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/* CPP Library - charsets

   Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006, 2008, 2009

   Free Software Foundation, Inc.

   Broken out of c-lex.c Apr 2003, adding valid C99 UCN ranges.

This program is free software; you can redistribute it and/or modify it

under the terms of the GNU General Public License as published by the

Free Software Foundation; either version 3, or (at your option) any

later version.

This program is distributed in the hope that it will be useful,

but WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

GNU General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; see the file COPYING3.  If not see

<http://www.gnu.org/licenses/>.  */

#include "config.h"

#include "system.h"

#include "cpplib.h"

#include "internal.h"

/* Character set handling for C-family languages.

   Terminological note: In what follows, "charset" or "character set"

   will be taken to mean both an abstract set of characters and an

   encoding for that set.

   The C99 standard discusses two character sets: source and execution.

   The source character set is used for internal processing in translation

   phases 1 through 4; the execution character set is used thereafter.

   Both are required by 5.2.1.2p1 to be multibyte encodings, not wide

   character encodings (see 3.7.2, 3.7.3 for the standardese meanings

   of these terms).  Furthermore, the "basic character set" (listed in

   5.2.1p3) is to be encoded in each with values one byte wide, and is

   to appear in the initial shift state.

   It is not explicitly mentioned, but there is also a "wide execution

   character set" used to encode wide character constants and wide

   string literals; this is supposed to be the result of applying the

   standard library function mbstowcs() to an equivalent narrow string

   (6.4.5p5).  However, the behavior of hexadecimal and octal

   \-escapes is at odds with this; they are supposed to be translated

   directly to wchar_t values (6.4.4.4p5,6).

   The source character set is not necessarily the character set used

   to encode physical source files on disk; translation phase 1 converts

   from whatever that encoding is to the source character set.

   The presence of universal character names in C99 (6.4.3 et seq.)

   forces the source character set to be isomorphic to ISO 10646,

   that is, Unicode.  There is no such constraint on the execution

   character set; note also that the conversion from source to

   execution character set does not occur for identifiers (5.1.1.2p1#5).

   For convenience of implementation, the source character set's

   encoding of the basic character set should be identical to the

   execution character set OF THE HOST SYSTEM's encoding of the basic

   character set, and it should not be a state-dependent encoding.

   cpplib uses UTF-8 or UTF-EBCDIC for the source character set,

   depending on whether the host is based on ASCII or EBCDIC (see

   respectively Unicode section 2.3/ISO10646 Amendment 2, and Unicode

   Technical Report #16).  With limited exceptions, it relies on the

   system library's iconv() primitive to do charset conversion

   (specified in SUSv2).  */

#if !HAVE_ICONV

/* Make certain that the uses of iconv(), iconv_open(), iconv_close()

   below, which are guarded only by if statements with compile-time

   constant conditions, do not cause link errors.  */

#define iconv_open(x, y) (errno = EINVAL, (iconv_t)-1)

#define iconv(a,b,c,d,e) (errno = EINVAL, (size_t)-1)

#define iconv_close(x)   (void)0

#define ICONV_CONST

#endif

#if HOST_CHARSET == HOST_CHARSET_ASCII

#define SOURCE_CHARSET "UTF-8"

#define LAST_POSSIBLY_BASIC_SOURCE_CHAR 0x7e

#elif HOST_CHARSET == HOST_CHARSET_EBCDIC

#define SOURCE_CHARSET "UTF-EBCDIC"

#define LAST_POSSIBLY_BASIC_SOURCE_CHAR 0xFF

#else

#error "Unrecognized basic host character set"

#endif

#ifndef EILSEQ

#define EILSEQ EINVAL

#endif

/* This structure is used for a resizable string buffer throughout.  */

/* Don't call it strbuf, as that conflicts with unistd.h on systems

   such as DYNIX/ptx where unistd.h includes stropts.h.  */

struct _cpp_strbuf

{

  uchar *text;

  size_t asize;

  size_t len;

};

/* This is enough to hold any string that fits on a single 80-column

   line, even if iconv quadruples its size (e.g. conversion from

   ASCII to UTF-32) rounded up to a power of two.  */

#define OUTBUF_BLOCK_SIZE 256

/* Conversions between UTF-8 and UTF-16/32 are implemented by custom

   logic.  This is because a depressing number of systems lack iconv,

   or have have iconv libraries that do not do these conversions, so

   we need a fallback implementation for them.  To ensure the fallback

   doesn't break due to neglect, it is used on all systems.

