Add Windows support.

This commit adds Windows support to Bolt. Windows memory maps return an address instead of a byte
slice so the DB.data field had to be refactored to be a pointer to a large byte array.

bolt_386.go

@@ -0,0 +1,4 @@
+package bolt
+
+// maxMapSize represents the largest mmap size supported by Bolt.
+const maxMapSize = 0xFFFFFFF // 256MB

bolt_amd64.go

@@ -0,0 +1,4 @@
+package bolt
+
+// maxMapSize represents the largest mmap size supported by Bolt.
+const maxMapSize = 0xFFFFFFFFFFFF // 256TB

bolt_darwin.go

@@ -3,6 +3,7 @@ package bolt
 import (
 	"os"
 	"syscall"
+	"unsafe"
 )
 
 var odirect int
@@ -22,12 +23,31 @@ func funlock(f *os.File) error {
 	return syscall.Flock(int(f.Fd()), syscall.LOCK_UN)
 }
 
-// mmap memory maps a file to a byte slice.
+// mmap memory maps a DB's data file.
-func mmap(f *os.File, sz int) ([]byte, error) {
+func mmap(db *DB, sz int) error {
-	return syscall.Mmap(int(f.Fd()), 0, sz, syscall.PROT_READ, syscall.MAP_SHARED)
+	b, err := syscall.Mmap(int(db.file.Fd()), 0, sz, syscall.PROT_READ, syscall.MAP_SHARED)
+	if err != nil {
+		return err
+	}
+
+	// Save the original byte slice and convert to a byte array pointer.
+	db.dataref = b
+	db.data = (*[maxMapSize]byte)(unsafe.Pointer(&b[0]))
+	db.datasz = sz
+	return nil
 }
 
-// munmap unmaps a pointer from a file.
+// munmap unmaps a DB's data file from memory.
-func munmap(b []byte) error {
+func munmap(db *DB) error {
-	return syscall.Munmap(b)
+	// Ignore the unmap if we have no mapped data.
+	if db.dataref == nil {
+		return nil
+	}
+
+	// Unmap using the original byte slice.
+	err := syscall.Munmap(db.dataref)
+	db.dataref = nil
+	db.data = nil
+	db.datasz = 0
+	return err
 }

bolt_linux.go

@@ -3,6 +3,7 @@ package bolt
 import (
 	"os"
 	"syscall"
+	"unsafe"
 )
 
 var odirect = syscall.O_DIRECT
@@ -22,12 +23,31 @@ func funlock(f *os.File) error {
 	return syscall.Flock(int(f.Fd()), syscall.LOCK_UN)
 }
 
-// mmap memory maps a file to a byte slice.
+// mmap memory maps a DB's data file.
-func mmap(f *os.File, sz int) ([]byte, error) {
+func mmap(db *DB, sz int) error {
-	return syscall.Mmap(int(f.Fd()), 0, sz, syscall.PROT_READ, syscall.MAP_SHARED)
+	b, err := syscall.Mmap(int(db.file.Fd()), 0, sz, syscall.PROT_READ, syscall.MAP_SHARED)
+	if err != nil {
+		return err
+	}
+
+	// Save the original byte slice and convert to a byte array pointer.
+	db.dataref = b
+	db.data = (*[maxMapSize]byte)(unsafe.Pointer(&b[0]))
+	db.datasz = sz
+	return nil
 }
 
-// munmap unmaps a pointer from a file.
+// munmap unmaps a DB's data file from memory.
-func munmap(b []byte) error {
+func munmap(db *DB) error {
-	return syscall.Munmap(b)
+	// Ignore the unmap if we have no mapped data.
+	if db.dataref == nil {
+		return nil
+	}
+
+	// Unmap using the original byte slice.
+	err := syscall.Munmap(db.dataref)
+	db.dataref = nil
+	db.data = nil
+	db.datasz = 0
+	return err
 }

bolt_windows.go

@@ -1,6 +1,7 @@
 package bolt
 
 import (
+	"fmt"
 	"os"
 	"syscall"
 	"unsafe"
@@ -23,36 +24,48 @@ func funlock(f *os.File) error {
 	return nil
 }
 
-// mmap memory maps a file to a byte slice.
+// mmap memory maps a DB's data file.
 // Based on: https://github.com/edsrzf/mmap-go
-func mmap(f *os.File, sz int) ([]byte, error) {
+func mmap(db *DB, sz int) error {
+	// Truncate the database to the size of the mmap.
+	if err := db.file.Truncate(int64(sz)); err != nil {
+		return fmt.Errorf("truncate: %s", err)
+	}
+
 	// Open a file mapping handle.
-	sizelo, sizehi := uint32(sz>>32), uint32(sz&0xffffffff)
+	sizelo := uint32(sz >> 32)
-	h, errno := syscall.CreateFileMapping(syscall.Handle(f.Fd()), nil, syscall.PAGE_READONLY, sizehi, sizelo, nil)
+	sizehi := uint32(sz & 0xffffffff)
+	h, errno := syscall.CreateFileMapping(syscall.Handle(db.file.Fd()), nil, syscall.PAGE_READONLY, sizelo, sizehi, nil)
 	if h == 0 {
-		return nil, os.NewSyscallError("CreateFileMapping", errno)
+		return os.NewSyscallError("CreateFileMapping", errno)
 	}
 
