/*

 * Copyright © 2011,2012,2014  Google, Inc.

 *

 *  This is part of HarfBuzz, a text shaping library.

 *

 * Permission is hereby granted, without written agreement and without

 * license or royalty fees, to use, copy, modify, and distribute this

 * software and its documentation for any purpose, provided that the

 * above copyright notice and the following two paragraphs appear in

 * all copies of this software.

 *

 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR

 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES

 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN

 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH

 * DAMAGE.

 *

 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,

 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND

 * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS

 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO

 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

 *

 * Google Author(s): Behdad Esfahbod

 */

#ifndef HB_UTF_PRIVATE_HH

#define HB_UTF_PRIVATE_HH

#include "hb-private.hh"

struct hb_utf8_t

{

  typedef uint8_t codepoint_t;

  static inline const uint8_t *

  next (const uint8_t *text,

        const uint8_t *end,

        hb_codepoint_t *unicode,

        hb_codepoint_t replacement)

  {

    /* Written to only accept well-formed sequences.

     * Based on ideas from ICU's U8_NEXT.

     * Generates one "replacement" for each ill-formed byte. */

    hb_codepoint_t c = *text++;

    if (c > 0x7Fu)

    {

      if (hb_in_range (c, 0xC2u, 0xDFu)) /* Two-byte */

      {

        unsigned int t1;

        if (likely (text < end &&

                    (t1 = text[0] - 0x80u) <= 0x3Fu))

        {

          c = ((c&0x1Fu)<<6) | t1;

          text++;

        }

        else

          goto error;

      }

      else if (hb_in_range (c, 0xE0u, 0xEFu)) /* Three-byte */

      {

        unsigned int t1, t2;

        if (likely (1 < end - text &&

                    (t1 = text[0] - 0x80u) <= 0x3Fu &&

                    (t2 = text[1] - 0x80u) <= 0x3Fu))

        {

          c = ((c&0xFu)<<12) | (t1<<6) | t2;

          if (unlikely (c < 0x0800u || hb_in_range (c, 0xD800u, 0xDFFFu)))

            goto error;

          text += 2;

        }

        else

          goto error;

      }

      else if (hb_in_range (c, 0xF0u, 0xF4u)) /* Four-byte */

      {

        unsigned int t1, t2, t3;

        if (likely (2 < end - text &&

                    (t1 = text[0] - 0x80u) <= 0x3Fu &&

                    (t2 = text[1] - 0x80u) <= 0x3Fu &&

                    (t3 = text[2] - 0x80u) <= 0x3Fu))

        {

          c = ((c&0x7u)<<18) | (t1<<12) | (t2<<6) | t3;

          if (unlikely (!hb_in_range (c, 0x10000u, 0x10FFFFu)))

            goto error;

          text += 3;

        }

        else

          goto error;

      }

      else

        goto error;

    }

    *unicode = c;

    return text;

  error:

    *unicode = replacement;

    return text;

  }

  static inline const uint8_t *

  prev (const uint8_t *text,

        const uint8_t *start,

        hb_codepoint_t *unicode,

        hb_codepoint_t replacement)

  {

    const uint8_t *end = text--;

    while (start < text && (*text & 0xc0) == 0x80 && end - text < 4)

      text--;

    if (likely (next (text, end, unicode, replacement) == end))

      return text;

    *unicode = replacement;

    return end - 1;

  }

  static inline unsigned int

  strlen (const uint8_t *text)

  {

    return ::strlen ((const char *) text);

  }

};

struct hb_utf16_t

{

  typedef uint16_t codepoint_t;

  static inline const uint16_t *

  next (const uint16_t *text,

        const uint16_t *end,

        hb_codepoint_t *unicode,

        hb_codepoint_t replacement)

  {

    hb_codepoint_t c = *text++;

    if (likely (!hb_in_range (c, 0xD800u, 0xDFFFu)))

    {

      *unicode = c;

      return text;

    }

    if (likely (hb_in_range (c, 0xD800u, 0xDBFFu)))

    {

      /* High-surrogate in c */

      hb_codepoint_t l;

      if (text < end && ((l = *text), likely (hb_in_range (l, 0xDC00u, 0xDFFFu))))

      {

        /* Low-surrogate in l */

        *unicode = (c << 10) + l - ((0xD800u << 10) - 0x10000u + 0xDC00u);

         text++;

         return text;

      }

    }

    /* Lonely / out-of-order surrogate. */

    *unicode = replacement;

    return text;

  }

  static inline const uint16_t *

  prev (const uint16_t *text,

        const uint16_t *start,

        hb_codepoint_t *unicode,

        hb_codepoint_t replacement)

  {

    const uint16_t *end = text--;

    hb_codepoint_t c = *text;

    if (likely (!hb_in_range (c, 0xD800u, 0xDFFFu)))

    {

      *unicode = c;

      return text;

    }

    if (likely (start < text && hb_in_range (c, 0xDC00u, 0xDFFFu)))

      text--;

    if (likely (next (text, end, unicode, replacement) == end))

      return text;

    *unicode = replacement;

    return end - 1;

  }

  static inline unsigned int

  strlen (const uint16_t *text)

  {

    unsigned int l = 0;

    while (*text++) l++;

    return l;

  }

};

template <bool validate=true>

struct hb_utf32_t

{

  typedef uint32_t codepoint_t;

  static inline const uint32_t *

  next (const uint32_t *text,

        const uint32_t *end HB_UNUSED,

        hb_codepoint_t *unicode,

        hb_codepoint_t replacement)

  {

    hb_codepoint_t c = *text++;

    if (validate && unlikely (c > 0x10FFFFu || hb_in_range (c, 0xD800u, 0xDFFFu)))

      goto error;

    *unicode = c;

    return text;

  error:

    *unicode = replacement;

    return text;

  }

  static inline const uint32_t *

  prev (const uint32_t *text,

        const uint32_t *start HB_UNUSED,

        hb_codepoint_t *unicode,

        hb_codepoint_t replacement)

  {

    next (text - 1, text, unicode, replacement);

    return text - 1;

  }

  static inline unsigned int

  strlen (const uint32_t *text)

  {

    unsigned int l = 0;

    while (*text++) l++;

    return l;

  }

};

struct hb_latin1_t

{

  typedef uint8_t codepoint_t;

  static inline const uint8_t *

  next (const uint8_t *text,

        const uint8_t *end HB_UNUSED,

        hb_codepoint_t *unicode,

        hb_codepoint_t replacement HB_UNUSED)

  {

    *unicode = *text++;

    return text;

  }

  static inline const uint8_t *

  prev (const uint8_t *text,

        const uint8_t *start HB_UNUSED,

        hb_codepoint_t *unicode,

        hb_codepoint_t replacement)

  {

    *unicode = *--text;

    return text;

  }

  static inline unsigned int

  strlen (const uint8_t *text)

  {

    unsigned int l = 0;

    while (*text++) l++;

    return l;

  }

};

#endif /* HB_UTF_PRIVATE_HH */