We are making a system that has a main swf for the application, and loads separate tools from separate swfs -- there will be versioning issues in the future since the separate swfs are coming from a cms (especially now since we're still developing, but also in the future when other developers might create an incompatible tool). I'm trying hard to prevent them as much as possible but I'd really like to be able to display a message to the user of the system when an incompatible swf is loaded.
This would mean that we need to catch that VerifyError or at least determine the loading failed for some reason - I've got no idea how to handle that at the moment. I suspect it might be possible using 10.1 and the uncaughtError system, but we are currently targeting flash player 10. Does anyone have a good idea? (we are already handling IOErrorEvent.IO_ERROR)
UPDATE: I've built a solution that scans the bytecode before importing, looks like that will work. I'll post the solution later.
To finally answer my own question, this is the utility class I've been using to detect possible errors. I load the SWF as a bytearray and scan the contents before loading it as an actual MovieClip.
As you can see my code heavily depends on the com.segfaultlabs.swfutils package
Important: I've stopped using this method of preventing errors, opting for the more manual approach of checking the files by actually trying to load them and see if they work. This is because the utility is not complete, and my current knowledge of the ABC format is not good enough to make sure I can develop a check that will always be correct.
Posting my code here as starting point for others who want to take a stab at it :-)
package nl.ijsfontein.utils
{
import com.segfaultlabs.swfutils.ABC.ABCCPool;
import com.segfaultlabs.swfutils.ABC.ABCClass;
import com.segfaultlabs.swfutils.ABC.ABCInstance;
import com.segfaultlabs.swfutils.ABC.ABCMethodInfo;
import com.segfaultlabs.swfutils.ABC.ABCMultiname;
import com.segfaultlabs.swfutils.ABC.ABCParser;
import com.segfaultlabs.swfutils.ABC.ABCTraitConstSlot;
import com.segfaultlabs.swfutils.ABC.ABCTraitsInfo;
import com.segfaultlabs.swfutils.ABC.ABCinfo;
import com.segfaultlabs.swfutils.SWFDataInput;
import com.segfaultlabs.swfutils.SWFFile;
import flash.system.ApplicationDomain;
import flash.utils.ByteArray;
/**
* utility to see which classes a swf uses, but doesn't contain itself
* - this can be used to detect possible VerifyErrors before they happen.
*/
public class SwfDependencyUtil
{
public function SwfDependencyUtil()
{
}
// return null if ok, or name of needed class if external depencendy
private static function resolveSuper(abc:ABCinfo, superClass:String):String
{
//if (superClass.indexOf("flash.") == 0 || superClass.indexOf("*") == 0 || superClass.indexOf("Object") == 0)
if (superClass.indexOf("*") == 0)
{
trace(' super: ' + superClass + " (ignore)");
}
else
{
var superClassClass:ABCClass = null;
for each ( var c:ABCClass in abc.classes )
{
if (c.name == superClass)
{
superClassClass = c;
}
}
if (superClassClass)
{
trace(' super: ' + superClass + " (resolved internally)");
return resolveSuper(abc, superClassClass.iref.base);
}
else
{
trace(' super: ' + superClass + " (NOTFOUND)");
return superClass;
}
}
return null;
}
/*
* checks: classes, superclasses, static variables, member variables
* TODO: function arguments
* won't check: method bodies
*
* TODO: refactor to multiple methods
*/
public static function getDependencies(swfBytes:ByteArray):Array /* of String */
{
var result:Array = [];
swfBytes.position = 0;
var swfr:SWFFile = new SWFFile(swfBytes);
var arr:Array;
if ( swfr.compressed )
{
swfr.dataInput = swfr.uncompress();
swfr.readHeader();
};
arr = swfr.parseTags();
if ( arr[82] != null )
{
var abc:ABCinfo = new ABCinfo();
var cpool:ABCCPool = new ABCCPool();
var abcparse:ABCParser = new ABCParser();
abcparse.readMethodBytes = true;
abcparse.readExceptions = false;
for ( var j:int = 0; j < arr[82].length; j += 1 )
{
swfr.dataInstance.position = arr[82][j].position;
try
{
abcparse.parse( swfr.dataInput as SWFDataInput, abc, cpool, new FakeLogger() );
for each ( var c:ABCClass in abc.classes )
{
trace('class:', c.name);
var superClass:String = c.iref.base;
var dependency:String = resolveSuper(abc, superClass);
if (dependency)
{
result.push(dependency);
}
for each (var mn:ABCMultiname in c.iref.interfaces)
{
var interfaceName:String = mn.nsset[0] != "" ? mn.nsset[0] + "::" + mn.name : mn.name;
var interfaceDependency:String = resolveSuper(abc, interfaceName);
if (interfaceDependency)
{
result.push(interfaceDependency);
}
}
for each (var ti:ABCTraitsInfo in c.traits)
{
if (ti is ABCTraitConstSlot)
{
var constName:String
if (QName(ABCTraitConstSlot(ti).type).uri)
{
constName = QName(ABCTraitConstSlot(ti).type).uri + "::" + QName(ABCTraitConstSlot(ti).type).localName
}
else
{
constName = QName(ABCTraitConstSlot(ti).type).localName
}
var constDependency:String = resolveSuper(abc, constName);
if (constDependency)
{
result.push(constDependency);
}
}
else if (ti is ABCMethodInfo)
{
trace('method', ABCMethodInfo(ti).name);
} else
{
trace(ti);
}
// trace(ti.type.localName);
}
// const (static?) members: c.traits
}
for each ( var i:ABCInstance in abc.instances )
{
// trace(i);
for each (var instanceTi:ABCTraitsInfo in i.traits)
{
if (instanceTi is ABCTraitConstSlot)
{
trace('instance:', createClassNameFromQname(ABCTraitConstSlot(instanceTi).type));
var csdep:String = resolveSuper(abc, createClassNameFromQname(ABCTraitConstSlot(instanceTi).type));
if (csdep)
{
result.push(csdep);
}
}
else if (instanceTi is ABCMethodInfo)
{
}
else
{
trace('unexpected trait type');
}
}
}
abc.dispose();
}
catch ( e:Error )
{
trace( " Error ",e.getStackTrace() );
};
};
cpool.dispose();
}
else
{
trace("No DoABC block... ;(");
}
return result;
}
private static function createClassNameFromQname(qn:QName):String
{
var result:String
if (qn.uri)
{
result = qn.uri + "::" + qn.localName
}
else
{
result = qn.localName
}
return result;
}
public static function getUnsatisfiedDependencies(swfBytes:ByteArray):Array /* of String */
{
var result:Array = [];
var dependencies:Array = SwfDependencyUtil.getDependencies(swfBytes)
for each (var dependency:String in dependencies)
{
if (ApplicationDomain.currentDomain.hasDefinition(dependency))
{
trace('ok: ', dependency);
}
else
{
trace('ERROR: unsatisfied dependency: ', dependency);
result.push(dependency);
}
}
return result;
}
}
}