flags & CODING_FLAG_ISO_SHORT_FORM)     	\
		|| reg != 0					       	\
		|| final_char < '@' || final_char > 'B')	       	\
	      *dst++ = (unsigned char) (intermediate_char_94[reg]);	\
	  }								\
	else								\
	  *dst++ = (unsigned char) (intermediate_char_96[reg]);  	\
      }									\
    *dst++ = final_char;				       		\
    CODING_SPEC_ISO_DESIGNATION (coding, reg) = charset;		\
  } while (0)

/* The following two macros produce codes (control character or escape
   sequence) for ISO2022 single-shift functions (single-shift-2 and
   single-shift-3).  */

#define ENCODE_SINGLE_SHIFT_2				\
  do {							\
    if (coding->flags & CODING_FLAG_ISO_SEVEN_BITS)	\
      *dst++ = ISO_CODE_ESC, *dst++ = 'N';		\
    else						\
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      {							\
	*dst++ = ISO_CODE_SS2;				\
	coding->fake_multibyte = 1;			\
      }							\
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    CODING_SPEC_ISO_SINGLE_SHIFTING (coding) = 1;	\
  } while (0)

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#define ENCODE_SINGLE_SHIFT_3				\
  do {							\
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    if (coding->flags & CODING_FLAG_ISO_SEVEN_BITS)	\
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      *dst++ = ISO_CODE_ESC, *dst++ = 'O';		\
    else						\
      {							\
	*dst++ = ISO_CODE_SS3;				\
	coding->fake_multibyte = 1;			\
      }							\
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    CODING_SPEC_ISO_SINGLE_SHIFTING (coding) = 1;	\
  } while (0)

/* The following four macros produce codes (control character or
   escape sequence) for ISO2022 locking-shift functions (shift-in,
   shift-out, locking-shift-2, and locking-shift-3).  */

#define ENCODE_SHIFT_IN			  	\
  do {					  	\
    *dst++ = ISO_CODE_SI;		  	\
    CODING_SPEC_ISO_INVOCATION (coding, 0) = 0;	\
  } while (0)

#define ENCODE_SHIFT_OUT		  	\
  do {					  	\
    *dst++ = ISO_CODE_SO;		  	\
    CODING_SPEC_ISO_INVOCATION (coding, 0) = 1;	\
  } while (0)

#define ENCODE_LOCKING_SHIFT_2			\
  do {						\
    *dst++ = ISO_CODE_ESC, *dst++ = 'n';	\
    CODING_SPEC_ISO_INVOCATION (coding, 0) = 2;	\
  } while (0)

#define ENCODE_LOCKING_SHIFT_3		  	\
  do {					  	\
    *dst++ = ISO_CODE_ESC, *dst++ = 'o';  	\
    CODING_SPEC_ISO_INVOCATION (coding, 0) = 3;	\
  } while (0)

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/* Produce codes for a DIMENSION1 character whose character set is
   CHARSET and whose position-code is C1.  Designation and invocation
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   sequences are also produced in advance if necessary.  */


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#define ENCODE_ISO_CHARACTER_DIMENSION1(charset, c1)			\
  do {									\
    if (CODING_SPEC_ISO_SINGLE_SHIFTING (coding))			\
      {									\
	if (coding->flags & CODING_FLAG_ISO_SEVEN_BITS)			\
	  *dst++ = c1 & 0x7F;						\
	else								\
	  *dst++ = c1 | 0x80;						\
	CODING_SPEC_ISO_SINGLE_SHIFTING (coding) = 0;			\
	break;								\
      }									\
    else if (charset == CODING_SPEC_ISO_PLANE_CHARSET (coding, 0))	\
      {									\
	*dst++ = c1 & 0x7F;						\
	break;								\
      }									\
    else if (charset == CODING_SPEC_ISO_PLANE_CHARSET (coding, 1))	\
      {									\
	*dst++ = c1 | 0x80;						\
	break;								\
      }									\
    else if (coding->flags & CODING_FLAG_ISO_SAFE			\
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	     && !coding->safe_charsets[charset])			\
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      {									\
	/* We should not encode this character, instead produce one or	\
	   two `?'s.  */						\
	*dst++ = CODING_INHIBIT_CHARACTER_SUBSTITUTION;			\
	if (CHARSET_WIDTH (charset) == 2)				\
	  *dst++ = CODING_INHIBIT_CHARACTER_SUBSTITUTION;		\
	break;								\
      }									\
    else								\
      /* Since CHARSET is not yet invoked to any graphic planes, we	\
	 must invoke it, or, at first, designate it to some graphic	\
	 register.  Then repeat the loop to actually produce the	\
	 character.  */							\
      dst = encode_invocation_designation (charset, coding, dst);	\
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  } while (1)