   UTF-32 encoding is nice and simple: a four-byte binary number,

   constrained to the range 00000000-7FFFFFFF to avoid questions of

   signedness.  We do have to cope with big- and little-endian

   variants.

   UTF-16 encoding uses two-byte binary numbers, again in big- and

   little-endian variants, for all values in the 00000000-0000FFFF

   range.  Values in the 00010000-0010FFFF range are encoded as pairs

   of two-byte numbers, called "surrogate pairs": given a number S in

   this range, it is mapped to a pair (H, L) as follows:

     H = (S - 0x10000) / 0x400 + 0xD800

     L = (S - 0x10000) % 0x400 + 0xDC00

   Two-byte values in the D800...DFFF range are ill-formed except as a

   component of a surrogate pair.  Even if the encoding within a

   two-byte value is little-endian, the H member of the surrogate pair

   comes first.

   There is no way to encode values in the 00110000-7FFFFFFF range,

   which is not currently a problem as there are no assigned code

   points in that range; however, the author expects that it will

   eventually become necessary to abandon UTF-16 due to this

   limitation.  Note also that, because of these pairs, UTF-16 does

   not meet the requirements of the C standard for a wide character

   encoding (see 3.7.3 and 6.4.4.4p11).

   UTF-8 encoding looks like this:

   value range         encoded as

   00000000-0000007F   0xxxxxxx

   00000080-000007FF   110xxxxx 10xxxxxx

   00000800-0000FFFF   1110xxxx 10xxxxxx 10xxxxxx

   00010000-001FFFFF   11110xxx 10xxxxxx 10xxxxxx 10xxxxxx

   00200000-03FFFFFF   111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx

   04000000-7FFFFFFF   1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx

   Values in the 0000D800 ... 0000DFFF range (surrogates) are invalid,

   which means that three-byte sequences ED xx yy, with A0 <= xx <= BF,

   never occur.  Note also that any value that can be encoded by a

   given row of the table can also be encoded by all successive rows,

   but this is not done; only the shortest possible encoding for any

   given value is valid.  For instance, the character 07C0 could be

   encoded as any of DF 80, E0 9F 80, F0 80 9F 80, F8 80 80 9F 80, or

   FC 80 80 80 9F 80.  Only the first is valid.

   An implementation note: the transformation from UTF-16 to UTF-8, or

   vice versa, is easiest done by using UTF-32 as an intermediary.  */

/* Internal primitives which go from an UTF-8 byte stream to native-endian

   UTF-32 in a cppchar_t, or vice versa; this avoids an extra marshal/unmarshal

   operation in several places below.  */

static inline int

one_utf8_to_cppchar (const uchar **inbufp, size_t *inbytesleftp,

                     cppchar_t *cp)

{

  static const uchar masks[6] = { 0x7F, 0x1F, 0x0F, 0x07, 0x03, 0x01 };

  static const uchar patns[6] = { 0x00, 0xC0, 0xE0, 0xF0, 0xF8, 0xFC };

  cppchar_t c;

  const uchar *inbuf = *inbufp;

  size_t nbytes, i;

  if (*inbytesleftp < 1)

    return EINVAL;

  c = *inbuf;

  if (c < 0x80)

    {

      *cp = c;

      *inbytesleftp -= 1;

      *inbufp += 1;

      return 0;

    }

  /* The number of leading 1-bits in the first byte indicates how many

     bytes follow.  */

  for (nbytes = 2; nbytes < 7; nbytes++)

    if ((c & ~masks[nbytes-1]) == patns[nbytes-1])

      goto found;

  return EILSEQ;

 found:

  if (*inbytesleftp < nbytes)

    return EINVAL;

  c = (c & masks[nbytes-1]);

  inbuf++;

  for (i = 1; i < nbytes; i++)

