‍swf文件格式解析入门（tag解析）

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‍swf文件格式解析入门（tag解析）
2010-12-02 11:29
上文把文件头解析完成了，接下来就是解析标签
swf文件把所有的资源都打包在标签内部
如字体，位图，嵌入的2进制，代码等等

tag有两种类型，1种为短tag，1种为长tag
短tag的长度是小于63个字节的

短标签格式
RECORDHEADER (short)
Field               Type    Comment
TagCodeAndLength    UI16    Upper 10 bits: tag type Lower 6 bits: tag length
高10位表示标签类型，低6位表示标签长度

长标签格式 长标签的TagCodeAndLength为0x3F (=63)
长标签使用Length来表示标签的长度
RECORDHEADER (long)
Field               Type    Comment
TagCodeAndLength    UI16    Tag type and length of 0x3F Packed together as in short header
Length              SI32    Length of tag

跟着标签头后面就是标签指定长度的数据
然后根据不同的标签类型来解析数据就可以了

每个tag读取结束后，后面的又重新字节对齐了，不用考虑剩余几个字节的问题


/**
* 读取tag类型，不移动position 
* @param bytes
* @return 
*/
private function readTagType(bytes:ByteArray):uint
{
    var result:uint = bytes.readUnsignedShort();
    result = result >> 6;
    
    bytes.position -= 2;
    
    return result;
}

/**
* 读取tag长度 不包括头本身占的长度 
* @param bytes
* @return 
* 
*/     
private function readTagLength(bytes:ByteArray):uint{
    var tagLength:uint = (bytes.readUnsignedShort() & 0x3F);
    if (tagLength == 0x3F){
        tagLength = bytes.readUnsignedInt();
    };
    if (tagLength < 0){
        throw (Error("SWFReader:无效的tag长度"));
    };
    
    return tagLength;
}


/**
* 读取tag列表 
* @param bytes
* 
*/     
private function readTags(bytes:ByteArray):Array
{
    var result:Array = [];
    
    var tagType:uint;
    var tagLength:uint;
    var start:int;
    var tag:Tag;
    var cl:Class;
    
    while(bytes.bytesAvailable > 0)
    {
        start = bytes.position;
        tagType = readTagType(bytes);
        tagLength = readTagLength(bytes);
        
        cl = TagTypes.getTagClassByTagType(tagType);
        if (cl == null)
        {
            trace("Tag Not Found, Type=" + tagType, tagLength);
            bytes.position += tagLength;// 跳过长度
            continue;
        }
        tag = new cl();
        tag.tagType = tagType;
        if( tagLength > 0)
            bytes.readBytes(tag.data, 0, tagLength);
        
        tag.data.endian = Endian.LITTLE_ENDIAN;
        tag.data.position = 0;
        
        // 调用解析方法
        tag.parse();
        
        result.push(tag);
        
        if (tagType == TagTypes.TAG_END)
            break;
    }
    
    return result;
}

// 所有的tag类型列表
package swf.file.tags
{
    import com.the9.nbu.swf.file.tags.actions.*;
    import com.the9.nbu.swf.file.tags.binary.*;
    import com.the9.nbu.swf.file.tags.bitmaps.*;
    import com.the9.nbu.swf.file.tags.buttons.*;
    import com.the9.nbu.swf.file.tags.control.*;
    import com.the9.nbu.swf.file.tags.displaylist.*;
    import com.the9.nbu.swf.file.tags.font.*;
    import com.the9.nbu.swf.file.tags.shapemorphing.*;
    import com.the9.nbu.swf.file.tags.shapes.*;
    import com.the9.nbu.swf.file.tags.sounds.*;
    import com.the9.nbu.swf.file.tags.sprite.*;
    import com.the9.nbu.swf.file.tags.text.*;
    import com.the9.nbu.swf.file.tags.video.*;
    import com.the9.nbu.swf.file.tags.unknown.*;
    
