Basic object encoding and storage

1 files changed, 107 insertions, 0 deletions

diff --git a/src/base64.h b/src/base64.h
new file mode 100644
index 0000000..324a5dd
--- /dev/null
+++ b/src/base64.h
@@ -0,0 +1,107 @@
+#pragma once
+
+#include <cstdint>
+#include <stdexcept>
+#include <string>
+#include <vector>
+
+namespace { namespace base64 {
+
+	const static char encodeLookup[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+	const static char padCharacter = '=';
+
+	std::string encode(const std::vector<uint8_t> & input)
+	{
+		std::string encoded;
+		encoded.reserve(((input.size()/3) + (input.size() % 3 > 0)) * 4);
+		uint32_t temp;
+		auto cursor = input.begin();
+		for (size_t i = 0; i < input.size() / 3; i++)
+		{
+			temp  = (*cursor++) << 16; // Convert to big endian
+			temp += (*cursor++) << 8;
+			temp += (*cursor++);
+			encoded.append(1, encodeLookup[(temp & 0x00FC0000) >> 18]);
+			encoded.append(1, encodeLookup[(temp & 0x0003F000) >> 12]);
+			encoded.append(1, encodeLookup[(temp & 0x00000FC0) >> 6 ]);
+			encoded.append(1, encodeLookup[(temp & 0x0000003F)      ]);
+		}
+		switch (input.size() % 3)
+		{
+		case 1:
+			temp  = (*cursor++) << 16; // Convert to big endian
+			encoded.append(1, encodeLookup[(temp & 0x00FC0000) >> 18]);
+			encoded.append(1, encodeLookup[(temp & 0x0003F000) >> 12]);
+			encoded.append(2, padCharacter);
+			break;
+		case 2:
+			temp  = (*cursor++) << 16; // Convert to big endian
+			temp += (*cursor++) << 8;
+			encoded.append(1, encodeLookup[(temp & 0x00FC0000) >> 18]);
+			encoded.append(1, encodeLookup[(temp & 0x0003F000) >> 12]);
+			encoded.append(1, encodeLookup[(temp & 0x00000FC0) >> 6 ]);
+			encoded.append(1, padCharacter);
+			break;
+		}
+		return encoded;
+	}
+
+	std::vector<uint8_t> decode(const std::string & input)
+	{
+		if (input.length() % 4) // Sanity check
+			throw std::runtime_error("Non-Valid base64!");
+
+		size_t padding = 0;
+		if (input.length()) {
+			if (input[input.length() - 1] == padCharacter)
+				padding++;
+			if (input[input.length() - 2] == padCharacter)
+				padding++;
+		}
+
+		// Setup a vector to hold the result
+		std::vector<uint8_t> decoded;
+		decoded.reserve(((input.length()/4)*3) - padding);
+		uint32_t temp = 0; // Holds decoded quanta
+		auto cursor = input.begin();
+		while (cursor < input.end())
+		{
+			for (size_t quantumPosition = 0; quantumPosition < 4; quantumPosition++)
+			{
+				temp <<= 6;
+				if      (*cursor >= 0x41 && *cursor <= 0x5A)   // This area will need tweaking if
+					temp |= *cursor - 0x41;                // you are using an alternate alphabet
+				else if (*cursor >= 0x61 && *cursor <= 0x7A)
+					temp |= *cursor - 0x47;
+				else if (*cursor >= 0x30 && *cursor <= 0x39)
+					temp |= *cursor + 0x04;
+				else if (*cursor == 0x2B)
+					temp |= 0x3E; // change to 0x2D for URL alphabet
+				else if (*cursor == 0x2F)
+					temp |= 0x3F; // change to 0x5F for URL alphabet
+				else if (*cursor == padCharacter) // pad
+				{
+					switch (input.end() - cursor)
+					{
+					case 1: //One pad character
+						decoded.push_back((temp >> 16) & 0x000000FF);
+						decoded.push_back((temp >> 8 ) & 0x000000FF);
+						return decoded;
+					case 2: //Two pad characters
+						decoded.push_back((temp >> 10) & 0x000000FF);
+						return decoded;
+					default:
+						throw std::runtime_error("Invalid Padding in Base 64!");
+					}
+				}  else
+					throw std::runtime_error("Non-Valid Character in Base 64!");
+				cursor++;
+			}
+			decoded.push_back((temp >> 16) & 0x000000FF);
+			decoded.push_back((temp >> 8 ) & 0x000000FF);
+			decoded.push_back((temp      ) & 0x000000FF);
+		}
+		return decoded;
+	}
+
+} }