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/* Produce codes for a DIMENSION2 character whose character set is
   CHARSET and whose position-codes are C1 and C2.  Designation and
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   invocation codes are also produced in advance if necessary.  */

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#define ENCODE_ISO_CHARACTER_DIMENSION2(charset, c1, c2)		\
  do {									\
    if (CODING_SPEC_ISO_SINGLE_SHIFTING (coding))			\
      {									\
	if (coding->flags & CODING_FLAG_ISO_SEVEN_BITS)			\
	  *dst++ = c1 & 0x7F, *dst++ = c2 & 0x7F;			\
	else								\
	  *dst++ = c1 | 0x80, *dst++ = c2 | 0x80;			\
	CODING_SPEC_ISO_SINGLE_SHIFTING (coding) = 0;			\
	break;								\
      }									\
    else if (charset == CODING_SPEC_ISO_PLANE_CHARSET (coding, 0))	\
      {									\
	*dst++ = c1 & 0x7F, *dst++= c2 & 0x7F;				\
	break;								\
      }									\
    else if (charset == CODING_SPEC_ISO_PLANE_CHARSET (coding, 1))	\
      {									\
	*dst++ = c1 | 0x80, *dst++= c2 | 0x80;				\
	break;								\
      }									\
    else if (coding->flags & CODING_FLAG_ISO_SAFE			\
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	     && !coding->safe_charsets[charset])			\
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      {									\
	/* We should not encode this character, instead produce one or	\
	   two `?'s.  */						\
	*dst++ = CODING_INHIBIT_CHARACTER_SUBSTITUTION;			\
	if (CHARSET_WIDTH (charset) == 2)				\
	  *dst++ = CODING_INHIBIT_CHARACTER_SUBSTITUTION;		\
	break;								\
      }									\
    else								\
      /* Since CHARSET is not yet invoked to any graphic planes, we	\
	 must invoke it, or, at first, designate it to some graphic	\
	 register.  Then repeat the loop to actually produce the	\
	 character.  */							\
      dst = encode_invocation_designation (charset, coding, dst);	\
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  } while (1)

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#define ENCODE_ISO_CHARACTER(charset, c1, c2)			\
  do {								\
    int c_alt, charset_alt;					\
    if (!NILP (translation_table)				\
	&& ((c_alt = translate_char (translation_table, -1,	\
				     charset, c1, c2))		\
	    >= 0))						\
      SPLIT_CHAR (c_alt, charset_alt, c1, c2);			\
    else							\
      charset_alt = charset;					\
    if (CHARSET_DIMENSION (charset_alt) == 1)			\
      {								\
	if (charset == CHARSET_ASCII				\
	    && coding->flags & CODING_FLAG_ISO_USE_ROMAN)	\
	  charset_alt = charset_latin_jisx0201;			\
	ENCODE_ISO_CHARACTER_DIMENSION1 (charset_alt, c1);	\
      }								\
    else							\
      {								\
	if (charset == charset_jisx0208				\
	    && coding->flags & CODING_FLAG_ISO_USE_OLDJIS)	\
	  charset_alt = charset_jisx0208_1978;			\
	ENCODE_ISO_CHARACTER_DIMENSION2 (charset_alt, c1, c2);	\
      }								\
    if (! COMPOSING_P (coding->composing))			\
      coding->consumed_char++;					\
  } while (0)
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/* Produce designation and invocation codes at a place pointed by DST
   to use CHARSET.  The element `spec.iso2022' of *CODING is updated.
   Return new DST.  */

unsigned char *
encode_invocation_designation (charset, coding, dst)
     int charset;
     struct coding_system *coding;
     unsigned char *dst;
{
  int reg;			/* graphic register number */

  /* At first, check designations.  */
  for (reg = 0; reg < 4; reg++)
    if (charset == CODING_SPEC_ISO_DESIGNATION (coding, reg))
      break;

  if (reg >= 4)
    {
      /* CHARSET is not yet designated to any graphic registers.  */
      /* At first check the requested designation.  */
      reg = CODING_SPEC_ISO_REQUESTED_DESIGNATION (coding, charset);
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      if (reg == CODING_SPEC_ISO_NO_REQUESTED_DESIGNATION)
	/* Since CHARSET requests no special designation, designate it
	   to graphic register 0.  */
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	reg = 0;

