//
// Created by YY on 2021/10/22.
//

#include <stdlib.h>
#include "charencode.h"

/*****************************************************************************
 * 将一个字符的Unicode(UCS-2和UCS-4)编码转换成UTF-8编码.
 *
 * 参数:
 *    unic     字符的Unicode编码值
 *    pOutput  指向输出的用于存储UTF8编码值的缓冲区的指针
 *    outsize  pOutput缓冲的大小
 *
 * 返回值:
 *    返回转换后的字符的UTF8编码所占的字节数, 如果出错则返回 0 .
 *
 * 注意:
 *     1. UTF8没有字节序问题, 但是Unicode有字节序要求;
 *        字节序分为大端(Big Endian)和小端(Little Endian)两种;
 *        在Intel处理器中采用小端法表示, 在此采用小端法表示. (低地址存低位)
 *     2. 请保证 pOutput 缓冲区有最少有 6 字节的空间大小!
 ****************************************************************************/
int enc_unicode_to_utf8_one(unsigned long unic, unsigned char *pOutput,
                            int outSize)
{
	if (pOutput == NULL || outSize < 6)
        return 0;

    if (unic <= 0x0000007F)
    {
        // * U-00000000 - U-0000007F:  0xxxxxxx
        *pOutput = (unic & 0x7F);
        return 1;
    }
    else if (unic >= 0x00000080 && unic <= 0x000007FF)
    {
        // * U-00000080 - U-000007FF:  110xxxxx 10xxxxxx
        *(pOutput + 1) = (unic & 0x3F) | 0x80;
        *pOutput = ((unic >> 6) & 0x1F) | 0xC0;
        return 2;
    }
    else if (unic >= 0x00000800 && unic <= 0x0000FFFF)
    {
        // * U-00000800 - U-0000FFFF:  1110xxxx 10xxxxxx 10xxxxxx
        *(pOutput + 2) = (unic & 0x3F) | 0x80;
        *(pOutput + 1) = ((unic >> 6) & 0x3F) | 0x80;
        *pOutput = ((unic >> 12) & 0x0F) | 0xE0;
        return 3;
    }
    else if (unic >= 0x00010000 && unic <= 0x001FFFFF)
    {
        // * U-00010000 - U-001FFFFF:  11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
        *(pOutput + 3) = (unic & 0x3F) | 0x80;
        *(pOutput + 2) = ((unic >> 6) & 0x3F) | 0x80;
        *(pOutput + 1) = ((unic >> 12) & 0x3F) | 0x80;
        *pOutput = ((unic >> 18) & 0x07) | 0xF0;
        return 4;
    }
    else if (unic >= 0x00200000 && unic <= 0x03FFFFFF)
    {
        // * U-00200000 - U-03FFFFFF:  111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
        *(pOutput + 4) = (unic & 0x3F) | 0x80;
        *(pOutput + 3) = ((unic >> 6) & 0x3F) | 0x80;
        *(pOutput + 2) = ((unic >> 12) & 0x3F) | 0x80;
        *(pOutput + 1) = ((unic >> 18) & 0x3F) | 0x80;
        *pOutput = ((unic >> 24) & 0x03) | 0xF8;
        return 5;
    }
    else if (unic >= 0x04000000 && unic <= 0x7FFFFFFF)
    {
        // * U-04000000 - U-7FFFFFFF:  1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
        *(pOutput + 5) = (unic & 0x3F) | 0x80;
        *(pOutput + 4) = ((unic >> 6) & 0x3F) | 0x80;
        *(pOutput + 3) = ((unic >> 12) & 0x3F) | 0x80;
        *(pOutput + 2) = ((unic >> 18) & 0x3F) | 0x80;
        *(pOutput + 1) = ((unic >> 24) & 0x3F) | 0x80;
        *pOutput = ((unic >> 30) & 0x01) | 0xFC;
        return 6;
    }

    return 0;
}

/*****************************************************************************
 * 将一个字符的UTF8编码转换成Unicode(UCS-2和UCS-4)编码.
 *
 * 参数:
 *    pInput      指向输入缓冲区, 以UTF-8编码
 *    Unic        指向输出缓冲区, 其保存的数据即是Unicode编码值,
 *                类型为unsigned long .
 *
 * 返回值:
 *    成功则返回该字符的UTF8编码所占用的字节数; 失败则返回0.
 *
 * 注意:
 *     1. UTF8没有字节序问题, 但是Unicode有字节序要求;
 *        字节序分为大端(Big Endian)和小端(Little Endian)两种;
 *        在Intel处理器中采用小端法表示, 在此采用小端法表示. (低地址存低位)
 ****************************************************************************/
int enc_utf8_to_unicode_one(const unsigned char* pInput, unsigned long *Unic)
{
    if (pInput == NULL || Unic == NULL)
        return 0;

