update version to the release

[gnash.git] / libcore / SWFStream.h

// stream.h - SWF stream reading class, for Gnash
// 
//   Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Free Software
//   Foundation, Inc
// 
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
// 
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

#ifndef GNASH_STREAM_H
#define GNASH_STREAM_H

#include "SWF.h"
#include "dsodefs.h" // still neded ?
#include "GnashException.h"

#include <string>
#include <sstream>
#include <vector> // for composition
#include <boost/cstdint.hpp> // for boost::?int??_t 

// Define the following macro if you want to want Gnash parser
// to assume the underlying SWF is well-formed. It would make
// parsing faster, but might result in horrible behaviour with
// malformed SWFs (like taking up all system memory, keeping
// CPU busy for a long long time, or simply corrupting memory)
//
// This might be eventually set by a --disable-swf-checks or similar
// configure switch...
//
//#define GNASH_TRUST_SWF_INPUT

namespace gnash {
        class IOChannel;
}

namespace gnash {

/// SWF stream wrapper class
//
/// This class is used for loading variable-length data
/// from a stream, and keeping track of SWF tag boundaries.
///
/// Provides 'aligned' and 'bitwise' read functions:
/// - aligned reads always start on a byte boundary
/// - bitwise reads can cross byte boundaries
/// 
class DSOEXPORT SWFStream
{
public:
        SWFStream(IOChannel* input);
        ~SWFStream();

        /// \brief
        /// Reads a bit-packed unsigned integer from the stream
        /// and returns it.  The given bitcount determines the
        /// number of bits to read.
        //
        /// bitwise read
        ///
        unsigned read_uint(unsigned short bitcount);

        /// \brief
        /// Reads a single bit off the stream
        /// and returns it.  
        //
        /// bitwise read
        ///
        bool read_bit();

        /// \brief
        /// Reads a bit-packed little-endian signed integer
        /// from the stream.  The given bitcount determines the
        /// number of bits to read.
        //
        /// bitwise read
        ///
        int     read_sint(unsigned short bitcount);

        /// Read a 16.16 fixed point signed value
        //
        /// aligned read
        ///
        float   read_fixed();

        /// Read a 16.16 fixed point unsigned value
        //
        /// aligned read
        ///
        float   read_ufixed();

        /// Read a 8.8 fixed point unsigned value
        //
        /// aligned read
        ///
        float   read_short_ufixed();

        /// Read a 8.8 fixed point signed value
        //
        /// aligned read
        ///
        float   read_short_sfixed();

        /// Read a 16bit (1:sign 5:exp 10:mantissa) floating point value
        //
        /// aligned read
        ///
        float   read_short_float();

        /// Read a 32bit (1:sign 8:exp 23:mantissa) floating point value
        //
        /// aligned read
        ///
        float   read_long_float();

        /// Read a 64-bit double value
        //
        /// aligned read
        ///
        double read_d64();

        /// Consume all bits of current byte
        //
        /// This method is implicitly called by all 'aligned' reads.
        ///
        /// NOTE:
        /// The position returned by tell() won't be changed
        /// by calls to this function, altought any subsequent reads
        /// will start on next byte. See tell() for more info.
        ///
        void    align()
        {
                m_unused_bits=0;
                // m_current_byte = 0; // this is not needed
        }

        /// Read <count> bytes from the source stream and copy that data to <buf>.
        //
        /// aligned read
        ///
        unsigned read(char *buf, unsigned count);
        
        /// Read a aligned unsigned 8-bit value from the stream.                
        //
        /// aligned read
        ///
        boost::uint8_t  read_u8();

        /// Read a aligned signed 8-bit value from the stream.          
        //
        /// aligned read
        ///
    boost::int8_t read_s8();

        /// Read a aligned unsigned 16-bit value from the stream.               
        //
        /// aligned read
        ///
        boost::uint16_t read_u16();

        /// Read a aligned signed 16-bit value from the stream.         
        //
        /// aligned read
        ///
        boost::int16_t  read_s16();

        /// Read a aligned unsigned 32-bit value from the stream.               
        //
        /// aligned read
        ///
        boost::uint32_t read_u32();

        /// \brief
        /// Read a aligned signed 32-bit value from the stream.         
        //
        /// aligned read
        ///
        boost::int32_t  read_s32();

        /// \brief
        /// Read a variable length unsigned 32-bit value from the stream.
        /// These values continue until either the high bit is not set or
        /// until 5 bytes have been read.
        //
        /// aligned read
        ///
        boost::uint32_t read_V32()
        {
        ensureBytes(1);
                boost::uint32_t res = read_u8();
                if (!(res & 0x00000080)) return res;
        
        ensureBytes(1);
                res = (res & 0x0000007F) | read_u8() << 7;
                if (!(res & 0x00004000)) return res;
        
        ensureBytes(1);
                res = (res & 0x00003FFF) | read_u8() << 14;
                if (!(res & 0x00200000)) return res;
        
        ensureBytes(1);
                res = (res & 0x001FFFFF) | read_u8() << 21;
                if (!(res & 0x10000000)) return res;
        
        ensureBytes(1);
                res = (res & 0x0FFFFFFF) | read_u8() << 28;
                return res;
        }

        /// \brief
        /// Skip a variable length unsigned 32-bit value in the stream.
        /// This is faster than doing the bitwise arithmetic of full reading.
        ///
        /// aligned read
        ///
        void skip_V32()
        {
        ensureBytes(1);
                if (!(read_u8() & 0x80)) return;
        ensureBytes(1);
                if (!(read_u8() & 0x80)) return;
        ensureBytes(1);
                if (!(read_u8() & 0x80)) return;
        ensureBytes(1);
                if (!(read_u8() & 0x80)) return;
        ensureBytes(1);
                static_cast<void> (read_u8());
        }

