godot/modules/fbx/fbx_parser/FBXBinaryTokenizer.cpp

/**************************************************************************/
/*  FBXBinaryTokenizer.cpp                                                */
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/*
Open Asset Import Library (assimp)
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Copyright (c) 2006-2019, assimp team


All rights reserved.

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  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
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* 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
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OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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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/print_string.h"

#include <stdint.h>

namespace FBXDocParser {
// ------------------------------------------------------------------------------------------------
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);
	}

	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