    // b1 表示UTF-8编码的pInput中的高字节, b2 表示次高字节, ...
    char b1, b2, b3, b4, b5, b6;

    *Unic = 0x0; // 把 *Unic 初始化为全零
    int utfbytes = enc_get_utf8_size(*pInput);
    unsigned char *pOutput = (unsigned char *)Unic;

    switch (utfbytes)
    {
        case 0:
            *pOutput = *pInput;
            utfbytes += 1;
            break;
        case 2:
            b1 = *pInput;
            b2 = *(pInput + 1);
            if ((b2 & 0xE0) != 0x80)
                return 0;
            *pOutput = (b1 << 6) + (b2 & 0x3F);
            *(pOutput + 1) = (b1 >> 2) & 0x07;
            break;
        case 3:
            b1 = *pInput;
            b2 = *(pInput + 1);
            b3 = *(pInput + 2);
            if (((b2 & 0xC0) != 0x80) || ((b3 & 0xC0) != 0x80))
                return 0;
            *pOutput = (b2 << 6) + (b3 & 0x3F);
            *(pOutput + 1) = (b1 << 4) + ((b2 >> 2) & 0x0F);
            break;
        case 4:
            b1 = *pInput;
            b2 = *(pInput + 1);
            b3 = *(pInput + 2);
            b4 = *(pInput + 3);
            if (((b2 & 0xC0) != 0x80) || ((b3 & 0xC0) != 0x80)
                || ((b4 & 0xC0) != 0x80))
                return 0;
            *pOutput = (b3 << 6) + (b4 & 0x3F);
            *(pOutput + 1) = (b2 << 4) + ((b3 >> 2) & 0x0F);
            *(pOutput + 2) = ((b1 << 2) & 0x1C) + ((b2 >> 4) & 0x03);
            break;
        case 5:
            b1 = *pInput;
            b2 = *(pInput + 1);
            b3 = *(pInput + 2);
            b4 = *(pInput + 3);
            b5 = *(pInput + 4);
            if (((b2 & 0xC0) != 0x80) || ((b3 & 0xC0) != 0x80)
                || ((b4 & 0xC0) != 0x80) || ((b5 & 0xC0) != 0x80))
                return 0;
            *pOutput = (b4 << 6) + (b5 & 0x3F);
            *(pOutput + 1) = (b3 << 4) + ((b4 >> 2) & 0x0F);
            *(pOutput + 2) = (b2 << 2) + ((b3 >> 4) & 0x03);
            *(pOutput + 3) = (b1 << 6);
            break;
        case 6:
            b1 = *pInput;
            b2 = *(pInput + 1);
            b3 = *(pInput + 2);
            b4 = *(pInput + 3);
            b5 = *(pInput + 4);
            b6 = *(pInput + 5);
            if (((b2 & 0xC0) != 0x80) || ((b3 & 0xC0) != 0x80)
                || ((b4 & 0xC0) != 0x80) || ((b5 & 0xC0) != 0x80)
                || ((b6 & 0xC0) != 0x80))
                return 0;
            *pOutput = (b5 << 6) + (b6 & 0x3F);
            *(pOutput + 1) = (b5 << 4) + ((b6 >> 2) & 0x0F);
            *(pOutput + 2) = (b3 << 2) + ((b4 >> 4) & 0x03);
            *(pOutput + 3) = ((b1 << 6) & 0x40) + (b2 & 0x3F);
            break;
        default:
            return 0;
            break;
    }

    return utfbytes;
}

int enc_get_utf8_size(const unsigned char pInput)
{
    unsigned char c = pInput;
    // 0xxxxxxx 返回0
    // 10xxxxxx 不存在
    // 110xxxxx 返回2
    // 1110xxxx 返回3
    // 11110xxx 返回4
    // 111110xx 返回5
    // 1111110x 返回6
    if(c< 0x80) return 0;
    if(c>=0x80 && c<0xC0) return -1;
    if(c>=0xC0 && c<0xE0) return 2;
    if(c>=0xE0 && c<0xF0) return 3;
    if(c>=0xF0 && c<0xF8) return 4;
    if(c>=0xF8 && c<0xFC) return 5;
    if(c>=0xFC) return 6;
}