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/* Coding system handler (conversion, detection, 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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   Copyright (C) 2001, 2002 Free Software Foundation, Inc.
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   Copyright (C) 2003
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     National Institute of Advanced Industrial Science and Technology (AIST)
     Registration Number H13PRO009
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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 ***

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  0. General comments
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  1. Preamble
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  2. Emacs' internal format (emacs-utf-8) handlers
  3. UTF-8 handlers
  4. UTF-16 handlers
  5. Charset-base coding systems handlers
  6. emacs-mule (old Emacs' internal format) handlers
  7. ISO2022 handlers
  8. Shift-JIS and BIG5 handlers
  9. CCL handlers
  10. C library functions
  11. Emacs Lisp library functions
  12. Postamble
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*/

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/*** 0. General comments ***
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CODING SYSTEM
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  A coding system is an object for an encoding mechanism that contains
  information about how to convert byte sequences to character
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  sequences and vice versa.  When we say "decode", it means converting
  a byte sequence of a specific coding system into a character
  sequence that is represented by Emacs' internal coding system
  `emacs-utf-8', and when we say "encode", it means converting a
  character sequence of emacs-utf-8 to a byte sequence of a specific
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  coding system.
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  In Emacs Lisp, a coding system is represented by a Lisp symbol.  In
  C level, a coding system is represented by a vector of attributes
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  stored in the hash table Vcharset_hash_table.  The conversion from
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  coding system symbol to attributes vector is done by looking up
  Vcharset_hash_table by the symbol.
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  Coding systems are classified into the following types depending on
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  the encoding mechanism.  Here's a brief description of the types.
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  o UTF-8

  o UTF-16

  o Charset-base coding system

  A coding system defined by one or more (coded) character sets.
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  Decoding and encoding are done by a code converter defined for each
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  character set.

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  o Old Emacs internal format (emacs-mule)
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  The coding system adopted by old versions of Emacs (20 and 21).
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  o ISO2022-base coding system
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  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 the Internet communication such as ISO-2022-JP are all
  variants of ISO2022.
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  o SJIS (or Shift-JIS or MS-Kanji-Code)
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  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 8.
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  o BIG5
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  A coding system to encode character sets: ASCII and Big5.  Widely
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  used for Chinese (mainly in Taiwan and Hong Kong).  Details are
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  described in section 8.  In this file, when we write "big5" (all
  lowercase), we mean the coding system, and when we write "Big5"
  (capitalized), we mean the character set.
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  o CCL
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  If a user wants to decode/encode text encoded in a coding system
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  not listed above, he can supply a decoder and an encoder for it in
  CCL (Code Conversion Language) programs.  Emacs executes the CCL
  program while decoding/encoding.
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  o Raw-text
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  A coding system for text containing raw eight-bit data.  Emacs
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  treats each byte of source text as a character (except for
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  end-of-line conversion).
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  o No-conversion

  Like raw text, but don't do end-of-line conversion.
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END-OF-LINE FORMAT
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  How text end-of-line is encoded depends on operating system.  For
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  instance, Unix's format is just one byte of LF (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 character encoding and end-of-line encoding are
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  independent, any coding system described above can take any format
  of end-of-line (except for no-conversion).
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STRUCT CODING_SYSTEM

  Before using a coding system for code conversion (i.e. decoding and
  encoding), we setup a structure of type `struct coding_system'.
  This structure keeps various information about a specific code
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  conversion (e.g. the location of source and destination data).
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*/

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/* COMMON MACROS */


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

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  These functions check if a byte sequence specified as a source in
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  CODING conforms to the format of XXX, and update the members of
  DETECT_INFO.
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  Return 1 if the byte sequence conforms to XXX, otherwise return 0.
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  Below is the template of these functions.  */

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#if 0
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static int
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detect_coding_XXX (coding, detect_info)
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     struct coding_system *coding;
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     struct coding_detection_info *detect_info;
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{
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  unsigned char *src = coding->source;
  unsigned char *src_end = coding->source + coding->src_bytes;
  int multibytep = coding->src_multibyte;
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  int consumed_chars = 0;
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  int found = 0;
  ...;

  while (1)
    {
      /* Get one byte from the source.  If the souce is exausted, jump
	 to no_more_source:.  */
      ONE_MORE_BYTE (c);
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      if (! __C_conforms_to_XXX___ (c))
	break;
      if (! __C_strongly_suggests_XXX__ (c))
	found = CATEGORY_MASK_XXX;
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    }
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  /* The byte sequence is invalid for XXX.  */
  detect_info->rejected |= CATEGORY_MASK_XXX;
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  return 0;
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 no_more_source:
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  /* The source exausted successfully.  */
  detect_info->found |= found;
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  return 1;
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}
#endif

