code: /*************************************************************************/
  /*  FBXUtil.cpp                                                          */
  /*************************************************************************/
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  /*
  Open Asset Import Library (assimp)
  ----------------------------------------------------------------------
  
  Copyright (c) 2006-2019, assimp team
  
  
  All rights reserved.
  
  Redistribution and use of this software in source and binary forms,
  with or without modification, are permitted provided that the
  following conditions are met:
  
  * Redistributions of source code must retain the above
    copyright notice, this list of conditions and the
    following disclaimer.
  
  * Redistributions in binary form must reproduce the above
    copyright notice, this list of conditions and the
    following disclaimer in the documentation and/or other
    materials provided with the distribution.
  
  * Neither the name of the assimp team, nor the names of its
    contributors may be used to endorse or promote products
    derived from this software without specific prior
    written permission of the assimp team.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  ----------------------------------------------------------------------
  */
  
  /** @file  FBXUtil.cpp
   *  @brief Implementation of internal FBX utility functions
   */
  
  #include "FBXUtil.h"
  #include "FBXTokenizer.h"
  #include <cstring>
  #include <string>
  
  namespace FBXDocParser {
  namespace Util {
  
  // ------------------------------------------------------------------------------------------------
  const char *TokenTypeString(TokenType t) {
  	switch (t) {
  		case TokenType_OPEN_BRACKET:
  			return "TOK_OPEN_BRACKET";
  
  		case TokenType_CLOSE_BRACKET:
  			return "TOK_CLOSE_BRACKET";
  
  		case TokenType_DATA:
  			return "TOK_DATA";
  
  		case TokenType_COMMA:
  			return "TOK_COMMA";
  
  		case TokenType_KEY:
  			return "TOK_KEY";
  
  		case TokenType_BINARY_DATA:
  			return "TOK_BINARY_DATA";
  	}
  
  	//ai_assert(false);
  	return "";
  }
  
  // Generated by this formula: T["ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"[i]] = i;
  static const uint8_t base64DecodeTable[128] = {
  	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 62, 255, 255, 255, 63,
  	52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255, 255, 255, 255, 255, 255,
  	255, 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, 255, 255, 255, 255, 255,
  	255, 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, 255, 255, 255, 255, 255
  };
  
  uint8_t DecodeBase64(char ch) {
  	const auto idx = static_cast<uint8_t>(ch);
  	if (idx > 127)
  		return 255;
  	return base64DecodeTable[idx];
  }
  
  size_t ComputeDecodedSizeBase64(const char *in, size_t inLength) {
  	if (inLength < 2) {
  		return 0;
  	}
  	const size_t equals = size_t(in[inLength - 1] == '=') + size_t(in[inLength - 2] == '=');
  	const size_t full_length = (inLength * 3) >> 2; // div by 4
  	if (full_length < equals) {
  		return 0;
  	}
  	return full_length - equals;
  }
  
  size_t DecodeBase64(const char *in, size_t inLength, uint8_t *out, size_t maxOutLength) {
  	if (maxOutLength == 0 || inLength < 2) {
  		return 0;
  	}
  	const size_t realLength = inLength - size_t(in[inLength - 1] == '=') - size_t(in[inLength - 2] == '=');
  	size_t dst_offset = 0;
  	int val = 0, valb = -8;
  	for (size_t src_offset = 0; src_offset < realLength; ++src_offset) {
  		const uint8_t table_value = Util::DecodeBase64(in[src_offset]);
  		if (table_value == 255) {
  			return 0;
  		}
  		val = (val << 6) + table_value;
  		valb += 6;
  		if (valb >= 0) {
  			out[dst_offset++] = static_cast<uint8_t>((val >> valb) & 0xFF);
  			valb -= 8;
  			val &= 0xFFF;
  		}
  	}
  	return dst_offset;
  }
  
  static const char to_base64_string[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  char EncodeBase64(char byte) {
  	return to_base64_string[(size_t)byte];
  }
  
  /** Encodes a block of 4 bytes to base64 encoding
  *  @param bytes Bytes to encode.
  *  @param out_string String to write encoded values to.
  *  @param string_pos Position in out_string.
  */
  void EncodeByteBlock(const char *bytes, std::string &out_string, size_t string_pos) {
  	char b0 = (bytes[0] & 0xFC) >> 2;
  	char b1 = (bytes[0] & 0x03) << 4 | ((bytes[1] & 0xF0) >> 4);
  	char b2 = (bytes[1] & 0x0F) << 2 | ((bytes[2] & 0xC0) >> 6);
  	char b3 = (bytes[2] & 0x3F);
  
  	out_string[string_pos + 0] = EncodeBase64(b0);
  	out_string[string_pos + 1] = EncodeBase64(b1);
  	out_string[string_pos + 2] = EncodeBase64(b2);
  	out_string[string_pos + 3] = EncodeBase64(b3);
  }
  
  std::string EncodeBase64(const char *data, size_t length) {
  	// calculate extra bytes needed to get a multiple of 3
  	size_t extraBytes = 3 - length % 3;
  
  	// number of base64 bytes
  	size_t encodedBytes = 4 * (length + extraBytes) / 3;
  
  	std::string encoded_string(encodedBytes, '=');
  
  	// read blocks of 3 bytes
  	for (size_t ib3 = 0; ib3 < length / 3; ib3++) {
  		const size_t iByte = ib3 * 3;
  		const size_t iEncodedByte = ib3 * 4;
  		const char *currData = &data[iByte];
  
  		EncodeByteBlock(currData, encoded_string, iEncodedByte);
  	}
  
  	// if size of data is not a multiple of 3, also encode the final bytes (and add zeros where needed)
  	if (extraBytes > 0) {
  		char finalBytes[4] = { 0, 0, 0, 0 };
  		memcpy(&finalBytes[0], &data[length - length % 3], length % 3);
  
  		const size_t iEncodedByte = encodedBytes - 4;
  		EncodeByteBlock(&finalBytes[0], encoded_string, iEncodedByte);
  
  		// add '=' at the end
  		for (size_t i = 0; i < 4 * extraBytes / 3; i++)
  			encoded_string[encodedBytes - i - 1] = '=';
  	}
  	return encoded_string;
  }
  } // namespace Util
  } // namespace FBXDocParser
  