1 files changed, 129 insertions, 0 deletions
diff --git a/src/runtime/mem_windows.go b/src/runtime/mem_windows.go
new file mode 100644
index 0000000..3a805b9
--- /dev/null
+++ b/src/runtime/mem_windows.go
@@ -0,0 +1,129 @@
+// Copyright 2010 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.
+
+package runtime
+
+import (
+	"unsafe"
+)
+
+const (
+	_MEM_COMMIT   = 0x1000
+	_MEM_RESERVE  = 0x2000
+	_MEM_DECOMMIT = 0x4000
+	_MEM_RELEASE  = 0x8000
+
+	_PAGE_READWRITE = 0x0004
+	_PAGE_NOACCESS  = 0x0001
+
+	_ERROR_NOT_ENOUGH_MEMORY = 8
+	_ERROR_COMMITMENT_LIMIT  = 1455
+)
+
+// 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 sysAlloc(n uintptr, sysStat *sysMemStat) unsafe.Pointer {
+	sysStat.add(int64(n))
+	return unsafe.Pointer(stdcall4(_VirtualAlloc, 0, n, _MEM_COMMIT|_MEM_RESERVE, _PAGE_READWRITE))
+}
+
+func sysUnused(v unsafe.Pointer, n uintptr) {
+	r := stdcall3(_VirtualFree, uintptr(v), n, _MEM_DECOMMIT)
+	if r != 0 {
+		return
+	}
+
+	// Decommit failed. Usual reason is that we've merged memory from two different
+	// VirtualAlloc calls, and Windows will only let each VirtualFree handle pages from
+	// a single VirtualAlloc. It is okay to specify a subset of the pages from a single alloc,
+	// just not pages from multiple allocs. This is a rare case, arising only when we're
+	// trying to give memory back to the operating system, which happens on a time
+	// scale of minutes. It doesn't have to be terribly fast. Instead of extra bookkeeping
+	// on all our VirtualAlloc calls, try freeing successively smaller pieces until
+	// we manage to free something, and then repeat. This ends up being O(n log n)
+	// in the worst case, but that's fast enough.
+	for n > 0 {
+		small := n
+		for small >= 4096 && stdcall3(_VirtualFree, uintptr(v), small, _MEM_DECOMMIT) == 0 {
+			small /= 2
+			small &^= 4096 - 1
+		}
+		if small < 4096 {
+			print("runtime: VirtualFree of ", small, " bytes failed with errno=", getlasterror(), "\n")
+			throw("runtime: failed to decommit pages")
+		}
+		v = add(v, small)
+		n -= small
+	}
+}
+
+func sysUsed(v unsafe.Pointer, n uintptr) {
+	p := stdcall4(_VirtualAlloc, uintptr(v), n, _MEM_COMMIT, _PAGE_READWRITE)
+	if p == uintptr(v) {
+		return
+	}
+
+	// Commit failed. See SysUnused.
+	// Hold on to n here so we can give back a better error message
+	// for certain cases.
+	k := n
+	for k > 0 {
+		small := k
+		for small >= 4096 && stdcall4(_VirtualAlloc, uintptr(v), small, _MEM_COMMIT, _PAGE_READWRITE) == 0 {
+			small /= 2
+			small &^= 4096 - 1
+		}
+		if small < 4096 {
+			errno := getlasterror()
+			switch errno {
+			case _ERROR_NOT_ENOUGH_MEMORY, _ERROR_COMMITMENT_LIMIT:
+				print("runtime: VirtualAlloc of ", n, " bytes failed with errno=", errno, "\n")
+				throw("out of memory")
+			default:
+				print("runtime: VirtualAlloc of ", small, " bytes failed with errno=", errno, "\n")
+				throw("runtime: failed to commit pages")
+			}
+		}
+		v = add(v, small)
+		k -= small
+	}
+}
+
+func sysHugePage(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 sysFree(v unsafe.Pointer, n uintptr, sysStat *sysMemStat) {
+	sysStat.add(-int64(n))
+	r := stdcall3(_VirtualFree, uintptr(v), 0, _MEM_RELEASE)
+	if r == 0 {
+		print("runtime: VirtualFree of ", n, " bytes failed with errno=", getlasterror(), "\n")
+		throw("runtime: failed to release pages")
+	}
+}
+
+func sysFault(v unsafe.Pointer, n uintptr) {
+	// SysUnused makes the memory inaccessible and prevents its reuse
+	sysUnused(v, n)
+}
+
+func sysReserve(v unsafe.Pointer, n uintptr) unsafe.Pointer {
+	// v is just a hint.
+	// First try at v.
+	// This will fail if any of [v, v+n) is already reserved.
+	v = unsafe.Pointer(stdcall4(_VirtualAlloc, uintptr(v), n, _MEM_RESERVE, _PAGE_READWRITE))
+	if v != nil {
+		return v
+	}
+
+	// Next let the kernel choose the address.
+	return unsafe.Pointer(stdcall4(_VirtualAlloc, 0, n, _MEM_RESERVE, _PAGE_READWRITE))
+}
+
+func sysMap(v unsafe.Pointer, n uintptr, sysStat *sysMemStat) {
+	sysStat.add(int64(n))
+}