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

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  These functions decode a byte sequence specified as a source by
  CODING.  The resulting multibyte text goes to a place pointed to by
  CODING->charbuf, the length of which should not exceed
  CODING->charbuf_size;
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  These functions set the information of original and decoded texts in
  CODING->consumed, CODING->consumed_char, and CODING->charbuf_used.
  They also set CODING->result to one of CODING_RESULT_XXX indicating
  how the decoding is finished.
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  Below is the template of these functions.  */
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#if 0
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static void
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decode_coding_XXXX (coding)
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     struct coding_system *coding;
{
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  unsigned char *src = coding->source + coding->consumed;
  unsigned char *src_end = coding->source + coding->src_bytes;
  /* SRC_BASE remembers the start position in source in each loop.
     The loop will be exited when there's not enough source code, or
     when there's no room in CHARBUF for a decoded character.  */
  unsigned char *src_base;
  /* A buffer to produce decoded characters.  */
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  int *charbuf = coding->charbuf + coding->charbuf_used;
  int *charbuf_end = coding->charbuf + coding->charbuf_size;
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  int multibytep = coding->src_multibyte;

  while (1)
    {
      src_base = src;
      if (charbuf < charbuf_end)
	/* No more room to produce a decoded character.  */
	break;
      ONE_MORE_BYTE (c);
      /* Decode it. */
    }

 no_more_source:
  if (src_base < src_end
      && coding->mode & CODING_MODE_LAST_BLOCK)
    /* If the source ends by partial bytes to construct a character,
       treat them as eight-bit raw data.  */
    while (src_base < src_end && charbuf < charbuf_end)
      *charbuf++ = *src_base++;
  /* Remember how many bytes and characters we consumed.  If the
     source is multibyte, the bytes and chars are not identical.  */
  coding->consumed = coding->consumed_char = src_base - coding->source;
  /* Remember how many characters we produced.  */
  coding->charbuf_used = charbuf - coding->charbuf;
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}
#endif

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

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  These functions encode SRC_BYTES length text at SOURCE of Emacs'
  internal multibyte format by CODING.  The resulting byte sequence
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  goes to a place pointed to by DESTINATION, the length of which
  should not exceed DST_BYTES.
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  These functions set the information of original and encoded texts in
  the members produced, produced_char, consumed, and consumed_char of
  the structure *CODING.  They also set the member result to one of
  CODING_RESULT_XXX indicating how the encoding finished.
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  DST_BYTES zero means that source area and destination area are
  overlapped, which means that we can produce a encoded text until it
  reaches at the head of not-yet-encoded source text.
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  Below is a template of these functions.  */
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#if 0
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static void
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encode_coding_XXX (coding)
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     struct coding_system *coding;
{
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  int multibytep = coding->dst_multibyte;
  int *charbuf = coding->charbuf;
  int *charbuf_end = charbuf->charbuf + coding->charbuf_used;
  unsigned char *dst = coding->destination + coding->produced;
  unsigned char *dst_end = coding->destination + coding->dst_bytes;
  unsigned char *adjusted_dst_end = dst_end - _MAX_BYTES_PRODUCED_IN_LOOP_;
  int produced_chars = 0;

  for (; charbuf < charbuf_end && dst < adjusted_dst_end; charbuf++)
    {
      int c = *charbuf;
      /* Encode C into DST, and increment DST.  */
    }
 label_no_more_destination:
  /* How many chars and bytes we produced.  */
  coding->produced_char += produced_chars;
  coding->produced = dst - coding->destination;
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}
#endif


/*** 1. Preamble ***/

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#include <config.h>
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#include <stdio.h>

#include "lisp.h"
#include "buffer.h"
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#include "character.h"
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#include "charset.h"
#include "ccl.h"
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#include "composite.h"
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#include "coding.h"
#include "window.h"

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Lisp_Object Vcoding_system_hash_table;
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Lisp_Object Qcoding_system, Qcoding_aliases, Qeol_type;
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Lisp_Object Qunix, Qdos;
extern Lisp_Object Qmac;	/* frame.c */
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Lisp_Object Qbuffer_file_coding_system;
Lisp_Object Qpost_read_conversion, Qpre_write_conversion;
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Lisp_Object Qdefault_char;
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Lisp_Object Qno_conversion, Qundecided;
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Lisp_Object Qcharset, Qiso_2022, Qutf_8, Qutf_16, Qshift_jis, Qbig5;
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Lisp_Object Qbig, Qlittle;
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Lisp_Object Qcoding_system_history;
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Lisp_Object Qvalid_codes;
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Lisp_Object QCcategory, QCmnemonic, QCdefalut_char;
Lisp_Object QCdecode_translation_table, QCencode_translation_table;
Lisp_Object QCpost_read_conversion, QCpre_write_conversion;
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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 Qinsufficient_source, Qinconsistent_eol, Qinvalid_source;
Lisp_Object Qinterrupted, Qinsufficient_memory;

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int coding_system_require_warning;

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Lisp_Object Vselect_safe_coding_system_function;

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/* Mnemonic string for each format of end-of-line.  */
Lisp_Object eol_mnemonic_unix, eol_mnemonic_dos, eol_mnemonic_mac;
/* Mnemonic string to indicate format of end-of-line is not yet
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   decided.  */
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Lisp_Object eol_mnemonic_undecided;
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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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Lisp_Object Qutf_8_emacs;
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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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/* Set to non-nil when an error is detected while code conversion.  */
Lisp_Object Vlast_code_conversion_error;
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/* A vector of length 256 which contains information about special
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   Latin codes (especially for dealing with Microsoft codes).  */
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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 inhibit ISO2022 escape sequence detection.  */
int inhibit_iso_escape_detection;

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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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Lisp_Object Vlocale_coding_system;

