godot/modules/fbx/fbx_parser/FBXBinaryTokenizer.cpp

/*************************************************************************/
/*  FBXBinaryTokenizer.cpp                                               */
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/*
Open Asset Import Library (assimp)
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  following disclaimer.

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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 {
// ------------------------------------------------------------------------------------------------
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 is bad.. :/
	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, bool &corrupt) {
	if (Offset(cursor, end) < 1) {
		TokenizeError("cannot ReadData, out of bounds reading length", input, cursor);
		corrupt = true;
		return;
	}

	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:
			corrupt = true; // must exit
			TokenizeError("cannot ReadData, unexpected type code: " + std::string(&type, 1), input, cursor);
			return;
	}

	if (cursor > end) {
		corrupt = true; // must exit
		TokenizeError("cannot ReadData, the remaining size is too small for the data type: " + std::string(&type, 1), input, cursor);
		return;
	}

	// 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, bool &corrupt) {
	// 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);
		corrupt = true;
		return false;
	} else if (end_offset < Offset(input, cursor)) {
		TokenizeError("block offset is negative out of range", input, cursor);
		corrupt = true;
		return false;
	}

	// 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 = nullptr, *send = nullptr;
	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, corrupt);
		if (corrupt) {
			return false;
		}

		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);
		corrupt = true;
		return false;
	}

	// 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, corrupt);
			if (corrupt) {
				return false;
			}
		}
		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);
				corrupt = true;
				return false;
			}
		}
		cursor += sentinel_block_length;
	}

	if (Offset(input, cursor) != end_offset) {
		TokenizeError("scope length not reached, something is wrong", input, cursor);
		corrupt = true;
		return false;
	}

	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, bool &corrupt) {
	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, corrupt)) {
			break;
		}
	}
}
} // namespace FBXDocParser