    {

      cppchar_t n = *inbuf++;

      if ((n & 0xC0) != 0x80)

        return EILSEQ;

      c = ((c << 6) + (n & 0x3F));

    }

  /* Make sure the shortest possible encoding was used.  */

  if (c <=      0x7F && nbytes > 1) return EILSEQ;

  if (c <=     0x7FF && nbytes > 2) return EILSEQ;

  if (c <=    0xFFFF && nbytes > 3) return EILSEQ;

  if (c <=  0x1FFFFF && nbytes > 4) return EILSEQ;

  if (c <= 0x3FFFFFF && nbytes > 5) return EILSEQ;

  /* Make sure the character is valid.  */

  if (c > 0x7FFFFFFF || (c >= 0xD800 && c <= 0xDFFF)) return EILSEQ;

  *cp = c;

  *inbufp = inbuf;

  *inbytesleftp -= nbytes;

  return 0;

}

static inline int

one_cppchar_to_utf8 (cppchar_t c, uchar **outbufp, size_t *outbytesleftp)

{

  static const uchar masks[6] =  { 0x00, 0xC0, 0xE0, 0xF0, 0xF8, 0xFC };

  static const uchar limits[6] = { 0x80, 0xE0, 0xF0, 0xF8, 0xFC, 0xFE };

  size_t nbytes;

  uchar buf[6], *p = &buf[6];

  uchar *outbuf = *outbufp;

  nbytes = 1;

  if (c < 0x80)

    *--p = c;

  else

    {

      do

        {

          *--p = ((c & 0x3F) | 0x80);

          c >>= 6;

          nbytes++;

        }

      while (c >= 0x3F || (c & limits[nbytes-1]));

      *--p = (c | masks[nbytes-1]);

    }

  if (*outbytesleftp < nbytes)

    return E2BIG;

  while (p < &buf[6])

    *outbuf++ = *p++;

  *outbytesleftp -= nbytes;

  *outbufp = outbuf;

  return 0;

}

/* The following four functions transform one character between the two

   encodings named in the function name.  All have the signature

   int (*)(iconv_t bigend, const uchar **inbufp, size_t *inbytesleftp,

           uchar **outbufp, size_t *outbytesleftp)

   BIGEND must have the value 0 or 1, coerced to (iconv_t); it is

   interpreted as a boolean indicating whether big-endian or

   little-endian encoding is to be used for the member of the pair

   that is not UTF-8.

   INBUFP, INBYTESLEFTP, OUTBUFP, OUTBYTESLEFTP work exactly as they

   do for iconv.

   The return value is either 0 for success, or an errno value for

   failure, which may be E2BIG (need more space), EILSEQ (ill-formed

   input sequence), ir EINVAL (incomplete input sequence).  */

static inline int

one_utf8_to_utf32 (iconv_t bigend, const uchar **inbufp, size_t *inbytesleftp,

                   uchar **outbufp, size_t *outbytesleftp)

{

  uchar *outbuf;

  cppchar_t s = 0;

  int rval;

  /* Check for space first, since we know exactly how much we need.  */

  if (*outbytesleftp < 4)

    return E2BIG;

  rval = one_utf8_to_cppchar (inbufp, inbytesleftp, &s);

  if (rval)

    return rval;

  outbuf = *outbufp;

  outbuf[bigend ? 3 : 0] = (s & 0x000000FF);

  outbuf[bigend ? 2 : 1] = (s & 0x0000FF00) >> 8;

  outbuf[bigend ? 1 : 2] = (s & 0x00FF0000) >> 16;

  outbuf[bigend ? 0 : 3] = (s & 0xFF000000) >> 24;

  *outbufp += 4;

  *outbytesleftp -= 4;

  return 0;

}

static inline int

one_utf32_to_utf8 (iconv_t bigend, const uchar **inbufp, size_t *inbytesleftp,

                   uchar **outbufp, size_t *outbytesleftp)