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#endif /* emacs */

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/* Flag to tell if we look up translation table on character code
   conversion.  */
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Lisp_Object Venable_character_translation;
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/* Standard translation table to look up on decoding (reading).  */
Lisp_Object Vstandard_translation_table_for_decode;
/* Standard translation table to look up on encoding (writing).  */
Lisp_Object Vstandard_translation_table_for_encode;
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Lisp_Object Qtranslation_table;
Lisp_Object Qtranslation_table_id;
Lisp_Object Qtranslation_table_for_decode;
Lisp_Object Qtranslation_table_for_encode;
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/* Alist of charsets vs revision number.  */
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static Lisp_Object Vcharset_revision_table;
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/* Default coding systems used for process I/O.  */
Lisp_Object Vdefault_process_coding_system;

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/* Char table for translating Quail and self-inserting input.  */
Lisp_Object Vtranslation_table_for_input;

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/* Two special coding systems.  */
Lisp_Object Vsjis_coding_system;
Lisp_Object Vbig5_coding_system;

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static void record_conversion_result (struct coding_system *coding,
				      enum coding_result_code result);
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static int detect_coding_utf_8 P_ ((struct coding_system *,
				    struct coding_detection_info *info));
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static void decode_coding_utf_8 P_ ((struct coding_system *));
static int encode_coding_utf_8 P_ ((struct coding_system *));

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static int detect_coding_utf_16 P_ ((struct coding_system *,
				     struct coding_detection_info *info));
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static void decode_coding_utf_16 P_ ((struct coding_system *));
static int encode_coding_utf_16 P_ ((struct coding_system *));

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static int detect_coding_iso_2022 P_ ((struct coding_system *,
				       struct coding_detection_info *info));
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static void decode_coding_iso_2022 P_ ((struct coding_system *));
static int encode_coding_iso_2022 P_ ((struct coding_system *));

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static int detect_coding_emacs_mule P_ ((struct coding_system *,
					 struct coding_detection_info *info));
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static void decode_coding_emacs_mule P_ ((struct coding_system *));
static int encode_coding_emacs_mule P_ ((struct coding_system *));

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static int detect_coding_sjis P_ ((struct coding_system *,
				   struct coding_detection_info *info));
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static void decode_coding_sjis P_ ((struct coding_system *));
static int encode_coding_sjis P_ ((struct coding_system *));

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static int detect_coding_big5 P_ ((struct coding_system *,
				   struct coding_detection_info *info));
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static void decode_coding_big5 P_ ((struct coding_system *));
static int encode_coding_big5 P_ ((struct coding_system *));

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static int detect_coding_ccl P_ ((struct coding_system *,
				  struct coding_detection_info *info));
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static void decode_coding_ccl P_ ((struct coding_system *));
static int encode_coding_ccl P_ ((struct coding_system *));

static void decode_coding_raw_text P_ ((struct coding_system *));
static int encode_coding_raw_text P_ ((struct coding_system *));


/* ISO2022 section */

#define CODING_ISO_INITIAL(coding, reg)			\
  (XINT (AREF (AREF (CODING_ID_ATTRS ((coding)->id),	\
		     coding_attr_iso_initial),		\
	       reg)))


#define CODING_ISO_REQUEST(coding, charset_id)	\
  ((charset_id <= (coding)->max_charset_id	\
    ? (coding)->safe_charsets[charset_id]	\
    : -1))


#define CODING_ISO_FLAGS(coding)	\
  ((coding)->spec.iso_2022.flags)
#define CODING_ISO_DESIGNATION(coding, reg)	\
  ((coding)->spec.iso_2022.current_designation[reg])
#define CODING_ISO_INVOCATION(coding, plane)	\
  ((coding)->spec.iso_2022.current_invocation[plane])
#define CODING_ISO_SINGLE_SHIFTING(coding)	\
  ((coding)->spec.iso_2022.single_shifting)
#define CODING_ISO_BOL(coding)	\
  ((coding)->spec.iso_2022.bol)
#define CODING_ISO_INVOKED_CHARSET(coding, plane)	\
  CODING_ISO_DESIGNATION ((coding), CODING_ISO_INVOCATION ((coding), (plane)))

/* Control characters of ISO2022.  */
			/* code */	/* function */
#define ISO_CODE_LF	0x0A		/* line-feed */
#define ISO_CODE_CR	0x0D		/* carriage-return */
#define ISO_CODE_SO	0x0E		/* shift-out */
#define ISO_CODE_SI	0x0F		/* shift-in */
#define ISO_CODE_SS2_7	0x19		/* single-shift-2 for 7-bit code */
#define ISO_CODE_ESC	0x1B		/* escape */
#define ISO_CODE_SS2	0x8E		/* single-shift-2 */
#define ISO_CODE_SS3	0x8F		/* single-shift-3 */
#define ISO_CODE_CSI	0x9B		/* control-sequence-introducer */

