/* Charset conversion.

   Copyright (C) 2001-2007, 2010-2026 Free Software Foundation, Inc.

   Written by Bruno Haible and Simon Josefsson.

   This file is free software: you can redistribute it and/or modify

   it under the terms of the GNU Lesser General Public License as

   published by the Free Software Foundation; either version 2.1 of the

   License, or (at your option) any later version.

   This file 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 Lesser General Public License for more details.

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

   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */

#include "striconv.h"

#include <errno.h>

#include <stdlib.h>

#include <string.h>

#if HAVE_ICONV

# include <iconv.h>

/* Get MB_LEN_MAX, CHAR_BIT.  */

# include <limits.h>

#endif

#include "c-strcase.h"

#ifndef SIZE_MAX

# define SIZE_MAX ((size_t) -1)

#endif

#if HAVE_ICONV

int

mem_cd_iconv (const char *src, size_t srclen, iconv_t cd,

              char **resultp, size_t *lengthp)

{

# define tmpbufsize 4096

  /* Set to the initial state.  */

  iconv (cd, NULL, NULL, NULL, NULL);

  /* Determine the length we need.  */

  size_t length;

  {

    size_t count = 0;

    /* The alignment is needed when converting e.g. to glibc's WCHAR_T or

       libiconv's UCS-4-INTERNAL encoding.  */

    union { unsigned int align; char buf[tmpbufsize]; } tmp;

# define tmpbuf tmp.buf

    const char *inptr = src;

    size_t insize = srclen;

    while (insize > 0)

      {

        char *outptr = tmpbuf;

        size_t outsize = tmpbufsize;

        size_t res = iconv (cd,

                            (ICONV_CONST char **) &inptr, &insize,

                            &outptr, &outsize);

        if (res == (size_t)(-1))

          {

            if (errno == E2BIG)

              ;

            else if (errno == EINVAL)

              break;

            else

              return -1;

          }

# if !(defined _LIBICONV_VERSION && !(_LIBICONV_VERSION == 0x10b && defined __APPLE__)) \

     && !(defined __GLIBC__ && !defined __UCLIBC__)

        /* NetBSD iconv() inserts a question mark if it cannot convert.

           Only GNU libiconv (excluding the bastard Apple iconv) and GNU libc

           are known to prefer to fail rather than doing a lossy conversion.  */

        else if (res > 0)

          {

            errno = EILSEQ;

            return -1;

          }

# endif

        count += outptr - tmpbuf;

      }

    {

      char *outptr = tmpbuf;

      size_t outsize = tmpbufsize;

      size_t res = iconv (cd, NULL, NULL, &outptr, &outsize);

      if (res == (size_t)(-1))

        return -1;

      count += outptr - tmpbuf;

    }

    length = count;

# undef tmpbuf

  }

  if (length == 0)

    {

      *lengthp = 0;

      return 0;

    }

  char *result;

  if (*resultp != NULL && *lengthp >= length)

    result = *resultp;

  else

    {

      result = (char *) malloc (length);

      if (result == NULL)

        {

          errno = ENOMEM;

          return -1;

        }

    }

  /* Return to the initial state.  */

  iconv (cd, NULL, NULL, NULL, NULL);

  /* Do the conversion for real.  */

  {

    const char *inptr = src;

    size_t insize = srclen;

    char *outptr = result;

    size_t outsize = length;

    while (insize > 0)

      {

        size_t res = iconv (cd,

                            (ICONV_CONST char **) &inptr, &insize,

                            &outptr, &outsize);

        if (res == (size_t)(-1))

          {

            if (errno == EINVAL)

              break;

            else

              goto fail;

          }

# if !(defined _LIBICONV_VERSION && !(_LIBICONV_VERSION == 0x10b && defined __APPLE__)) \

     && !(defined __GLIBC__ && !defined __UCLIBC__)

        /* NetBSD iconv() inserts a question mark if it cannot convert.

           Only GNU libiconv (excluding the bastard Apple iconv) and GNU libc

           are known to prefer to fail rather than doing a lossy conversion.  */

        else if (res > 0)

          {

            errno = EILSEQ;

            goto fail;

          }

# endif

      }

    {

      size_t res = iconv (cd, NULL, NULL, &outptr, &outsize);

      if (res == (size_t)(-1))

        goto fail;

    }

    if (outsize != 0)

      abort ();

  }

  *resultp = result;

  *lengthp = length;

  return 0;

 fail:

  {

    if (result != *resultp)

      free (result);

    return -1;

  }

# undef tmpbufsize

}

char *

str_cd_iconv (const char *src, iconv_t cd)

{

  /* For most encodings, a trailing NUL byte in the input will be converted

     to a trailing NUL byte in the output.  But not for UTF-7.  So that this

     function is usable for UTF-7, we have to exclude the NUL byte from the

     conversion and add it by hand afterwards.  */

# if !(defined _LIBICONV_VERSION && !(_LIBICONV_VERSION == 0x10b && defined __APPLE__)) \

     && !(defined __GLIBC__ && !defined __UCLIBC__)

  /* NetBSD iconv() inserts a question mark if it cannot convert.

