From 1579e12011fbf6249c507f9acae6b610e2870a71 Mon Sep 17 00:00:00 2001
From: Fabian Reinartz <fab.reinartz@gmail.com>
Date: Tue, 4 Apr 2017 15:59:52 +0200
Subject: [PATCH] Add cross-platform mmap

---
 db_unix.go    | 17 +++--------------
 db_windows.go | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 14 deletions(-)
 create mode 100644 db_windows.go

diff --git a/db_unix.go b/db_unix.go
index 2e673f951..814bee851 100644
--- a/db_unix.go
+++ b/db_unix.go
@@ -4,24 +4,13 @@ package tsdb
 
 import (
 	"os"
-	"unsafe"
-
-	"golang.org/x/sys/unix"
+	"syscall"
 )
 
 func mmap(f *os.File, length int) ([]byte, error) {
-	return unix.Mmap(int(f.Fd()), 0, length, unix.PROT_READ, unix.MAP_SHARED)
+	return syscall.Mmap(int(f.Fd()), 0, length, syscall.PROT_READ, syscall.MAP_SHARED)
 }
 
 func munmap(b []byte) (err error) {
-	return unix.Munmap(b)
-}
-
-// unix.Madvise is not defined for darwin, so we define it ourselves.
-func madvise(b []byte, advice int) (err error) {
-	_, _, e1 := unix.Syscall(unix.SYS_MADVISE, uintptr(unsafe.Pointer(&b[0])), uintptr(len(b)), uintptr(advice))
-	if e1 != 0 {
-		err = e1
-	}
-	return
+	return syscall.Munmap(b)
 }
diff --git a/db_windows.go b/db_windows.go
new file mode 100644
index 000000000..6285e6df7
--- /dev/null
+++ b/db_windows.go
@@ -0,0 +1,34 @@
+package tsdb
+
+import (
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+func mmap(f *os.File, sz int) ([]byte, error) {
+	low, high := uint32(size), uint32(size>>32)
+
+	h, errno := syscall.CreateFileMapping(syscall.Handle(f.Fd()), nil, syscall.PAGE_READONLY, low, high, nil)
+	if h == 0 {
+		return os.NewSyscallError("CreateFileMapping", errno)
+	}
+
+	addr, errno := syscall.MapViewOfFile(h, syscall.FILE_MAP_READ, 0, 0, uintptr(sz))
+	if addr == 0 {
+		return os.NewSyscallError("MapViewOfFile", errno)
+	}
+
+	if err := syscall.CloseHandle(syscall.Handle(h)); err != nil {
+		return os.NewSyscallError("CloseHandle", err)
+	}
+
+	return (*[1 << 30]byte)(unsafe.Pointer(addr))[:sz], nil
+}
+
+func munmap(b []byte) error {
+	if err := syscall.UnmapViewOfFile((uintptr)(unsafe.Pointer(&b[0]))); err != nil {
+		return os.NewSyscallError("UnmapViewOfFile", err)
+	}
+	return nil
+}