diff --git a/uppsrc/Core/Other.h b/uppsrc/Core/Other.h
index 01d90b113..5e317fdf5 100644
--- a/uppsrc/Core/Other.h
+++ b/uppsrc/Core/Other.h
@@ -119,6 +119,8 @@ class Bits : Moveable<Bits> {
 	dword      *bp;
 	
 	void Expand(int q);
+	void Realloc(int nalloc);
+	void Free();
 
 public:
 	void   Clear();
@@ -127,9 +129,16 @@ public:
 	bool   Get(int i) const        { ASSERT(i >= 0 && alloc >= 0); int q = i >> 5;
 	                                 return q < alloc ? bp[q] & (1 << (i & 31)) : false; }
 	bool   operator[](int i) const { return Get(i); }
+	
+	void   Reserve(int nbits);
+	void   Shrink();
+
+	dword       *CreateRaw(int n_dwords);
+	const dword *Raw(int& n_dwords) const { n_dwords = alloc; return bp; }
+	dword       *Raw(int& n_dwords)       { n_dwords = alloc; return bp; }
 
 	Bits()                         { bp = NULL; alloc = 0; }
-	~Bits()                        { Clear(); }
+	~Bits()                        { Free(); }
 
 	Bits(Bits&& b)                 { alloc = b.alloc; bp = b.bp; b.bp = NULL; }
 	void operator=(Bits&& b)       { if(this != &b) { Clear(); alloc = b.alloc; bp = b.bp; b.bp = NULL; } }
diff --git a/uppsrc/Core/Vcont.cpp b/uppsrc/Core/Vcont.cpp
index 634af60e6..45af62f6a 100644
--- a/uppsrc/Core/Vcont.cpp
+++ b/uppsrc/Core/Vcont.cpp
@@ -83,26 +83,60 @@ thread__ int   invector_cache_blki_;
 thread__ int   invector_cache_offset_;
 thread__ int   invector_cache_end_;
 
+void Bits::Free()
+{
+	if(bp)
+		MemoryFree(bp);
+}
 
 void Bits::Clear()
 {
-	if(bp)
-		delete[] bp;
 	alloc = 0;
 	bp = NULL;
 }
 
-void Bits::Expand(int q)
+void Bits::Realloc(int nalloc)
 {
-	int nalloc = 4 * q / 3 + 1;
-	dword *nbp = new dword[nalloc];
+	size_t sz = sizeof(dword) * nalloc;
+	dword *nbp = (dword *)MemoryAllocSz(sz);
+	nalloc = sz / sizeof(dword);
 	if(bp) {
-		Copy(nbp, bp, bp + alloc);
-		delete[] bp;
+		Copy(nbp, bp, bp + min(alloc, nalloc));
+		Free();
 	}
-	Fill(nbp + alloc, nbp + nalloc, (dword)0);
+	if(nalloc > alloc)
+		Fill(nbp + alloc, nbp + nalloc, (dword)0);
 	bp = nbp;
 	alloc = nalloc;
 }
 
+void Bits::Expand(int q)
+{
+	Realloc(3 * q / 2 + 1);
+}
+
+void Bits::Reserve(int nbits)
+{
+	int n = (nbits + 31) >> 5;
+	if(n > alloc)
+		Realloc(n);
+}
+
+void Bits::Shrink()
+{
+	int lasti = alloc - 1;
+	while(lasti > 0 && bp[lasti] == 0)
+		lasti--;
+	int nalloc = lasti + 1;
+	if(nalloc != alloc)
+		Realloc(nalloc);
+}
+
+dword *Bits::CreateRaw(int n_dwords)
+{
+	Clear();
+	Realloc(n_dwords);
+	return bp;
+}
+
 }
diff --git a/uppsrc/Core/src.tpp/Bits$en-us.tpp b/uppsrc/Core/src.tpp/Bits$en-us.tpp
index a74f971d9..6bd51e27f 100644
--- a/uppsrc/Core/src.tpp/Bits$en-us.tpp
+++ b/uppsrc/Core/src.tpp/Bits$en-us.tpp
@@ -35,4 +35,28 @@ onst]&]
 [s5;:Bits`:`:operator`[`]`(int`)const: [@(0.0.255) bool]_[* operator`[`]]([@(0.0.255) int]_
 [*@3 i])_[@(0.0.255) const]&]
 [s2;%% Returns the value of bool [%-*@3 i].&]
+[s4; &]
+[s5;:Upp`:`:Bits`:`:Reserve`(int`): [@(0.0.255) void]_[* Reserve]([@(0.0.255) int]_[*@3 nbits
+])&]
+[s2;%% Preallocates internal storage for [%-*@3 nbits] bits, avoiding 
+further reallocations during Set (as long as only nbits are used).&]
+[s3;%% &]
+[s4; &]
+[s5;:Upp`:`:Bits`:`:Shrink`(`): [@(0.0.255) void]_[* Shrink]()&]
+[s2;%% Tries to reduce internal storage.&]
+[s3; &]
+[s4; &]
+[s5;:Upp`:`:Bits`:`:CreateRaw`(int`): [_^Upp`:`:dword^ dword]_`*[* CreateRaw]([@(0.0.255) i
+nt]_[*@3 n`_dwords])&]
+[s2;%% Creates a new internal storage for [%-*@3 n`_dwords] dwords 
+(sizeof(dword) `* [%-*@3 n`_dwords] bits) and returns a pointer 
+to it. Bits are numbered from LSB.&]
+[s3;%% &]
+[s4; &]
+[s5;:Upp`:`:Bits`:`:Raw`(int`&`)const: [@(0.0.255) const]_[_^Upp`:`:dword^ dword]_`*[* Raw](
+[@(0.0.255) int`&]_[*@3 n`_dwords])_[@(0.0.255) const]&]
+[s5;:Upp`:`:Bits`:`:Raw`(int`&`): [_^Upp`:`:dword^ dword]_`*[* Raw]([@(0.0.255) int`&]_[*@3 n
+`_dwords])&]
+[s2;%% Returns a pointer to internal storage and the size of internal 
+storage.&]
 [s0;%% ]]
\ No newline at end of file