     Only GNU libiconv (excluding the bastard Apple iconv) and GNU libc are

     known to prefer to fail rather than doing a lossy conversion.  For other

     iconv() implementations, we have to look at the number of irreversible

     conversions returned; but this information is lost when iconv() returns

     for an E2BIG reason.  Therefore we cannot use the second, faster

     algorithm.  */

  char *result = NULL;

  size_t length = 0;

  int retval = mem_cd_iconv (src, strlen (src), cd, &result, &length);

  if (retval < 0)

    {

      if (result != NULL)

        abort ();

      return NULL;

    }

  /* Add the terminating NUL byte.  */

  char *final_result =

    (result != NULL ? realloc (result, length + 1) : malloc (length + 1));

  if (final_result == NULL)

    {

      free (result);

      errno = ENOMEM;

      return NULL;

    }

  final_result[length] = '\0';

  return final_result;

# else

  /* This algorithm is likely faster than the one above.  But it may produce

     iconv() returns for an E2BIG reason, when the output size guess is too

     small.  Therefore it can only be used when we don't need the number of

     irreversible conversions performed.  */

  size_t inbytes_remaining = strlen (src);

  /* Make a guess for the worst-case output size, in order to avoid a

     realloc.  It's OK if the guess is wrong as long as it is not zero and

     doesn't lead to an integer overflow.  */

  size_t result_size = inbytes_remaining;

  {

    size_t approx_sqrt_SIZE_MAX = SIZE_MAX >> (sizeof (size_t) * CHAR_BIT / 2);

    if (result_size <= approx_sqrt_SIZE_MAX / MB_LEN_MAX)

      result_size *= MB_LEN_MAX;

  }

  result_size += 1; /* for the terminating NUL */

  char *result = (char *) malloc (result_size);

  if (result == NULL)

    {

      errno = ENOMEM;

      return NULL;

    }

  /* Set to the initial state.  */

  iconv (cd, NULL, NULL, NULL, NULL);

  /* Do the conversion.  */

  size_t length;

  const char *inptr = src;

  {

    char *outptr = result;

    size_t outbytes_remaining = result_size - 1;

    for (;;)

      {

        /* Here inptr + inbytes_remaining = src + strlen (src),

                outptr + outbytes_remaining = result + result_size - 1.  */

        size_t res = iconv (cd,

                            (ICONV_CONST char **) &inptr, &inbytes_remaining,

                            &outptr, &outbytes_remaining);

        if (res == (size_t)(-1))

          {

            if (errno == EINVAL)

              break;

            else if (errno == E2BIG)

              {

                size_t used = outptr - result;

                size_t newsize = result_size * 2;

                char *newresult;

                if (!(newsize > result_size))

                  {

                    errno = ENOMEM;

                    goto failed;

                  }

                newresult = (char *) realloc (result, newsize);

                if (newresult == NULL)

                  {

                    errno = ENOMEM;

                    goto failed;

                  }

                result = newresult;

                result_size = newsize;

                outptr = result + used;

                outbytes_remaining = result_size - 1 - used;

              }

            else

              goto failed;

          }

        else

          break;

      }

    for (;;)

      {

        /* Here outptr + outbytes_remaining = result + result_size - 1.  */

        size_t res = iconv (cd, NULL, NULL, &outptr, &outbytes_remaining);

        if (res == (size_t)(-1))

          {

            if (errno == E2BIG)

              {

                size_t used = outptr - result;

                size_t newsize = result_size * 2;

                char *newresult;

                if (!(newsize > result_size))

                  {

                    errno = ENOMEM;

                    goto failed;

                  }

                newresult = (char *) realloc (result, newsize);

                if (newresult == NULL)

                  {

                    errno = ENOMEM;

                    goto failed;

                  }

                result = newresult;

                result_size = newsize;

                outptr = result + used;

                outbytes_remaining = result_size - 1 - used;

              }

            else

              goto failed;

          }

        else

          break;

      }

    /* Add the terminating NUL byte.  */

    *outptr++ = '\0';

    length = outptr - result;

  }

  /* Give away unused memory.  */

  if (length < result_size)

    {

      char *smaller_result = (char *) realloc (result, length);

      if (smaller_result != NULL)

        result = smaller_result;

    }

  return result;

 failed:

  free (result);

  return NULL;

# endif

}

#endif

char *

str_iconv (const char *src, const char *from_codeset, const char *to_codeset)

{

  if (*src == '\0' || c_strcasecmp (from_codeset, to_codeset) == 0)

    {

      char *result = strdup (src);

      if (result == NULL)

        errno = ENOMEM;

      return result;

    }

  else

    {

#if HAVE_ICONV

      iconv_t cd = iconv_open (to_codeset, from_codeset);

      if (cd == (iconv_t) -1)

        return NULL;

      char *result = str_cd_iconv (src, cd);

      if (result == NULL)

        {

          /* Close cd, but preserve the errno from str_cd_iconv.  */

          int saved_errno = errno;

          iconv_close (cd);

          errno = saved_errno;

        }

      else

        {

          if (iconv_close (cd) < 0)

            {

              free (result);

              return NULL;

            }

        }

      return result;

#else

      /* This is a different error code than if iconv_open existed but didn't

         support from_codeset and to_codeset, so that the caller can emit

         an error message such as

           "iconv() is not supported. Installing GNU libiconv and

            then reinstalling this package would fix this."  */

      errno = ENOSYS;

      return NULL;

#endif

    }

}