{

  cppchar_t s;

  int rval;

  const uchar *inbuf;

  if (*inbytesleftp < 4)

    return EINVAL;

  inbuf = *inbufp;

  s  = inbuf[bigend ? 0 : 3] << 24;

  s += inbuf[bigend ? 1 : 2] << 16;

  s += inbuf[bigend ? 2 : 1] << 8;

  s += inbuf[bigend ? 3 : 0];

  if (s >= 0x7FFFFFFF || (s >= 0xD800 && s <= 0xDFFF))

    return EILSEQ;

  rval = one_cppchar_to_utf8 (s, outbufp, outbytesleftp);

  if (rval)

    return rval;

  *inbufp += 4;

  *inbytesleftp -= 4;

  return 0;

}

static inline int

one_utf8_to_utf16 (iconv_t bigend, const uchar **inbufp, size_t *inbytesleftp,

                   uchar **outbufp, size_t *outbytesleftp)

{

  int rval;

  cppchar_t s = 0;

  const uchar *save_inbuf = *inbufp;

  size_t save_inbytesleft = *inbytesleftp;

  uchar *outbuf = *outbufp;

  rval = one_utf8_to_cppchar (inbufp, inbytesleftp, &s);

  if (rval)

    return rval;

  if (s > 0x0010FFFF)

    {

      *inbufp = save_inbuf;

      *inbytesleftp = save_inbytesleft;

      return EILSEQ;

    }

  if (s < 0xFFFF)

    {

      if (*outbytesleftp < 2)

        {

          *inbufp = save_inbuf;

          *inbytesleftp = save_inbytesleft;

          return E2BIG;

        }

      outbuf[bigend ? 1 : 0] = (s & 0x00FF);

      outbuf[bigend ? 0 : 1] = (s & 0xFF00) >> 8;

      *outbufp += 2;

      *outbytesleftp -= 2;

      return 0;

    }

  else

    {

      cppchar_t hi, lo;

      if (*outbytesleftp < 4)

        {

          *inbufp = save_inbuf;

          *inbytesleftp = save_inbytesleft;

          return E2BIG;

        }

      hi = (s - 0x10000) / 0x400 + 0xD800;

      lo = (s - 0x10000) % 0x400 + 0xDC00;

      /* Even if we are little-endian, put the high surrogate first.

         ??? Matches practice?  */

      outbuf[bigend ? 1 : 0] = (hi & 0x00FF);

      outbuf[bigend ? 0 : 1] = (hi & 0xFF00) >> 8;

      outbuf[bigend ? 3 : 2] = (lo & 0x00FF);

      outbuf[bigend ? 2 : 3] = (lo & 0xFF00) >> 8;

      *outbufp += 4;

      *outbytesleftp -= 4;

      return 0;

    }

}

static inline int

one_utf16_to_utf8 (iconv_t bigend, const uchar **inbufp, size_t *inbytesleftp,

                   uchar **outbufp, size_t *outbytesleftp)

{

  cppchar_t s;

  const uchar *inbuf = *inbufp;

  int rval;

  if (*inbytesleftp < 2)

    return EINVAL;

  s  = inbuf[bigend ? 0 : 1] << 8;

  s += inbuf[bigend ? 1 : 0];

  /* Low surrogate without immediately preceding high surrogate is invalid.  */

  if (s >= 0xDC00 && s <= 0xDFFF)

    return EILSEQ;

  /* High surrogate must have a following low surrogate.  */

  else if (s >= 0xD800 && s <= 0xDBFF)

    {

      cppchar_t hi = s, lo;

      if (*inbytesleftp < 4)

        return EINVAL;

      lo  = inbuf[bigend ? 2 : 3] << 8;

      lo += inbuf[bigend ? 3 : 2];

      if (lo < 0xDC00 || lo > 0xDFFF)

        return EILSEQ;

      s = (hi - 0xD800) * 0x400 + (lo - 0xDC00) + 0x10000;

    }

  rval = one_cppchar_to_utf8 (s, outbufp, outbytesleftp);

  if (rval)

    return rval;

  /* Success - update the input pointers (one_cppchar_to_utf8 has done

     the output pointers for us).  */

  if (s <= 0xFFFF)

