// Copyright 2006 Nemanja Trifunovic

/*

Permission is hereby granted, free of charge, to any person or organization

obtaining a copy of the software and accompanying documentation covered by

this license (the "Software") to use, reproduce, display, distribute,

execute, and transmit the Software, and to prepare derivative works of the

Software, and to permit third-parties to whom the Software is furnished to

do so, all subject to the following:

The copyright notices in the Software and this entire statement, including

the above license grant, this restriction and the following disclaimer,

must be included in all copies of the Software, in whole or in part, and

all derivative works of the Software, unless such copies or derivative

works are solely in the form of machine-executable object code generated by

a source language processor.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT

SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE

FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,

ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER

DEALINGS IN THE SOFTWARE.

*/

#ifndef UTF8_FOR_CPP_CORE_H_2675DCD0_9480_4c0c_B92A_CC14C027B731

#define UTF8_FOR_CPP_CORE_H_2675DCD0_9480_4c0c_B92A_CC14C027B731

#include <iterator>

namespace utf8

{

    // The typedefs for 8-bit, 16-bit and 32-bit unsigned integers

    // You may need to change them to match your system.

    // These typedefs have the same names as ones from cstdint, or boost/cstdint

    typedef unsigned char   uint8_t;

    typedef unsigned short  uint16_t;

    typedef unsigned int    uint32_t;

// Helper code - not intended to be directly called by the library users. May be changed at any time

namespace internal

{

    // Unicode constants

    // Leading (high) surrogates: 0xd800 - 0xdbff

    // Trailing (low) surrogates: 0xdc00 - 0xdfff

    const uint16_t LEAD_SURROGATE_MIN  = 0xd800u;

    const uint16_t LEAD_SURROGATE_MAX  = 0xdbffu;

    const uint16_t TRAIL_SURROGATE_MIN = 0xdc00u;

    const uint16_t TRAIL_SURROGATE_MAX = 0xdfffu;

    const uint16_t LEAD_OFFSET         = LEAD_SURROGATE_MIN - (0x10000 >> 10);

    const uint32_t SURROGATE_OFFSET    = 0x10000u - (LEAD_SURROGATE_MIN << 10) - TRAIL_SURROGATE_MIN;

    // Maximum valid value for a Unicode code point

    const uint32_t CODE_POINT_MAX      = 0x0010ffffu;

    template<typename octet_type>

    inline uint8_t mask8(octet_type oc)

    {

        return static_cast<uint8_t>(0xff & oc);

    }

    template<typename u16_type>

    inline uint16_t mask16(u16_type oc)

    {

        return static_cast<uint16_t>(0xffff & oc);

    }

    template<typename octet_type>

    inline bool is_trail(octet_type oc)

    {

        return ((utf8::internal::mask8(oc) >> 6) == 0x2);

    }

    template <typename u16>

    inline bool is_lead_surrogate(u16 cp)

    {

        return (cp >= LEAD_SURROGATE_MIN && cp <= LEAD_SURROGATE_MAX);

    }

    template <typename u16>

    inline bool is_trail_surrogate(u16 cp)

    {

        return (cp >= TRAIL_SURROGATE_MIN && cp <= TRAIL_SURROGATE_MAX);

    }

    template <typename u16>

    inline bool is_surrogate(u16 cp)

    {

        return (cp >= LEAD_SURROGATE_MIN && cp <= TRAIL_SURROGATE_MAX);

    }

    template <typename u32>

    inline bool is_code_point_valid(u32 cp)

    {

        return (cp <= CODE_POINT_MAX && !utf8::internal::is_surrogate(cp));

    }

    template <typename octet_iterator>

    inline typename std::iterator_traits<octet_iterator>::difference_type

    sequence_length(octet_iterator lead_it)

    {

        uint8_t lead = utf8::internal::mask8(*lead_it);

        if (lead < 0x80)

            return 1;

        else if ((lead >> 5) == 0x6)

            return 2;

        else if ((lead >> 4) == 0xe)

            return 3;

        else if ((lead >> 3) == 0x1e)

            return 4;

        else

            return 0;

    }

    template <typename octet_difference_type>

    inline bool is_overlong_sequence(uint32_t cp, octet_difference_type length)

    {

        if (cp < 0x80) {

            if (length != 1)

                return true;

        }

        else if (cp < 0x800) {

            if (length != 2)

                return true;

        }

        else if (cp < 0x10000) {

            if (length != 3)

                return true;

        }

        return false;

    }

    enum utf_error {UTF8_OK, NOT_ENOUGH_ROOM, INVALID_LEAD, INCOMPLETE_SEQUENCE, OVERLONG_SEQUENCE, INVALID_CODE_POINT};

    /// Helper for get_sequence_x

    template <typename octet_iterator>

    utf_error increase_safely(octet_iterator& it, octet_iterator end)

    {

        if (++it == end)

            return NOT_ENOUGH_ROOM;

        if (!utf8::internal::is_trail(*it))

            return INCOMPLETE_SEQUENCE;

        return UTF8_OK;

    }

    #define UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR(IT, END) {utf_error ret = increase_safely(IT, END); if (ret != UTF8_OK) return ret;}