/* All code (1-byte) of ISO2022 is classified into one of the
   followings.  */
enum iso_code_class_type
  {
    ISO_control_0,		/* Control codes in the range
				   0x00..0x1F and 0x7F, except for the
				   following 5 codes.  */
    ISO_shift_out,		/* ISO_CODE_SO (0x0E) */
    ISO_shift_in,		/* ISO_CODE_SI (0x0F) */
    ISO_single_shift_2_7,	/* ISO_CODE_SS2_7 (0x19) */
    ISO_escape,			/* ISO_CODE_SO (0x1B) */
    ISO_control_1,		/* Control codes in the range
				   0x80..0x9F, except for the
				   following 3 codes.  */
    ISO_single_shift_2,		/* ISO_CODE_SS2 (0x8E) */
    ISO_single_shift_3,		/* ISO_CODE_SS3 (0x8F) */
    ISO_control_sequence_introducer, /* ISO_CODE_CSI (0x9B) */
    ISO_0x20_or_0x7F,		/* Codes of the values 0x20 or 0x7F.  */
    ISO_graphic_plane_0,	/* Graphic codes in the range 0x21..0x7E.  */
    ISO_0xA0_or_0xFF,		/* Codes of the values 0xA0 or 0xFF.  */
    ISO_graphic_plane_1		/* Graphic codes in the range 0xA1..0xFE.  */
  };
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/** The macros CODING_ISO_FLAG_XXX defines a flag bit of the
    `iso-flags' attribute of an iso2022 coding system.  */
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/* If set, produce long-form designation sequence (e.g. ESC $ ( A)
   instead of the correct short-form sequence (e.g. ESC $ A).  */
#define CODING_ISO_FLAG_LONG_FORM	0x0001
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/* If set, reset graphic planes and registers at end-of-line to the
   initial state.  */
#define CODING_ISO_FLAG_RESET_AT_EOL	0x0002
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/* If set, reset graphic planes and registers before any control
   characters to the initial state.  */
#define CODING_ISO_FLAG_RESET_AT_CNTL	0x0004
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/* If set, encode by 7-bit environment.  */
#define CODING_ISO_FLAG_SEVEN_BITS	0x0008
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/* If set, use locking-shift function.  */
#define CODING_ISO_FLAG_LOCKING_SHIFT	0x0010
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/* If set, use single-shift function.  Overwrite
   CODING_ISO_FLAG_LOCKING_SHIFT.  */
#define CODING_ISO_FLAG_SINGLE_SHIFT	0x0020
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/* If set, use designation escape sequence.  */
#define CODING_ISO_FLAG_DESIGNATION	0x0040
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/* If set, produce revision number sequence.  */
#define CODING_ISO_FLAG_REVISION	0x0080
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/* If set, produce ISO6429's direction specifying sequence.  */
#define CODING_ISO_FLAG_DIRECTION	0x0100
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/* If set, assume designation states are reset at beginning of line on
   output.  */
#define CODING_ISO_FLAG_INIT_AT_BOL	0x0200
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/* If set, designation sequence should be placed at beginning of line
   on output.  */
#define CODING_ISO_FLAG_DESIGNATE_AT_BOL 0x0400
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/* If set, do not encode unsafe charactes on output.  */
#define CODING_ISO_FLAG_SAFE		0x0800
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/* If set, extra latin codes (128..159) are accepted as a valid code
   on input.  */
#define CODING_ISO_FLAG_LATIN_EXTRA	0x1000
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#define CODING_ISO_FLAG_COMPOSITION	0x2000
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#define CODING_ISO_FLAG_EUC_TW_SHIFT	0x4000
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#define CODING_ISO_FLAG_USE_ROMAN	0x8000
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#define CODING_ISO_FLAG_USE_OLDJIS	0x10000
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#define CODING_ISO_FLAG_FULL_SUPPORT	0x100000
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/* A character to be produced on output if encoding of the original
   character is prohibited by CODING_ISO_FLAG_SAFE.  */
#define CODING_INHIBIT_CHARACTER_SUBSTITUTION  '?'
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/* UTF-16 section */
#define CODING_UTF_16_BOM(coding)	\
  ((coding)->spec.utf_16.bom)
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#define CODING_UTF_16_ENDIAN(coding)	\
  ((coding)->spec.utf_16.endian)
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#define CODING_UTF_16_SURROGATE(coding)	\
  ((coding)->spec.utf_16.surrogate)
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/* CCL section */
#define CODING_CCL_DECODER(coding)	\
  AREF (CODING_ID_ATTRS ((coding)->id), coding_attr_ccl_decoder)
#define CODING_CCL_ENCODER(coding)	\
  AREF (CODING_ID_ATTRS ((coding)->id), coding_attr_ccl_encoder)
#define CODING_CCL_VALIDS(coding)					   \
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  (SDATA (AREF (CODING_ID_ATTRS ((coding)->id), coding_attr_ccl_valids)))
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/* Index for each coding category in `coding_categories' */
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enum coding_category
  {
    coding_category_iso_7,
    coding_category_iso_7_tight,
    coding_category_iso_8_1,
    coding_category_iso_8_2,
    coding_category_iso_7_else,
    coding_category_iso_8_else,
    coding_category_utf_8,
    coding_category_utf_16_auto,
    coding_category_utf_16_be,
    coding_category_utf_16_le,
    coding_category_utf_16_be_nosig,
    coding_category_utf_16_le_nosig,
    coding_category_charset,
    coding_category_sjis,
    coding_category_big5,
    coding_category_ccl,
    coding_category_emacs_mule,
    /* All above are targets of code detection.  */
    coding_category_raw_text,
    coding_category_undecided,
    coding_category_max
  };