    {

      *inbufp += 2;

      *inbytesleftp -= 2;

    }

  else

    {

      *inbufp += 4;

      *inbytesleftp -= 4;

    }

  return 0;

}

/* Helper routine for the next few functions.  The 'const' on

   one_conversion means that we promise not to modify what function is

   pointed to, which lets the inliner see through it.  */

static inline bool

conversion_loop (int (*const one_conversion)(iconv_t, const uchar **, size_t *,

                                             uchar **, size_t *),

                 iconv_t cd, const uchar *from, size_t flen, struct _cpp_strbuf *to)

{

  const uchar *inbuf;

  uchar *outbuf;

  size_t inbytesleft, outbytesleft;

  int rval;

  inbuf = from;

  inbytesleft = flen;

  outbuf = to->text + to->len;

  outbytesleft = to->asize - to->len;

  for (;;)

    {

      do

        rval = one_conversion (cd, &inbuf, &inbytesleft,

                               &outbuf, &outbytesleft);

      while (inbytesleft && !rval);

      if (__builtin_expect (inbytesleft == 0, 1))

        {

          to->len = to->asize - outbytesleft;

          return true;

        }

      if (rval != E2BIG)

        {

          errno = rval;

          return false;

        }

      outbytesleft += OUTBUF_BLOCK_SIZE;

      to->asize += OUTBUF_BLOCK_SIZE;

      to->text = XRESIZEVEC (uchar, to->text, to->asize);

      outbuf = to->text + to->asize - outbytesleft;

    }

}

/* These functions convert entire strings between character sets.

   They all have the signature

   bool (*)(iconv_t cd, const uchar *from, size_t flen, struct _cpp_strbuf *to);

   The input string FROM is converted as specified by the function

   name plus the iconv descriptor CD (which may be fake), and the

   result appended to TO.  On any error, false is returned, otherwise true.  */

/* These four use the custom conversion code above.  */

static bool

convert_utf8_utf16 (iconv_t cd, const uchar *from, size_t flen,

                    struct _cpp_strbuf *to)

{

  return conversion_loop (one_utf8_to_utf16, cd, from, flen, to);

}

static bool

convert_utf8_utf32 (iconv_t cd, const uchar *from, size_t flen,

                    struct _cpp_strbuf *to)

{

  return conversion_loop (one_utf8_to_utf32, cd, from, flen, to);

}

static bool

convert_utf16_utf8 (iconv_t cd, const uchar *from, size_t flen,

                    struct _cpp_strbuf *to)

{

  return conversion_loop (one_utf16_to_utf8, cd, from, flen, to);

}

static bool

convert_utf32_utf8 (iconv_t cd, const uchar *from, size_t flen,

                    struct _cpp_strbuf *to)

{

  return conversion_loop (one_utf32_to_utf8, cd, from, flen, to);

}

/* Identity conversion, used when we have no alternative.  */

static bool

convert_no_conversion (iconv_t cd ATTRIBUTE_UNUSED,

                       const uchar *from, size_t flen, struct _cpp_strbuf *to)

{

  if (to->len + flen > to->asize)

    {

      to->asize = to->len + flen;

      to->text = XRESIZEVEC (uchar, to->text, to->asize);

    }

  memcpy (to->text + to->len, from, flen);

  to->len += flen;

  return true;

}

/* And this one uses the system iconv primitive.  It's a little

   different, since iconv's interface is a little different.  */

#if HAVE_ICONV

#define CONVERT_ICONV_GROW_BUFFER \

  do { \

      outbytesleft += OUTBUF_BLOCK_SIZE; \

      to->asize += OUTBUF_BLOCK_SIZE; \

      to->text = XRESIZEVEC (uchar, to->text, to->asize); \

      outbuf = (char *)to->text + to->asize - outbytesleft; \

  } while (0)

static bool

convert_using_iconv (iconv_t cd, const uchar *from, size_t flen,

                     struct _cpp_strbuf *to)

{

  ICONV_CONST char *inbuf;

  char *outbuf;

  size_t inbytesleft, outbytesleft;