        /// \brief
        /// Read a length in a byte or three.
        //
        /// If the byte == 0xff, read the lenght in 
        /// next two bytes.
        ///
        /// Takes care of integrity check (ensureByte)
        ///
        /// aligned read
        ///
        unsigned read_variable_count()
        {
                ensureBytes(1);
                unsigned count = read_u8();
                if (count == 0xFF)
                {
                        ensureBytes(2);
                        count = read_u16();
                }
                return count;
        };

        /// \brief
        /// Reads a null-terminated string from the given file and
        /// assigns it to the given std::string, overriding any
        /// previous value of it.
        ///
        /// aligned read
        ///
        /// Will throw ParserException if no terminating null is found within
    /// tag boundaries
        void read_string(std::string& to);

        /// Reads a sized string into a provided std::string.
        //
        /// Length of string is read from the first byte.
        ///
        /// @param to
        ///     Output argument. Any previous value will be overriden.
        ///
        /// aligned read
        ///
        /// Will throw ParserException if advertised length crosses tag boundaries
        ///
        void    read_string_with_length(std::string& to);

        /// Reads a sized string into a provided std::string.
        //
        ///
        /// @param len
        ///     Length of string to read.
        ///
        /// @param to
        ///     Output argument. Any previous value will be overriden.
        ///
        /// aligned read
        ///
        /// Will throw ParserException if len crosses tag boundaries
        ///
        void    read_string_with_length(unsigned len, std::string& to);

        /// Return our current (byte) position in the input stream.
        //
        /// NOTE:
        /// This is not necessarely the byte you'll read on next read.
        /// - For bitwise reads the currenty byte will be used only if not
        ///   completely consumed. See align().
        /// - For aligned reads the current byte will not be used
        ///   (already used)
        ///
        unsigned long tell();

        /// Set the file position to the given value (byte aligned)
        //
        /// If we're scanning a tag, don't allow seeking past
        /// the end or before start of it.
        ///
        /// @return true on success, false on failure
        ///     Possible failures:
        ///     - given position is after end of stream.
        ///     - given position is after end of current tag, if any.
        ///     - given position is before start of current tag, if any.
        ///
        bool seek(unsigned long pos);

        /// Return the file position of the end of the current tag.
        unsigned long get_tag_end_position();

        /// Open an SWF tag and return it's type.
        //
        /// aligned read
        ///
        SWF::TagType    open_tag();

        /// Seek to the end of the most-recently-opened tag.
        void    close_tag();

        /// Discard given number of bytes
        //
        ///
        /// @return true on success, false on failure
        ///     Possible failures:
        ///     - skipping given number of bytes reaches end of stream.
        ///     - skipping given number of bytes reaches end of
        ///       current tag, if any.
        ///
        /// WARNING: alignment is not specified here, the method uses
        ///          tell() which is known NOT to consider
        ///          a fully-read byte as already "skipped"
        ///          TODO: force alignment and see what happens !!
        ///
        bool skip_bytes(unsigned num)
        {
                // there's probably a better way, but
                // it's the interface that counts atm
                size_t curpos = tell();
                return seek(curpos+num);
        }

        /// Discard all bytes up to end of tag
        void skip_to_tag_end()
        {
                // seek will call align...
                seek(get_tag_end_position());
        }

        /// \brief
        /// Ensure the requested number of bytes are available for an aligned read
        /// in the currently opened tag.
        //
        /// Throws a ParserException on a short count.
        /// This method should be called before any attempt to read
        /// fields from the SWF.
        ///
        /// NOTE: if GNASH_TRUST_SWF_INPUT is defined this function is a no-op 
        ///
        void ensureBytes(unsigned long needed);

        /// \brief
        /// Ensure the requested number of bits are available for a bitwise read
        /// in currently opened tag.
        //
        /// Throws a ParserException on a short count.
        /// This method should be called before any attempt to read
        /// bits from the SWF.
        ///
        /// NOTE: if GNASH_TRUST_SWF_INPUT is defined this function is a no-op 
        ///
        void ensureBits(unsigned long needed)
        {
#ifndef GNASH_TRUST_SWF_INPUT
                if ( _tagBoundsStack.empty() ) return; // not in a tag (should we check file length ?)
                unsigned long int bytesLeft = get_tag_end_position() - tell();
                unsigned long int bitsLeft = (bytesLeft*8)+m_unused_bits;
                if ( bitsLeft < needed )
                {
                        std::stringstream ss;
                        ss << "premature end of tag: need to read " << needed << " bytes, but only " << bitsLeft << " left in this tag";
                        throw ParserException(ss.str());
                }
#endif
        }

        /// Consume any pending input
        //
        /// This method is useful to force full consumption
        /// of the SWFStream's underlying IOChannel for the 
        /// cases in which it is a pipe and a writer would
        /// hang on it unless someone is reading.
        ///
        /// This method will NOT be called automatically
        /// on SWFStream destruction as in the current 
        /// design SWFStream does NOT own the underlying 
        /// IOChannel. TODO: rethink about ownership.
        ///
        /// NOTE: the stream position will be updated by
        ///       this call, so that ::tell will basically
        ///       return the full input size.
        ///
        void consumeInput();

private:

        IOChannel*      m_input;
        boost::uint8_t  m_current_byte;
        boost::uint8_t  m_unused_bits;

        typedef std::pair<unsigned long,unsigned long> TagBoundaries;
        // position of start and end of tag
        std::vector<TagBoundaries> _tagBoundsStack;
};


} // namespace gnash


#endif // GNASH_STREAM_H


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