/* Definitions of flag bits used in detect_coding_XXXX.  */
#define CATEGORY_MASK_ISO_7		(1 << coding_category_iso_7)
#define CATEGORY_MASK_ISO_7_TIGHT	(1 << coding_category_iso_7_tight)
#define CATEGORY_MASK_ISO_8_1		(1 << coding_category_iso_8_1)
#define CATEGORY_MASK_ISO_8_2		(1 << coding_category_iso_8_2)
#define CATEGORY_MASK_ISO_7_ELSE	(1 << coding_category_iso_7_else)
#define CATEGORY_MASK_ISO_8_ELSE	(1 << coding_category_iso_8_else)
#define CATEGORY_MASK_UTF_8		(1 << coding_category_utf_8)
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#define CATEGORY_MASK_UTF_16_AUTO	(1 << coding_category_utf_16_auto)
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#define CATEGORY_MASK_UTF_16_BE		(1 << coding_category_utf_16_be)
#define CATEGORY_MASK_UTF_16_LE		(1 << coding_category_utf_16_le)
#define CATEGORY_MASK_UTF_16_BE_NOSIG	(1 << coding_category_utf_16_be_nosig)
#define CATEGORY_MASK_UTF_16_LE_NOSIG	(1 << coding_category_utf_16_le_nosig)
#define CATEGORY_MASK_CHARSET		(1 << coding_category_charset)
#define CATEGORY_MASK_SJIS		(1 << coding_category_sjis)
#define CATEGORY_MASK_BIG5		(1 << coding_category_big5)
#define CATEGORY_MASK_CCL		(1 << coding_category_ccl)
#define CATEGORY_MASK_EMACS_MULE	(1 << coding_category_emacs_mule)
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#define CATEGORY_MASK_RAW_TEXT		(1 << coding_category_raw_text)
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/* This value is returned if detect_coding_mask () find nothing other
   than ASCII characters.  */
#define CATEGORY_MASK_ANY		\
  (CATEGORY_MASK_ISO_7			\
   | CATEGORY_MASK_ISO_7_TIGHT		\
   | CATEGORY_MASK_ISO_8_1		\
   | CATEGORY_MASK_ISO_8_2		\
   | CATEGORY_MASK_ISO_7_ELSE		\
   | CATEGORY_MASK_ISO_8_ELSE		\
   | CATEGORY_MASK_UTF_8		\
   | CATEGORY_MASK_UTF_16_BE		\
   | CATEGORY_MASK_UTF_16_LE		\
   | CATEGORY_MASK_UTF_16_BE_NOSIG	\
   | CATEGORY_MASK_UTF_16_LE_NOSIG	\
   | CATEGORY_MASK_CHARSET		\
   | CATEGORY_MASK_SJIS			\
   | CATEGORY_MASK_BIG5			\
   | CATEGORY_MASK_CCL			\
   | CATEGORY_MASK_EMACS_MULE)


#define CATEGORY_MASK_ISO_7BIT \
  (CATEGORY_MASK_ISO_7 | CATEGORY_MASK_ISO_7_TIGHT)

#define CATEGORY_MASK_ISO_8BIT \
  (CATEGORY_MASK_ISO_8_1 | CATEGORY_MASK_ISO_8_2)

#define CATEGORY_MASK_ISO_ELSE \
  (CATEGORY_MASK_ISO_7_ELSE | CATEGORY_MASK_ISO_8_ELSE)

#define CATEGORY_MASK_ISO_ESCAPE	\
  (CATEGORY_MASK_ISO_7			\
   | CATEGORY_MASK_ISO_7_TIGHT		\
   | CATEGORY_MASK_ISO_7_ELSE		\
   | CATEGORY_MASK_ISO_8_ELSE)

#define CATEGORY_MASK_ISO	\
  (  CATEGORY_MASK_ISO_7BIT	\
     | CATEGORY_MASK_ISO_8BIT	\
     | CATEGORY_MASK_ISO_ELSE)

#define CATEGORY_MASK_UTF_16		\
  (CATEGORY_MASK_UTF_16_BE		\
   | CATEGORY_MASK_UTF_16_LE		\
   | CATEGORY_MASK_UTF_16_BE_NOSIG	\
   | CATEGORY_MASK_UTF_16_LE_NOSIG)


/* List of symbols `coding-category-xxx' ordered by priority.  This
   variable is exposed to Emacs Lisp.  */
static Lisp_Object Vcoding_category_list;

/* Table of coding categories (Lisp symbols).  This variable is for
   internal use oly.  */
static Lisp_Object Vcoding_category_table;

/* Table of coding-categories ordered by priority.  */
static enum coding_category coding_priorities[coding_category_max];

/* Nth element is a coding context for the coding system bound to the
   Nth coding category.  */
static struct coding_system coding_categories[coding_category_max];

