code: /*************************************************************************/
  /*  FBXBinaryTokenizer.cpp                                               */
  /*************************************************************************/
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  /*
  Open Asset Import Library (assimp)
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  Copyright (c) 2006-2019, assimp team
  
  
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  /** @file  FBXBinaryTokenizer.cpp
   *  @brief Implementation of a fake lexer for binary fbx files -
   *    we emit tokens so the parser needs almost no special handling
   *    for binary files.
   */
  
  #include "ByteSwapper.h"
  #include "FBXTokenizer.h"
  #include "core/string/print_string.h"
  
  #include <stdint.h>
  
  namespace FBXDocParser {
  //enum Flag
  //{
  //   e_unknown_0 = 1 << 0,
  //   e_unknown_1 = 1 << 1,
  //   e_unknown_2 = 1 << 2,
  //   e_unknown_3 = 1 << 3,
  //   e_unknown_4 = 1 << 4,
  //   e_unknown_5 = 1 << 5,
  //   e_unknown_6 = 1 << 6,
  //   e_unknown_7 = 1 << 7,
  //   e_unknown_8 = 1 << 8,
  //   e_unknown_9 = 1 << 9,
  //   e_unknown_10 = 1 << 10,
  //   e_unknown_11 = 1 << 11,
  //   e_unknown_12 = 1 << 12,
  //   e_unknown_13 = 1 << 13,
  //   e_unknown_14 = 1 << 14,
  //   e_unknown_15 = 1 << 15,
  //   e_unknown_16 = 1 << 16,
  //   e_unknown_17 = 1 << 17,
  //   e_unknown_18 = 1 << 18,
  //   e_unknown_19 = 1 << 19,
  //   e_unknown_20 = 1 << 20,
  //   e_unknown_21 = 1 << 21,
  //   e_unknown_22 = 1 << 22,
  //   e_unknown_23 = 1 << 23,
  //   e_flag_field_size_64_bit = 1 << 24, // Not sure what is
  //   e_unknown_25 = 1 << 25,
  //   e_unknown_26 = 1 << 26,
  //   e_unknown_27 = 1 << 27,
  //   e_unknown_28 = 1 << 28,
  //   e_unknown_29 = 1 << 29,
  //   e_unknown_30 = 1 << 30,
  //   e_unknown_31 = 1 << 31
  //};
  //
  //bool check_flag(uint32_t flags, Flag to_check)
  //{
  //	return (flags & to_check) != 0;
  //}
  // ------------------------------------------------------------------------------------------------
  Token::Token(const char *sbegin, const char *send, TokenType type, size_t offset) :
  		sbegin(sbegin),
  		send(send),
  		type(type),
  		line(offset),
  		column(BINARY_MARKER) {
  #ifdef DEBUG_ENABLED
  	contents = std::string(sbegin, static_cast<size_t>(send - sbegin));
  #endif
  	// calc length
  	// measure from sBegin to sEnd and validate?
  }
  
  namespace {
  
  // ------------------------------------------------------------------------------------------------
  // signal tokenization error
  void TokenizeError(const std::string &message, size_t offset) {
  	print_error("[FBX-Tokenize] " + String(message.c_str()) + ", offset " + itos(offset));
  }
  
  // ------------------------------------------------------------------------------------------------
  size_t Offset(const char *begin, const char *cursor) {
  	//ai_assert(begin <= cursor);
  
  	return cursor - begin;
  }
  
  // ------------------------------------------------------------------------------------------------
  void TokenizeError(const std::string &message, const char *begin, const char *cursor) {
  	TokenizeError(message, Offset(begin, cursor));
  }
  
  // ------------------------------------------------------------------------------------------------
  uint32_t ReadWord(const char *input, const char *&cursor, const char *end) {
  	const size_t k_to_read = sizeof(uint32_t);
  	if (Offset(cursor, end) < k_to_read) {
  		TokenizeError("cannot ReadWord, out of bounds", input, cursor);
  	}
  
  	uint32_t word;
  	::memcpy(&word, cursor, 4);
  	AI_SWAP4(word);
  
  	cursor += k_to_read;
  
  	return word;
  }
  
  // ------------------------------------------------------------------------------------------------
  uint64_t ReadDoubleWord(const char *input, const char *&cursor, const char *end) {
  	const size_t k_to_read = sizeof(uint64_t);
  	if (Offset(cursor, end) < k_to_read) {
  		TokenizeError("cannot ReadDoubleWord, out of bounds", input, cursor);
  	}
  
  	uint64_t dword /*= *reinterpret_cast<const uint64_t*>(cursor)*/;
  	::memcpy(&dword, cursor, sizeof(uint64_t));
  	AI_SWAP8(dword);
  
  	cursor += k_to_read;
  
  	return dword;
  }
  
  // ------------------------------------------------------------------------------------------------
  uint8_t ReadByte(const char *input, const char *&cursor, const char *end) {
  	if (Offset(cursor, end) < sizeof(uint8_t)) {
  		TokenizeError("cannot ReadByte, out of bounds", input, cursor);
  	}
  