    /// get_sequence_x functions decode utf-8 sequences of the length x

    template <typename octet_iterator>

    utf_error get_sequence_1(octet_iterator& it, octet_iterator end, uint32_t& code_point)

    {

        if (it == end)

            return NOT_ENOUGH_ROOM;

        code_point = utf8::internal::mask8(*it);

        return UTF8_OK;

    }

    template <typename octet_iterator>

    utf_error get_sequence_2(octet_iterator& it, octet_iterator end, uint32_t& code_point)

    {

        if (it == end)

            return NOT_ENOUGH_ROOM;

        code_point = utf8::internal::mask8(*it);

        UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR(it, end)

        code_point = ((code_point << 6) & 0x7ff) + ((*it) & 0x3f);

        return UTF8_OK;

    }

    template <typename octet_iterator>

    utf_error get_sequence_3(octet_iterator& it, octet_iterator end, uint32_t& code_point)

    {

        if (it == end)

            return NOT_ENOUGH_ROOM;

        code_point = utf8::internal::mask8(*it);

        UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR(it, end)

        code_point = ((code_point << 12) & 0xffff) + ((utf8::internal::mask8(*it) << 6) & 0xfff);

        UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR(it, end)

        code_point += (*it) & 0x3f;

        return UTF8_OK;

    }

    template <typename octet_iterator>

    utf_error get_sequence_4(octet_iterator& it, octet_iterator end, uint32_t& code_point)

    {

        if (it == end)

           return NOT_ENOUGH_ROOM;

        code_point = utf8::internal::mask8(*it);

        UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR(it, end)

        code_point = ((code_point << 18) & 0x1fffff) + ((utf8::internal::mask8(*it) << 12) & 0x3ffff);

        UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR(it, end)

        code_point += (utf8::internal::mask8(*it) << 6) & 0xfff;

        UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR(it, end)

        code_point += (*it) & 0x3f;

        return UTF8_OK;

    }

    #undef UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR

    template <typename octet_iterator>

    utf_error validate_next(octet_iterator& it, octet_iterator end, uint32_t& code_point)

    {

        // Save the original value of it so we can go back in case of failure

        // Of course, it does not make much sense with i.e. stream iterators

        octet_iterator original_it = it;

        uint32_t cp = 0;

        // Determine the sequence length based on the lead octet

        typedef typename std::iterator_traits<octet_iterator>::difference_type octet_difference_type;

        const octet_difference_type length = utf8::internal::sequence_length(it);

        // Get trail octets and calculate the code point

        utf_error err = UTF8_OK;

        switch (length) {

            case 0:

                return INVALID_LEAD;

            case 1:

                err = utf8::internal::get_sequence_1(it, end, cp);

                break;

            case 2:

                err = utf8::internal::get_sequence_2(it, end, cp);

            break;

            case 3:

                err = utf8::internal::get_sequence_3(it, end, cp);

            break;

            case 4:

                err = utf8::internal::get_sequence_4(it, end, cp);

            break;

        }

        if (err == UTF8_OK) {

            // Decoding succeeded. Now, security checks...

            if (utf8::internal::is_code_point_valid(cp)) {

                if (!utf8::internal::is_overlong_sequence(cp, length)){

                    // Passed! Return here.

                    code_point = cp;

                    ++it;

                    return UTF8_OK;

                }

                else

                    err = OVERLONG_SEQUENCE;

            }

            else

                err = INVALID_CODE_POINT;

        }

        // Failure branch - restore the original value of the iterator

        it = original_it;

        return err;

    }

    template <typename octet_iterator>

    inline utf_error validate_next(octet_iterator& it, octet_iterator end) {

        uint32_t ignored;

        return utf8::internal::validate_next(it, end, ignored);

    }

} // namespace internal

    /// The library API - functions intended to be called by the users

    // Byte order mark

    const uint8_t bom[] = {0xef, 0xbb, 0xbf};

    template <typename octet_iterator>

    octet_iterator find_invalid(octet_iterator start, octet_iterator end)

    {

        octet_iterator result = start;

        while (result != end) {

            utf8::internal::utf_error err_code = utf8::internal::validate_next(result, end);

            if (err_code != internal::UTF8_OK)

                return result;

        }

        return result;

    }

    template <typename octet_iterator>

    inline bool is_valid(octet_iterator start, octet_iterator end)

    {

        return (utf8::find_invalid(start, end) == end);

    }

    template <typename octet_iterator>

    inline bool starts_with_bom (octet_iterator it, octet_iterator end)

    {

        return (

            ((it != end) && (utf8::internal::mask8(*it++)) == bom[0]) &&

            ((it != end) && (utf8::internal::mask8(*it++)) == bom[1]) &&

            ((it != end) && (utf8::internal::mask8(*it))   == bom[2])

           );

    }

    //Deprecated in release 2.3

    template <typename octet_iterator>

    inline bool is_bom (octet_iterator it)

    {

        return (

            (utf8::internal::mask8(*it++)) == bom[0] &&

            (utf8::internal::mask8(*it++)) == bom[1] &&

            (utf8::internal::mask8(*it))   == bom[2]

           );

    }

} // namespace utf8

#endif // header guard