/*** Commonly used macros and functions ***/

#ifndef min
#define min(a, b) ((a) < (b) ? (a) : (b))
#endif
#ifndef max
#define max(a, b) ((a) > (b) ? (a) : (b))
#endif
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#define CODING_GET_INFO(coding, attrs, charset_list)	\
  do {							\
    (attrs) = CODING_ID_ATTRS ((coding)->id);		\
    (charset_list) = CODING_ATTR_CHARSET_LIST (attrs);	\
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  } while (0)
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/* Safely get one byte from the source text pointed by SRC which ends
   at SRC_END, and set C to that byte.  If there are not enough bytes
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   in the source, it jumps to `no_more_source'.  If multibytep is
   nonzero, and a multibyte character is found at SRC, set C to the
   negative value of the character code.  The caller should declare
   and set these variables appropriately in advance:
	src, src_end, multibytep */
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#define ONE_MORE_BYTE(c)				\
  do {							\
    if (src == src_end)					\
      {							\
	if (src_base < src)				\
	  record_conversion_result			\
	    (coding, CODING_RESULT_INSUFFICIENT_SRC);	\
	goto no_more_source;				\
      }							\
    c = *src++;						\
    if (multibytep && (c & 0x80))			\
      {							\
	if ((c & 0xFE) == 0xC0)				\
	  c = ((c & 1) << 6) | *src++;			\
	else						\
	  {						\
	    c = - string_char (--src, &src, NULL);	\
	    record_conversion_result			\
	      (coding, CODING_RESULT_INVALID_SRC);	\
	  }						\
      }							\
    consumed_chars++;					\
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  } while (0)


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#define ONE_MORE_BYTE_NO_CHECK(c)			\
  do {							\
    c = *src++;						\
    if (multibytep && (c & 0x80))			\
      {							\
	if ((c & 0xFE) == 0xC0)				\
	  c = ((c & 1) << 6) | *src++;			\
	else						\
	  {						\
	    c = - string_char (--src, &src, NULL);	\
	    record_conversion_result			\
	      (coding, CODING_RESULT_INVALID_SRC);	\
	  }						\
      }							\
    consumed_chars++;					\
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  } while (0)


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/* Store a byte C in the place pointed by DST and increment DST to the
   next free point, and increment PRODUCED_CHARS.  The caller should
   assure that C is 0..127, and declare and set the variable `dst'
   appropriately in advance.
*/
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#define EMIT_ONE_ASCII_BYTE(c)	\
  do {				\
    produced_chars++;		\
    *dst++ = (c);		\
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  } while (0)
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/* Like EMIT_ONE_ASCII_BYTE byt store two bytes; C1 and C2.  */
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#define EMIT_TWO_ASCII_BYTES(c1, c2)	\
  do {					\
    produced_chars += 2;		\
    *dst++ = (c1), *dst++ = (c2);	\
  } while (0)
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/* Store a byte C in the place pointed by DST and increment DST to the
   next free point, and increment PRODUCED_CHARS.  If MULTIBYTEP is
   nonzero, store in an appropriate multibyte from.  The caller should
   declare and set the variables `dst' and `multibytep' appropriately
   in advance.  */

#define EMIT_ONE_BYTE(c)		\
  do {					\
    produced_chars++;			\
    if (multibytep)			\
      {					\
	int ch = (c);			\
	if (ch >= 0x80)			\
	  ch = BYTE8_TO_CHAR (ch);	\
	CHAR_STRING_ADVANCE (ch, dst);	\
      }					\
    else				\
      *dst++ = (c);			\
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  } while (0)


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/* Like EMIT_ONE_BYTE, but emit two bytes; C1 and C2.  */
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#define EMIT_TWO_BYTES(c1, c2)		\
  do {					\
    produced_chars += 2;		\
    if (multibytep)			\
      {					\
	int ch;				\
					\
	ch = (c1);			\
	if (ch >= 0x80)			\
	  ch = BYTE8_TO_CHAR (ch);	\
	CHAR_STRING_ADVANCE (ch, dst);	\
	ch = (c2);			\
	if (ch >= 0x80)			\
	  ch = BYTE8_TO_CHAR (ch);	\
	CHAR_STRING_ADVANCE (ch, dst);	\
      }					\
    else				\
      {					\
	*dst++ = (c1);			\
	*dst++ = (c2);			\
      }					\
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  } while (0)


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#define EMIT_THREE_BYTES(c1, c2, c3)	\
  do {					\
    EMIT_ONE_BYTE (c1);			\
    EMIT_TWO_BYTES (c2, c3);		\
  } while (0)
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#define EMIT_FOUR_BYTES(c1, c2, c3, c4)		\
  do {						\
    EMIT_TWO_BYTES (c1, c2);			\
    EMIT_TWO_BYTES (c3, c4);			\
  } while (0)
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static void
record_conversion_result (struct coding_system *coding,
			  enum coding_result_code result)
{
  coding->result = result;
  switch (result)
    {
    case CODING_RESULT_INSUFFICIENT_SRC:
      Vlast_code_conversion_error = Qinsufficient_source;
      break;
    case CODING_RESULT_INCONSISTENT_EOL:
      Vlast_code_conversion_error = Qinconsistent_eol;
      break;
    case CODING_RESULT_INVALID_SRC:
      Vlast_code_conversion_error = Qinvalid_source;
      break;
    case CODING_RESULT_INTERRUPT:
      Vlast_code_conversion_error = Qinterrupted;
      break;
    case CODING_RESULT_INSUFFICIENT_MEM:
      Vlast_code_conversion_error = Qinsufficient_memory;
      break;
    }
}

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#define CODING_DECODE_CHAR(coding, src, src_base, src_end, charset, code, c) \
  do {									     \
    charset_map_loaded = 0;						     \
    c = DECODE_CHAR (charset, code);					     \
    if (charset_map_loaded)						     \
      {									     \
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	const unsigned char *orig = coding->source;			     \
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	EMACS_INT offset;						     \
									     \
	coding_set_source (coding);					     \
	offset = coding->source - orig;					     \
	src += offset;							     \
	src_base += offset;						     \
	src_end += offset;						     \
      }									     \
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  } while (0)