  	uint8_t word; /* = *reinterpret_cast< const uint8_t* >( cursor )*/
  	::memcpy(&word, cursor, sizeof(uint8_t));
  	++cursor;
  
  	return word;
  }
  
  // ------------------------------------------------------------------------------------------------
  unsigned int ReadString(const char *&sbegin_out, const char *&send_out, const char *input,
  		const char *&cursor, const char *end, bool long_length = false, bool allow_null = false) {
  	const uint32_t len_len = long_length ? 4 : 1;
  	if (Offset(cursor, end) < len_len) {
  		TokenizeError("cannot ReadString, out of bounds reading length", input, cursor);
  	}
  
  	const uint32_t length = long_length ? ReadWord(input, cursor, end) : ReadByte(input, cursor, end);
  
  	if (Offset(cursor, end) < length) {
  		TokenizeError("cannot ReadString, length is out of bounds", input, cursor);
  	}
  
  	sbegin_out = cursor;
  	cursor += length;
  
  	send_out = cursor;
  
  	if (!allow_null) {
  		for (unsigned int i = 0; i < length; ++i) {
  			if (sbegin_out[i] == '\0') {
  				TokenizeError("failed ReadString, unexpected NUL character in string", input, cursor);
  			}
  		}
  	}
  
  	return length;
  }
  
  // ------------------------------------------------------------------------------------------------
  void ReadData(const char *&sbegin_out, const char *&send_out, const char *input, const char *&cursor, const char *end) {
  	if (Offset(cursor, end) < 1) {
  		TokenizeError("cannot ReadData, out of bounds reading length", input, cursor);
  	}
  
  	const char type = *cursor;
  	sbegin_out = cursor++;
  
  	switch (type) {
  		// 16 bit int
  		case 'Y':
  			cursor += 2;
  			break;
  
  			// 1 bit bool flag (yes/no)
  		case 'C':
  			cursor += 1;
  			break;
  
  			// 32 bit int
  		case 'I':
  			// <- fall through
  
  			// float
  		case 'F':
  			cursor += 4;
  			break;
  
  			// double
  		case 'D':
  			cursor += 8;
  			break;
  
  			// 64 bit int
  		case 'L':
  			cursor += 8;
  			break;
  
  			// note: do not write cursor += ReadWord(...cursor) as this would be UB
  
  			// raw binary data
  		case 'R': {
  			const uint32_t length = ReadWord(input, cursor, end);
  			cursor += length;
  			break;
  		}
  
  		case 'b':
  			// TODO: what is the 'b' type code? Right now we just skip over it /
  			// take the full range we could get
  			cursor = end;
  			break;
  
  			// array of *
  		case 'f':
  		case 'd':
  		case 'l':
  		case 'i':
  		case 'c': {
  			const uint32_t length = ReadWord(input, cursor, end);
  			const uint32_t encoding = ReadWord(input, cursor, end);
  
  			const uint32_t comp_len = ReadWord(input, cursor, end);
  
  			// compute length based on type and check against the stored value
  			if (encoding == 0) {
  				uint32_t stride = 0;
  				switch (type) {
  					case 'f':
  					case 'i':
  						stride = 4;
  						break;
  
  					case 'd':
  					case 'l':
  						stride = 8;
  						break;
  
  					case 'c':
  						stride = 1;
  						break;
  
  					default:
  						break;
  				};
  				//ai_assert(stride > 0);
  				if (length * stride != comp_len) {
  					TokenizeError("cannot ReadData, calculated data stride differs from what the file claims", input, cursor);
  				}
  			}
  			// zip/deflate algorithm (encoding==1)? take given length. anything else? die
  			else if (encoding != 1) {
  				TokenizeError("cannot ReadData, unknown encoding", input, cursor);
  			}
  			cursor += comp_len;
  			break;
  		}
  
  			// string
  		case 'S': {
  			const char *sb, *se;
  			// 0 characters can legally happen in such strings
  			ReadString(sb, se, input, cursor, end, true, true);
  			break;
  		}
  		default:
  			TokenizeError("cannot ReadData, unexpected type code: " + std::string(&type, 1), input, cursor);
  	}
  
  	if (cursor > end) {
  		TokenizeError("cannot ReadData, the remaining size is too small for the data type: " + std::string(&type, 1), input, cursor);
  	}
  
  	// the type code is contained in the returned range
  	send_out = cursor;
  }
  
  // ------------------------------------------------------------------------------------------------
  bool ReadScope(TokenList &output_tokens, const char *input, const char *&cursor, const char *end, bool const is64bits) {
  	// the first word contains the offset at which this block ends
  	const uint64_t end_offset = is64bits ? ReadDoubleWord(input, cursor, end) : ReadWord(input, cursor, end);
  
