// Copyright 1998-2014 Epic Games, Inc. All Rights Reserved.

#include "HttpPrivatePCH.h"
#include "Base64.h"


/** The table used to encode a 6 bit value as an ascii character */
uint8 FBase64::EncodingAlphabet[64] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L',
	'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e',
	'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
	'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/' };

/** The table used to convert an ascii character into a 6 bit value */
uint8 FBase64::DecodingAlphabet[256] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
	0xFF, 0x3E, 0xFF, 0xFF, 0xFF, 0x3F, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D,
	0xFF, 0xFF, 0xFF, 0x00, 0xFF, 0xFF, 0xFF, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
	0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
	0x19, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22,
	0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32,
	0x33, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };

/**
 * Encodes a binary uint8 array into a Base64 string
 *
 * @param Source the binary data to convert
 *
 * @return a string that encodes the binary data in a way that can be safely transmitted via various Internet protocols
 */
FString FBase64::Encode(const TArray<uint8>& Source)
{
	return Encode((uint8*)Source.GetTypedData(), Source.Num());
}

/**
 * Decodes a Base64 string into an array of bytes
 *
 * @param Source the stringified data to convert
 * @param Dest the out buffer that will be filled with the decoded data
 *
 * @return true if the buffer was decoded, false if it failed to decode
 */
bool FBase64::Decode(const FString& Source, TArray<uint8>& Dest)
{
	uint32 Length = Source.Len();
	// Size must be a multiple of 4
	if (Length % 4)
	{
		return false;
	}
	// Each 4 uint8 chunk of characters is 3 bytes of data
	uint32 ExpectedLength = Length / 4 * 3;
	// Add the number we need for output
	Dest.AddZeroed(ExpectedLength);
	uint8* Buffer = Dest.GetTypedData();
	uint32 PadCount = 0;
	bool bWasSuccessful = Decode(TCHAR_TO_ANSI(*Source), Length, Dest.GetTypedData(), PadCount);
	if (bWasSuccessful)
	{
		if (PadCount > 0)
		{
			Dest.RemoveAt(ExpectedLength - PadCount, PadCount);
		}
	}
	return bWasSuccessful;
}

/**
 * Encodes a FString into a Base64 string
 *
 * @param Source the string data to convert
 *
 * @return a string that encodes the binary data in a way that can be safely transmitted via various Internet protocols
 */
FString FBase64::Encode(const FString& Source)
{
	return Encode((uint8*)TCHAR_TO_ANSI(*Source), Source.Len());
}

/**
 * Decodes a Base64 string into a FString
 *
 * @param Source the stringified data to convert
 * @param Dest the out buffer that will be filled with the decoded data
 */
bool FBase64::Decode(const FString& Source, FString& Dest)
{
	uint32 Length = Source.Len();
	// Size must be a multiple of 4
	if (Length % 4)
	{
		return false;
	}
	// Each 4 uint8 chunk of characters is 3 bytes of data
	uint32 ExpectedLength = Length / 4 * 3;
	TArray<ANSICHAR> TempDest;
	TempDest.AddZeroed(ExpectedLength);
	uint8* Buffer = (uint8*)TempDest.GetTypedData();
	uint32 PadCount = 0;

	bool bWasSuccessful = Decode(TCHAR_TO_ANSI(*Source), Length, Buffer, PadCount);
	if (bWasSuccessful)
	{
		if (PadCount > 0)
		{
			Buffer[ExpectedLength - PadCount] = 0;
		}
		else
		{
			TempDest.Add('\0');
		}
		Dest = ANSI_TO_TCHAR(TempDest.GetTypedData());
	}
	return bWasSuccessful;
}

/**
 * Encodes the source into a Base64 string
 *
 * @param Source the binary payload to stringify
 * @param Length the length of the payload that needs encoding
 *
 * @return the stringified form of the binary data
 */
FString FBase64::Encode(uint8* Source, uint32 Length)
{
	// Each 3 uint8 set of data expands to 4 bytes and must be padded to 4 bytes
	uint32 ExpectedLength = (Length + 2) / 3 * 4;
	FString OutBuffer;
	OutBuffer.Empty(ExpectedLength);