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#define ASSURE_DESTINATION(bytes)				\
  do {								\
    if (dst + (bytes) >= dst_end)				\
      {								\
	int more_bytes = charbuf_end - charbuf + (bytes);	\
								\
	dst = alloc_destination (coding, more_bytes, dst);	\
	dst_end = coding->destination + coding->dst_bytes;	\
      }								\
  } while (0)
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static void
coding_set_source (coding)
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     struct coding_system *coding;
{
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  if (BUFFERP (coding->src_object))
    {
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      struct buffer *buf = XBUFFER (coding->src_object);
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      if (coding->src_pos < 0)
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	coding->source = BUF_GAP_END_ADDR (buf) + coding->src_pos_byte;
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      else
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	coding->source = BUF_BYTE_ADDRESS (buf, coding->src_pos_byte);
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    }
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  else if (STRINGP (coding->src_object))
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    {
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      coding->source = SDATA (coding->src_object) + coding->src_pos_byte;
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    }
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  else
    /* Otherwise, the source is C string and is never relocated
       automatically.  Thus we don't have to update anything.  */
    ;
}
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static void
coding_set_destination (coding)
     struct coding_system *coding;
{
  if (BUFFERP (coding->dst_object))
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    {
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      if (coding->src_pos < 0)
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	{
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	  coding->destination = BEG_ADDR + coding->dst_pos_byte - 1;
	  coding->dst_bytes = (GAP_END_ADDR
			       - (coding->src_bytes - coding->consumed)
			       - coding->destination);
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	}
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      else
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	{
	  /* We are sure that coding->dst_pos_byte is before the gap
	     of the buffer. */
	  coding->destination = (BUF_BEG_ADDR (XBUFFER (coding->dst_object))
				 + coding->dst_pos_byte - 1);
	  coding->dst_bytes = (BUF_GAP_END_ADDR (XBUFFER (coding->dst_object))
			       - coding->destination);
	}
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    }
  else
    /* Otherwise, the destination is C string and is never relocated
       automatically.  Thus we don't have to update anything.  */
    ;
}


static void
coding_alloc_by_realloc (coding, bytes)
     struct coding_system *coding;
     EMACS_INT bytes;
{
  coding->destination = (unsigned char *) xrealloc (coding->destination,
						    coding->dst_bytes + bytes);
  coding->dst_bytes += bytes;
}

static void
coding_alloc_by_making_gap (coding, bytes)
     struct coding_system *coding;
     EMACS_INT bytes;
{
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  if (BUFFERP (coding->dst_object)
      && EQ (coding->src_object, coding->dst_object))
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    {
      EMACS_INT add = coding->src_bytes - coding->consumed;

      GAP_SIZE -= add; ZV += add; Z += add; ZV_BYTE += add; Z_BYTE += add;
      make_gap (bytes);
      GAP_SIZE += add; ZV -= add; Z -= add; ZV_BYTE -= add; Z_BYTE -= add;
    }
  else
    {
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      Lisp_Object this_buffer;

      this_buffer = Fcurrent_buffer ();
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      set_buffer_internal (XBUFFER (coding->dst_object));
      make_gap (bytes);
      set_buffer_internal (XBUFFER (this_buffer));
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    }
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}
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static unsigned char *
alloc_destination (coding, nbytes, dst)
     struct coding_system *coding;
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     EMACS_INT nbytes;
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     unsigned char *dst;
{
  EMACS_INT offset = dst - coding->destination;

  if (BUFFERP (coding->dst_object))
    coding_alloc_by_making_gap (coding, nbytes);
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  else
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    coding_alloc_by_realloc (coding, nbytes);
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  record_conversion_result (coding, CODING_RESULT_SUCCESS);
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  coding_set_destination (coding);
  dst = coding->destination + offset;
  return dst;
}
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/** Macros for annotations.  */

/* Maximum length of annotation data (sum of annotations for
   composition and charset).  */
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#define MAX_ANNOTATION_LENGTH (4 + (MAX_COMPOSITION_COMPONENTS * 2) - 1 + 4)
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/* An annotation data is stored in the array coding->charbuf in this
   format:
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     [ -LENGTH ANNOTATION_MASK NCHARS ... ]
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   LENGTH is the number of elements in the annotation.
   ANNOTATION_MASK is one of CODING_ANNOTATE_XXX_MASK.
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   NCHARS is the number of characters in the text annotated.
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   The format of the following elements depend on ANNOTATION_MASK.

   In the case of CODING_ANNOTATE_COMPOSITION_MASK, these elements
   follows:
     ... METHOD [ COMPOSITION-COMPONENTS ... ]
   METHOD is one of enum composition_method.
   Optionnal COMPOSITION-COMPONENTS are characters and composition
   rules.

