C++ base64编解码

static std::string base64_chars = 
	"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
	"abcdefghijklmnopqrstuvwxyz"
	"0123456789+/";
 
 
static bool is_base64(unsigned char c) {
	return (isalnum(c) || (c == '+') || (c == '/'));
}
 
std::string base64_encode(const unsigned char* bytes_to_encode,unsigned int in_len);
int base64_decode(std::string const& encoded_string,unsigned char* pObject);
 
std::string base64_encode(const unsigned char* bytes_to_encode,unsigned int in_len)
{
	std::string ret;
	int i = 0;
	int j = 0;
	unsigned char char_array_3[3];
	unsigned char char_array_4[4];
 
	while (in_len--) {
		char_array_3[i++] = *(bytes_to_encode++);
		if (i == 3) {
			char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
			char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
			char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
			char_array_4[3] = char_array_3[2] & 0x3f;
 
			for(i = 0; (i <4) ; i++)
				ret += base64_chars[char_array_4[i]];
			i = 0;
		}
	}
 
	if (i)
	{
		for(j = i; j < 3; j++)
			char_array_3[j] = '\0';
 
		char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
		char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
		char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
		char_array_4[3] = char_array_3[2] & 0x3f;
 
		for (j = 0; (j < i + 1); j++)
			ret += base64_chars[char_array_4[j]];
 
		while((i++ < 3))
			ret += '=';
 
	}
 
	return ret;
 
}
 
int base64_decode(std::string const& encoded_string,unsigned char* pObject)
{
	int in_len = encoded_string.size();
	int i = 0;
	int j = 0;
	int in_ = 0;
	int iNum = 0;
	unsigned char char_array_4[4], char_array_3[3];
	std::string ret;
 
	while (in_len-- && ( encoded_string[in_] != '=') && is_base64(encoded_string[in_])) {
		char_array_4[i++] = encoded_string[in_]; in_++;
		if (i ==4) {
			for (i = 0; i <4; i++)
				char_array_4[i] = base64_chars.find(char_array_4[i]);
 
			char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
			char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
			char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
 
			for (i = 0; (i < 3); i++)
			{
				ret += char_array_3[i];
				iNum++;
			}
			i = 0;
		}
	}
 
	if (i) {
		for (j = i; j <4; j++)
			char_array_4[j] = 0;
 
		for (j = 0; j <4; j++)
			char_array_4[j] = base64_chars.find(char_array_4[j]);
 
		char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
		char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
		char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
 
		for (j = 0; (j < i - 1); j++)
		{
			ret += char_array_3[j];
			iNum++;
		}
	}
 
	memcpy(pObject,ret.c_str(),iNum);
	return iNum;
}