  	// we may get 0 if reading reached the end of the file -
  	// fbx files have a mysterious extra footer which I don't know
  	// how to extract any information from, but at least it always
  	// starts with a 0.
  	if (!end_offset) {
  		return false;
  	}
  
  	if (end_offset > Offset(input, end)) {
  		TokenizeError("block offset is out of range", input, cursor);
  	} else if (end_offset < Offset(input, cursor)) {
  		TokenizeError("block offset is negative out of range", input, cursor);
  	}
  
  	// the second data word contains the number of properties in the scope
  	const uint64_t prop_count = is64bits ? ReadDoubleWord(input, cursor, end) : ReadWord(input, cursor, end);
  
  	// the third data word contains the length of the property list
  	const uint64_t prop_length = is64bits ? ReadDoubleWord(input, cursor, end) : ReadWord(input, cursor, end);
  
  	// now comes the name of the scope/key
  	const char *sbeg, *send;
  	ReadString(sbeg, send, input, cursor, end);
  
  	output_tokens.push_back(new_Token(sbeg, send, TokenType_KEY, Offset(input, cursor)));
  
  	// now come the individual properties
  	const char *begin_cursor = cursor;
  	for (unsigned int i = 0; i < prop_count; ++i) {
  		ReadData(sbeg, send, input, cursor, begin_cursor + prop_length);
  
  		output_tokens.push_back(new_Token(sbeg, send, TokenType_DATA, Offset(input, cursor)));
  
  		if (i != prop_count - 1) {
  			output_tokens.push_back(new_Token(cursor, cursor + 1, TokenType_COMMA, Offset(input, cursor)));
  		}
  	}
  
  	if (Offset(begin_cursor, cursor) != prop_length) {
  		TokenizeError("property length not reached, something is wrong", input, cursor);
  	}
  
  	// at the end of each nested block, there is a NUL record to indicate
  	// that the sub-scope exists (i.e. to distinguish between P: and P : {})
  	// this NUL record is 13 bytes long on 32 bit version and 25 bytes long on 64 bit.
  	const size_t sentinel_block_length = is64bits ? (sizeof(uint64_t) * 3 + 1) : (sizeof(uint32_t) * 3 + 1);
  
  	if (Offset(input, cursor) < end_offset) {
  		if (end_offset - Offset(input, cursor) < sentinel_block_length) {
  			TokenizeError("insufficient padding bytes at block end", input, cursor);
  		}
  
  		output_tokens.push_back(new_Token(cursor, cursor + 1, TokenType_OPEN_BRACKET, Offset(input, cursor)));
  
  		// XXX this is vulnerable to stack overflowing ..
  		while (Offset(input, cursor) < end_offset - sentinel_block_length) {
  			ReadScope(output_tokens, input, cursor, input + end_offset - sentinel_block_length, is64bits);
  		}
  		output_tokens.push_back(new_Token(cursor, cursor + 1, TokenType_CLOSE_BRACKET, Offset(input, cursor)));
  
  		for (unsigned int i = 0; i < sentinel_block_length; ++i) {
  			if (cursor[i] != '\0') {
  				TokenizeError("failed to read nested block sentinel, expected all bytes to be 0", input, cursor);
  			}
  		}
  		cursor += sentinel_block_length;
  	}
  
  	if (Offset(input, cursor) != end_offset) {
  		TokenizeError("scope length not reached, something is wrong", input, cursor);
  	}
  
  	return true;
  }
  } // anonymous namespace
  
  // ------------------------------------------------------------------------------------------------
  // TODO: Test FBX Binary files newer than the 7500 version to check if the 64 bits address behaviour is consistent
  void TokenizeBinary(TokenList &output_tokens, const char *input, size_t length) {
  	if (length < 0x1b) {
  		//TokenizeError("file is too short",0);
  	}
  
  	//uint32_t offset = 0x15;
  	/*    const char* cursor = input + 0x15;
      const uint32_t flags = ReadWord(input, cursor, input + length);
      const uint8_t padding_0 = ReadByte(input, cursor, input + length); // unused
      const uint8_t padding_1 = ReadByte(input, cursor, input + length); // unused*/
  
  	if (strncmp(input, "Kaydara FBX Binary", 18)) {
  		TokenizeError("magic bytes not found", 0);
  	}
  
  	const char *cursor = input + 18;
  	/*Result ignored*/ ReadByte(input, cursor, input + length);
  	/*Result ignored*/ ReadByte(input, cursor, input + length);
  	/*Result ignored*/ ReadByte(input, cursor, input + length);
  	/*Result ignored*/ ReadByte(input, cursor, input + length);
  	/*Result ignored*/ ReadByte(input, cursor, input + length);
  	const uint32_t version = ReadWord(input, cursor, input + length);
  	print_verbose("FBX Version: " + itos(version));
  	//ASSIMP_LOG_DEBUG_F("FBX version: ", version);
  	const bool is64bits = version >= 7500;
  	const char *end = input + length;
  	while (cursor < end) {
  		if (!ReadScope(output_tokens, input, cursor, input + length, is64bits)) {
  			break;
  		}
  	}
  }
  } // namespace FBXDocParser
  