   In the case of CODING_ANNOTATE_CHARSET_MASK, one element CHARSET-ID
   follows.  */

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#define ADD_ANNOTATION_DATA(buf, len, mask, nchars)	\
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  do {							\
    *(buf)++ = -(len);					\
    *(buf)++ = (mask);					\
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    *(buf)++ = (nchars);				\
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    coding->annotated = 1;				\
  } while (0);

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#define ADD_COMPOSITION_DATA(buf, nchars, method)			    \
  do {									    \
    ADD_ANNOTATION_DATA (buf, 4, CODING_ANNOTATE_COMPOSITION_MASK, nchars); \
    *buf++ = method;							    \
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  } while (0)


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#define ADD_CHARSET_DATA(buf, nchars, id)				\
  do {									\
    ADD_ANNOTATION_DATA (buf, 4, CODING_ANNOTATE_CHARSET_MASK, nchars);	\
    *buf++ = id;							\
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  } while (0)

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/*** 2. Emacs' internal format (emacs-utf-8) ***/




/*** 3. UTF-8 ***/

/* See the above "GENERAL NOTES on `detect_coding_XXX ()' functions".
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   Check if a text is encoded in UTF-8.  If it is, return 1, else
   return 0.  */
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#define UTF_8_1_OCTET_P(c)         ((c) < 0x80)
#define UTF_8_EXTRA_OCTET_P(c)     (((c) & 0xC0) == 0x80)
#define UTF_8_2_OCTET_LEADING_P(c) (((c) & 0xE0) == 0xC0)
#define UTF_8_3_OCTET_LEADING_P(c) (((c) & 0xF0) == 0xE0)
#define UTF_8_4_OCTET_LEADING_P(c) (((c) & 0xF8) == 0xF0)
#define UTF_8_5_OCTET_LEADING_P(c) (((c) & 0xFC) == 0xF8)

static int
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detect_coding_utf_8 (coding, detect_info)
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     struct coding_system *coding;
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     struct coding_detection_info *detect_info;
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{
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  const unsigned char *src = coding->source, *src_base;
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  const unsigned char *src_end = coding->source + coding->src_bytes;
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  int multibytep = coding->src_multibyte;
  int consumed_chars = 0;
  int found = 0;

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  detect_info->checked |= CATEGORY_MASK_UTF_8;
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  /* A coding system of this category is always ASCII compatible.  */
  src += coding->head_ascii;

  while (1)
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    {
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      int c, c1, c2, c3, c4;
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      src_base = src;
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      ONE_MORE_BYTE (c);
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      if (c < 0 || UTF_8_1_OCTET_P (c))
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	continue;
      ONE_MORE_BYTE (c1);
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      if (c1 < 0 || ! UTF_8_EXTRA_OCTET_P (c1))
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	break;
      if (UTF_8_2_OCTET_LEADING_P (c))
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	{
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	  found = CATEGORY_MASK_UTF_8;
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	  continue;
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	}
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      ONE_MORE_BYTE (c2);
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      if (c2 < 0 || ! UTF_8_EXTRA_OCTET_P (c2))
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	break;
      if (UTF_8_3_OCTET_LEADING_P (c))
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	{
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	  found = CATEGORY_MASK_UTF_8;
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	  continue;
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	}
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      ONE_MORE_BYTE (c3);
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      if (c3 < 0 || ! UTF_8_EXTRA_OCTET_P (c3))
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	break;
      if (UTF_8_4_OCTET_LEADING_P (c))
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	{
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	  found = CATEGORY_MASK_UTF_8;
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	  continue;
	}
      ONE_MORE_BYTE (c4);
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      if (c4 < 0 || ! UTF_8_EXTRA_OCTET_P (c4))
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	break;
      if (UTF_8_5_OCTET_LEADING_P (c))
	{
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	  found = CATEGORY_MASK_UTF_8;
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	  continue;
	}
      break;
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    }
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  detect_info->rejected |= CATEGORY_MASK_UTF_8;
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  return 0;
1148

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 no_more_source:
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  if (src_base < src && coding->mode & CODING_MODE_LAST_BLOCK)
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    {
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      detect_info->rejected |= CATEGORY_MASK_UTF_8;
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      return 0;
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    }
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  detect_info->found |= found;
  return 1;
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}

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static void
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decode_coding_utf_8 (coding)
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     struct coding_system *coding;
{
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  const unsigned char *src = coding->source + coding->consumed;
  const unsigned char *src_end = coding->source + coding->src_bytes;
  const unsigned char *src_base;
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  int *charbuf = coding->charbuf + coding->charbuf_used;
  int *charbuf_end = coding->charbuf + coding->charbuf_size;
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  int consumed_chars = 0, consumed_chars_base;
  int multibytep = coding->src_multibyte;
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  Lisp_Object attr, charset_list;
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  CODING_GET_INFO (coding, attr, charset_list);
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  while (1)
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    {
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      int c, c1, c2, c3, c4, c5;
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      src_base = src;
      consumed_chars_base = consumed_chars;
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      if (charbuf >= charbuf_end)
	break;

      ONE_MORE_BYTE (c1);
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      if (c1 < 0)
	{
	  c = - c1;
	}
      else if (UTF_8_1_OCTET_P(c1))
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	{
	  c = c1;
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	}
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      else
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	{
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	  ONE_MORE_BYTE (c2);
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	  if (c2 < 0 || ! UTF_8_EXTRA_OCTET_P (c2))
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	    goto invalid_code;
	  if (UTF_8_2_OCTET_LEADING_P (c1))
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	    {
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	      c = ((c1 & 0x1F) << 6) | (c2 & 0x3F);
	      /* Reject overlong sequences here and below.  Encoders
		 producing them are incorrect, they can be misleading,
		 and they mess up read/write invariance.  */
	      if (c < 128)
		goto invalid_code;