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

#include "build.h"

const char* fromchar_unicode(unsigned int* uc, const char* s) {
    unsigned char* p;
    unsigned int   v;
    unsigned char  n;

    if (*(p = (void*)s) <= 0x7f) {
        *uc = *s;
        return s + 1;
    }

    memcpy(&v, s, 4);

    *uc = 0;

    if (IS_LITTLE_ENDIAN) {
        if ((v&0x0000c0e0) == 0x000080c0) {
            n = 2;
            *uc |= *(p++)&0x1f;
        } else {
            if ((v&0x00c0c0f0) == 0x008080e0) {
                n = 3;
                *uc |= *(p++)&0x0f;
            } else if ((v&0xc0c0c0f8) == 0x808080f0) {
                n = 4;
                *uc  |= *(p++)&0x07;
                *uc <<= 6;
                *uc  |= *(p++)&0x3f;
            } else return (void*)(size_t)(*uc = 0);

            *uc <<= 6;
            *uc  |= *(p++)&0x3f;
        }
    } else {
        if ((v&0xe0c00000) == 0xc0800000) {
            n = 2;
            *uc |= *(p++)&0x1f;
        } else {
            if ((v&0xf8c0c0c0) == 0xf0808080) {
                n = 3;
                *uc |= *(p++)&0x0f;
            } else if ((v&0xf0c0c000) == 0xe0808000) {
                n = 4;
                *uc  |= *(p++)&0x07;
                *uc <<= 6;
                *uc  |= *(p++)&0x3f;
            } else return (void*)(size_t)(*uc = 0);

            *uc <<= 6;
            *uc  |= *(p++)&0x3f;
        }
    }

    *uc <<= 6;
    *uc  |= *(p++)&0x3f;

  #ifndef UNICODE_CHARSIZE_CHECK_DISABLE
    if ((n == 2 && *uc > 0x0007ff) ||
        (n == 3 && *uc > 0x00ffff) ||
        (n == 4 && *uc > 0x10ffff))
            return (void*)(size_t)(*uc = 0);
  #endif

    return s + n;
}