diff --git a/uppsrc/Core/FilterStream.cpp b/uppsrc/Core/FilterStream.cpp
index 1dc82d504..64726e380 100644
--- a/uppsrc/Core/FilterStream.cpp
+++ b/uppsrc/Core/FilterStream.cpp
@@ -13,6 +13,8 @@ void InFilterStream::Init()
 	ptr = rdlim = h;
 	in = NULL;
 	eof = false;
+	style = STRM_READ|STRM_LOADING;
+	SetLoading();
 }
 
 dword InFilterStream::Avail()
@@ -100,7 +102,8 @@ void OutFilterStream::Init()
 	wrlim = ~buffer + 4096;
 	ptr = ~buffer;
 	out = NULL;
-	count = 0;
+	count = in_count = 0;
+	style = STRM_WRITE;
 }
 
 OutFilterStream::~OutFilterStream()
@@ -122,11 +125,18 @@ void OutFilterStream::Close()
 void OutFilterStream::FlushOut()
 {
 	if(ptr != ~buffer) {
-		Filter(~buffer, (int)(ptr - ~buffer));
+		int sz = (int)(ptr - ~buffer);
+		in_count += sz;
+		Filter(~buffer, sz);
 		ptr = ~buffer;
 	}
 }
 
+int64 OutFilterStream::GetInCount() const
+{
+	return buffer ? in_count + (int)(ptr - ~buffer) : in_count;
+}
+
 void OutFilterStream::_Put(int w)
 {
 	FlushOut();
diff --git a/uppsrc/Core/FilterStream.h b/uppsrc/Core/FilterStream.h
index f2ae50c20..40e1c7f21 100644
--- a/uppsrc/Core/FilterStream.h
+++ b/uppsrc/Core/FilterStream.h
@@ -8,7 +8,7 @@ protected:
 	virtual   dword _Get(void *data, dword size);
 
 	Vector<byte> buffer;
-	bool eof;
+	bool         eof;
 
 	void   Init();
 	void   Fetch(int size);
@@ -44,6 +44,7 @@ protected:
 
 	Buffer<byte> buffer;
 	int64        count;
+	int64        in_count;
 
 	void   FlushOut();
 	dword  Avail()               { return dword(4096 - (ptr - ~buffer)); }
@@ -56,6 +57,7 @@ public:
 	void                         Out(const void *ptr, int size);
 	
 	int64                        GetCount() const             { return count; }
+	int64                        GetInCount() const;
 
 	template <class F>
 	void Set(Stream& out_, F& filter) {
diff --git a/uppsrc/Core/src.tpp/OutFilterStream$en-us.tpp b/uppsrc/Core/src.tpp/OutFilterStream$en-us.tpp
index bba8e190b..0b047cfa2 100644
--- a/uppsrc/Core/src.tpp/OutFilterStream$en-us.tpp
+++ b/uppsrc/Core/src.tpp/OutFilterStream$en-us.tpp
@@ -49,7 +49,16 @@ size), also keeps track of output bytes written (see GetCount).&]
 [s4; &]
 [s5;:OutFilterStream`:`:GetCount`(`)const: [@(0.0.255) int64]_[* GetCount]()_[@(0.0.255) co
 nst]&]
-[s2;%% Returns a number of bytes written to the output.&]
+[s2;%% Returns a number of bytes written to the output stream (if 
+OutFilterStream is used for compression, this is the compressed 
+size). Note that this number is `'complete`' only after the OutFilterStream 
+is closed, because of buffering of data chunks.&]
+[s3; &]
+[s4; &]
+[s5;:OutFilterStream`:`:GetInCount`(`)const: [@(0.0.255) int64]_[* GetInCount]()_[@(0.0.255) c
+onst]&]
+[s2;%% Returns a number of bytes written to OutFilterStream (if OutFilterStream 
+is used for compression, this is the uncompressed size).&]
 [s3; &]
 [s4;%% &]
 [s5;:OutFilterStream`:`:Set`(Stream`&`,F`&`): [@(0.0.255) template]_<[@(0.0.255) class]_[*@4 F