1 files changed, 85 insertions, 0 deletions
diff --git a/src/runtime/mem_js.go b/src/runtime/mem_js.go
new file mode 100644
index 0000000..e87c5f2
--- /dev/null
+++ b/src/runtime/mem_js.go
@@ -0,0 +1,85 @@
+// Copyright 2018 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.
+
+//go:build js && wasm
+
+package runtime
+
+import (
+	"unsafe"
+)
+
+// Don't split the stack as this function may be invoked without a valid G,
+// which prevents us from allocating more stack.
+//
+//go:nosplit
+func sysAllocOS(n uintptr) unsafe.Pointer {
+	p := sysReserveOS(nil, n)
+	sysMapOS(p, n)
+	return p
+}
+
+func sysUnusedOS(v unsafe.Pointer, n uintptr) {
+}
+
+func sysUsedOS(v unsafe.Pointer, n uintptr) {
+}
+
+func sysHugePageOS(v unsafe.Pointer, n uintptr) {
+}
+
+// Don't split the stack as this function may be invoked without a valid G,
+// which prevents us from allocating more stack.
+//
+//go:nosplit
+func sysFreeOS(v unsafe.Pointer, n uintptr) {
+}
+
+func sysFaultOS(v unsafe.Pointer, n uintptr) {
+}
+
+var reserveEnd uintptr
+
+func sysReserveOS(v unsafe.Pointer, n uintptr) unsafe.Pointer {
+	// TODO(neelance): maybe unify with mem_plan9.go, depending on how https://github.com/WebAssembly/design/blob/master/FutureFeatures.md#finer-grained-control-over-memory turns out
+
+	if v != nil {
+		// The address space of WebAssembly's linear memory is contiguous,
+		// so requesting specific addresses is not supported. We could use
+		// a different address, but then mheap.sysAlloc discards the result
+		// right away and we don't reuse chunks passed to sysFree.
+		return nil
+	}
+
+	// Round up the initial reserveEnd to 64 KiB so that
+	// reservations are always aligned to the page size.
+	initReserveEnd := alignUp(lastmoduledatap.end, physPageSize)
+	if reserveEnd < initReserveEnd {
+		reserveEnd = initReserveEnd
+	}
+	v = unsafe.Pointer(reserveEnd)
+	reserveEnd += alignUp(n, physPageSize)
+
+	current := currentMemory()
+	// reserveEnd is always at a page boundary.
+	needed := int32(reserveEnd / physPageSize)
+	if current < needed {
+		if growMemory(needed-current) == -1 {
+			return nil
+		}
+		resetMemoryDataView()
+	}
+
+	return v
+}
+
+func currentMemory() int32
+func growMemory(pages int32) int32
+
+// resetMemoryDataView signals the JS front-end that WebAssembly's memory.grow instruction has been used.
+// This allows the front-end to replace the old DataView object with a new one.
+func resetMemoryDataView()
+
+func sysMapOS(v unsafe.Pointer, n uintptr) {
+}