    /**
     * TagTypes
     * @author 任冬 [e-mail]
     * $Id: TagTypes.as 499 2010-11-19 10:02:56Z rendong $
     * @version 1.0
     */
    public class TagTypes
    {
        // Flash 1 tags
        public static const TAG_END:uint = 0;
        public static const TAG_SHOWFRAME:uint = 1;
        public static const TAG_DEFINESHAPE:uint = 2;
        public static const TAG_FREECHARACTER:uint = 3;
        public static const TAG_PLACEOBJECT:uint = 4;
        public static const TAG_REMOVEOBJECT:uint = 5;
        public static const TAG_DEFINEBITS:uint = 6;
        public static const TAG_DEFINEBUTTON:uint = 7;
        public static const TAG_JPEGTABLES:uint = 8;
        public static const TAG_SETBACKGROUNDCOLOR:uint = 9;
        public static const TAG_DEFINEFONT:uint = 10;
        public static const TAG_DEFINETEXT:uint = 11;
        public static const TAG_DOACTION:uint = 12;
        public static const TAG_DEFINEFONTINFO:uint = 13;
        public static const TAG_DEFINESOUND:uint = 14;
        public static const TAG_STARTSOUND:uint = 15;
        public static const TAG_STOPSOUND:uint = 16;
        public static const TAG_DEFINEBUTTONSOUND:uint = 17;
        public static const TAG_SOUNDSTREAMHEAD:uint = 18;
        public static const TAG_SOUNDSTREAMBLOCK:uint = 19;
        // Flash 2 tags
        public static const TAG_DEFINEBITSLOSSLESS:uint = 20;
        public static const TAG_DEFINEBITSJPEG2:uint = 21;
        public static const TAG_DEFINESHAPE2:uint = 22;
        public static const TAG_DEFINEBUTTONCXFORM:uint = 23;
        public static const TAG_PROTECT:uint = 24;
        public static const TAG_PATHSAREPOSTSCRIPT:uint = 25;
        // Flash 3 tags
        public static const TAG_PLACEOBJECT2:uint = 26;
        
        public static const TAG_REMOVEOBJECT2:uint = 28;
        public static const TAG_SYNCFRAME:uint = 29;
        
        public static const TAG_FREEALL:uint = 31;
        public static const TAG_DEFINESHAPE3:uint = 32;
        public static const TAG_DEFINETEXT2:uint = 33;
        public static const TAG_DEFINEBUTTON2:uint = 34;
        public static const TAG_DEFINEBITSJPEG3:uint = 35;
        public static const TAG_DEFINEBITSLOSSLESS2:uint = 36;
        // Flash 4 tags
        public static const TAG_DEFINEEDITTEXT:uint = 37;
        public static const TAG_DEFINEVIDEO:uint = 38;
        public static const TAG_DEFINESPRITE:uint = 39;
        public static const TAG_NAMECHARACTER:uint = 40;
        public static const TAG_PRODUCTINFO:uint = 41;
        public static const TAG_DEFINETEXTFORMAT:uint = 42;
        public static const TAG_FRAMELABEL:uint = 43;
        // Flash 5 tags
        public static const TAG_DEFINEBEHAVIOR:uint = 44;
        public static const TAG_SOUNDSTREAMHEAD2:uint = 45;
        public static const TAG_DEFINEMORPHSHAPE:uint = 46;
        public static const TAG_FRAMETAG:uint = 47;
        public static const TAG_DEFINEFONT2:uint = 48;
        public static const TAG_GENCOMMAND:uint = 49;
        public static const TAG_DEFINECOMMANDOBJ:uint = 50;
        public static const TAG_CHARACTERSET:uint = 51;
        public static const TAG_FONTREF:uint = 52;
        public static const TAG_DEFINEFUNCTION:uint = 53;
        public static const TAG_PLACEFUNCTION:uint = 54;
        public static const TAG_GENTAGOBJECT:uint = 55;
        public static const TAG_EXPORTASSETS:uint = 56;
        public static const TAG_IMPORTASSETS:uint = 57;
        public static const TAG_ENABLEDEBUGGER:uint = 58;
        // Flash 6 tags
        public static const TAG_DOINITACTION:uint = 59;
        public static const TAG_DEFINEVIDEOSTREAM:uint = 60;
        public static const TAG_VIDEOFRAME:uint = 61;
        public static const TAG_DEFINEFONTINFO2:uint = 62;
        public static const TAG_DEBUGID:uint = 63;
        public static const TAG_ENABLEDEBUGGER2:uint = 64;
        public static const TAG_SCRIPTLIMITS:uint = 65;
        // Flash 7 tags
        public static const TAG_SETTABINDEX:uint = 66;
        // Flash 8 tags
        
        
        public static const TAG_FILEATTRIBUTES:uint = 69;
        public static const TAG_PLACEOBJECT3:uint = 70;
        public static const TAG_IMPORTASSETS2:uint = 71;
        public static const TAG_DOABC:uint = 72;
        public static const TAG_DEFINEFONTALIGNZONES:uint = 73;
        public static const TAG_CSMTEXTSETTINGS:uint = 74;
        public static const TAG_DEFINEFONT3:uint = 75;
        public static const TAG_SYMBOLCLASS:uint = 76;
        public static const TAG_METADATA:uint = 77;
        public static const TAG_SCALINGGRID:uint = 78;
        
        
        
        public static const TAG_DOABC2:uint = 82;
        public static const TAG_DEFINESHAPE4:uint = 83;
        public static const TAG_DEFINEMORPHSHAPE2:uint = 84;
        
        // Flash 9 tags
        public static const TAG_DEFINESCENEANDFRAMELABELDATA:uint = 86;
        public static const TAG_DEFINEBINARYDATA:uint = 87;
        public static const TAG_DEFINEFONTNAME:uint = 88;
        public static const TAG_STARTSOUND2:uint = 89;
        public static const TAG_DEFINEBITSJPEG4:uint = 90;
        // Flash 10 tags
        public static const TAG_DEFINEFONT4:uint = 91;