 	// Create the memory map.
 	addr, errno := syscall.MapViewOfFile(h, syscall.FILE_MAP_READ, 0, 0, uintptr(sz))
 	if addr == 0 {
-		return nil, os.NewSyscallError("MapViewOfFile", errno)
+		return os.NewSyscallError("MapViewOfFile", errno)
 	}
 
 	// Close mapping handle.
 	if err := syscall.CloseHandle(syscall.Handle(h)); err != nil {
-		return nil, os.NewSyscallError("CloseHandle", err)
+		return os.NewSyscallError("CloseHandle", err)
 	}
 
-	// Convert to a byte slice.
+	// Convert to a byte array.
-	b := ((*[0xFFFFFFF]byte)(unsafe.Pointer(addr)))[0:sz]
+	db.data = ((*[maxMapSize]byte)(unsafe.Pointer(addr)))
-	return b, nil
+	db.datasz = sz
+
+	return nil
 }
 
 // munmap unmaps a pointer from a file.
 // Based on: https://github.com/edsrzf/mmap-go
-func munmap(b []byte) error {
+func munmap(db *DB) error {
-	addr := (uintptr)(unsafe.Pointer(&b[0]))
+	if db.data == nil {
+		return nil
+	}
+
+	addr := (uintptr)(unsafe.Pointer(&db.data[0]))
 	if err := syscall.UnmapViewOfFile(addr); err != nil {
 		return os.NewSyscallError("UnmapViewOfFile", err)
 	}

db.go

@@ -67,7 +67,9 @@ type DB struct {
 
 	path     string
 	file     *os.File
-	data     []byte
+	dataref  []byte
+	data     *[maxMapSize]byte
+	datasz   int
 	meta0    *meta
 	meta1    *meta
 	pageSize int
@@ -191,13 +193,8 @@ func (db *DB) mmap(minsz int) error {
 	}
 	size = db.mmapSize(size)
 
-	// Truncate the database to the size of the mmap.
-	if err := db.file.Truncate(int64(size)); err != nil {
-		return fmt.Errorf("truncate: %s", err)
-	}
-
 	// Memory-map the data file as a byte slice.
-	if db.data, err = mmap(db.file, size); err != nil {
+	if err := mmap(db, size); err != nil {
 		return err
 	}
 
@@ -218,12 +215,9 @@ func (db *DB) mmap(minsz int) error {
 
 // munmap unmaps the data file from memory.
 func (db *DB) munmap() error {
-	if db.data != nil {
+	if err := munmap(db); err != nil {
-		if err := munmap(db.data); err != nil {
 		return fmt.Errorf("unmap error: " + err.Error())
 	}
-		db.data = nil
-	}
 	return nil
 }
 
@@ -507,7 +501,7 @@ func (db *DB) Stats() Stats {
 // This is for internal access to the raw data bytes from the C cursor, use
 // carefully, or not at all.
 func (db *DB) Info() *Info {
-	return &Info{db.data, db.pageSize}
+	return &Info{uintptr(unsafe.Pointer(&db.data[0])), db.pageSize}
 }
 
 // page retrieves a page reference from the mmap based on the current page size.
@@ -544,7 +538,7 @@ func (db *DB) allocate(count int) (*page, error) {
 	// Resize mmap() if we're at the end.
 	p.id = db.rwtx.meta.pgid
 	var minsz = int((p.id+pgid(count))+1) * db.pageSize
-	if minsz >= len(db.data) {
+	if minsz >= db.datasz {
 		if err := db.mmap(minsz); err != nil {
 			return nil, fmt.Errorf("mmap allocate error: %s", err)
 		}
@@ -579,7 +573,7 @@ func (s *Stats) add(other *Stats) {
 }
 
 type Info struct {
-	Data     []byte
+	Data     uintptr
 	PageSize int
 }
 

doc.go

@@ -12,6 +12,9 @@ rolled back in the event of a crash.
 
 The design of Bolt is based on Howard Chu's LMDB database project.
 
+Bolt currently works on Windows, Mac OS X, and Linux.
+
+
 Basics
 
 There are only a few types in Bolt: DB, Bucket, Tx, and Cursor. The DB is
@@ -33,7 +36,5 @@ values returned from Bolt cannot be changed. Writing to a read-only byte slice
 will cause Go to panic. If you need to work with data returned from a Get() you
 need to first copy it to a new byte slice.
 
-Bolt currently works on Mac OS and Linux. Windows support is coming soon.
-
 */
 package bolt