	ANSICHAR EncodedBytes[5];
	// Null terminate this so we can append it easily as a string
	EncodedBytes[4] = 0;
	// Loop through the buffer converting 3 bytes of binary data at a time
	while (Length >= 3)
	{
		uint8 A = *Source++;
		uint8 B = *Source++;
		uint8 C = *Source++;
		Length -= 3;
		// The algorithm takes 24 bits of data (3 bytes) and breaks it into 4 6bit chunks represented as ascii
		uint32 ByteTriplet = A << 16 | B << 8 | C;
		// Use the 6bit block to find the representation ascii character for it
		EncodedBytes[3] = EncodingAlphabet[ByteTriplet & 0x3F];
		// Shift each time to get the next 6 bit chunk
		ByteTriplet >>= 6;
		EncodedBytes[2] = EncodingAlphabet[ByteTriplet & 0x3F];
		ByteTriplet >>= 6;
		EncodedBytes[1] = EncodingAlphabet[ByteTriplet & 0x3F];
		ByteTriplet >>= 6;
		EncodedBytes[0] = EncodingAlphabet[ByteTriplet & 0x3F];
		// Now we can append this buffer to our destination string
		OutBuffer += EncodedBytes;
	}
	// Since this algorithm operates on blocks, we may need to pad the last chunks
	if (Length > 0)
	{
		uint8 A = *Source++;
		uint8 B = 0;
		uint8 C = 0;
		// Grab the second character if it is a 2 uint8 finish
		if (Length == 2)
		{
			B = *Source;
		}
		uint32 ByteTriplet = A << 16 | B << 8 | C;
		// Pad with = to make a 4 uint8 chunk
		EncodedBytes[3] = '=';
		ByteTriplet >>= 6;
		// If there's only one 1 uint8 left in the source, then you need 2 pad chars
		if (Length == 1)
		{
			EncodedBytes[2] = '=';
		}
		else
		{
			EncodedBytes[2] = EncodingAlphabet[ByteTriplet & 0x3F];
		}
		// Now encode the remaining bits the same way
		ByteTriplet >>= 6;
		EncodedBytes[1] = EncodingAlphabet[ByteTriplet & 0x3F];
		ByteTriplet >>= 6;
		EncodedBytes[0] = EncodingAlphabet[ByteTriplet & 0x3F];
		OutBuffer += EncodedBytes;
	}
	return OutBuffer;
}

/**
 * Decodes a Base64 string into an array of bytes
 *
 * @param Source the stringified data to convert
 * @param Length the length of the buffer being converted
 * @param Dest the out buffer that will be filled with the decoded data
 * @param PadCount the out count of the padding on the orignal buffer (0 to 2)
 *
 * @return true if the buffer was decoded, false if it failed to decode
 */
bool FBase64::Decode(const ANSICHAR* Source, uint32 Length, uint8* Dest, uint32& PadCount)
{
	PadCount = 0;
	uint8 DecodedValues[4];
	while (Length)
	{
		// Decode the next 4 BYTEs
		for (int32 Index = 0; Index < 4; Index++)
		{
			// Tell the caller if there were any pad bytes
			if (*Source == '=')
			{
				PadCount++;
			}
			DecodedValues[Index] = DecodingAlphabet[(int32)(*Source++)];
			// Abort on values that we don't understand
			if (DecodedValues[Index] == -1)
			{
				return false;
			}
		}
		Length -= 4;
		// Rebuild the original 3 bytes from the 4 chunks of 6 bits
		uint32 OriginalTriplet = DecodedValues[0];
		OriginalTriplet <<= 6;
		OriginalTriplet |= DecodedValues[1];
		OriginalTriplet <<= 6;
		OriginalTriplet |= DecodedValues[2];
		OriginalTriplet <<= 6;
		OriginalTriplet |= DecodedValues[3];
		// Now we can tear the uint32 into bytes
		Dest[2] = OriginalTriplet & 0xFF;
		OriginalTriplet >>= 8;
		Dest[1] = OriginalTriplet & 0xFF;
		OriginalTriplet >>= 8;
		Dest[0] = OriginalTriplet & 0xFF;
		Dest += 3;
	}
	return true;
}