refactor sqlite locking constants

constants are shared between os lock implementations, so move them
out of os-specific files

also camelcases them

Author: ecordell

db/pager.go

@@ -1,5 +1,12 @@
 package db
 
+const (
+	sqlitePendingByte  = 0x40000000
+	sqliteReservedByte = sqlitePendingByte + 1
+	sqliteSharedFirst  = sqlitePendingByte + 2
+	sqliteSharedSize   = 510
+)
+
 type pager interface {
 	// load a page from storage.
 	page(n int, pagesize int) ([]byte, error)

db/pager_unix.go

@@ -14,11 +14,7 @@ import (
 )
 
 const (
-	seek_set             = 0 // should be defined in syscall
-	sqlite_pending_byte  = 0x40000000
-	sqlite_reserved_byte = sqlite_pending_byte + 1
-	sqlite_shared_first  = sqlite_pending_byte + 2
-	sqlite_shared_size   = 510
+	seekSet = 0 // should be defined in syscall
 )
 
 type filePager struct {
@@ -64,8 +60,8 @@ func (f *filePager) RLock() error {
 	// - get PENDING lock
 	pending := &unix.Flock_t{
 		Type:   unix.F_RDLCK,
-		Whence: seek_set,
-		Start:  sqlite_pending_byte,
+		Whence: seekSet,
+		Start:  sqlitePendingByte,
 		Len:    1,
 	}
 	if err := f.lock(pending); err != nil {
@@ -81,9 +77,9 @@ func (f *filePager) RLock() error {
 	// Get the read-lock
 	read := &unix.Flock_t{
 		Type:   unix.F_RDLCK,
-		Whence: seek_set,
-		Start:  sqlite_shared_first,
-		Len:    sqlite_shared_size,
+		Whence: seekSet,
+		Start:  sqliteSharedFirst,
+		Len:    sqliteSharedSize,
 	}
 	if err := f.lock(read); err != nil {
 		return err
@@ -107,8 +103,8 @@ func (f *filePager) CheckReservedLock() (bool, error) {
 	// per SQLite's unixCheckReservedLock()
 	lock := &unix.Flock_t{
 		Type:   unix.F_WRLCK,
-		Whence: seek_set,
-		Start:  sqlite_reserved_byte,
+		Whence: seekSet,
+		Start:  sqliteReservedByte,
 		Len:    1,
 	}
 	err := unix.FcntlFlock(f.f.Fd(), unix.F_GETLK, lock)

db/pager_windows.go

@@ -17,13 +17,6 @@ import (
 	"golang.org/x/sys/windows"
 )
 
-const (
-	sqlite_pending_byte  = 0x40000000
-	sqlite_reserved_byte = sqlite_pending_byte + 1
-	sqlite_shared_first  = sqlite_pending_byte + 2
-	sqlite_shared_size   = 510
-)
-
 const (
 	reserved uint32 = 0
 )
@@ -94,7 +87,7 @@ func (f *filePager) RLock() error {
 	//
 	// source: https://github.com/sqlite/sqlite/blob/c398c65bee850b6b8f24a44852872a27f114535d/src/os_win.c#L3280
 	for i := 0; i < 3; i++ {
-		err := f.lock(sqlite_pending_byte, 1)
+		err := f.lock(sqlitePendingByte, 1)
 		if err == nil {
 			break
 		}
@@ -106,11 +99,11 @@ func (f *filePager) RLock() error {
 
 	defer func() {
 		// - drop the pending lock. No idea what to do with the error :/
-		f.unlock(sqlite_pending_byte, 1)
+		f.unlock(sqlitePendingByte, 1)
 	}()
 
 	// Get the read-lock
-	if err := f.lock(sqlite_shared_first, sqlite_shared_size); err != nil {
+	if err := f.lock(sqliteSharedFirst, sqliteSharedSize); err != nil {
 		return err
 	}
 	f.state = Locked
@@ -121,7 +114,7 @@ func (f *filePager) RUnlock() error {
 	if f.state == Unlocked {
 		return errors.New("trying to unlock an unlocked lock") // panic?
 	}
-	if err := f.unlock(sqlite_shared_first, sqlite_shared_size); err != nil {
+	if err := f.unlock(sqliteSharedFirst, sqliteSharedSize); err != nil {
 		return err
 	}
 	f.state = Unlocked
@@ -131,9 +124,9 @@ func (f *filePager) RUnlock() error {
 // True if there is a 'reserved' lock on the database, by any process.
 func (f *filePager) CheckReservedLock() (bool, error) {
 	// per SQLite's winCheckReservedLock()
-	err := f.lock(sqlite_reserved_byte, 1)
+	err := f.lock(sqliteReservedByte, 1)
 	if err == nil {
-		f.unlock(sqlite_reserved_byte, 1)
+		f.unlock(sqliteReservedByte, 1)
 	}
 	return err == nil, err
 }