1 files changed, 76 insertions, 0 deletions
diff --git a/src/pkg/runtime/mheapmap32.h b/src/pkg/runtime/mheapmap32.h
new file mode 100644
index 000000000..0a16ccd10
--- /dev/null
+++ b/src/pkg/runtime/mheapmap32.h
@@ -0,0 +1,76 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Free(v) must be able to determine the MSpan containing v.
+// The MHeapMap is a 2-level radix tree mapping page numbers to MSpans.
+
+typedef struct MHeapMapNode2 MHeapMapNode2;
+
+enum
+{
+	// 32 bit address - 12 bit page size = 20 bits to map
+	MHeapMap_Level1Bits = 10,
+	MHeapMap_Level2Bits = 10,
+
+	MHeapMap_TotalBits =
+		MHeapMap_Level1Bits +
+		MHeapMap_Level2Bits,
+
+	MHeapMap_Level1Mask = (1<<MHeapMap_Level1Bits) - 1,
+	MHeapMap_Level2Mask = (1<<MHeapMap_Level2Bits) - 1,
+};
+
+struct MHeapMap
+{
+	void *(*allocator)(uintptr);
+	MHeapMapNode2 *p[1<<MHeapMap_Level1Bits];
+};
+
+struct MHeapMapNode2
+{
+	MSpan *s[1<<MHeapMap_Level2Bits];
+};
+
+void	MHeapMap_Init(MHeapMap *m, void *(*allocator)(uintptr));
+bool	MHeapMap_Preallocate(MHeapMap *m, PageID k, uintptr npages);
+MSpan*	MHeapMap_Get(MHeapMap *m, PageID k);
+MSpan*	MHeapMap_GetMaybe(MHeapMap *m, PageID k);
+void	MHeapMap_Set(MHeapMap *m, PageID k, MSpan *v);
+
+
+// Much of the time, free(v) needs to know only the size class for v,
+// not which span it came from.  The MHeapMap finds the size class
+// by looking up the span.
+//
+// An MHeapMapCache is a simple direct-mapped cache translating
+// page numbers to size classes.  It avoids the expensive MHeapMap
+// lookup for hot pages.
+//
+// The cache entries are 32 bits, with the page number in the low part
+// and the value at the top.
+//
+// NOTE(rsc): On a machine with 32-bit addresses (= 20-bit page numbers),
+// we can use a 16-bit cache entry by not storing the redundant 12 bits
+// of the key that are used as the entry index.  For now, keep it simple.
+enum
+{
+	MHeapMapCache_HashBits = 12
+};
+
+struct MHeapMapCache
+{
+	uint32 array[1<<MHeapMapCache_HashBits];
+};
+
+// All macros for speed (sorry).
+#define HMASK	((1<<MHeapMapCache_HashBits)-1)
+#define KBITS	MHeapMap_TotalBits
+#define KMASK	((1LL<<KBITS)-1)
+
+#define MHeapMapCache_SET(cache, key, value) \
+	((cache)->array[(key) & HMASK] = (key) | ((uintptr)(value) << KBITS))
+
+#define MHeapMapCache_GET(cache, key, tmp) \
+	(tmp = (cache)->array[(key) & HMASK], \
+	 (tmp & KMASK) == (key) ? (tmp >> KBITS) : 0)