/*
begin library headers
*/

/*
cdecode.h - c header for a base64 decoding algorithm

This is part of the libb64 project, and has been placed in the public domain.
For details, see http://sourceforge.net/projects/libb64
*/
#ifndef BASE64_CDECODE_H
#define BASE64_CDECODE_H

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

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

void base64_init_decodestate(base64_decodestate* state_in);

int base64_decode_value(char value_in);

int base64_decode_block(const char* code_in, const int length_in, char* plaintext_out, base64_decodestate* state_in);

#endif /* BASE64_CDECODE_H */

/*
end library headers
*/

#include "ua_base64.h"

UA_Int32 UA_base64_getDecodedSize(UA_String* const base64EncodedData){
	//note that base64-encoded data length is always divisible by 4
	UA_Int32 temp = base64EncodedData->length * 3 / 4;

	//subtract padding
	if(base64EncodedData->data[base64EncodedData->length-1] == '=') {
		temp--;
		if(base64EncodedData->data[base64EncodedData->length-2] == '=') {
			temp--;
		}
	}

	return temp;
}

UA_Int32 UA_base64_decode(UA_String* const base64EncodedData, UA_Byte* target){
	if(target == UA_NULL){
		return UA_ERROR;
	}
	base64_decodestate state;
	base64_init_decodestate(&state);
	base64_decode_block((char*)(base64EncodedData->data), base64EncodedData->length, (char*)target, &state);
	return UA_NO_ERROR;
}

/*
begin library code
*/

/*
cdecoder.c - c source to a base64 decoding algorithm implementation

This is part of the libb64 project, and has been placed in the public domain.
For details, see http://sourceforge.net/projects/libb64
*/

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 > 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;
	signed char fragment;
	
	*plainchar = state_in->plainchar;
	
	switch (state_in->step)
	{
		while (1)
		{
	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;
}