#include <iconv.h> 
#include <string.h>
#include <malloc.h>

#include "iconv-utils.h"

int preNUm(unsigned char byte) 
{
	unsigned char mask = 0x80;
	int num = 0;
	for (int i = 0; i < 8; i++) 
	{
		if ((byte & mask) == mask) 
		{
			mask = mask >> 1;
			num++;
		}
		else 
		{
			break;
		}
	}
	return num;
}


bool isUtf8(unsigned char* data, int len) 
{
	int num = 0;
	int i = 0;
	while (i < len) 
	{
		if ((data[i] & 0x80) == 0x00) 
		{
			// 0XXX_XXXX
			i++;
			continue;
		}
		else if ((num = preNUm(data[i])) > 2) 
		{
			// 110X_XXXX 10XX_XXXX
			// 1110_XXXX 10XX_XXXX 10XX_XXXX
			// 1111_0XXX 10XX_XXXX 10XX_XXXX 10XX_XXXX
			// 1111_10XX 10XX_XXXX 10XX_XXXX 10XX_XXXX 10XX_XXXX
			// 1111_110X 10XX_XXXX 10XX_XXXX 10XX_XXXX 10XX_XXXX 10XX_XXXX
			// preNUm() 返回首个字节8个bits中首�?0bit前面1bit的个数，该数量也是该字符所使用的字节数        
			i++;
			for (int j = 0; j < num - 1; j++) 
			{
				//判断后面num - 1 个字节是不是都是10开
				if ((data[i] & 0xc0) != 0x80) 
				{
					return false;
				}
				i++;
			}
		}
		else 
		{
			//其他情况说明不是utf-8
			return false;
		}
	}
	return true;
}

bool isGBK(unsigned char* data, int len) 
{
	int i = 0;
	while (i < len) 
	{
		if (data[i] <= 0x7f) 
		{
			//编码小于等于127,只有一个字节的编码，兼容ASCII
			i++;
			continue;
		}
		else 
		{
			//大于127的使用双字节编码
			if (data[i] >= 0x81 &&
				data[i] <= 0xfe &&
				data[i + 1] >= 0x40 &&
				data[i + 1] <= 0xfe &&
				data[i + 1] != 0xf7) 
			{
				i += 2;
				continue;
			}
			else
			{
				return false;
			}
		}
	}
	return true;
}

//需要说明的是，isGBK()是通过双字节是否落在gbk的编码范围内实现的，
//而utf-8编码格式的每个字节都是落在gbk的编码范围内�?
//所以只有先调用isUtf8()先判断不是utf-8编码，再调用isGBK()才有意义
CODING GetCoding(unsigned char* data, int len) 
{
	CODING coding;
	if (isUtf8(data, len) == true) 
	{
		coding = UTF8;
	}
	else if (isGBK(data, len) == true) 
	{
		coding = GBK;
	}
	else 
	{
		coding = UNKOWN;
	}
	return coding;
}

int code_convert(const char* from_charset, const char* to_charset, char* inbuf, size_t inlen, char* outbuf, size_t outlen) 
{
	iconv_t cd;
	char** pin = &inbuf;
	char** pout = &outbuf;

	cd = iconv_open(to_charset, from_charset);
	if (cd == 0)
		return -1;

	memset(outbuf, 0, outlen);

	if ((int)iconv(cd, pin, &inlen, pout, &outlen) == -1)
	{
		iconv_close(cd);
		return -1;
	}
	iconv_close(cd);
#ifndef _WIN32
	* pout = '\0';
#else
	*pout = (char*)'\0';
#endif
	return 0;
}

int u2g(char* inbuf, size_t inlen, char* outbuf, size_t outlen) 
{
	return code_convert("utf-8", "gb2312", inbuf, inlen, outbuf, outlen);
}

int g2u(char* inbuf, size_t inlen, char* outbuf, size_t outlen) 
{
	return code_convert("gb2312", "utf-8", inbuf, inlen, outbuf, outlen);
}

bool GBKToUTF8(const std::string& strGBK,std::string& str_result)
{
	int length = strGBK.size() * 2 + 1;

	char* temp = (char*)malloc(sizeof(char) * length);

	if (g2u((char*)strGBK.c_str(), strGBK.size(), temp, length) >= 0)
	{
		str_result.append(temp);
		free(temp);
		return true;
	}
	else
	{
		free(temp);
		str_result = "";
		return false;
	}
}

bool UTFtoGBK(const char* utf8, std::string& str_result)
{
	int length = strlen(utf8);

	char* temp = (char*)malloc(sizeof(char) * length);

	if (u2g((char*)utf8, length, temp, length) >= 0)
	{
		str_result.append(temp);
		free(temp);

		return true;
	}
	else
	{
		free(temp);
		str_result = "";
		return false;
	}
}