/* This software is licensed by the MIT License, see LICENSE file */
/*                                Copyright © 2022 Gregory Lirent */

#include "build.h"

const char16_t* fromchar16_unicode(unsigned int* uc, const char16_t* s) {

    unsigned char   n;
    unsigned short* p;
    unsigned int    v;

    *uc = n = 0;
    p   = (void*)s;

    memcpy(&v, s, 4);

    if (IS_LITTLE_ENDIAN) {
        if ((v&0xfc00fc00) == 0xdc00d800) {
            *uc   = *(p++)&0x03ff;
            *uc <<= 10;
            *uc  |= (*p&0x03ff);
            *uc  += 0x010000;

            n = 2;

        } else if ((v&0x0000f800) != 0x0000d800) {
            *uc = *p;
            n   = 2;
        }
    } else {
        if ((v&0xfc00fc00) == 0xd800dc00) {
            *uc   = *(p++)&0x03ff;
            *uc <<= 10;
            *uc  |= (*p&0x03ff);
            *uc  += 0x010000;

            n = 2;
        } else if ((v&0xf8000000) != 0xd8000000) {
            *uc = *p;
            n   = 1;
        }
    }

  #ifndef UNICODE_CHARSIZE_CHECK_DISABLE
    if (n == 1 && *uc >= 0xd800 && *uc <= 0xdfff)
        return (void*)(size_t)(*uc = 0);
  #endif

    if (n) return s + n;

    return (void*)0;
}