FBXBinaryTokenizer.cpp

/*
Open Asset Import Library (assimp)
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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.
 */

#ifndef ASSIMP_BUILD_NO_FBX_IMPORTER

#include "FBXTokenizer.h"
#include "FBXUtil.h"
#include <assimp/defs.h>
#include <stdint.h>
#include "Exceptional.h"
#include "ByteSwapper.h"

namespace Assimp {
namespace FBX {

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, unsigned int offset)
    :
    #ifdef DEBUG
    contents(sbegin, static_cast<size_t>(send-sbegin)),
    #endif
    sbegin(sbegin)
    , send(send)
    , type(type)
    , line(offset)
    , column(BINARY_MARKER)
{
    ai_assert(sbegin);
    ai_assert(send);

    // binary tokens may have zero length because they are sometimes dummies
    // inserted by TokenizeBinary()
    ai_assert(send >= sbegin);
}


namespace {

// ------------------------------------------------------------------------------------------------
// signal tokenization error, this is always unrecoverable. Throws DeadlyImportError.
AI_WONT_RETURN void TokenizeError(const std::string& message, unsigned int offset) AI_WONT_RETURN_SUFFIX;
AI_WONT_RETURN void TokenizeError(const std::string& message, unsigned int offset)
{
    throw DeadlyImportError(Util::AddOffset("FBX-Tokenize",message,offset));
}


// ------------------------------------------------------------------------------------------------
uint32_t Offset(const char* begin, const char* cursor)
{
    ai_assert(begin <= cursor);
    return static_cast<unsigned int>(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 = *reinterpret_cast<const uint32_t*>(cursor);
    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);
    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);
    ++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':   {

        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;

            default:
                ai_assert(false);
            };
            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, uint32_t const flags)
{
    // the first word contains the offset at which this block ends
    const uint64_t end_offset = /*check_flag(flags, e_flag_field_size_64_bit) ? 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 = /*check_flag(flags, e_flag_field_size_64_bit) ? ReadDoubleWord(input, cursor, end) : */ReadWord(input, cursor, end);

    // the third data word contains the length of the property list
    const uint64_t prop_length = /*check_flag(flags, e_flag_field_size_64_bit) ? 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 = /*check_flag(flags, e_flag_field_size_64_bit) ? (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, flags);
        }
        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;
}


}

// ------------------------------------------------------------------------------------------------
void TokenizeBinary(TokenList& output_tokens, const char* input, unsigned int length)
{
    ai_assert(input);

    if(length < 0x1b) {
        TokenizeError("file is too short",0);
    }

    if (strncmp(input,"Kaydara FBX Binary",18)) {
        TokenizeError("magic bytes not found",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

    while (cursor < input + length)
    {
        if(!ReadScope(output_tokens, input, cursor, input + length, flags)) {
            break;
        }
    }
}

} // !FBX
} // !Assimp

#endif