      ENCODE_DESIGNATION (charset, reg, coding);
    }

  if (CODING_SPEC_ISO_INVOCATION (coding, 0) != reg
      && CODING_SPEC_ISO_INVOCATION (coding, 1) != reg)
    {
      /* Since the graphic register REG is not invoked to any graphic
	 planes, invoke it to graphic plane 0.  */
      switch (reg)
	{
	case 0:			/* graphic register 0 */
	  ENCODE_SHIFT_IN;
	  break;

	case 1:			/* graphic register 1 */
	  ENCODE_SHIFT_OUT;
	  break;

	case 2:			/* graphic register 2 */
	  if (coding->flags & CODING_FLAG_ISO_SINGLE_SHIFT)
	    ENCODE_SINGLE_SHIFT_2;
	  else
	    ENCODE_LOCKING_SHIFT_2;
	  break;

	case 3:			/* graphic register 3 */
	  if (coding->flags & CODING_FLAG_ISO_SINGLE_SHIFT)
	    ENCODE_SINGLE_SHIFT_3;
	  else
	    ENCODE_LOCKING_SHIFT_3;
	  break;
	}
    }
  return dst;
}

/* The following two macros produce codes for indicating composition.  */
#define ENCODE_COMPOSITION_NO_RULE_START  *dst++ = ISO_CODE_ESC, *dst++ = '0'
#define ENCODE_COMPOSITION_WITH_RULE_START  *dst++ = ISO_CODE_ESC, *dst++ = '2'
#define ENCODE_COMPOSITION_END    *dst++ = ISO_CODE_ESC, *dst++ = '1'

/* The following three macros produce codes for indicating direction
   of text.  */
#define ENCODE_CONTROL_SEQUENCE_INTRODUCER	    	\
  do {						    	\
    if (coding->flags == CODING_FLAG_ISO_SEVEN_BITS)	\
      *dst++ = ISO_CODE_ESC, *dst++ = '[';	    	\
    else					    	\
      *dst++ = ISO_CODE_CSI;			    	\
  } while (0)

#define ENCODE_DIRECTION_R2L	\
  ENCODE_CONTROL_SEQUENCE_INTRODUCER, *dst++ = '2', *dst++ = ']'

#define ENCODE_DIRECTION_L2R	\
  ENCODE_CONTROL_SEQUENCE_INTRODUCER, *dst++ = '0', *dst++ = ']'

/* Produce codes for designation and invocation to reset the graphic
   planes and registers to initial state.  */
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#define ENCODE_RESET_PLANE_AND_REGISTER					    \
  do {									    \
    int reg;								    \
    if (CODING_SPEC_ISO_INVOCATION (coding, 0) != 0)			    \
      ENCODE_SHIFT_IN;							    \
    for (reg = 0; reg < 4; reg++)					    \
      if (CODING_SPEC_ISO_INITIAL_DESIGNATION (coding, reg) >= 0	    \
	  && (CODING_SPEC_ISO_DESIGNATION (coding, reg)			    \
	      != CODING_SPEC_ISO_INITIAL_DESIGNATION (coding, reg)))	    \
	ENCODE_DESIGNATION						    \
	  (CODING_SPEC_ISO_INITIAL_DESIGNATION (coding, reg), reg, coding); \
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  } while (0)

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/* Produce designation sequences of charsets in the line started from
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   SRC to a place pointed by *DSTP, and update DSTP.
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   If the current block ends before any end-of-line, we may fail to
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   find all the necessary designations.  */

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void
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encode_designation_at_bol (coding, table, src, src_end, dstp)
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     struct coding_system *coding;
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     Lisp_Object table;
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     unsigned char *src, *src_end, **dstp;
{
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  int charset, c, found = 0, reg;
  /* Table of charsets to be designated to each graphic register.  */
  int r[4];
  unsigned char *dst = *dstp;

  for (reg = 0; reg < 4; reg++)
    r[reg] = -1;

  while (src < src_end && *src != '\n' && found < 4)
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    {
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      int bytes = BYTES_BY_CHAR_HEAD (*src);
      
      if (NILP (table))
	charset = CHARSET_AT (src);
      else
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	{
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	  int c_alt;
	  unsigned char c1, c2;
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	  SPLIT_STRING(src, bytes, charset, c1, c2);
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	  if ((c_alt = translate_char (table, -1, charset, c1, c2)) >= 0)
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	    charset = CHAR_CHARSET (c_alt);
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	}