EHS/src/Base64.cpp

#include "ehs/Base64.h"

namespace ehs
{
	const char Base64::ascii[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
	
	Str_8 Base64::Encode(const Str_8 &input)
	{
		UInt_64 input_length = input.Size();

		// Calculate the output length
		UInt_64 output_length = 4 * ((input_length + 2) / 3);

		// Allocate memory for the output
		Str_8 result(output_length);

		// Loop through the input and fill the output
		for (int i = 0, j = 0; i < input_length;) {

			// Take first byte and shift right by 2 bits
			UInt_32 octet_a = i < input_length ? input[i++] : 0;
			UInt_32 octet_b = i < input_length ? input[i++] : 0;
			UInt_32 octet_c = i < input_length ? input[i++] : 0;

			UInt_32 triple = (octet_a << 0x10) + (octet_b << 0x08) + octet_c;

			// Encode the 24-bits into four 6-bits integers
			result[j++] = ascii[(triple >> 3 * 6) & 0x3F];
			result[j++] = ascii[(triple >> 2 * 6) & 0x3F];
			result[j++] = ascii[(triple >> 1 * 6) & 0x3F];
			result[j++] = ascii[(triple >> 0 * 6) & 0x3F];
		}

		// Add padding '='
		if (input_length % 3 == 1) {
			result[output_length - 1] = '=';
			result[output_length - 2] = '=';
		} else if (input_length % 3 == 2) {
			result[output_length - 1] = '=';
		}

		return result;
	}
	
	Str_8 Base64::Decode(const Str_8 &input)
	{
		UInt_64 in_len = input.Size();
		int i = 0;
		int j = 0;
		int in_ = 0;
		char char_array_4[4], char_array_3[3];
		Str_8 ret;

		while (in_len-- && ( input[in_] != '=') && IsBase64(input[in_]))
		{
			char_array_4[i++] = input[in_]; in_++;
			
			if (i ==4)
			{
				for (i = 0; i <4; i++)
					char_array_4[i] = 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];

				i = 0;
			}
		}

		if (i)
		{
			for (j = 0; j < i; j++)
				char_array_4[j] = 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);

			for (j = 0; (j < i - 1); j++)
				ret += char_array_3[j];
		}

		return ret;
	}
	
	char Base64::Find(const char c)
	{
		for (char i = 0; i < (char)sizeof(ascii); ++i)
		{
			if (ascii[i] == c)
				return i;
		}
		
		return EHS_SINT_8_MAX;
	}
	
	bool Base64::IsBase64(const char c)
	{
		return (c > 47 && c < 58) || (c > 64 && c < 91) || (c > 96 && c < 123) || (c == '+') || (c == '/');
	}
}