        
        /**
         * tagType => tag 名称 
         */     
        private static const TAG_NAMES:Array =["End","ShowFrame","DefineShape","FreeCharacter","PlaceObject","RemoveObject","DefineBits","DefineButton","JPEGTables","SetBackgroundColor","DefineFont","DefineText","DoAction","DefineFontInfo","DefineSound","StartSound","StopSound","DefineButtonSound","SoundStreamHead","SoundStreamBlock","DefineBitsLossless","DefineBitsJPEG2","DefineShape2","DefineButtonCxform","Protect","PathsArePostScript","PlaceObject2","27 (invalid)","RemoveObject2","SyncFrame","30 (invalid)","FreeAll","DefineShape3","DefineText2","DefineButton2","DefineBitsJPEG3","DefineBitsLossless2","DefineEditText","DefineVideo","DefineSprite","NameCharacter","ProductInfo","DefineTextFormat","FrameLabel","DefineBehavior","SoundStreamHead2","DefineMorphShape","FrameTag","DefineFont2","GenCommand","DefineCommandObj","CharacterSet","FontRef","DefineFunction","PlaceFunction","GenTagObject","ExportAssets","ImportAssets","EnableDebugger","DoInitAction","DefineVideoStream","VideoFrame","DefineFontInfo2","DebugID","EnableDebugger2","ScriptLimits","SetTabIndex","67 (invalid)","68 (invalid)","FileAttributes","PlaceObject3","ImportAssets2","DoABC","DefineFontAlignZones","CSMTextSettings","DefineFont3","SymbolClass","Metadata","ScalingGrid","79 (invalid)","80 (invalid)","81 (invalid)","DoABC2","DefineShape4","DefineMorphShape2","85 (invalid)","DefineSceneAndFrameLabelData","DefineBinaryData","DefineFontName","StartSound2","DefineBitsJPEG4","DefineFont4"];

        /**
         * tagType => tag class
         */     
        private static const TAG_CLASS:Array = [EndTag,ShowFrameTag,DefineShapeTag,FreeCharacterTag,PlaceObjectTag,RemoveObjectTag,DefineBitsTag,DefineButtonTag,JPEGTablesTag,SetBackgroundColorTag,DefineFontTag,DefineTextTag,DoActionTag,DefineFontInfoTag,DefineSoundTag,StartSoundTag,StopSoundTag,DefineButtonSoundTag,SoundStreamHeadTag,SoundStreamBlockTag,DefineBitsLosslessTag,DefineBitsJPEG2Tag,DefineShape2Tag,DefineButtonCxformTag,ProtectTag,PathsArePostScriptTag,PlaceObject2Tag,null,RemoveObject2Tag,SyncFrameTag,null,FreeAllTag,DefineShape3Tag,DefineText2Tag,DefineButton2Tag,DefineBitsJPEG3Tag,DefineBitsLossless2Tag,DefineEditTextTag,DefineVideoTag,DefineSpriteTag,NameCharacterTag,ProductInfoTag,DefineTextFormatTag,FrameLabelTag,DefineBehaviorTag,SoundStreamHead2Tag,DefineMorphShapeTag,FrameTagTag,DefineFont2Tag,GenCommandTag,DefineCommandObjTag,CharacterSetTag,FontRefTag,DefineFunctionTag,PlaceFunctionTag,GenTagObjectTag,ExportAssetsTag,ImportAssetsTag,EnableDebuggerTag,DoInitActionTag,DefineVideoStreamTag,VideoFrameTag,DefineFontInfo2Tag,DebugIDTag,EnableDebugger2Tag,ScriptLimitsTag,SetTabIndexTag,null,null,FileAttributesTag,PlaceObject3Tag,ImportAssets2Tag,DoABCTag,DefineFontAlignZonesTag,CSMTextSettingsTag,DefineFont3Tag,SymbolClassTag,MetadataTag,ScalingGridTag,null,null,null,DoABCTag,DefineShape4Tag,DefineMorphShape2Tag,null,DefineSceneAndFrameLabelDataTag,DefineBinaryDataTag,DefineFontNameTag,StartSound2Tag,DefineBitsJPEG4Tag,DefineFont4Tag];
        
        
        /**
         * 根据编号获取tag名称 
         * @param tagType
         * @return 
         * 
         */     
        public static function getTagNameByTagType(tagType:int):String
        {
            return TAG_NAMES[tagType] || null;
        }
        
        /**
         * 根据变化获取tag class 
         * @param tagType
         * @return 
         * 
         */     
        public static function getTagClassByTagType(tagType:int):Class
        {
            return TAG_CLASS[tagType] || null;
        }
    }
}
 


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