#include "pch.h"
#include "l2c_utils.h"

// This is an example of an exported variable
//L2C_UTILS_API int nl2c_utils=0;

L2C_UTILS_API void l2c_ansi_to_unicode( const char *ansi, wchar_t *unicode, size_t maxLen )
{
	memset( unicode, 0, maxLen*2 );
	MultiByteToWideChar( CP_ACP, 0, ansi, -1, unicode, (int)maxLen );
	unicode[maxLen-1] = 0;
}

L2C_UTILS_API void l2c_unicode_to_ansi( const wchar_t *unicode, char *ansi, size_t maxLen )
{
	memset( ansi, 0, maxLen );
	WideCharToMultiByte( CP_ACP, 0, unicode, -1, ansi, (int)maxLen, NULL, NULL );
	ansi[maxLen-1] = 0;
}


const int L2C_BASE64_CHARS_PER_LINE = 72;

typedef enum
{
	step_A, step_B, step_C
} base64_encodestep;

typedef struct
{
	base64_encodestep step;
	char result;
	int stepcount;
} base64_encodestate;

typedef enum
{
	step_a, step_b, step_c, step_d
} base64_decodestep;

typedef struct
{
	base64_decodestep step;
	char plainchar;
} base64_decodestate;

void base64_init_encodestate(base64_encodestate* state_in)
{
	state_in->step = step_A;
	state_in->result = 0;
	state_in->stepcount = 0;
}

char base64_encode_value(char value_in)
{
	static const char* encoding = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
	if (value_in > 63) return '=';
	return encoding[(int)value_in];
}

int base64_encode_block(const char* plaintext_in, int length_in, char* code_out, base64_encodestate* state_in)
{
	const char* plainchar = plaintext_in;
	const char* const plaintextend = plaintext_in + length_in;
	char* codechar = code_out;
	char result;
	char fragment;
	
	result = state_in->result;
	
	switch (state_in->step)
	{
#pragma warning( disable: 4127 ) // conditional expression is constant
		while (1)
#pragma warning( default: 4127 ) // conditional expression is constant
		{
	case step_A:
			if (plainchar == plaintextend)
			{
				state_in->result = result;
				state_in->step = step_A;
				return codechar - code_out;
			}
			fragment = *plainchar++;
			result = (fragment & 0x0fc) >> 2;
			*codechar++ = base64_encode_value(result);
			result = (fragment & 0x003) << 4;
	case step_B:
			if (plainchar == plaintextend)
			{
				state_in->result = result;
				state_in->step = step_B;
				return codechar - code_out;
			}
			fragment = *plainchar++;
			result |= (fragment & 0x0f0) >> 4;
			*codechar++ = base64_encode_value(result);
			result = (fragment & 0x00f) << 2;
	case step_C:
			if (plainchar == plaintextend)
			{
				state_in->result = result;
				state_in->step = step_C;
				return codechar - code_out;
			}
			fragment = *plainchar++;
			result |= (fragment & 0x0c0) >> 6;
			*codechar++ = base64_encode_value(result);
			result  = (fragment & 0x03f) >> 0;
			*codechar++ = base64_encode_value(result);
			
			++(state_in->stepcount);
			if (state_in->stepcount == L2C_BASE64_CHARS_PER_LINE/4)
			{
				//*codechar++ = '\n';
				state_in->stepcount = 0;
			}
		}
	}
	/* control should not reach here */
	return codechar - code_out;
}

int base64_encode_blockend(char* code_out, base64_encodestate* state_in)
{
	char* codechar = code_out;
	
	switch (state_in->step)
	{
	case step_B:
		*codechar++ = base64_encode_value(state_in->result);
		*codechar++ = '=';
		*codechar++ = '=';
		break;
	case step_C:
		*codechar++ = base64_encode_value(state_in->result);
		*codechar++ = '=';
		break;
	case step_A:
		break;
	}
	//*codechar++ = '\n';
	*codechar++ = '\0';
	
	return codechar - code_out;
}

int base64_decode_value(char value_in)
{
	static const char decoding[] = {62,-1,-1,-1,63,52,53,54,55,56,57,58,59,60,61,-1,-1,-1,-2,-1,-1,-1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,-1,-1,-1,-1,-1,-1,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51};
	static const char decoding_size = sizeof(decoding);
	value_in -= 43;
	if (value_in < 0 || value_in > decoding_size) return -1;
	return decoding[(int)value_in];
}

void base64_init_decodestate(base64_decodestate* state_in)
{
	state_in->step = step_a;
	state_in->plainchar = 0;
}

int base64_decode_block(const char* code_in, const int length_in, char* plaintext_out, base64_decodestate* state_in)
{
	const char* codechar = code_in;
	char* plainchar = plaintext_out;
	char fragment;
	
	*plainchar = state_in->plainchar;
	
	switch (state_in->step)
	{
#pragma warning( disable: 4127 ) // conditional expression is constant
		while (1)
#pragma warning( default: 4127 ) // conditional expression is constant
		{
	case step_a:
			do {
				if (codechar == code_in+length_in)
				{
					state_in->step = step_a;
					state_in->plainchar = *plainchar;
					return plainchar - plaintext_out;
				}
				fragment = (char)base64_decode_value(*codechar++);
			} while (fragment < 0);
			*plainchar    = (fragment & 0x03f) << 2;
	case step_b:
			do {
				if (codechar == code_in+length_in)
				{
					state_in->step = step_b;
					state_in->plainchar = *plainchar;
					return plainchar - plaintext_out;
				}
				fragment = (char)base64_decode_value(*codechar++);
			} while (fragment < 0);
			*plainchar++ |= (fragment & 0x030) >> 4;
			*plainchar    = (fragment & 0x00f) << 4;
	case step_c:
			do {
				if (codechar == code_in+length_in)
				{
					state_in->step = step_c;
					state_in->plainchar = *plainchar;
					return plainchar - plaintext_out;
				}
				fragment = (char)base64_decode_value(*codechar++);
			} while (fragment < 0);
			*plainchar++ |= (fragment & 0x03c) >> 2;
			*plainchar    = (fragment & 0x003) << 6;
	case step_d:
			do {
				if (codechar == code_in+length_in)
				{
					state_in->step = step_d;
					state_in->plainchar = *plainchar;
					return plainchar - plaintext_out;
				}
				fragment = (char)base64_decode_value(*codechar++);
			} while (fragment < 0);
			*plainchar++   |= (fragment & 0x03f);
		}
	}
	/* control should not reach here */
	return plainchar - plaintext_out;
}

L2C_UTILS_API void base64_encode_string( const char *str_in, int len_in, char *str_out )
{
	base64_encodestate state;
	base64_init_encodestate( &state );
	int len_coded = base64_encode_block( str_in, len_in, str_out, &state );
	base64_encode_blockend( str_out+len_coded, &state );
}

L2C_UTILS_API void base64_decode_string( const char *str_in, int len_in, char *str_out )
{
	base64_decodestate state;
	base64_init_decodestate( &state );
	base64_decode_block( str_in, len_in, str_out, &state );
}