  /* Reset conversion descriptor and check that it is valid.  */

  if (iconv (cd, 0, 0, 0, 0) == (size_t)-1)

    return false;

  inbuf = (ICONV_CONST char *)from;

  inbytesleft = flen;

  outbuf = (char *)to->text + to->len;

  outbytesleft = to->asize - to->len;

  for (;;)

    {

      iconv (cd, &inbuf, &inbytesleft, &outbuf, &outbytesleft);

      if (__builtin_expect (inbytesleft == 0, 1))

        {

          /* Close out any shift states, returning to the initial state.  */

          if (iconv (cd, 0, 0, &outbuf, &outbytesleft) == (size_t)-1)

            {

              if (errno != E2BIG)

                return false;

              CONVERT_ICONV_GROW_BUFFER;

              if (iconv (cd, 0, 0, &outbuf, &outbytesleft) == (size_t)-1)

                return false;

            }

          to->len = to->asize - outbytesleft;

          return true;

        }

      if (errno != E2BIG)

        return false;

      CONVERT_ICONV_GROW_BUFFER;

    }

}

#else

#define convert_using_iconv 0 /* prevent undefined symbol error below */

#endif

/* Arrange for the above custom conversion logic to be used automatically

   when conversion between a suitable pair of character sets is requested.  */

#define APPLY_CONVERSION(CONVERTER, FROM, FLEN, TO) \

   CONVERTER.func (CONVERTER.cd, FROM, FLEN, TO)

struct conversion

{

  const char *pair;

  convert_f func;

  iconv_t fake_cd;

};

static const struct conversion conversion_tab[] = {

  { "UTF-8/UTF-32LE", convert_utf8_utf32, (iconv_t)0 },

  { "UTF-8/UTF-32BE", convert_utf8_utf32, (iconv_t)1 },

  { "UTF-8/UTF-16LE", convert_utf8_utf16, (iconv_t)0 },

  { "UTF-8/UTF-16BE", convert_utf8_utf16, (iconv_t)1 },

  { "UTF-32LE/UTF-8", convert_utf32_utf8, (iconv_t)0 },

  { "UTF-32BE/UTF-8", convert_utf32_utf8, (iconv_t)1 },

  { "UTF-16LE/UTF-8", convert_utf16_utf8, (iconv_t)0 },

  { "UTF-16BE/UTF-8", convert_utf16_utf8, (iconv_t)1 },

};

/* Subroutine of cpp_init_iconv: initialize and return a

   cset_converter structure for conversion from FROM to TO.  If

   iconv_open() fails, issue an error and return an identity

   converter.  Silently return an identity converter if FROM and TO

   are identical.  */

static struct cset_converter

init_iconv_desc (cpp_reader *pfile, const char *to, const char *from)

{

  struct cset_converter ret;

  char *pair;

  size_t i;

  if (!strcasecmp (to, from))

    {

      ret.func = convert_no_conversion;

      ret.cd = (iconv_t) -1;

      ret.width = -1;

      return ret;

    }

  pair = (char *) alloca(strlen(to) + strlen(from) + 2);

  strcpy(pair, from);

  strcat(pair, "/");

  strcat(pair, to);

  for (i = 0; i < ARRAY_SIZE (conversion_tab); i++)

    if (!strcasecmp (pair, conversion_tab[i].pair))

      {

        ret.func = conversion_tab[i].func;

        ret.cd = conversion_tab[i].fake_cd;

        ret.width = -1;

        return ret;

      }

  /* No custom converter - try iconv.  */

  if (HAVE_ICONV)

    {

      ret.func = convert_using_iconv;

      ret.cd = iconv_open (to, from);

      ret.width = -1;

      if (ret.cd == (iconv_t) -1)

        {

          if (errno == EINVAL)

            cpp_error (pfile, CPP_DL_ERROR, /* FIXME should be DL_SORRY */

                       "conversion from %s to %s not supported by iconv",

                       from, to);

          else

            cpp_errno (pfile, CPP_DL_ERROR, "iconv_open");

          ret.func = convert_no_conversion;

        }

    }

  else